Dumpsite leachate as a hotspot of multidrug resistant Enterobacteriaceae harbouring extended spectrum and AmpC β-lactamase genes; a case study of Awotan municipal solid waste dumpsite in Southwest Nigeria

Abstract

Leachates generated by solid waste dumpsites could be a factor in the development of antibiotic resistance in environmental bacteria. In Nigeria, there is a dearth of information on the contribution of leachates from dumpsite to the ever-increasing trend of antibiotic resistance. A total of 250 cefotaxime-resistant bacteria recovered from dumpsite leachate was screened for extended spectrum β-lactamase (ESBL) production using the double disc synergy test and 41 were ESBL producers. The ESBL producers belonged to four genera and were identified as Escherichia (20), Citrobacter (13), Enterobacter (6) and Raoultella (2). Antibiotic susceptibility testing was carried out using disk diffusion method, while detection of extended spectrum and AmpC β-lactamase genes was done using Real-Time PCR. All the ESBL- producing bacteria were multidrug resistant, with 100% resistance observed to cefotaxime, cefpodoxime, tetracycline, sulfonamide, ciprofloxacin, ampicillin, ertapenem and imipenem, while 81.6% and 63.1% of the ESBL producers showed resistance to ceftazidime and amoxicillin-clavulanate respectively. blaCTX-M-1 and blaCTX-M-9 groups of CTX-M β-lactamases were detected in 33 (80.5%) of the isolates, while 26 (63.4%) harboured the blaCTX-M-2, blaCTX-M-8 and blaCTX-M-25 groups. blaTEM was detected in 31 (75.6%) of the ESBL producers, while blaSHV was detected in 13 (31.7%). One isolate (E. coli AW-32) carried blaCMY-1 gene. None of the isolates carried blaKPC, blaNDM-1 and blaampC genes, while seven isolates were devoid of any gene. There was co-occurrence of resistance genes in thirty of the isolates. This study has revealed that dumpsite leachates could be important reservoirs of multidrug resistant Enterobacteriaceae harbouring extended spectrum and AmpC β-lactamases genes.