Formal Recommendation 

 From: National Organic Standards Board (NOSB)

 To: the National Organic Program (NOP)

Date: 

Subject: 

Chair: 

The NOSB hereby recommends to the NOP the following: 

Rulemaking Action:

Guidance Statement:

Other:

Statement of Recommendation:;DŽƚŝŽŶηϭͿ

 

Rationale Supporting Recommendation (including consistency with OFPA and NOP):

 

Committee Vote:

 

Moved: 

Seconded: 

Yes: No: Abstain: Absent: Recuse: 

 

 

 
Rationale Supporting Recommendation (including consistency with OFPA and NOP):

Statement of Recommendation:;DŽƚŝŽŶηϮͿ





Committee Vote:

 

 Moved: 

Seconded: 

 Yes: No: Abstain: Absent: Recuse: 

 

 

 

 
National Organic Standards Board

Crops Subcommittee

Petitioned Material Proposal

Streptomycin

August 6, 2013

*Reviewed and revised February 18, 2014

Discussion Summary: 

The NOSB has been petitioned to remove the existing expiration date of October 21, 2014 for 

Streptomycin and replace it with a new one of Oct 21, 2017, for both apples and pears. The 

petitioner states that this would allow adequate time for the transition from strep over to nonantibiotic, biological alternatives for fire blight control.

There are two different positions on this subject: those that support the petition request for an 

extension and those that oppose an extension.

Both sides agree that it is time for a phase out for the allowed use of strep. The supporters 

believe that three additional years until October 2017 is reasonable, and opponents believe that 

yet another extension offers no assurance of phase out.

Proponents of an extension feel that:

~Because of the investment involved to establish an orchard (as well as the businesses 

established to handle this produce) in both time, money, and the need for completion 

of existing research of materials, that a slowdown (or extension) of the expiration date 

is needed, especially for pear growers.

~This slow down would benefit growers, processors, producers, handlers, and 

consumers alike.

~Alternative materials are still not readily showing consistent control and one material’s 

registration (Previsto copper) has been delayed by EPA. Thus, the farmers still need 

some additional time in order to prepare for the transition to a non-antibiotic fire blight 

control period in time.

•Opponents feel that:

~Fire blight resistance to streptomycin is widespread in the U.S.

~Raise the question of essentiality, based on the significant percentage of growers 

selling to markets that do not allow antibiotic treatments.

~Organic integrity and sales are threatened because of consumer expectation that 

antibiotics are not used in organic production.

•Both sides agree that the “core” issue here is whether or not there is a risk of enhancing 

antibiotic resistance in human pathogens. There is science that supports both sides of this 

argument and the level of concerns that are raised by this particular use pattern. Supporters cite 

issues of use patterns and limits of residues as indicative of no evidence of harm. Opponents 

cite resistant human pathogens in strep treated orchards and horizontal gene transfer identified 

as leading to antibiotic resistance.

•While there has been a direct linkage shown to exist between infection and colonization of 

humans by antibiotic resistant bacteria in animals (Larsen et al 2010), supporters cite no direct 

linkage has been demonstrated between antibiotic resistant bacteria in humans and antibiotic 

sprays applied to plants (Stockwell and Duffy, 2012), such as the current use of strep in apples 

and pears for fire blight control. Lab results vary in their conclusions. Opponents cite evidence 
that bacteria, including Erwinia amylovora and human pathogens, share a common genetic 

basis for resistance, transmitted by plasmids, to streptomycin in particular. (McGhee et al, 2010; 

Sundin, 2000; Sundin and Bender, 1996; Pezzella et al, 2004; Scherer et al, 2013; Foster et al, 

2004.)

•Proponents state: there is no evidence that applications of antibiotics to orchards during bloom 

contributes to antibiotic resistance in human pathogens. The amount and timing of the use of 

strep in an orchard environment does not contribute to any human health concerns, especially 

in light of streptomycin being ineffective in humans when ingested orally.

•Opponents state: there is evidence that an application of strep leads to an increase in 

resistance to streptomycin in orchard bacteria, that human pathogens and fire blight bacteria 

share the same gene pool of genes resistant to streptomycin (i.e. that the same genes 

responsible for resistance in Erwinia amylovora are also responsible for resistance in human 

pathogens), that human pathogens do not need to be present in the orchard to obtain resistance 

genes acquired by and augmented in orchard bacteria, that strep residues are sometimes 

present in treated fruit, and that strep is still a critically important antimicrobial for use against 

human pathogens.

•The primary point of discussion here is whether to grant an extension or not to the current 

expiration date for streptomycin in October 2014. The points proponents say should be 

considered are: What impact does an extension/or non-extension have on the stakeholders that 

either use this material or have built their businesses around expanded crop availability; How 

will a decision impact the supply chain, How will a decision impact the consumer (all consumers, 

not just a select group(s)), What are the risks/if any for granting an extension or not, and would 

granting a short extension for allowed use knowing what the use patterns are pose any 

significant increases in human health concerns from resistance than currently exist today? 

•The points opponents say should be considered are: What impact does yet another extension, 

which was first called for by the NOSB in 1995, have on the integrity of the organic label? What 

are the public health hazards of using antibiotics for nontherapeutic uses and why are infectious 

disease doctors concerned? What is the threat of low-level environmental exposure to 

antibiotics? What are the alternative strategies that are used to manage or prevent fire blight?

•Remember, according to proponents, this is not a new material, but one that has been on the 

National List of Approved Materials for a number of years as being allowed for use by organic 

growers to use on their organically grown and certified crops. Opponents point to long-standing 

NOSB attempts to phase out the use of antibiotics in organic apple and pear production, with 

votes by previous boards to phase-out, only to have subsequent boards issue extensions.

•One other point of discussion, proponents state that this would be a way to ensure a full 

expiration of strep from the National List, if an extension for use were to happen. They ask, how 

could we ensure all stakeholders that there would be an absolute point when this usage would 

truly expire? Opponents, who would like the 2014 antibiotic expiration date to take effect, 

believe that the debate on antibiotics and votes to phase them out by previous boards have 

resulted in only extended deadlines for too long, and organic should not in any way contribute to 

the worldwide crisis in antibiotic resistance, while ultimately threatening consumer confidence in 

the organic label.

New text: 

Oral and written public comments (Docket AMS-NOP-13-0049) from pear growers noted that 

especially in the 2013 season, Blossom Protect did not work well in the Pacific Northwest and 

California. (The manufacturer of Blossom Protect does not agree with this statement and voiced 
their disagreement during the written public comment period prior to the canceled fall 2013 

NOSB meeting.) It was an unusually warm spring. The copper material that is very promising 

has been delayed in registration until at least 2014 nationwide and 2015 in California.

