Phenotypic and genotypic comparison of biofilm producers among carbapenem susceptible and resistant Klebsiella pneumoniae strains

BACKGROUND: About one third of all Gram-negative bacterial infections globally are caused by Klebsiella pneumoniae. These bacteria readily become drug resistant and form biofilms that significantly complicates treatment of infections. OBJECTIVE: This study aimed to compare biofilm production in carbapenem-resistant (CR) and carbapenem-susceptible (CS) Klebsiella pneumoniae strains and to evaluate the association between biofilm production, carbapenem resistance and the presence of virulence genes mrkA , wbbM , wzm , luxS implicated in biofilm formation. METHODS: A total of 37 CR and 63 CS K. pneumoniae isolates were included in the study. Antibiotic susceptibility testing was performed using an automated Vitek 2 system. The presence of virulence genes ( mrkA , wbbM , wzm , luxS ) was investigated by PCR. Biofilm formation was assessed using the spectrophotometric microplate method. RESULTS: Overall, 65% of isolates were multidrug-resistant (MDR). The carbapenem resistance rate was 37%. CR strains showed significantly higher resistance to multiple antibiotics compared with CS strains. Biofilm production was detected in 76% of all isolates: 100% of CR strains and 61.9% of CS strains. The most frequently detected gene was mrkA (73%), followed by wbbM (57%), luxS (52%), and wzm (32%). CONCLUSION: MDR rates were higher in CR strains and in isolates with biofilm production. MIC values for ertapenem, meropenem, amikacin, piperacillin-tazobactam, cefoxitin, ceftazidime, and ceftriaxone were higher in biofilm-producing strains. Biofilm production was statistically significantly associated with MDR and strongly associated with carbapenem resistance, whereas the presence of individual virulence genes did not show any statistically significant association with it.