Veterinary Services 

Centers for Epidemiology and Animal Health December 2008 

_________________________________________________________________________________________________________________________

Campylobacter on U.S. 

Swine Sites—Antimicrobial 

Susceptibility 

Background 

In 2006, there were 17,252 cases of laboratorydiagnosed foodborne illnesses in humans attributed to 

10 organisms under surveillance by the Centers for 

Disease Control and Prevention (CDC) in 10 States.1

Campylobacter was the second most common bacterial 

pathogen identified, accounting for 33.1 percent of 

cases. However, Campylobacter from pork was not 

frequently a cause of foodborne illnesses.2 3

Most human illness from Campylobacter is 

attributable to C. jejuni. Campylobacter causes fever, 

abdominal cramping, and diarrhea in humans and can 

lead to Guillain-Barré syndrome and reactive arthritis.4 

Foodborne transmission of Campylobacter can 

occur through fecal contamination of food, water, and 

carcasses at slaughter. Although Campylobacter can be 

considered normal flora in livestock, it may cause 

diarrhea in young pigs. Both C. jejuni and C. coli can be 

shed by asymptomatic carriers through the feces; 

however, C. coli is the predominant species present in 

pig intestines.5

Campylobacter on U.S. swine sites 

In 2006, the USDA’s National Animal Health 

Monitoring System (NAHMS) conducted a study on 

swine health and management practices from a random 

sample of swine production sites with 100 or more pigs 

in 17 States.* These States represented approximately 

94 percent of U.S. pig inventory and 94 percent of U.S. 

pork producers with 100 or more pigs. 

As part of Swine 2006, fecal samples were collected 

from pen floors on 135 sites. On each site, up to 15 fecal 

samples were collected from pens containing 

grower/finisher pigs and cultured for Campylobacter. 

From September 5, 2006, through March 15, 2007, 

1,951 samples were cultured for Campylobacter. 

Overall, at least one sample was found culturepositive for Campylobacter on 98.5 percent of sites, 

88.5 percent of barns, and 64.8 percent of pens. 

Additionally, 51.6 percent of samples were culture- 

 

*

States 

Arkansas, Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, 

Minnesota, Missouri, Nebraska, North Carolina, Ohio

Oklahoma, Pennsylvania, South Dakota, Texas, and Wisconsin.

positive. Of these isolates, 92.2 percent (928) were 

identified as C. coli, 0.4 percent (4) as C. jejuni, and 

7.4 percent (75) died before speciation. 

Antimicrobial susceptibility 

The 932 C. coli and C. jejuni isolates were tested for 

resistance to a panel of 9 antimicrobial drugs: 

azithromycin, ciprofloxacin, clindamycin, erythromycin, 

florfenicol, gentamicin, nalidixic acid, telithromycin, and 

tetracycline. Resistance break points used by the 

National Antimicrobial Resistance Monitoring System 

were used to classify isolates as susceptible, 

intermediate, or resistant.6

Of the four C. jejuni isolates, one was resistant to 

azithromycin, clindamycin, erythromycin, and 

telithromycin, and all four were resistant to tetracycline. 

Due to the small number of C. jejuni isolated, the 

remainder of this information sheet focuses on C. coli. 

Resistance to tetracycline was most common 

(82.9 percent of isolates). Nearly 60 percent of isolates 

were resistant to erythromycin and azithromycin (59.4 

and 59.1 percent, respectively). All C. coli isolates were 

susceptible to florfenicol. Table 1 depicts the resistance 

of all isolates to the nine antimicrobial drugs. 

Table 1. Number and Percentage of C. coli Isolates 

Resistant* to the Following Antimicrobials 

Antimicrobial Number Percent 

Tetracycline 769 82.9 

Erythromycin 551 59.4 

Azithromycin 548 59.1 

Clindamycin 328 35.3 

Telithromycin 327 35.2 

Nalidixic acid 34 3.7 

Ciprofloxacin 31 3.3 

Gentamicin 1 0.1 

Florfenicol 0 0.0 

*Intermediate isolates were classified as not resistant.

Table 2 depicts the resistance patterns from 

C. coli isolates. Resistance to tetracycline alone was 

most common (29.6 percent of isolates). Resistance to 

azithromycin, clindamycin, erythromycin, telithromycin, 
and tetracycline was seen in 20.7 percent of isolates. 

