Need to Re-Think Campy Antibiotic Resistance

US - Researchers at universities across the country investigating the prevalence and antibiotic resistance of Campylobacter species found evidence of resistance in both pig herds using both conventional and antibiotic-free production methods.
calendar icon 14 December 2010
clock icon 3 minute read

Wondwossen A. Gebreyes of Ohio State University and colleagues there and at other US universities have recorded the prevalence and antimicrobial resistance of Campylobacter species in local pig farms that use conventional or antibiotic-free production methods. In their paper is to be published in Foodborne Pathogens and Disease, the researchers remark that ciprofloxacin resistance was found, even in herds not using antibiotics.

Gebreyes and co-authors conducted the study to compare the prevalence and antimicrobial resistance profile of Campylobacter isolated from 34 farm-slaughter pair cohorts of pigs raised in conventional and antimicrobial-free (ABF) production systems. Isolates originated from four different states of two geographic regions (region 1, Ohio and Michigan; region 2, Wisconsin and Iowa).

A total of 838 faecal and 1173 carcass samples were examined. Campylobacter isolates were speciated using multiplex polymerase chain reaction targeting ceuE and hipO genes. The minimum inhibitory concentration was determined using agar dilution to a panel of six antimicrobials: chloramphenicol, erythromycin, gentamicin, ciprofloxacin, nalidixic acid and tetracycline.

Campylobacter was isolated from 472 of 838 pigs (56.3 per cent). Campylobacter prevalence did not vary significantly based on production system (conventional, 58.9 per cent; and ABF, 53.7 per cent; odds ratio [OR] 1.4; 95 per cent confidence interval [CI] 0.8–2.6; p=0.24) or geographic region (region 1, 54.1 per cent; region 2, 58.2 per cent; OR, 1.02; 95 per cent CI 0.6–1.9, p=0.92).

At the slaughter plant, Campylobacter prevalence varied based on processing stages – 19.4 per cent at pre-evisceration, 25.3 per cent at post-evisceration and 3.2 per cent at post-chill.

Resistance was common to tetracycline (64.5 per cent), erythromycin (47.9 per cent) and nalidixic acid (23.5 per cent).

Campylobacter isolates from conventional production systems were more likely to be erythromycin-resistant than from ABF (OR, 3.2; 95 per cent; CI, 1.4 to 7.2; p=0.01). The proportion of ciprofloxacin-resistant Campylobacter coli isolates were 3.7 per cent and 1.2 per cent from ABF and conventional production systems, respectively. Thirty-seven out of 1,257 C. coli (2.9 per cent) were resistant to both erythromycin and ciprofloxacin, drugs of choice for treatment of invasive human campylobacteriosis.

The finding of ciprofloxacin resistance, particularly from ABF herds, has significant implications on the potential role of risk factors other than mere antimicrobial use for production purposes, concluded Gebreyes and co-authors.


Tadesse D.A., P.B. Bahnson, J.A. Funk, S. Thakur, W.E.M. Morrow, T.Wittum, F. DeGraves, P. Rajala-Schultz and W.A Gebreyes. 2010. Prevalence and antimicrobial resistance profile of Campylobacter spp. isolated from conventional and antimicrobial-free swine production systems from different US regions. Foodborne Pathogens and Disease. doi:10.1089/fpd.2010.0665.

Further Reading

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