Characterisation of integrons which potentially mediate dissemination of antibiotic resistance in enterobacteriaceae isolated from healthy community members

Abstract

Antibiotic resistance has become a global public health concern, by limiting the number of drugs used to treat bacterial infections. Antimicrobial resistance and multidrug resistance (MDR) therefore increase morbidity and mortality of people having bacterial infections in the community. Integrons are known as the genetic agents responsible for the capture and spread of antibiotic resistance determinants among diverse Gram-negative bacteria isolates. The activities of integrons have assisted the introduction of antibiotic resistance into genes pathogens and commensals of humans. Several studies have shown that integrons play a significant role in the spread of antibiotic resistance. This study examined the role of integrons in the spread of antibiotic resistance in Enterobacteriaceae from faeces of healthy community members. The antibiotic resistance patterns of 32 Escherichia coli and 8 Klebsiella pneumoniae isolates were determined by Kirby disk diffusion and conjugation was used to determine the transfer rates of antibiotic resistance. The 40 bacteria isolates were then tested for presence of integrons by polymerase chain reaction and the integrons present characterised by amplifying the integron variable region. The PCR amplicons of the integron variable region were then sequenced to determine the antibiotic resistance gene cassettes present. The isolates were found to have high resistance to beta-lactams (100%), sulphonamides (100%) and fluoroquinolones (88%). A high frequency of transfer ranging from 9×10-2 to 1.1×103 transconjugants per recipient E. coli J53 strain was recorded. The prevalence of class 1, class 2 and class 3 integrons were 100%, 35% and 0%. The integron cassette profiles were aadA1 (70%), dfrA17 (50%) and dfrA7 (10%) and they confer resistance to aminoglycosides and trimethoprim. The study revealed that 23 (58%) Escherichia coli and 2 (5%) Klebsiella pneumoniae isolates were MDR. The study also revealed that integrons with antibiotic resistance genes aadA1, dfrA7 and dfrA17are present in the isolates from healthy community members, thus they have a potential to capture genes which confer resistance to various antibiotics. The study recommends proper use of antibiotics, improved personal hygiene and sanitation to minimize the oral faecal spread of antibiotic resistance in the community. The study also recommends characterisation of transconjugants to determine which resistance gene cassettes are most disseminated.