Overall, 8.8 percent of C. Coli isolates were susceptible 

to all antimicrobial drugs tested. 

Table 2. Number and Percentage of C. Coli Isolates 

by Antimicrobial Resistance Pattern 

C. Coli Isolates 

Resistance Pattern* Number Percent 

Susceptible to all 

antimicrobials 82 8.8 

Tetracycline 275 29.6 

Azithromycin, clindamycin, 

erythromycin, telithromycin, 

tetracycline 192 20.7 

Azithromycin, erythromycin, 

tetracycline 120 12.9 

Azithromycin, erythromycin, 

telithromycin, tetracycline 79 8.5 

Azithromycin, clindamycin, 

erythromycin, tetracycline 67 7.2 

Azithromycin, clindamycin, 

erythromycin, telithromycin 39 4.2 

Other 74 8.1 

Total 928 100.0 

*Intermediate isolates were classified as not resistant. 

Table 3 shows the multidrug resistance of the 928 

C. coli isolates tested. Overall, 91.2 percent of C. coli

isolates were resistant to at least one antimicrobial drug, 

and 61.6 percent were resistant to more than one 

antimicrobial drug. The highest percentage of isolates 

(29.6 percent) were resistant to only one drug. Eleven 

C. coli isolates (1.2 percent) were resistant to 7 drugs. 

 

Table 3. Number of Antimicrobials by Number and 

Percentage of C. coli Isolates Showing Resistance* 

Number of 

Antimicrobials 

Number 

C. coli Isolates 

Percent 

C. coli Isolates 

0 82 8.8 

1 275 29.6 

2 23 2.5 

3 154 16.6 

4 188 20.3 

5 193 20.8 

6 2 0.2 

7 11 1.2 

*Intermediate isolates were classified as not resistant. 

Conclusions 

The prevalence of C. jejuni on swine sites remains 

very low, while the prevalence of C. coli is expectedly 

high. Resistance of C. coli to antimicrobial drugs on 

swine sites, particularly tetracycline and erythromycin, is 

an issue of concern. 

References 

1 Centers for Disease Control and Prevention. 2007. 

Preliminary FoodNet data on the incidence of infection 

with pathogens transmitted commonly through food-10 

States, 2006. MMWR Morb Mortal Wkly Rep; 56:336-

339. 

2 Centers for Disease Control and Prevention. 2006. 

Surveillance for foodborne-disease outbreaks-United 

States, 1998-2002. MMWR; 55(SS-10):28-29. 

3 Duffy, E.A., K.E. Belk, J.N. Sofos, G.R. Bellinger, A. 

Pape, and G.C. Smith. 2001. Extent of microbial 

contamination in United States pork retail products. J 

Food Prot; 64(2):172-178. 

4 Beers, M.H., and R.B. Berkow (eds.). 1999. In: The 

Merck Manual 17th ed. Merck Research Laboratories, 

Division of Merck & Co., Inc., Whitehouse Station, N.J. 

p. 1174-1175. 

5 Cliver, D.O., and H.P. Riemann. 2002. Foodborne 

Diseases 2nd ed. Academic Press, San Diego, CA. p. 

106-108. 

6 http://ars.usda.gov/SP2UserFiles/Place/66120508/ 

NARMS/animal_campy/CampyMICdistribution-2006.pdf 

For more information, contact: 

USDA-APHIS-VS:CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

E-mail: NAHMS@aphis.usda.gov 

http://nahms.aphis.usda.gov 

N535.1208 

The U.S. Department of Agriculture (USDA) prohibits discrimination in 

all its programs and activities on the basis of race, color, national 

origin, sex, religion, age, disability, political beliefs, sexual orientation, 

or marital status or family status. (Not all prohibited bases apply to all 

programs.) Persons with disabilities who require alternative means for 

communication of program information (Braille, large print, audiotape, 

etc.) should contact USDA’s TARGET Center at (202) 720-2600 . 

To file a complaint of discrimination, write USDA, Director, Office of 

Civil Rights, Room 326-W, Whitten Building, 1400 Independence 

Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 

(voice and TDD). USDA is an equal opportunity provider and employer. 

Mention of companies or commercial products does not imply 

recommendation or endorsement by the USDA over others not 

mentioned. USDA neither guarantees nor warrants the standard of any 

product mentioned. Product names are mentioned solely to report 

factually on available data and to provide specific information.