ABSTRACT
This research investigates the transferability of plasmid-mediated quinolone resistance (PMQR) genes among enteric bacteria isolates in human and animal samples, as well as its implication on resistance of recipient cells. A total of 1,964 strains of five different enteric bacteria species (Escherichia coli, Salmonella sp., Shigella sp., Klebsiella sp. and Aeromonas sp.) were screened for plasmid-mediated quinolone resistance (PMQR) genes from a population of quinolone resistant (Q-r) isolates. Screening for PMQR isolates was achieved by plasmid curing using sub-lethal concentration of Sodium Dodecyl Sulphate and PMQR genes (qnrA, qnrB, qnrS, Aac(6')-Ib-crand Qep A) were detected by polymerase chain reaction (PCR). Conjugation and transformation experiments were attempted to ascertain transfer of genes from the Q-r isolates to a susceptible, standard recipient, E. coli J53-2. The minimum inhibitory concentration (MIC) was determined before and after gene transfer, using E-test strips. Results indicate that percentage resistance to the quinolones (Qs): Nalidixic acid, Ciprofloxacin, Pefloxacin and Ofloxacin determined by agar plate diffusion technique stood at 52.6, 47.3, 50.5, 70.6 and 46.0% for Escherichia coli, Salmonella sp., Shigellasp., Klebsiella sp. and Aeromonas sp. respectively. Analysis of variance indicated the occurrence of significant differences (F, 46.77-613.30; 0.00) in the resistance to each tested Qs. Generally, Human isolates showed greater resistance than Animal isolates (57.4 vs 47.2%). Investigation with specific primers indicated 11, 15, 7, 1 and 0 for qnrA, qnrB, qnrS, qepA and Aac(6')-Ib-cr genes respectively, out of 1018 Q-r and 29 PMQR isolates. Gene transfer experiments indicated the transfer of all genes except qepA either by conjugation or transformation. The MIC of tested Qs on recipient bacterium before gene transfer greatly increased from 0.0625 to 0.25 µg/mL, after transfer. This study demonstrates that PMQR genes amongst enteric bacteria in the Niger delta of Nigeria were transferable and transfer conferred a higher Q- resistance on recipient bacterium.
ABSTRACT
Plasmid mediated quinolone resistance (PMQR) is a public health challenge arising among other things, from indiscriminate use of the floroquinolones (FQr) prophylactically in animal husbandry. This study examines the occurrence of PMQR genes amongst enteric bacteria isolated from human and animal sources. A total of 720 (360 stool and 360 fish pond water/poultry litter) samples were examined for fluoroquinolone resistant (FQr) bacteria. Percentage FQr was generally higher among human isolates than isolates from animals. Proportion of PMQR amongst FQr isolates were (1.05 and 4.32) % for E. coli from human and animal sources. For Salmonella spp., Shigella spp., Klebsiella spp. and Aeromonas spp., percentages PMQR were 0.00 & 6.93, 0.00 & 6.38, 4.26 & 5.26 and 0.00 &3.03 for human and animal sources respectively, for the isolates. The PMQR genes: qnrA, qnr B, qnr S and qep A were 11, 15, 7 and 1 amongst a total of 1018 FQr and 29 PMQR isolates respectively. The aac (6')-Ib-cr gene was not detected in this study. Approximate Plasmid bands of PCR amplicon for qnr A, qnr B, qnr S and qep A respectively were established. The proportion of PMQR genes especially among isolates from animal sources is of public health concern due to the higher possibility of a horizontal FQ resistance transfer to humans.
