Abstract:
Introduction. Antimicrobial resistance is a long-standing problem of significant
magnitude, and its rapid spread has made it the most serious current public
health issue globally. Among the many bacterial infections, S. aureus is the leading
cause of nosocomial infections by gram-positive bacteria. The increasing incidence of bacterial infections in therapeutic failure in recent years is explained by
the unjustified use of antimicrobials and the dissemination of antibiotic resistance
factors. The increasing resistance of S. aureus strains to antimicrobials, together
with methicillin resistance and biofilm formation poses serious challenges for the
treatment of infections caused by this species.
Aim. The study elucidated the biofilm formation capacity of S. aureus strains and
its association with antimicrobial resistance.
Material and methods. The antimicrobial susceptibility of 189 Staphylococcus
aureus strains isolated from various clinical biosubstrates was studied. The
pathological specimens were cultured on selective and non-selective media, and
the identification was based on cultural and morphological characteristics, the
presence of coagulase and biochemical properties. Antibiotic susceptibility was
determined by the Kirby-Bauer diffusion metric method and the VITEK 2 COMPACT system. The methodology of the determination and the interpretation of
antibiotic susceptibility were carried out in a standardized way, in accordance
with EUCAST guidelines. Biofilm production by S. aureus strains was quantitatively determined using the microtitration method.
Results. The results of the research showed that S. aureus strains exhibited a high
degree of resistance to fluoroquinolones (ciprofloxacin – 69.9%; levofloxacin –
59.7%) and macrolides, lincosamides, streptogramins (erythromycin – 56.8%). S.
aureus strains were found to be more sensitive to tetracyclines (tetracycline –
93.9%), amphenicols (chloramphenicol – 91.1%) and oxazolidones (linezolid –
80.2%). Notably, no strain of S. aureus showed resistance to vancomycin. 81
(42.9%) of the strains analyzed showed resistance to methicillin and 108 (57.1%)
were sensitive to this preparation. Methicillin-resistant S. aureus strains exhibited
higher resistance to all antibiotic groups than methicillin-sensitive strains. Of the
189 clinical strains of S. aureus, 74 (39.2%) produced detectable biofilm, and 115
(60.8%) did not produce biofilm. Among the biofilm-producing strains, 29
(39.2%) strains produced strongly adherent biofilm, 28 (37.8%) – moderately
adherent biofilm and 17 (23.0%) – weakly adherent biofilm. A higher level of resistance was recorded in biofilm-producing S. aureus strains compared to nonproducing ones.
Conclusions.The study results indicate a high capacity for biofilm formation in
clinical strains of S. aureus and the predominance of high rate of antimicrobial
resistance. The data obtained show a strong correlation between the formation of
biofilms and antimicrobial resistance patterns. The implementation of relevant
tests to determine the antimicrobial susceptibility of biofilm-producing strains
will improve the management of cases of infections caused by these microorganisms and will facilitate the development of feasible strategies to prevent their
spread.
