Abstract
BackgroundMultidrug resistant Pseudomonas aeruginosa harbours integrons and other mobile genetic elements such as plasmids and transposons, which easily disseminate antibiotic resistance genes among clinical strains of P. aeruginosa.MethodologyPlasmid extraction of 54 clinical isolates of P. aeruginosa was carried out by alkaline lysis method; and plasmid size estimation was done by using E. coli V517 standard plasmid marker. Fifty-four clinical strains of P. aeruginosa were isolated from 5 hospitals in 3 Southwestern states of Nigeria between March and September 2010. Plasmid extraction of isolates was carried out by alkaline lysis method; and plasmid size estimation was done by using E. coli V517 standard plasmid marker. PCR amplification for the 3 classes of resistance integrons, and gene cassette characterization were carried out using specific primers and by sequencing of PCR products. Conjugal mating of the integron positive P. aeruginosa strains with E. coli DH5α was performed to demonstrate transferability of integrons and gene cassettes.ResultAgarose gel electrophoresis of plasmid DNA revealed that all the 54 P. aeruginosa harboured 1–4 plasmids with sizes ranging from 2.2 – >58 kb. Class 1 integron was identified in 31 (57%) strains; but none of them carried class 2 and class 3 integrons. High prevalence of aadA gene conferring resistance to streptomycin/spectinomycin was detected in the strains positive for class 1 integron. Sequencing of the 1.6 kb and 1.2 kb amplified band of gene cassettes revealed the presence of aadA6-orfD and aadA13 respectively.ConclusionThis study demonstrates the presence of plasmids and integrons harbouring resistance gene cassettes, which may collectively constitute an efficient system for dissemination of resistance genes in P. aeruginosa. Disturbingly, the rapid and unabated spread of class 1 integron-associated multidrug resistant P. aeruginosa in Southwest Nigeria may greatly hamper successful treatment of infections caused by such strains. This necessitates the establishment of functional antimicrobial resistance surveillance programmes in Nigeria.
Highlights
The worldwide threat of nosocomial multidrug resistant Pseudomonas aeruginosa is a growing concern among hospitalized patients
This study demonstrates the presence of plasmids and integrons harbouring resistance gene cassettes, which may collectively constitute an efficient system for dissemination of resistance genes in P. aeruginosa
The rapid and unabated spread of class 1 integron-associated multidrug resistant P. aeruginosa in Southwest Nigeria may greatly hamper successful treatment of infections caused by such strains
Summary
The worldwide threat of nosocomial multidrug resistant Pseudomonas aeruginosa is a growing concern among hospitalized patients. P. aeruginosa is naturally resistant to many structurally unrelated antibiotics because of its dominant array of chromosomal and plasmid-mediated antibiotic resistance factors [1]; as well as its dynamic propensity to acquire newer resistance genes from bacteria from other genera such as Acinetobacter baumannii, Klebsiella pneumoniae and Salmonella spp [2]. Mobile genetic elements such as plasmids, transposons and integrons are means of acquiring resistance mechanisms contributing to P. aeruginosa multidrug resistance [2]. Multidrug resistant Pseudomonas aeruginosa harbours integrons and other mobile genetic elements such as plasmids and transposons, which disseminate antibiotic resistance genes among clinical strains of P. aeruginosa
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