Prevalence and antimicrobial resistance of zoonotic campylobacter isolated from livestock and rodents in urban informal settlements in Nairobi

Abstract

Campylobacter is a pathogenic zoonotic bacterium that causes mild to fatal illnesses in livestock while in humans, Campylobacter symptoms may range from transient watery diarrhoea to bloody diarrhoea and may lead to development of serious chronic effects. Campylobacteriosis is the highest aetiology of human enteric diseases in industrialized countries. However, there is limited knowledge on whether livestock in developing countries like Kenya are important reservoirs of zoonotic Campylobacter and also limited information concerning the drug resistance patterns and resistance genes present in the zoonotic species in Kenya. Thus, the study sought to describe the epidemiology and antimicrobial resistance associated with zoonotic Campylobacter species in informal settlements in Nairobi. This study covered Korogocho and Viwandani informal settlements in Nairobi, Kenya, representing the densely populated urban settlements. Livestock samples (cloacal swabs from poultry, and faecal samples from rabbits, cattle, pigs and goats) were collected and the prevalence of Campylobacter identified by culture, biochemical characterization and Polymerase Chain Reaction. A questionnaire was administered to each household head or spouse to gather information on the associated risk factors. Agar dilution technique was employed to test for antimicrobial susceptibility in confirmed isolated Campylobacter and genes responsible for resistance to the tested drugs identified using primer specific PCR. Representative samples were then sequenced using the ABI 3130XL genetic analyzer to investigate presence of mutations that could result in quinolone and macrolide resistance. The summary statistics, chi square test as well as logistic regression were used in the analysis and the data was interpreted at 95% confidence interval. Eight hundred two (802) livestock and 16 rodent samples were collected from (203) households. The overall prevalence of Campylobacter from livestock and rodents was 21% with Prevalence in livestock being 170 (21.2%) and that of rodents being 12.5% (2/16). Two zoonotic Campylobacter species were identified and confirmed from the livestock samples: Campylobacter jejuni (16%)and Campylobacter coli (0.6%). Bands specific for a third zoonotic species; Campylobacter hyointestinalis, were identified in five isolates (3% prevalence). Upon sequencing however, these were found not to be C.hyointestinalis. The two Campylobacter isolates from rodents did not belong to any of the identified zoonotic species. Results from the questionnaire administered were used to identify associated factors and the presence of livestock faecal matter in the drinking water of the livestock was a risk factor for Campylobacter infections in livestock. On the other hand, livestock drinking water from road surfaces, awareness on antibiotic resistance and zoonoses were identified as protective factors that contributed to reduced Campylobacter infections in the livestock. The prevalence of resistance to the tested drugs (gentamycin, erythromycin, tetracycline, chloramphenicol, ciprofloxacin and nalidixic acid) shows a worrying trend. Resistance genes for tetracycline (tet O gene), betalactams (TEM and OXA genes) and aminoglycosides (aac 6 lb cr gene). The risk posed by the potential transmission of these zoonotic isolates is that of possible transmission of the identified resistance genes to humans. The aac6 lb cr gene mediates resistance to aminoglycosides as well as quinolones in other bacteria, but has not yet been studied in Campylobacter. Several missense mutations were seen and have been reported from the DNA gyrase genes and the 23S RNA gene that are responsible for resistance to quinolones and macrolides respectively. However, mutations linked with quinolone resistance were absent in the five isolates sequenced suggesting that the resistance may be mediated by other means. Nevertheless, a larger sample size needs to be studied to draw a more conclusive picture concerning mutations in these genes. In conclusion Campylobacter has been shown to be an important pathogen in livestock in densely populated urban settling. The potential risk of transmission of these pathogenic strains and their drug resistance genes to humans and the environment is of great concern. This study has demonstrated that awareness in the society on zoonoses and antimicrobial resistance is important in trying to reduce or control infections. The study recommends creation of public awareness and further studies to be undertaken to identify i) The other species of Campylobacter not identified and their importance; ii) The prevalence of Campylobacter in humans in densely populated informal settlements and iii) The significance of the role played by the aac6 lb cr gene in Campylobacter isolates and lastly this study recommends education on prudent use of antimicrobials by farmers.