In Vitro Studing of the Effect of Antibiotics on Planktonic Cells and Biofilm Clinical Isolates of Enterococcus

Enterococci are part of the normal flora intestinal tract of human and animal. In contrast to the beneficial role that Enterococci play in intestinal homeostasis،becoming important to human health as leading cause of nosocomial infections. The most important characteristics of Enterococci is the considerable amount of antibiotic resistance. Some strains of E. faecalis can form biofilm، which increase their ability to colonize patients and persist at infection sites. Bacteria in biofilms are generally showing more resistance to the antibiotics in planktonic condition. In this study، strains Enterococci isolated from some patients following the determination of antibiotic resistance and measured amount MIC and MBC، The most sensible strains were chose for the biofilm modeling invitro. The effect of antibiotic have been studied on biofilm. The most and the least antibiotic resistance of Enterococci strain was determined respectively to Penicillin (100%) and Nitrofurantoin (7%). Antibiotics Ampicilin،Gentamicin،Tetracycline even in densities 10times more than MIC of planktonic condition were disable in obliterating of the biofilm of strains. Different densities of Nitrofurantoin antibiotic collapsed bacterial biofilm absolutely. The least density 256 µg/ml was seen in one-day biofilm and the most density 1024 µg/ml،on the fifth day. Discussion and The results of bactericidal activities confirm the overt difference between planktonic cells and biofilm showing resistance of biofilm toward planktonic. According to the results obtained، it seems that Nitrofurantoin antibiotic is more effective for treatment of Enterococci in planktonic and biofilm condition.