Correlation between antimicrobial resistance and biofilm formation capability among Klebsiella pneumoniae strains isolated from hospitalized patients in Iran

BACKGROUND: Klebsiella pneumoniae is a common cause of nosocomial infections. Antibiotic resistance and ability to form biofilm, as two key virulence factors of K. pneumoniae, are involved in the persistence of infections. The purpose of this study was to investigate the correlation between antimicrobial resistance and biofilm formation capability among K. pneumoniae strains isolated from hospitalized patients in Iran. METHODS: Over a 10-month period, a total of 100 non-duplicate K. pneumoniae strains were collected. Antibiotic susceptibility was determined by Kirby–Bauer disk diffusion method according to CLSI. Biofilm production was assessed by tissue culture plate method. Finally, polymerase chain reaction was conducted to detect four families of carbapenemase: bla(IMP), bla(VIM), bla(NDM), bla(OXA−48); biofilm formation associated genes: treC, wza, luxS; and K. pneumoniae confirming gene: rpoB. RESULTS: Most of the isolates were resistant to trimethoprim-sulfamethoxazole (52 %), cefotaxime (51 %), cefepime (43 %), and ceftriaxone (43 %). Among all the 100 isolates, 67 were multidrug-resistant (MDR), and 11 were extensively drug-resistant (XDR). The prevalence of the bla(VIM), bla(IMP), bla(NDM), and bla(OXA−48) genes were 7 , 11 , 5 , and 28 %, respectively. The results of biofilm formation in the tissue culture plate assay indicated that 75 (75 %) strains could produce biofilm and only 25 (25 %) isolates were not able to form biofilm. Among these isolates, 25 % formed fully established biofilms, 19 % were categorized as moderately biofilm-producing, 31 % formed weak biofilms, and 25 % were non-biofilm-producers. The antimicrobial resistance among biofilm former strains was found to be significantly higher than that of non-biofilm former strains (p < 0.05). Molecular distribution of biofilm formation genes revealed that 98 , 96 , and 34 % of the isolates carried luxS, treC, and wza genes, respectively. CONCLUSIONS: The rise of antibiotic resistance among biofilm-producer strains demonstrates a serious concern about limited treatment options in the hospital settings. All of the data suggest that fundamental actions and introduction of novel strategies for controlling of K. pneumoniae biofilm-related infections is essential.