# Presentation: 742109

## 21 CFR 558.15 “Studies”:  A brief history

- Jeffrey M. Gilbert, Ph.D.
- Microbial Food Safety Team (HFV-157)
- Center for Veterinary Medicine

## Situation in the 1960s

- 	Issue:  What is the impact of antimicrobial drug use in animals on the potential development of antimicrobial resistant, zoonotic foodborne pathogens, and their subsequent transmission to humans as food contaminants?

## In the 1970s...

- _Antibiotic in Animal Feed Task Force_ (FDA)
- 	The task force was formed to address safety and effectiveness issues associated with antibiotics administered in animal feed.

## Task force findings:

- Therapeutic Abx used to relieve animal disease thought to pose a small risk (high dose/short duration in young animals)
- The benefits to animals were thought to outweigh potential risks to humans
- Identifiable need for using Abx in animals to relieve pain and suffering
- Healthy animals = safer food supply

## Task force conclusions:

- 	Pre-approval studies are needed to support microbiological safety of Abx in food-producing animals intended for _*sub-therapeutic uses only*_, including growth promotion and feed efficiency.

## Title 21 CFR Part 558.15

- 	1) Sponsors of Abx are required to submit study results demonstrating that their product _does not promote bacterial drug resistance,_ only when their product is intended to be administered for greater than 14 days, and for non-prescription use in food-producing animals

## 21 CFR 558.15 (b) (1) - (b) (3)	

- 	2) Sponsors are required to submit all information to the Agency on the impact of their drugs on the *Salmonella* reservoir in food-producing animals by specified dates depending on the drug class

## 21 CFR 558.15 by July 19, 1973...

- 	“...records and reports of completed, ongoing, or planned studies, including protocols, on the tetracyclines, streptomycin, dihydrostreptomycin, penicillin, and the sulfonamides...”

## 21 CFR 558.15 by October 17, 1973...

- 	“...records and reports of completed, ongoing, or planned studies, including protocols, on all other antibiotics...”

## 21 CFR 558.15 by March 4, 1974...

- 	“...records and reports of completed, ongoing, or planned studies, including protocols, on nitrofurans...”

## 21 CFR 558.15 by April 20, 1974...

- 	“...data from completed studies on the _tetracyclines_, _streptomycin_, _dihydrostreptomycin_, the _sulfonamides_, and _penicillin_ assessing the effect of the subtherapeutic use of these drugs in the feed on the *Salmonella* reservoir in the target animal as compared to that in non-medicated controls...”

## 21 CFR 558.15 by April 20, 1975...

- 	“...data satisfying all other specified criteria for safety and effectiveness, including the effect on the *Salmonella* reservoir for _any antibiotic_ or _sulfonamide_ drug approved for sub-therpeutic use in animal feeds...”

## 21 CFR 558.15 by September 5, 1975...

- 	“...data satisfying all other specified criteria for safety and effectiveness, including the effect on the *Salmonella* reservoir for the _nitrofuran_ drugs approved for sub-therapeutic use in animal feeds...”

## 21 CFR 558.15 Study design

- Studies were a set, including a shedding and resistance component
- Studies included a negative control and a treated group
- Animals were inoculated with a lab strain of *Salmonella typhimurium* (NAL resistant)
- Strain free of transferable R elements

## 21 CFR 558.15 Study design (cont’d)

*Salmonella  *were* *enumerated and tested for susceptibility
*E. coli*  were tested for susceptibility
- Studies were generally 8 weeks long
- Test animals were not required to be near market age or weight

## Parameters examined were:

- Drug effect on pathogen quantity, prevalence, and duration of shedding
- Drug effect on *Salmonella*  antibiotic susceptibility
- Drug effect on resident *E. coli*  antibiotic susceptibility

## FDA guidance on 558.15 studies

- Guideline 18 - Human Health Safety Criteria
- Guideline 19 - Animal Health Safety Criteria
- Guidelines were the product of the task force
- Guidelines can be found at:
- 			http://_www.fda.gov/cvm_

## Integrity measurements evaluated:

- Did the product have Abx properties?
- Cross-contamination?
- Animal numbers sufficient?
- Enough drug consumed to test highest proposed dose?
- Any other drug(s) given?
- Any naturally occurring *Salmonella  *present?

## Integrity measurements evaluated (cont’d)

*Salmonella*  marker stable?
- Could *Salmonella*  receive R factors?
- Could *Salmonella*  colonize the animals?
- Appropriate micro methodology used?
- What tissues were examined?
- How often were samples taken?
- Was study length adequate?

## RESULTS (TOTALS reflective of final decision)

**	****Drug class****	****	****Total      Drug/Animal     Pass     Fail        Reject**
**	****____________________________________________________________****	**
- 	Macro/Linco	    	  9	    4/3	          4	         2	         3
- 	Ionophores	  	13	    7/3	        10	         0	         3
- 	Unclassified Gm+      	15	    6/3	          9	         2	         4
- 	Streptogramins	    	  1	    1/1	          1	         0	         0
- 	Glycopeptides	   	  2	    2/1	          1	         0	         1
- 	Bambermycins	   	  2	    1/2	          2	         0	         0
- 	Broad spectrum	  	  2	    2/2	          1	         1	         0
- 	____________________________________________________________
- 	TOTALS		44		        28            5             11

##  Studies REJECTED because...

*Salmonella*  or coliform susceptibility results not submitted
- Susceptibility test QC inadequate
- Shedding too long to measure prevalence or duration
- Environmental control animals contaminated or not included

## Studies REJECTED because...(cont’d)

- Animals failed to meet inclusion criteria
- Data too disorganized to interpret
- Too few animals in study

## Problems identified following retrospective analysis:

- Drug spectrum matched *Salmonella*  and
*     **E. coli*  in 2/44 study sets
- Limited info on susceptibility changes in naturally occurring flora
- Artificially high inocula
- Lab strain of *Salmonella*  not representative
- Small numbers of animals tested

## Summary

- Most studies that failed did so due to pathogen shedding
- Problems with design and interpretation
- Based on policy and regulation of the time
- History helpful in steering current and future efforts on this topic