Abstract:
Introduction. The advancement of biomedical science has enabled to study the microorganisms in their natural environment, whereas over 95% of microorganisms existing in
nature are in biofilms. Biofilm formation is an important strategy by which microorganisms survive and adapt in natural environments. Bacteria living in a biofilm usually have
significantly different properties from free-floating bacteria of the same species, being protected by a dense biofilm structure, which allows them to cooperate and interact in different manners. The main features of the biofilms are their high resistance to disinfectants
and antimicrobial drugs, whereas the thick extracellular matrix and the outer layer cells
protect the interior of the community. It is estimated that microbial biofilms play a major
role in over 80% of infections. Sixty percent of healthcare-associated infections are due to
biofilm formation on medical implants. Moreover, many chronic diseases are associated
with biofilms, such as infectious endocarditis, cystic fibrosis pneumonia, periodontitis,
chronic rhinosinusitis, trophic ulcers and otitis media.
Material and methods. The study was carried on 128 samples isolated from trophic ulcers. The microbial strains involved in the process were isolated in pure cultures, under
laboratory conditions, and subsequently identified by classical microbiological methods
and Vitek2 Compact system (BioMerieux), based on the morpho-biological, coloring and
biochemical properties. The antimicrobial susceptibility and biofilm-forming ability testing was performed using the Kirby-Bauer disk diffusion technique and the quantitative
adhesion test, respectively. Strains that showed resistance to three or more antibiotic
groups were considered poly-resistant ones.
Results. Bacteriological examination was carried out on 128 samples collected from patients with trophic ulcers. A single species of microorganisms was isolated in 35.9% of
cases, two and more species in 53.1% and no microorganisms were isolated in 10.9% of
cases. A total of 211 microbial strains were isolated and identified. The antibiotic susceptibility tests of strains isolated from trophic ulcers showed a high level of resistance to drug
preparations. Of the 211 microbial strains isolated from trophic ulcers, 147 (69.7%) strains
produced detectable biofilms (OD>0.112). As regarding the biofilm status, 58 (39.5%) isolates produced strong biofilms (OD>0.220), 67 isolates (45.6%) – moderate biofilms (OD
0.112-0.220) and 22 isolates (14.9%) – weak biofilms. The antibiotic resistance of biofilmforming compared to non-biofilm-forming strains showed that biofilm-forming strains had
a higher resistance to all groups of drugs tested.
Conclusions. The study results revealed a higher biofilm formation capacity at the strains
isolated from trophic ulcers, as well as higher rates of antimicrobial resistance in biofilmproducing strains compared to non-producing ones. The obtained data proves a strong correlation between biofilm formation capacity and antimicrobial resistance patterns. The implementation of the relevant antimicrobial susceptibility testing of biofilm-producing
strains will improve the management of infections caused by these microorganisms, as well
as provide feasible strategies to prevent their spread.
