Effect of sub-inhibitory antibiotic concentrations on the production and structural density of biofilm by methicillin- resistant Staphylococcus aureus

Background and Aim : The ability of Staphylococcus spp. to form biofilm is one of the virulence factors that facilitate the adhesion and colonization on the different surface, a fact that leads to recurrent or persistent infections. One of the factors of the increased resistance of biofilms is the protection by a self-produced extracellular polymeric substance (EPS), which is a matrix made up of proteins, polysaccharides, lipids, and nucleic acids. There is a subtle change of micro-organism behavior caused by antibiotics. Studies showed that low quantities of antibiotics and other pharmaceutical drugs can either induce or repress growth of micro-organisms. One of the concerns of these changes is the either induced or reduced biofilm formation by low levels of antibiotics.Methods : In this study, effects of sub minimum inhibitory concentration of some antibiotics evaluated on reduction or induction of biofilm producing ability in ۲۹ isolates of methicillin resistance staphylococcus aureus. Also, increase or decrease of N-acetylglucoseamine in inducted biofilm was studied. For this aim, antibiogram and biofilm producing ability of studied isolates was done by Kirby-bauer and microtitre plate crystal violet methods, respectively. Vancomycin, trimethoprim-sulfamethoxazole and clindamycin used in antibiogram. After extraction of exopolysaccharide (EPS), amount of N-acetylglucoseamine in inducted biofilm evaluated by TLC methodResults : Based on results, all the isolates were susceptible to vancomycin and biofilm producing ability in weak and average levels. Sub minimum inhibitory concentration of vancomycin increased biofilm producing ability in ۳۸% of isolates. Increase of N-acetylglucoseamine was not demonstrated in isolates with inducted strong producing ability of biofilm.Conclusion : Based on literature review, it could be based on absence of this compound or its changing to different composition which need to complementary studies.

کلیدواژه ها:

Antibiotic ، Biofilm ، Methicillin ، Staphylococcus aureus