Evaluation of the effects of subinhibitory concentrations of gentamicin on alginate production of Pseudomonas aeruginosa clinical isolates

Background and Aim : Pseudomonas aeruginosa is one of the most common human opportunistic pathogen which is considerable due to cause acute and chronic infections. Alginate is an important virulence factor of this organism which has essential role in establishment of chronic infections. This study aimed to investigate the effect of subinhibitory (sub-MIC) concentrations of gentamicin on alginate production of P. aeruginosa clinical isolates and standard strain ۸۸۲۱M.Methods : In this study, a total of ۸۳ P. aeruginosa clinical isolates were isolated from different clinical specimens. P. aeruginosa clinical isolates were identified by standard bacteriological and biochemical tests. The effects of sub-MIC concentrations (۱/۲ × ۱/۴MIC) of gentamicin on alginate production of P. aeruginosa clinical isolates and standard strain ۸۸۲۱M were assesed by carbazole method. The presence of alginate in clinical isolates was confirmed by detection of alginate genes (algD, algU) by PCR method.Results : All the isolates had the ability of alginate production and were positive for algD and algU genes. sub-MIC concentrations of gentamicin significantly increased alginate production of ۴۹ isolates (۵۹%). On other hand, in ۳۴ isolates (۴۱%) and standard strain ۸۸۲۱M, alginate production decreased significantly in the presence of sub-MIC concentrations of gentamicin.Conclusion : This study showed different effects of sub-MIC concentrations of gentamicin on alginate production of P. aeruginosa clinical isolates. It seems that bacterial reaction to sub-MIC concentrations of antibiotics depends on isolates type. Further studies are required to understand the mechanism of different responses of P. aeruginosa clinical isolates to sub-MIC concentrations of an antibiotic.

کلیدواژه ها:

Alginate ، Gentamicin ، Pseudomonas aeruginosa