Antimicrobial susceptibility in thermophilic Campylobacter species isolated from pigs and chickens in South Africa

Abstract

The thermophilic Campylobacters, Campylobacter jejuni and Campylobacter coli are found as commensals in the intestinal tract of healthy mammals and birds. Campylobacter jejuni is one of the leading causes of sporadic food-borne bacterial disease in humans which is predominantly contracted from poultry products. Although the vast majority of these infections are mild, life-threatening complications should be treated with antimicrobials. Patients are usually treated with either macrolides of fluoroquinolones. However, globally there is an increased trend in the development of resistance to these antibiotics. This trend has also been observed in infection of poultry and pigs. The aim of this investigation was to determine antimicrobial sensitivity of thermophilic Campylobacters isolated from pigs and poultry by broth microdilution minimum inhibitory concentration testing. A total of 482 samples of the small intestinal content from poultry and pigs from the Western Cape and Gauteng Provinces were collected and analysed. Thirty-eight Campylobacter isolates were obtained. Statistical analyses included percentage resistance, minimum inhibitory concentrations (MIC50 and MIC90) as well as the distribution percentages of the MICs. The non-parametric Mann-Whitney U test was used to establish any significant differences at an interspecies, interhost and interprovincial level. Analyses of the data obtained revealed indications of decreasing susceptibility to several antibiotic groups including the tetracyclines, macrolides, erythromycin and tylosin, as well as the lincoasamides, and fluoroquinolones. It was found that isolates from the Western Cape were more likely to be resistant to the fluoroquinolones (p = 0.0392), macrolides (p = 0.0262), and lincoasmides (p = 0.0001) and, as well as to a certain extent the pleuromutulins (p = 0.0985), whereas isolates from Gauteng were more resistant to the tetracycyclines (p = <.0001). Poultry Campylobacter spp. were more prone to be resistant to enrofloxacin (p = 0.0021). Campylobacter jejuni, mainly isolated from poultry, was more liable to be resistant to the tetracyclines (chlrotetracycline p= 0.0307), whereas C. coli, predominatly isolated from pigs was more likely to be resistant to the macrolides (tylosin p= 0.063). Four of the bacteria isolated from the Western Cape were resistant to three or more antibiotic classes, namely; tetracyclines, macrolides, lincosamides, pleuromutulins and fluoroquinolones. No multi-resistant Campylobacter spp. were isolated from the flocks in Gauteng. With the exception of tiamulin, the bacterial populations could clearly be divided into resistant and susceptible populations. As consequence of the increased resistance to the antimicrobial classes used for human therapy and the geographical differences in antimicrobial susceptibility, it is recommended that an antimicrobial resistance monitoring system for the thermophilic Campylobacter spp. be initiated in the South Africa National Veterinary Surveillance and Monitoring Programme for Resistance to Antimicorbial Drugs (SANVAD) Copyright