Summary of Proposed Action:

The Crops Subcommittee proposes to: 

Remove the existing expiration date of October 21, 2014 for streptomycin and replace it with a 

new expiration date of October 21, 2017. This would be for use in both apples and pears for 

control of fire blight.

The Crops Subcommittee puts forward this resolution:

Resolution: The National Organic Standards Board is committed to the phase out of this 

material. Between now and the expiration date the Board urges growers and certifiers to include 

in organic systems plans an annual increase in the extent and/or number of alternative practices 

and materials that are trialed for controlling fire blight. In addition, the board strongly advocates 

to USDA a high priority for increased support for research into these alternative practices and 

materials.

Introduction

A Petition to the National Organic Standards Board (NOSB) was received for the Removal of 

the Expiration Date (October 21, 2014) for streptomycin and the establishment of October 21, 

2017 as its sunset date, in order to allow for adequate time for the transition to proven effective 

non-antibiotic, i.e. biological alternatives for fire blight control in apples and pears.

Because this subject is complex and there are two different positions to be represented, this 

recommendation is organized to present two separate positions - those for and those against an 

extension. These are designed to supplement the points raised in the checklist. Most of the 

same background presented in the spring 2013 Recommendation for Oxytetracycline is relevant 

to Streptomycin, except for the 2007 and 2008 actions.

The subcommittee acknowledges the concerns of consumers and previous NOSB members 

who feel that it is time to phase this material out from organic agriculture. The two positions 

represented in the discussion section of this document differ on the timing of the phase-out. 

Additional concerns are being put forward in a separate resolution on the subject.

Points of Agreement and Disagreement

This section focusses on how the material is used in the context of both plant and human 

health. Because much of the general information was covered in the proposal for 

Oxytetracycline, this review focusses on the differences and similarities between the two 

materials. Specific portions address Checklist categories as noted.

1. Fire blight control

Proponents of both positions agree that orchard establishment requires a large investment of 

time and money, that apples and pears are grown in a variety of locations that require different 

management plans, and that more research is needed into systems for preventing fire blight 

damage. 
Proponents of extending the expiration date of streptomycin say:

• Because of the very large investment of time and money that establishing an orchard 

entails, the variety of locations that apples and pears are grown, and the very 

rudimentary state of research on alternatives to this material in that variety of locations, 

we are supporting slowing down the removal of streptomycin from the National List.

• Since the organic pear industry is more at risk to fire blight than apples there is concern 

that pear research and control measures are lagging behind and that an expanded time 

frame will be needed. Streptomycin is still fairly widely used in pears, especially those 

grown in areas with high humidity and warm springs.

• A slightly extended date of 2017 will benefit consumers and growers alike. The few more 

seasons of research will enable new products to be tested in both apples and pears in a 

variety of weather conditions.

• In 2009, about 15% of the total apple area and 40% of the pears (organic and 

conventional) were treated with streptomycin or oxytetracycline for control of Fireblight, 

the disease caused by the bacteria Erwinia amylovora.

1

• Experience of pear growers especially in the 2013 season has shown that Blossom 

Protect has not worked well in the Pacific Northwest or California. It was an unusually 

warm spring. The copper material that is very promising has been delayed in registration 

until at least 2014 nationwide and 2015 in California.

Opponents to extending the expiration date of streptomycin say:

• Like most challenges in organic production systems, with fire blight there is no one 

material and no one practice that will eliminate the problem. Fire blight must be met with 

a truly organic systems approach that is sensitive to the potential adverse health and 

environmental effects of inputs and consumer expectations.2

 

• Fire blight resistance to streptomycin is widespread in the United States. Streptomycinresistant strains of fire blight have been found in California, Oregon, Washington, 

Michigan, New York,3 Missouri,4 and Utah.5 Plasmid-borne genes have been found to 

confer resistance in California, Michigan,6 and New York.7

 

• With regard to the “essentiality” of streptomycin, not all organic apple and pear growers 

depend on antibiotics. In fact, there is a sizeable proportion of growers of both apples 

and pears who do not use antibiotics. 

• As of March 10, 2011, there were 96 businesses certified as EU-compliant organic 

producers of apples and/or pears in the state of Washington alone, representing about 

one third of the state’s organic apple and one fourth of the state’s organic pear 

production. EU-compliant organic apple and pear growers cannot use antibiotics, and 

face a three-year ban from selling in the EU if they do.8 In addition, cultural changes in 

the orchard environment have contributed to epidemics of fire blight.9

 

2. Need for phase out of streptomycin

The sub-committee acknowledges the concerns of consumers and previous NOSB members 

who feel that it is time to phase this material out from organic agriculture. The two positions 

represented in the discussion section of this document differ on the timing of the phase-out.
Proponents of an extension for streptomycin say:

Because of the need to make sure that this material is phased out, a resolution motion has been 

added to affirm the commitment by the NOSB to all organic stakeholders. The NOSB must 

ensure that the decisions made reflect due consideration of the various needs and concerns of 

the vast array of all our organic stakeholders, especially when dealing with complicated issues, 

such as this one. 

Additionally, in spite of the claims below about the threat of spreading resistance to 

streptomycin, most of the research on this subject has been conducted with antibiotics used in 

livestock and very little in orchard environments. Some very recent research specifically for an 

orchard situation noted that more streptomycin-resistant isolates were cultured from nonsprayed orchards compared to sprayed orchards.10

Opponents of an extension for streptomycin say:

Streptomycin is an antibiotic considered by the World Health Organization to be of critical 

importance to human medicine.11 Streptomycin is used in a way that exposes bacteria in the 

orchard to the antibiotic.12 Current science shows that environmental exposure to antibiotic use 

in the environment is the major cause of development and spread of antibiotic resistance in 

human pathogens.13The spread of antibiotic resistance does not require contact between the 

antibiotic and human pathogens because the major means of spreading antibiotic resistance is 

through the transfer of genes between different bacteria. Uses resulting in low residues 

(subtherapeutic or subinhibitory levels) can create a high health risk.14 Streptomycin resistance 

is evident and expected to grow if urgent use precaution is not exercised.15 Organic production 

should not be contributing to the problem of antibiotic resistance. 

3. Antibiotic Resistance

Proponents and opponents of extending the expiration date of streptomycin agree that the core 

issue here is whether there is a risk of enhancing antibiotic resistance in human pathogens. The 

most astute and experienced scientists in this area realize that science and medicine have to 

find a way to co-exist with resistance, including managing reservoirs of resistance in the 

environment and preventing development of new forms of resistance. (Am. Academy of 

Microbiology, 2009).

