Influence of ß-lactam antibiotics on the activity of K. pneumoniae bacteria biofilm forms isolated from wounds of patients with chronic osteomyelitis.

One of the reasons for the emergence of highly resistant strains is associated with the ability of bacteria to form biofilms on various surfaces. The formation of a biofilm by pathogens leads to a decrease in the activity of the antibiotic, an increase in the time for the production of stress response genes by bacteria, and, as a result, an increase in antimicrobial tolerance. To investigate the effect of imipenem and cefepime on the activity of biofilm forms of K. pneumoniae bacteria isolated from the wounds of patients with chronic osteomyelitis. The object of the study is clinical strains of K. pneumoniae isolated from the wounds of patients with chronic osteomyelitis. In the control series, the level of biofilm formation of K. pneumoniae strains was assessed after 48 hours of cultivation on coverslips and 96-well polystyrene plates. In the second and third series, the biofilm form of K. pneumoniae bacteria was exposed to imipenem and cefepime, and after 24 hours the activity of biofilm formation was assessed according to previously developed criteria. The structure of the emerging biofilm on the surface of the coverslip in all series of the experiment was represented by single adherent cells and microcolonies of various sizes. Cultivation with antibiotics led to a decrease in the number of microcolonies ranging in size from 10 to 10,000 µm2 in the second and third series, however, significant differences from the control series were found only when exposed to cefepime. The intensity of film formation of K. pneumoniae in the control series by the tablet method was 0.350 (0.334; 0.368) units opt.pl. When cultivating biofilms together with antibacterial drugs, the biofilm-forming activity after 24 hours of the experiment was significantly lower than in the control group in all experimental series. K. pneumoniae bacteria isolated from patients with chronic osteomyelitis, when cultivated on polystyrene plates and on the surface of coverslips, actively form a biofilm, exhibiting highly adhesive properties. The studied antibiotics were shown to have a bacteriostatic effect on biofilm forms of K. pneumoniae bacteria. The bactericidal effect of imipenem and cefepime on biofilm forms was not revealed.