Chlorhexidine effect on bacterial biofilms isoleated from nosocomial infections

Biofilms are population of bacteria cells that cause irreversible binding to the surfaces by producing extracellular polymers. Biofilm formation in bacteria causes resistance to antimicrobial agents and can lead to severe problems in this ground. The purpose of this study was to evaluate biofilm formation in some isolates of Pseudomonas aeruginosa (13 case), Staphylococcus aureus (13 case), Enterobacter (13 case) and Acinetobacter (13 case) which were collected from human infections of Alzahra hospital in Isfahan. Also the minimum inhibitory concentration of chlorhexidine and its impact on the growth of planktonic and biofilm formation for these isolates were determined. Statistical analysis and graphing have been carried out by using SPSS software (version 20) and Excel. All isolates (52 isolates) have produced biofilm. The mean of MIC of chlorehexidine antiseptic for the p.aeruginosa, S.aureus, Enterobacter and Acinetobacter were 0/001, 0/00013, 0/001, 0/0003 g/ml respectively. Planktonic bacterial growth inhibition from p.aeruginosa and Enterobacter in 1/4 MIC and 1/8 MIC respectively was seen in 40 and 60 % cases. Acinetobacter and Staphylobacter aureus, have been controlled in 40 % of cases in 1/4 MIC and 60 % of cases in 1/8 MIC. Biofilm has not been produced in any of MIC and 2MIC dilution, and the power of biofilm formation had been increased significantly by reducing concentration of chlorhexidine dilution.Discussion and The results indicate that the use of chlorhexidine in appropriate concentrations (MIC) can prevent bacterial growth and biofilm formation in different species causing hospital infections, but doses of chlorhexidine that are less than the MIC can stimulate biofilm formation.