Proponents of extending the expiration date of streptomycin say:

• Antibiotic-resistant bacteria that are competent phyllosphere colonisers can persist in the 

environment, evidently independent of antibiotic use, as shown by Yashiro and McManus 

(2012). They demonstrated that long-term applications of streptomycin alone did not alter 

the bacterial communities on apple leaves. They sampled leaves from four orchards that 

were treated with spring-time applications of streptomycin over 10 years and from four 

orchards that were not sprayed with antibiotics. The bacterial genera Massilia, 

Methylobacterium, Pantoea, Pseudomonas, and Sphingomonas were detected from all 

orchards, regardless of spray history. More streptomycin-resistant isolates (65%) were 

cultured from non-sprayed orchards compared to sprayed orchards (50%). They concluded 

that factors other than streptomycin influence both the proportion of streptomycin-resistant 

bacteria and phylogenetic makeup of bacterial communities on apple leaves (Yashiro and 

McManus, 2012).

• There are numerous reports that the use of antibiotics in animal production is associated 

with increase of antibiotic-resistant bacteria in animals, waste-water, and manure (for some 

examples see Larsen 2010, Wright 2010). A direct linkage was reported between infection 

and colonization of humans by antibiotic resistant bacteria from farm animals (Larsen et al 

2010). No direct linkage has been demonstrated between antibiotic resistant bacteria in 

humans and antibiotic sprays on plants (Stockwell and Duffy, 2012).
Opponents of extending the expiration date of streptomycin say:

• Application of streptomycin leads to an increase of streptomycin resistance in the fireblight 

organism and other bacteria in the orchard. 

Selection of bacteria resistant to streptomycin occurs at extremely low antibiotic 

concentrations.16 It is accepted that reliance on streptomycin for fireblight control resulted in the 

development and spread of resistance to streptomycin in E. amylovora.17 Resistance genes are 

prevalent in treated soils,18 and researchers have concluded that resistance is often acquired 

through gene transfer.19 Some researchers found the highest concentration of streptomycinresistant bacteria in the phylloplane of treated crops,20 but Yashiro and McManus (2012)21 found 

a higher percentage of cultured phyllosphere bacteria resistant to streptomycin at non-sprayed 

orchards than at sprayed orchards. But they stated, 

However, our conclusion does not absolve streptomycin of all risk associated with its 

use. For example, it is possible that streptomycin could select for novel resistance genes 

in apple orchards, even if the overall frequency of resistant bacteria is not increased. A 

greater diversity of mobile resistance genes in apple orchards could lead to horizontal 

transfer of resistance among a greater range of bacteria, which in turn could be 

consumed on fresh produce.

• Streptomycin resistance genes from the orchard are transferable to other bacteria.

Streptomycin resistance in E. amylovora may come from a chromosomal or two known 

streptomycin resistance genes carried on plasmids.22 “The carriage of strA-strB within an 

integron, a transposon, and on broad-host-range plasmids has facilitated the world-wide 

dissemination of this determinant among at least 21 bacterial genera.”23 The streptomycin 

resistance genes (strA-strB) are known to be carried on transposons and spread by horizontal 

gene transfer, but are unlikely to have been transferred directly –it is more likely that they are 

spread through intermediate bacteria. “The distribution of the strA-strB genes in the environment 

clearly illustrates the expansiveness of a common microbial gene pool and the rapid 

dissemination of Abr determinants in bacterial populations.” 24 This has been confirmed by a 

several researchers.25

• Streptomycin is a critically important antimicrobial.

Streptomycin is classified as a critically important antimicrobial by the World Health 

Organization. It is a limited therapy as part of treatment of enterococcal endocarditis and MultiDrug Resistant (MDR) tuberculosis.26 It is also effective in treating Brucella

(brucellosis), Calymmatobacterium granulomatis (donovanosis, granuloma 

inguinale), Escherichia coli, Proteus spp., Aerobacter aerogenes, Klebsiella pneumoniae,

and Enterococcus faecalis in urinary tract infections, Francisella tularensis, Haemophilus 

ducreyi (chancroid), Haemophilus influenzae (in respiratory, endocardial, and meningeal 

infections - concomitantly with another antibacterial agent), Klebsiella pneumoniae pneumonia 

(concomitantly with another antibacterial agent), Mycobacterium tuberculosis, Pasteurella 

pestis, Streptococcus viridans, Enterococcus faecalis (in endocardial infections - concomitantly 

with penicillin).27 

4. Ecological Impacts

Opponents of extending the use of streptomycin say:

• Streptomycin use may have unforeseen ecological impacts.

Since resistance to antibiotics is more prevalent in some groups of microorganisms than others, 

the dispersal of streptomycin in the environment can disrupt the microbial ecology. For instance, 

blue-green algae, which are important in sequestering carbon dioxide and releasing oxygen 

gas, are as a group susceptible to antibiotics.28 
Differences between Streptomycin and Oxytetracycline

•• Use: While tetracycline is only used during bloom and will only be present on fruit that set 

early in the bloom period while the late blooms are being sprayed, streptomycin is registered 

for use from early bloom until 45 days before harvest. 

•• Mode of Action: Streptomycin binds irreversibly to bacterial ribosomes and block synthesis of 

proteins (51). Oxytetracycline binds reversibly to these proteins (McManus et al., 2002). 

(Category 1, Question 9]

•• Mechanism of Resistance: There are 2 mechanisms of resistance to streptomycin in fire 

blight bacteria: spontaneous mutation of a chromosomal gene which encodes production of 

ribosomal protein, thus strep cannot bind to ribosome and bacteria become immune to 

antibiotic. This is most common in the US. Acquired resistance has been detected 

occasionally in MI and CA. The pathogen acquired plasmids that contained genes encoding 

an enzyme that inactivates strep. These resistant isolates of fire blight were detected in an 

orchard ten years after applications were stopped (34). The fire blight bacteria have not 

been known to develop resistance to tetracycline in the laboratory, and little is known about 

the mechanisms for resistance to tetracycline in that bacteria.

** Genetics of Resistance: The genes for resistance to streptomycin that are transferred by 

plasmid are the same genes known to confer resistance to streptomycin in human 

pathogens.29 This is a step in the chain of causation that is not known for tetracycline.

