Resistance of nosocomial strains to antibacterial drugs and its link to biofilm formation

摘要

The problem of nosocomial infections is considered in connection with more frequent formation and wide distribution in clinical practice of new strains of hospital bacteria that have a cross-resistence to antibacterial drugs. The?nosocomial agents were isolated from wounds and identified as Staphylococcus aureus and Pseudomonas aeruginosa. 72.0% of S. aureus strains and 61.5% of P. aeruginosa clinical isolates had the capability of forming biofilms. The sensitivity to antibiotics of all isolated strains was investigated with tne agar diffusion test. This method showed that all strains of S. aureus with the capability to form biofilms had resistence to erythromycin, gentamycin, ciprofloxacin and levofloxacin. The had the greatest sensitivity to klindamycin (90.3%), vancomycin (80.6%) and gatifloxacin (80.6% cultures). The strains of S. aureus with the capability to form biofilms were more resistent to antibiotics than strains of S. aureus without such properties. Only cefotaxim suppressed the growth of 75.0% of strains of staphylococci. All isolated strains of S. aureus without the capability to form biofilms were sensitive to doxycyclin, gentamycin, ciprofloxacin, levofloxacin and klindamycin. All clinical isolates of P. aeruginosa with capability to form biofilms had resistence to ampicillin, gentamycin, imipenem, cefotaxime and ceftriaxone. They were most sensitive (75.0%) to piperacillin and cefoperazone/sulbactam. The strains of P. aeruginosa without the capability to form biofilms kept the resistence to gentamycin, imipenem and ceftriaxone. They showed the greatest sensitivity (75.0%) to ciprofloxacin (80.0% isolates) and also to amikacin, ampicillin, meropenem, norfloxacin and cefotaxime (60.0% cultures). We investigated the minimum inhibitory concentrations of gentamycin and ciprofloxacin, which appeared higher for P. aeruginosa than for S. aureus. The most effective disinfectant against all isolated nosocomial agents without the capacity for biofilm formation was “Desactin” in a concentration 0.1% or 0.2%. For strains of staphylococci with this capability, the efficiency of “Desactin” went down by 9.7%. The best biocide effect against the strains of P.?aeruginosa with the capability of forming biofilms was shown by 0.1% solution of “Neochlorine tabs”, which suppressed the growth of 75.0% of tested cultures. As a result, we detected a direct relationship between resistance to antibiotics and disinfectants and the capacities for biofilm formation among the nosocomial agents S. aureus and P.?aeruginosa.?.