Effect of biocides on biofilms of some multidrug resistant clinical bacterial isolates

Abstract

The biofilm production ability of some multidrug resistant clinical bacterial isolates was determined in the presence of four biocides – chlorhexidine gluconate (3%), cetrimide (0.75%), sodium hypochlorite (3.5%) and chloxylenol BPC (3.8%) – using the modified microplate method. The multi drug resistant clinical isolates used in this study are Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella aerogenes, Proteus mirabilis and Citrobacter freundii. These bacteria showed resistance to at least 5 antibiotics. Quantitative microtiter plate assay showed that 24 (58.55%) out of the 41 biofilms producers produced strong biofilms with optical density ranging from 0.25 to 0.35.The result demonstrated that sodium hypochlorite was more effective in inhibiting biofilm formation in the bacterial isolates. Lower concentrations of the biocides were more effective in inhibiting biofilm formation by bacteria. The ability of Escherichia coli and Klebsiella aerogenes to form biofilms was most affected. There was little inhibition of biofilm formation by the biocides on Staphylococcus aureus. This study has shown a relationship between biocide and multidrug resistance.

Keywords: Biocides, Multi drug resistance, sodium hypochlorite, Staphylococcus aureus