•• Residue on Fruit: While there were not specific studies besides EPA data that set ADI limits 

that showed residue of tetracycline on fruit, one study in Austrian orchards showed detection 

of streptomycin residues (33) in apples, with the highest concentrations in the apple core. 

Apple fruit were collected about three months after bloom and tested for streptomycin. The 

level of detection was 2 μg/kg (0.002 ppm or 2 ppb) and the limit of quantification was 

identified as 7 μg/kg (0.007 ppm or 7 ppb). They reported that the highest concentration of 

streptomycin detected was 18 μg/kg (0.018 ppm), well below the EPA tolerance of 250 

μg/kg (0.25 ppm). The Austrian ADI for streptomycin is 0.03 mg per kg of body mass per 

day (0.03 ppm). The study did not report on exactly what spray practices led to this 

result.)[Category 1, Question 9]

•• Use in medicine: Both tetracycline and streptomycin are classified as critically important 

antimicrobials by the World Health Organization. Tetracycline is one of a limited number of 

therapies for infections due to Brucella, Chlamydia spp. and Rickettsia spp. Streptomycin is 

a Limited therapy as part of treatment of enterococcal endocarditis and Multi-Drug Resistant 

(MDR) tuberculosis. Tetracycline has a higher priority because it is used more frequently for 

specific uses, which could lead to faster spread of resistance. Tetracycline is administered 

orally, while streptomycin is administered by injection.30 It is unclear what link there may be 

between oral ingestion and the build-up of resistance to injected streptomycin.

Conclusions

Those supporting an extension of streptomycin use say:

There is no evidence that applications of antibiotics to orchards during bloom contributes to 

antibiotic-resistance in human pathogens. Human pathogens have not been found in orchards 

and would have to be present for the resistance genes to transfer. Naturally occurring 

streptomycin resistant bacteria may be minor components of the overall bacterial communities 

found on apple flowers and in soils, but their presence is independent of the antibiotic 

application. The amount and timing of the use of this material in an orchard environment does 
not contribute to any human health concerns, especially in light of streptomycin being ineffective 

in humans when ingested orally.

Those opposing an extension of streptomycin use say:

There is evidence that application of streptomycin leads to increase resistance to streptomycin 

in orchard bacteria, that human pathogens and the fire blight bacteria share the same gene pool 

of genes resistant to streptomycin (i.e., that the same genes responsible for resistance in 

Erwinia amylovora are also responsible for resistance in human pathogens), that human 

pathogens do not need to be present in the orchard to obtain resistance genes acquired by and 

augmented in orchard bacteria, that streptomycin residues are sometimes present in treated 

fruit, and that streptomycin is still a critically important antimicrobial for use against human 

pathogens. In light of the crisis of antibiotic resistance, we cannot allow streptomycin use to be 

extended in organic production.

Evaluation Criteria (see attached checklist for criteria in each category)

 

 Criteria Satisfied? 

1. Impact on Humans and Environment ☒ Yes ☐ No ☐ N/A 

2. Essential & Availability Criteria ☒ Yes ☐ No ☐ N/A

3. Compatibility & Consistency ☒ Yes ☐ No ☐ N/A 

Substance Fails Criteria Category: NA 

Recommended Subcommittee Action & Vote, including classification recommendation (state 

actual motion):

Classification Motion: Streptomycin is synthetic and is already classified as such on the 

National List so there is no need to make a motion to that effect.

Listing Motion

Motion to remove the existing expiration date of October 21, 2014 for streptomycin at

§205.601(i)(11), and replace it with an expiration date of October 21, 2017, so that the listing 

reads: (11) Streptomycin, for fire blight control in apples and pears only until October 21, 

2017

Motion by: Harold Austin 

Seconded by: Zea Sonnabend

Yes: 5 No: 3 Absent: 0 Abstain: 0 Recuse: 0 

Additional Motion: Resolution: The National Organic Standards Board is committed to the 

phase out of this material. Between now and the expiration date the Board urges growers 

and certifiers to include in organic systems plans an annual increase in the extent and/or 

number of alternative practices and materials that are trialed for controlling fire blight. In 

addition, the board strongly advocates to USDA a high priority for increased support for 

research into these alternative practices and materials.

Motion by: Harold Austin 

Seconded by: Zea Sonnabend

Yes: 8 No: 0 Absent: 0 Abstain: 0 Recuse: 0 

 Approved by Jay Feldman, Subcommittee Chair, to transmit to NOSB August 6, 2013
NOSB Evaluation Criteria for Substances Added To the National List: Crops 

Category 1. Adverse impacts on humans or the environment? Streptomycin 

Question Yes No N/A Comments/Documentation (TAP; petition; 

regulatory agency; other)

1. Is there a probability of 

environmental contamination 

during use or misuse? 

[§6518(m)(3)]

X X The petition claims the manufacturing process 

as CBI. However, the 2011 TR (lines 314-315) 

states, “Dzhedzhev et al. (1975) reported that 

the manufacture of streptomycin resulted in 

high atmospheric concentrations of the 

solvents butyl alcohol and butyl acetate in the 

workplace.” The TR also says (lines 315-332) 

Streptomycin is produced using fermentation, 

a process that usually involves the use of 

solvents and gases that may be discharged 

into water or air, subject to EPA permits. The 

TR concludes (lines 326-328) that assuming 

streptomycin manufacturers comply with 

applicable water and air regulations; it is 

unlikely that environmental contamination will 

result from the fermentation process. (March 

8, 2011 TR – lines 326-328) also in that same 

TR, lines 334-341 states that no surface 

residue can be found on pear or apple trees 

after four to six weeks following a spray 

application(Gardan and Manceau (1984)). 

Also in this same section the EPA (1988) 

states streptomycin residues are nondetectable (<0.5ppm) on crops when treated 

according to label use rates and directions. 

TR lines 414-415 states that the RED for 

streptomycin concluded that agricultural 

streptomycin products, labeled and used 

according to EPA regulations, will not pose 

unreasonable risks or adverse effects to the 

environment (EPA 1992). There is an EPA 

registration review of streptomycin underway 

that is scheduled to be completed in 2014.

2. Is there a probability of 

environmental contamination 

during, manufacture or disposal? 

[§6518(m)(3)]

X X See above for detailed explanation

3. Does the substance contain inerts 

classified by EPA as ‘inerts of 

toxicological concern’? [§6517 

(c)(1)(B)(ii)]

X

4. Is there potential for detrimental 

chemical interaction with other 

materials used in organic farming 

systems? 

