ABSTRACT
This study was conducted to determine the prevalence of ESBL-producing enterobacteria in chickens and cattle slaughtered at Ikpa market, Nsukka; to identify the types of ESBL enzymes harboured by the ESBL-producing bacteria isolates and to determine the antibacterial résistance phenotype and genotype of the ESBL-producing isolates. This study adopted a survey design. It was conducted at Ikpa market, Nsukka, Enugu State Nigeria. The market was purposively selected because it is a major market in Nsukka Agricultural zone where large number of chickens and cattle are sold or slaughtered. The chickens and cattle used for the study were selected by systematic random sampling of those slaughtered. A total of 210 cloacal and rectal swab samples each were collected from slaughtered chickens and cattle, respectively, between April and June, 2012. The samples were streaked on MacConkey agar supplemented with cefotaxime (2µg/ml) and incubated at 37o C for 24 hours. Colonies on this medium were purified and identified using colonial, microscopic and biochemical characteristics following standard procedures. Detection of ESBL production among the isolates was done by the double disc synergy test using Oxoid cefpodoxime kit and in accordance with the manufacturer’s instructions. The types of ESBL enzymes in 8 of the ESBL-producing E. coli isolate were determined by screening the isolates for presence of genes encoding TEM-, OXA-, SHV- and CTX-M-type β-lactamases, by polymerase chain reaction (PCR) following standard procedures. Phenotypic resistance of the isolates to 21 antimicrobial agents was assessed using the disc diffusion method according to the Clinical Laboratory Standards Institute. Genes encoding resistance to tetracycline, streptomycin and gentamicin were studied by PCR according to standard procedures. Data generated were subjected to descriptive statistics and the results were expressed in percentages. Fifteen (7.1%) of the 210 chicken cloacal swab samples yielded microbial growth, while none (0.0%) of the 210 cattle rectal swab samples yielded microbial growth. The isolates from the 15 chickens were all positive for ESBL production. Thirteen (86.7%) of the ESBL-producing isolates were E. coli while 2 (13.3%) were Klebsiella species. The ESBL enzyme in 6 (75.0%) and 2 (33.3%) of the 8 E. coli strains characterized belonged to the CTX-M-15 and CTX-M-1 types, respectively. Three (37.5%) and 2 (33.3%) of the 8 E. coli strains characterized also haboured the TEM- and OXA-1- type β-lactamases, respectively. Both Klebsiella species contained the CTX-M-15 type ESBL enzyme, one of them also haboured SHV-81 β-lactamase. All (100.0%) the ESBL-producing E. coli strains were resistant to cefotaxime, cefuroxime, cefpodoxime, ceftriaxone, ampicillin and tetracycline while 92.3% were resistant to streptomycin and aztreonam. Resistance to trimethoprim, ciprofloxacin, nalidixic acid, norfloxacin, levofloxacin, enrofloxacin, ceftazidime and ampicillin was exhibited by 62.0% to 76.9% of the E. coli strains while 38.5% were resistant to gentamicin and tobramycin. The two ESBL-producing Klebsiella strains were resistant to norfloxacin, ciprofloxacin, enrofloxacin, nalidixic acid, streptomycin, tobramycin, cefotaxime, ampicillin, trimethoprim, chloramphenicol and tetracycline while one was resistant to levofloxacin and gentamicin. Six (40.0%) of the 15 ESBL-positive isolates demonstrated resistance to greater than 5 classes of the antimicrobial agents tested. Six (75.5%) of the 8 E. coli isolates characterized were positive for tetracycline resistance gene, tetA, while 2 (25.0%) were positive for both tetB and aminoglycoside resistance gene, aac-3. The two Klebsiella isolates were positive for both tetA and aac-3genes.This study has shown the presence of MDR ESBL-producing Esherichia coli and Klebsiella in chickens at Ikpa Market Nsukka, Nigeria.