Detection of antibiotic resistance and virulence genes in Escherichia coli from broiler chicken at Tigoni processing plant in Limuru, Kenya
The use of antibiotics and disinfectant in broiler farms is common compared to other poultry farms. Antimicrobial usage is considered the most important risk factor promoting the emergence, selection and spread of antimicrobial-resistant micro organisms in environment, veterinary and human medicine. The aim of this study was to investigate antibiotic resistance and prevalence of virulence related genes in caecal Escherichia coli isolates from healthy broiler chicken at slaughter time. One hundred and seventy three E. coli isolated from caecal samples of broiler chickens were screened by disc diffusion to determine their susceptibility profile for six commonly used antibiotics. Sixty four samples were analyzed for virulence related genes using multiplex PCR. Extraction of DNA was done on sixty four isolates as follows; overnight broth bacterial suspensions were adjusted to 0.5 McFarland standard in sterile deionised water, boiled for 10 minutes and centrifuged for 5 min at 10,000RPM high speed then 5111of supernatant was used for PCR. Seven sets of primers were used in two multiplex reaction tubes. Seven virulence related genes were investigated but nine isolates were positive for verotoxin and three for intimin. Serotyping was done only for positive by slide agglutination, E.coli was grown overnight on suitable agar media (beef extracted agar) not inhibiting motility. High resistance levels were detected for most commonly used drugs like tetracycline (75.9%) and Cotrimoxazole (72.4%). One hundred and seventeen isolates showed resistance to two and more antibiotics. Different farm treatments were a significant factor for multidrug resistance (p:SO.OOI). The E. coli isolates showed twenty-one different multidrug resistant patterns with tetracyc\ine/cotrimoxazole being the most common. Serotype 0111, 0126, 06 and 078 were positive for verotoxin, 0126 and 0111 were positive for intimin. There was no significant relationship between virulence and multi-drug resistance (p:SO.05). The present study highlights the presence of multi-drug resistant and virulent E. coli among healthy broilers chicken in Nairobi- Kenya. The source of antibiotic resistance in the broilers is thought to be due selective pressure by the commonly used drugs. Other antibiotics like ampicillin (39%), chloramphenicol (13.2%) and ciprofloxacin (19%) recorded relatively high resistance levels yet rarely used in poultry farming, this may have been due co-selection phenomenon. Co-selection is thought to have contributed significantly to the increase in multiple drug resistance. The observation of the verotoxin and the intimin proteins from the isolates could mean that poultry are potential carriers of human diarrhoeaganic E. coli. Since the bacteria are pathogenic this is of public health importance. Therefore care should be taken during processing and production of poultry meat not to pass the pathogenic bacteria to humans.