[§6518(m)(1)]

X Streptomycin should not be applied following 

an application of a Bordeaux mixture and it is 

incompatible with lime sulfur (according to the 

2002 HSDB) (March 8, 2011 TR lines 357 & 

358).
5. Is there a toxic or other adverse 

action of the material or its 

breakdown products?

[§6518(m)(2)]

XX March 8, 2011 TR (lines 338) states that strep 

breakdowns into products that include 

methylamine, carbon dioxide, and urea, all of 

which occur naturally in the environment. 

(EPA 1988, 1992) EPA cited data that showed 

that streptomycin biodegrades relatively 

quickly in soil and water.

Streptomycin can be phytotoxic to plants; 

therefore it is sprayed on the surface of plants 

rather than injected (McManus and Stockwell, 

2000). Most apple and pear producers are 

prudent in their use of streptomycin sprays to 

reduce costs and to prevent the development 

of streptomycin-resistant strains of Erwinia 

amylovora. Disease risk models help 

producers optimize the timing of antibiotic 

sprays and reduce the total number of 

applications. These measures can help 

reduce the development of antibiotic 

resistance. (March 8, 2011 TR lines 111-115)

There is a high probability that streptomycin 

resistant bacteria are present in the 

environment as a consequence of pesticidal 

use of streptomycin (EPA, 2006a). (TR lines 

429-431) The HED Chapter of the TRED 

states that there have been reports of adverse 

effects resulting from use of streptomycin as a 

pesticide (EPA, 2006a). (TR lines 449-450) 

Because of the risk to workers, personal 

protective equipment is advised to prevent 

skin contact with streptomycin, and workers 

are not permitted re-entry into treated areas 

for at least 12 hours. (TR lines 454-456)

6. Is there persistence or 

concentration of the material or 

breakdown products in the 

environment? [§6518(m)(2)]

XX A certain background level of streptomycin is 

expected in soil due to the natural presence of 

the bacterium Streptomyces griseus (Brosche, 

2010). EPA (1988, 1992) cited data that show 

that streptomycin biodegrades relatively 

quickly in soil and water. (TR lines 207-210). 

The breakdown products include 

methylamine, carbon dioxide, and urea, all of 

which occur naturally in the environment. 

Therefore, the application of streptomycin for 

control of fire blight in apples and in pears in 

accordance with labeled instructions is 

unlikely to contaminate the environment. (TR 

lines 337-341).

According to EPA, streptomycin is moderately 

persistent in aerobic soil (a single value of 

t1/2= 17.5 days was determined). EPI Suite 

estimated a shorter aerobic soil half-life (t1/2= 

25 days) and a longer sediment half-life (t1/2= 

100 days). Given the moderate 
persistence/high mobility and solubility of 

streptomycin, the chemical is expected to 

dissipate relatively slowly and at the same 

time be vulnerable to leaching/run-off. (TR 

lines 217-225) Gardan and Manceau (1984) 

reported that no surface residue of 

streptomycin was detectable on pear or apple 

trees after four to six weeks following spray 

application. However, Mayerhofer et al. (2009) 

showed that the use of streptomycin sprays 

can lead to detectable concentrations of 

streptomycin in apples. Streptomycin was 

detected in 20 of 41 samples from orchards 

that were treated one to three times with 

streptomycin sprays. The concentration of 

streptomycin was highest in the apple cores 

and skin and ranged from 1.9 to 18.4 μg/kg 

(equivalent to 0.0019 to 0.0184 ppm, well 

below the EPA’s established tolerance of 0.25 

ppm). (TR lines 238-244)

7. Would the use of the substance be 

harmful to human health or the 

environment? [§6517 (c)(1)(A)(i); 

§6517 (c)(2)(A)(i); §6518(m)(4)]

X X The TRED for streptomycin concluded that 

“there is reasonable certainty that no harm to 

any population subgroup will result from 

exposure to streptomycin (EPA, 2006b). 

(March 8, 2011 TR lines 438 – 439) Also, in 

the TR lines 441-444 states that “Current 

tolerances (maximum residue limits) for 

streptomycin on or in apples and pears is 

0.25ppm. Assuming that the maximum 

amount of streptomycin residues are present 

in all types of food which may contain 

residues, EPA determined that chronic 

aggregate dietary exposure from streptomycin 

residues in food and water is not considered 

to be a human health concern (EPA, 2006a).

Bacterial resistance to streptomycin as a 

result of pesticidal use has the potential to 

cause adverse public health consequences if 

human bacterial pathogens are present in 

orchards and develop resistance or if nonpathogenic bacteria in orchards develop 

resistance and later transfer the resistance to 

human bacterial pathogens. EPA’s 

assessment concluded that “the possibility of 

antibiotic resistance resulting in adverse 

human health consequences was of medium 

concern following occupational application 

and was of high concern following application 

by residential users” (EPA, 2006a, pg. 3). (TR 

lines 645-650) Streptomycin remains 

important in modern medicine, and an 

increase in streptomycin-resistant bacteria in 
the environment and in humans may lead to 

adverse human health consequences. 

Streptomycin is used today in medicine in 

combination therapy to treat tuberculosis (due 

to increasing resistance to other anti-

tubercular drugs) and enterococcal 

endocarditis (when there is resistance to 

gentamicin). It is also used to treat the plague 

and tularemia. (TR lines 634-638)

See also question #5. 

Streptomycin is toxic to algae (Qian et al.,

2012) and therefore the EPA requires a 

warning on any streptomycin label include a 

warning not to apply directly to water or in 

areas where surface water is present, and to 

not contaminate water during cleaning of 

equipment or disposal of wastes. TR lines 

414-415 states that the RED for streptomycin 

concluded that agricultural streptomycin 

products, labeled and used according to EPA 

regulations, will not pose unreasonable risks 

or adverse effects to the environment (EPA 

1992). There is an EPA registration review of 

streptomycin underway that is scheduled to be 

completed in 2014.

8. Are there adverse biological and 

chemical interactions in the agro-

ecosystem, including biodiversity? 

[§6518(m)(5)]

X Toxic to bacteria and algae. See question #7. 

The ammonium-Nitrogen concentration was 

significantly increased following application of 

streptomycin, possibly indicating that nitrifying 

bacteria were susceptible to this bactericide. 

