SENSITIVITY TO ANTIBIOTICS OF BIOFILM-FORMING HOSPITAL STRAINS OF BACTERIA
Karbovska A, Adamova P, Honcharco M, Lavrentieva K, Sklyar T.
Oles Honchar Dnipro National University
e-mail: microviro@ukr.net
Distinctive properties of many nosocomial pathogens from other microorganisms are high levels of antibiotic resistance and the ability to form biofilms in the environment, including non-biological materials, which, when in contact with the patient’s body, increases the risk of septic conditions.
The aim of the study was to assess the level of antibiotic resistance of biofilm-forming and nonbiofilm-forming clinical strains of microorganisms – pathogens of nosocomial infections.
Samples of detachable wounds of patients with nosocomial infections were taken in accordance with the guidelines for compliance with the sanitary-epidemiological regime in health care facilities of Ukraine. The ability to form biofilms was detected by using a modified method (O’Toole et al., 2000). The sensitivity of isolated strains – pathogens of nosocomial infections to antibiotics was determined by disco-diffusion method.
Among the clinical samples, 43 strains of Staphylococcus aureus were isolated, of which 72.1% had the biofilm-forming ability, and 39 strains of Pseudomonas aeruginosa, of which 61.5% were biofilm-forming. During the antibiotic susceptibility determination of isolated cultures of S. aureus, it was found that all strains capable of biofilm formation were resistant to erythromycin, gentamicin, ciprofloxacin, and levofloxacin; 90.3% of isolates – to cefotaxime and 80.6% – to tetracycline and doxycycline. The most sensitive biofilm-forming strains of S. aureus were to clindamycin (90.3%), vancomycin, and gatifloxacin (80.6% of cultures). Nonbiofilm-forming strains of S. aureus were less resistant to antibiotics than biofilm-forming isolates. All experimental cultures were sensitive to doxycycline, gentamicin, ciprofloxacin, levofloxacin, and clindamycin. 75.0% of nonbiofilm-forming strains of S. aureus were sensitive to vancomycin, oxacillin, gatifloxacin, and norfloxacin. All the biofilm-forming bacterial isolates of P. aeruginosa showed resistance to ampicillin, gentamicin, imipenem, cefotaxime, and ceftriaxone. A significant number of P. aeruginosa strains (75%) were resistant to ciprofloxacin. For other antibiotics, the percentage of resistant isolates was less than 50.0%. The biofilm-forming strains of P. aeruginosa (75%) were the most sensitive to piperacillin and cefoperazone/sulbactam. Nonbiofilm-forming variants of P. aeruginosa remained resistant to gentamicin, imipenem, and ceftriaxone. A high percentage (80%) of stable nonbiofilm-forming isolates was observed for cefoperazone, cefoperazone/sulbactam, piperacillin, and cefepime. They were most sensitive to ciprofloxacin (80% of isolates), as well as to amikacin, ampicillin, meropenem, norfloxacin, and cefotaxime (60% of cultures).
Thus, the isolated strains of S. aureus and P. aeruginosa, not capable of biofilm formation, were characterized by a higher level of sensitivity to the tested antibiotic drugs than biofilm-forming isolates. The biofilm-forming strains of S. aureus and P. aeruginosa were the most resistant to gentamicin, cefotaxime and ciprofloxacin.