Impact of Probiotic Lactococcus lactis and Titanium Dioxide Nanoparticles on the Expression of Klebsiella pneumoniae Biofilm Genes; a Comparative Study

The ability of nosocomial opportunistic microorganism, K. pneumoniae, to produce biofilms on food and hospital surfaces is crucial to the development of infection which has adverse effects on patient outcome and survival. The present study aimed to evaluate the impact of probiotic Nisin producing L. lactis and TiO2 NPs on the biofilm formation of K. pneumoniae. L. lactis isolates were commercially obtained and TiO2 NPs were produced using a sol–gel method. 62 K. pneumoniae strains were isolated in three hospitals in Tehran, and food samples. The antimicrobial activity of L. lactis and TiO2 NPs against antibiotic-resistant biofilm producing strains was determined via well-diffusion method. Definitive identification of isolates was performed through conventional biochemical tests and 16SrRNA PCR. The biofilm formation ability among the isolates obtained from sputum was higher than other isolates (p < 0.001). The L. lactis inhibited biofilm production in 4 isolates, but failed to prevent the growth of the 13 isolates. Additionally, TiO2 NPs inhibited 14 isolates to form a biofilm at 256 μg/mL. Comparison of LuxS gene expression in K. pneumoniae untreated and treated with TiO2 NPs alone and TiO2 + L. lactis showed –2.04 and –3.85 fold changes (CI = 95%, p = 0.006 and p = 0.002, respectively). The synthesized TiO2 nanoparticles are effective against these biofilms forming multidrug resistant K. pneumoniae strains and can be considered as reliable and operative inorganic antimicrobial agents. Antimicrobial and antibiofilm effects of TiO2 nanoparticles can be synergically elevated in combination with probiotic Nisin producing L. lactis.