This study also found that application of 

streptomycin at a rate of 3 mg/g soil caused a 

continuing reduction in the total bacterial 

population which lasted longer than the study 

(22 days). Streptomycin applied at 3 mg/g soil 

also reduced active hyphae only on the first 

day following application. A broad-spectrum 

antibiotic like streptomycin would be expected 

to inhibit the nitrification process in soil. The 

presence of streptomycin in three different 

types of soils affected the ecological balance 

in the soil, causing the elimination of some 

bacterial populations. The eliminated species 

were described as beneficial bacteria involved 

in various metabolic processes, mineralization 

of organic compounds, degradation of toxic 

compounds, or creating soil structure. This 

study also isolated from the soils many strains 

of bacteria demonstrating resistance to 

streptomycin, including opportunistic 

pathogens of humans and/or animals. (2011 

TR lines 377-378, 379-382, 386-387, 389-391, 

395-398)
Based on the limited data available, it is still 

unclear if the use of streptomycin for control of 

fire blight has significant negative effects on 

interactions in the agro-ecosystem, including 

soil organisms. There are no studies available 

in the field and the studies in the laboratory 

with soil bacterial populations appear to be 

contradictory. (TR lines 404-407)

9. Are there detrimental physiological 

effects on soil organisms, crops, or 

livestock? [§6518(m)(5)]

X Toxic to algae. (TR line 347) Algae are 

present in most of the soils where moisture 

and sunlight are available, mostly blue-green 

(Cyanophyta) and green (Chlorophyta). Soil 

algae are important in maintaining fertility, 

building soil organic matter, building soil 

structure, increasing water holding capacity, 

and aerating soils.31

Category 2. Is the Substance Essential for Organic Production? Streptomycin

Question Yes No N/A Comments/Documentation (TAP; 

petition; regulatory agency; other)

1. Is the substance agricultural? 

[§6502(1)]

X

2. Is the substance formulated or 

manufactured by a chemical 

process? [§6502(21)]

X

3. Is the substance formulated or 

manufactured by a process that 

chemically changes a substance 

extracted from naturally occurring 

plant, animal, or mineral sources? 

[§6502(21)]

X Streptomycin is a naturally occurring 

compound which is produced by the soil 

bacterium Streptomyces griseus.

Agricultural streptomycin is produced on a 

large scale by aerobic fermentation of 

Streptomyces griseus followed by isolation 

and purification by ion exchange (HSDB, 

2002; EPA, 1992) March 8, 2011 TR lines 

172-174. Also, TR lines 199-200 states that 

Streptomycin is produced through a 

naturally occurring process (aerobic 

fermentation), but the processes used to 

isolate and purify the substance are not 

naturally occurring. The forms of 

streptomycin currently on the National List 

as approved are listed as synthetic 

substances.

4. Is the substance created by 

naturally occurring biological 

processes? [§6502(21)]

X X Streptomycin is a naturally occurring 

compound which is produced by the soil 

bacterium Streptomyces griseus. 

Commercially, streptomycin is produced 

through a naturally occurring process 

(aerobic fermentation), but the processes 

used to isolate and purify the substance are 

not naturally occurring. (TR lines 199-201)
5. Is there a natural source of the 

substance? [§ 205.600(b)(1)]

X

6. Is there an organic substitute? 

[§205.600(b)(1)]

X

7. Is there a wholly natural substitute 

product?

[§6517(c)(1)(A)(ii)]

XX There are several biological control agents 

(such as bacteria or yeast) that are used to 

try to outcompete the fire blight pathogen 

where it occurs on the blossom. These 

materials are used for fire blight 

suppression. Two strains of beneficial 

bacterium, Pantoea agglomerans, are: 

Bloomtime Biological and Blight Ban C9-1. 

The bacterium Pseudomonas fluorescens 

A506 is marketed as Blight Ban A506. There 

are two strains of yeast Aureobasidium 

pullulans that are used to make up the 

product Blossom Protect (Bio-ferm, 

Germany) which has recently been 

introduced into the market to help in 

controlling fire blight. TR 2011 lines 468-

486. In this same TR, Blight Ban A506 is 

rated as being poor to fair for effectiveness, 

lines 493-505 (Johnson et al.,2009) in 

inoculated trials and slightly better in field 

trials (Johnson 2010). Johnson further states 

that Bloomtime and Blight Ban C9-1 both 

performed slightly better with about 50% 

reduction in disease incidence observed in 

the inoculated field tests. He rates 

Bloomtime Biological as poor to good and 

the effectiveness of Serenade Max and 

Blossom Protect as fair to good for 

effectiveness for fire blight suppression. By 

comparison, the antibiotic treatment 

oxytetracycline is described as fair to very 

good, and treatment with streptomycin is 

poor to excellent (the poor rating is due to 

widespread pathogen resistance to 

streptomycin within the western states). (TR 

lines 493-507) Disease control was more 

consistent in field trials conducted with 

compatible mixtures of antagonistic 

organisms than with single strains –up to 68 

and 71% disease reduction on average, 

compared to 39% and 81% on average, for 

oxytetracycline and streptomycin, 

respectively. (TR lines 517-532) In 

Germany, treatment with Blossom Protect 

resulted in an average efficiency of 82% 

reduction in fire blight incidence (results 

from six different trials). (TR lines 547-548) 

Johnson (2010) reports that he and his 

colleagues evaluated Blossom Protect in an 
inoculated fire blight trial in 2008 (also using 

four applications during bloom). They found 

this product to be nearly as effective as 

streptomycin (Agri-Mycin) in an orchard with 

high disease pressure. (TR lines 552-555) A 

large amount of public comment received in 

written form to FR Docket AMS-NOP-12-

0070 and verbally at the Spring 2013 

meeting indicated that the above "substitute 

products" did not work well in certain regions 

or agricultural systems and therefore were 

not true substitutes.

8. Are there any alternative 

substances? 

[§6518(m)(6)]

X Besides the biologicals, there are 

alternative substances that are listed as 

having some control of fire blight and of 

these oxytetracycline is by far the best 

alternative substance. Other materials listed 

are various copper mixtures (a couple of 

new products currently being looked at by 

researchers), lime-sulfur, and Peracetic acid 

(which is as a disinfectant and not as a 

spray replacement material).

9. Are there other practices that would 

make the substance unnecessary? 

[§6518(m)(6)]

XX No one practice can eliminate fire blight, 

including the use of antibiotics. There are 

practices that can help in reducing fire blight 

potential in an orchard as part of a systems 

approach. Some of these would include 

using fire blight prediction models to assist 

in proper timing of materials applications, 

monitoring and removal of infected plant 

tissue, planting of resistant root stocks (this 

would only protect the root system and not 

the fruit producing portion of the tree), 

ground cover and water management to 

help reduce humidity levels within an 

orchard, and also planting of more fire blight 

resistant cultivars. (TR lines 601-617, 671-

701)
Category 3. Is the substance compatible with organic production practices? Streptomycin 

Question Yes No N/A Comments/Documentation (TAP; 

petition; regulatory agency; other)

1. Is the substance consistent with organic 

farming and handling? 

[§6517(c)(1)(A)(iii); 6517(c)(2)(A)(ii)]

X X It is currently included on the National List 

of Allowed and Prohibited Substances, as 

a synthetic substance allowed in organic 

crop production for fire blight control in 

apples and pears only [7 CFR 205.601 

(i)(11)] as previously /currently 

approved by the NOSB and implemented 

into policy by the NOP. Contrary to 

consumer expectations. Inconsistent with 

prohibition on antibiotics in livestock. 

Inconsistent with European requirements.

2. Is the substance compatible with a 

system of sustainable agriculture? 

[§6518(m)(7)]

X X If it is used as part of an organic systems 

plan in a rotational manner, to enhance 

resistance management in an effort to 

minimize the potential for resistance to 

fire blight to develop.

Increases likelihood of antibiotic 

resistance in pathogenic organisms. It is 

not sustainable because the fire blight 

organism will develop resistance.

3. If used in livestock feed or pet food, Is 

the nutritional quality of the food 

maintained with the substance? 

[§205.600(b)(3)]

X

4. If used in livestock feed or pet food, Is 

the primary use as a preservative? 

[§205.600(b)(4)]

X

5. If used in livestock feed or pet food, Is 

the primary use to recreate or improve 

flavors, colors, textures, or nutritive value 

lost in processing (except when required 

by law)? [§205.600(b)(4)]

X

6. Is the substance used in production, and 

does it contain an active synthetic 

ingredient in the following categories: 

[§6517(c)(1)(B)(i);

copper and sulfur compounds

X

toxins derived from bacteria X

pheromones, soaps, horticultural oils, 

fish emulsions, treated seed, vitamins 

and minerals

X

livestock parasiticides and medicines X

production aids including netting, tree 

wraps and seals, insect traps, sticky 

barriers, row covers, and equipment 

cleansers

X
1 Stockwell, V.O., and Duffy, B., 2012. Use of antibiotics in plant agriculture. Rev. Sci. Tech. Off. Int. 

Epiz., 31:199-210.

2 As reported in Ostenson, H.T. 2010. Organic pome and cherry production and marketing issues: Past, 

present and future. Acta Hort. (ISHS) 873:137-144, and presented to IFOAM, “Over the last ten years, the 

Hartman Group (Bellevue, Washington, USA) has studied changes in consumer attitudes, backgrounds, 

and buying characteristics related to the organic market. The Hartman Group surveyed about two 

thousand household consumers across four regions of the USA. They found that the ‘traditional’ 

properties suggested by ‘organic’ were no longer the same properties held by the new organic consumer. 

The survey indicated that traditional properties such as ‘locally-grown,’ Fair Trade, ‘tastes better,’ and 

sustainable production ranked at the bottom. The new organic consumers made it clear that they want, 

plain and simple, a product centered around the ‘absence of all health concerns,’ and the absence of 

pesticides, growth hormones, GMO’s, antibiotics, and BSE.”

3 McGhee, G. C., Guasco, J., Bellomo, L. M., Blumer-Schuette, S. E., Shane, W. W., Irish-Brown, A., and 

Sundin, G. W., 2011. Genetic analysis of streptomycin-resistant (SmR) strains of Erwinia amylovora 

suggests that dissemination of two genotypes is responsible for the current distribution of SmR E. 

amylovora in Michigan. Phytopathology 101:182- 191.

4 Russo, N. L., Burr, T. J., Breth, D. I., and Aldwinckle, H. S., 2008. Isolation of streptomycin resistant 

isolates of Erwinia amylovora in New York. Plant Dis. 92:714-718.

5 Claudia Nischwitz, Christine Dhiman, 2012. Streptomycin resistance of Erwinia amylovora, causal 

agent of fire blight. Utah State University Extension and Utah Plant Pest Diagnostic Laboratory, PLP-018.

6 McGhee, G. C., Guasco, J., Bellomo, L. M., Blumer-Schuette, S. E., Shane, W. W., Irish-Brown, A., and 

Sundin, G. W. 2011. Genetic analysis of streptomycin-resistant (SmR) strains of Erwinia amylovora 

suggests that dissemination of two genotypes is responsible for the current distribution of SmR E. 

amylovora in Michigan. Phytopathology 101:182- 191.

7 Russo, N. L., Burr, T. J., Breth, D. I., and Aldwinckle, H. S., 2008. Isolation of streptomycin resistant 

isolates of Erwinia amylovora in New York. Plant Dis. 92:714-718.

8

Instead, these growers rely on a number of other practices, allowing them to avoid fire blight damage to 

susceptible varieties. Balancing nutrients and avoiding over-application of nitrogen fertilizers, especially 

on susceptible varieties of apples or pears; avoidance of over-pruning in the dormant season; use of prebloom foliar nutrient sprays even though there is no foliage; use of copper materials on the trees between 

delayed dormant and tight cluster sages as preventive measures against overwintering FB; use of lime 

sulfur during bloom to thin apples; and, use of Serenade MAX (in the future, perhaps Blossom Protect) 

post-bloom and at petal-fall, with good spray coverage. (With some differences for pears.) 9 In response, the following is suggested: Increase species diversity; decrease tree density; use resistant 

cultivars and rootstocks; plant a variety of cultivars on a variety of rootstocks.

10 Yashiro, E & McManus, P. 2012 Effect of streptomycin treatment on bacterial community structure in 

the apple phyllosphere. PLoS ONE 7(5): e37131. doi:10.1371/journal.pone.0037131

11 WHO, 2009. Critically Important Antimicrobials for Human Medicine, 

http://www.who.int/foodsafety/foodborne_disease/CIA_2nd_rev_2009.pdf See Table 1.

12 Streptomycin TR, 2011. Lines 423-431.

13 American Academy of Microbiology, 2009. Antibiotic Resistance: An Ecological Perspective on an Old 

Problem. http://academy.asm.org/images/stories/documents/antibioticresistance.pdf (pp.1-5, 10.) 14 American Academy of Microbiology, 2009. (p.8.) 15 Streptomycin TR, 2011. Lines 632-633. American Academy of Microbiology, 2009. (p.2.) 16 Gullberg E, Cao S, Berg OG, Ilbäck C, Sandegren L, et al., 2011. Selection of Resistant Bacteria at 

Very Low Antibiotic Concentrations. PLoS Pathog 7(7): 1-9.

17 McGhee, G. C., Guasco, J., Bellomo, L. M., Blumer-Schuette, S. E., Shane, W. W., Irish-Brown, A., and 

Sundin, G. W. 2011. Genetic analysis of streptomycin-resistant (SmR) strains of Erwinia amylovora 

suggests that dissemination of two genotypes is responsible for the current distribution of SmR E. 

amylovora in Michigan. Phytopathology 101:182-191. Alan L. Jones and Elise L. Schnabel, 2000. The 

Development of Streptomycin-resistant Strains of Erwinia amylovora, in J.L. Vanneste (ed.), Fire Blight 

The Disease and its Causative Agent, Erwinia amylovora, CAB International, UK. Pp. 235-254.

18 S. Tolba et al., 2002. Distribution of streptomycin resistance and biosynthesis genes in streptomycetes 

recovered from different soil sites. FEMS Microbiology Ecology 42: 269-276
19 Egan, S., Wiener, P., Kalli¢das, D. and Wellington, E.M.H. (2001) Phylogeny of Streptomyces species 

and evidence of horizontal transfer of entire and partial antibiotic gene clusters. Antonie Van 

Leeuwenhoek 79, 127-133. Wiener, P., Egan, S. and Wellington, E.M.H. (1998) Evidence of transfer of 

antibiotic-resistance genes in soil populations of streptomycetes. Mol. Ecol. 7, 1205-1216.

20 George W. Sundin, Dave E. Monks, Carol L. Bender, 1995. Distribution of the streptomycin-resistance 

transposon Tn5393 among phylloplane and soil bacteria from managed agricultural habitats. Canadian 

Journal of Microbiology, 41(9): 792-799.

21 Yashiro E, McManus PS, 2012. Effect of Streptomycin Treatment on Bacterial Community Structure in 

the Apple Phyllosphere. PLoS ONE 7(5): e37131

22 McGhee, G. C., Guasco, J., Bellomo, L. M., Blumer-Schuette, S. E., Shane, W. W., Irish-Brown, A., and 

Sundin, G. W. 2011. Genetic analysis of streptomycin-resistant (SmR) strains of Erwinia amylovora 

suggests that dissemination of two genotypes is responsible for the current distribution of SmR E. 

amylovora in Michigan. Phytopathology 101:182- 191.

23 Sundin, G. W. 2002. Distinct recent lineages of the strA-strB streptomycin-resistance genes in clinical 

and environmental bacteria. Curr.Microbiol. 45:63-69.

24 GW Sundin and CL Bender, 1996. Dissemination of the strA-strB streptomycin-resistance genes 

among commensal and pathogenic bacteria from humans, animals, and plants, Molecular Ecology 5, 

133-143

25 See for example, Cristina Pezzella, Antonia Ricci, Elisabetta DiGiannatale, Ida Luzzi, and Alessandra 

Carattoli, 2004. Tetracycline and Streptomycin Resistance Genes, Transposons, and Plasmids in 

Salmonella enterica Isolates from Animals in Italy. Antimicrobial Agents and Chemotherapy, 48 (3): 903–

908. Alexandre Scherer, Hans-Rudolf Vogt, Edy M. Vilei, Joachim Frey, and Vincent Perreten, 2013. 

Enhanced antibiotic multi-resistance in nasal and faecal bacteria after agricultural use of streptomycin, 

Environmental Microbiology 15(1), 297–304. (“This study shows that the application of low concentrations 

of streptomycin on grass, as occurs during the spraying of orchards, selects for multidrug-resistant nasal 

and enteric bacterial flora, including extended-spectrum beta-lactamase-producing E. coli.”) Foster, G. C., 

McGhee, G. C., Jones, A. L., and Sundin, G. W. 2004. Nucleotide sequences, genetic organization, and 

distribution of pEU30 and pEL60 from Erwinia amylovora. Appl. Environ. Microbiol. 70:7539-7544.

26 WHO, 2009. Critically Important Antimicrobials for Human Medicine, 

http://www.who.int/foodsafety/foodborne_disease/CIA_2nd_rev_2009.pdf See Table 1. Tuberculosis is 

rapidly developing resistance to all known antimicrobials. Phillip Trollip, 2013. Emergence and Spread of 

Extensively and Totally Drug-Resistant Tuberculosis, South Africa. Emerging Infectious Diseases, 19 (3): 

449-455 www.cdc.gov/eid 27 http://www.drugs.com/pro/streptomycin.html 28 Jose Luis Martinez, 2009. Environmental pollution by antibiotics and by antibiotic resistance 

determinants. Environmental Pollution 157: 2893–2902.

29 See, for example, the following articles. C.-S. Chiou and A. L. Jones, 1993. Nucleotide Sequence 

Analysis of a Transposon (Tn5393) Carrying Streptomycin Resistance Genes in Erwinia amylovora and 

Other Gram-Negative Bacteria. Journal of Bacteriology, Vol. 175, (3): 732-740. GW Sundin and CL 

Bender, 1996. Dissemination of the strA-strB streptomycin-resistance genes among commensal and 

pathogenic bacteria from humans, animals, and plants, Molecular Ecology 5, 133-143. McGhee, G. C., 

and Sundin, G. W. 2011. Evaluation of kasugamycin for fire blight management, effect on nontarget 

bacteria, and assessment of kasugamycin resistance potential in Erwinia amylovora. Phytopathology 

101:192-204. Cristina Pezzella, Antonia Ricci, Elisabetta DiGiannatale, Ida Luzzi, and Alessandra 

Carattoli, 2004. Tetracycline and Streptomycin Resistance Genes, Transposons, and Plasmids in 

Salmonella enterica Isolates from Animals in Italy. Antimicrobial Agents and Chemotherapy, 48 (3): 903–

908. Alexandre Scherer, Hans-Rudolf Vogt, Edy M. Vilei, Joachim Frey, and Vincent Perreten, 2013. 

Enhanced antibiotic multi-resistance in nasal and faecal bacteria after agricultural use of streptomycin, 

Environmental Microbiology 15(1), 297–304.

30 WHO, 2009. Critically Important Antimicrobials for Human Medicine, 

http://www.who.int/foodsafety/foodborne_disease/CIA_2nd_rev_2009.pdf See Table 1. 

31 “Soil microorganism—algae” My Agriculture Information Bank 

http://agriinfo.in/?page=topic&superid=5&topicid=150 

Zancan, S., Trevisan, R., & Paoletti, M. G. (2006). Soil algae composition under different agroecosystems in North-Eastern Italy. Agriculture, ecosystems & environment, 112(1), 1-12.