Analysis of uropathogenic Escherichia coli biofilm formation under different growth conditions

Abstract

The ability to form different types of biofilm enables bacteria to survive in a harsh or toxic environment. Different structures of biofilms are related to different surfaces and environment of bacterial growth. The aim of this study was analysis of the biofilm formation of 115 clinical uropathogenic Escherichia coli strains under different growth conditions: surface for biofilm formation, medium composition and time of incubation. The biofilm formation after 24 h, 48 h, 72 h and 96 h was determined spectrophotometrically (A531) after crystal violet staining and it was correlated with bacterial growth (A600). The live and dead cells in biofilm structures was also observed on the glass surface by an epi-fluorescence microscope. Additionally, the presence of rpoS, sdiA and rscA genes was analyzed. The statistical significance was estimated by paired T-test. The observed biofilms were different for each particular strain. The biofilm formation was the highest in the rich medium (LB) after 24 h and its level hasn't changed in time. When biofilm level was compared to bacterial growth (relative biofilm) - it was higher in a minimal medium in comparison to enriched medium. These results suggest that most of the bacterial cells prefer to live in a biofilm community under the difficult environmental conditions. Moreover, biofilm formation on polyurethane surface did not correlate with biofilm formation on glass. It suggests that mechanisms of biofilm formation can be correlated with other bacterial properties. This phenomenon may explain different types of biofilm formation among one species and even one pathotype - uropathogenic Escherichia coli.

Ciprofloxacin, amoxicillin, and aminoglycosides stimulate genetic and phenotypic changes in uropathogenic Escherichia coli strains

“…Five clinical Escherichia coli strains isolated from the urine of patients suffering from urinary tract infection were selected for this study. They belong to the characterized bacterial collection used in previous studies [30,32,33]. The basic criteria for their selection were the sensitivity to all analyzed antibiotics and the varied occurrence of virulence factor genes.…”

“…The biofilm formation assay was carried out by 0.3% crystal violet staining according to the protocol described previously [32]. The bacteria were grown in triplicate on the 96-well plates at 37°C in the LB broth.…”

Correlation of pathogenic factors with antimicrobial resistance of clinicalProteus mirabilisstrains

“…The decrease of the P. mirabilis growth rate might inhibit the biofilm formation, unlike in E. coli . We also observed that the biofilm formation on the glass correlated proportionally with that on the polyurethane, which was again in contrast to E. coli [46]. Czerwonka et al [11] reported that high hydrophobicity of the P. mirabilis cell surface correlated with low biofilm amount, which is important for hydrophobic surfaces like glass.…”

“…The ability to form biofilm varies remarkably, even among strains of the same species [43–45]. Our results (Fig 7) indicate that the P. mirabilis biofilm may be stronger than that of E. coli [46]. That may mean that P. mirabilis grows faster, providing greater biofilm yield, which might be important during the host invasion.…”

“…The ability of P. mirabilis strains to form biofilm was analyzed on glass and polyurethane surfaces according to the method described previously [46]. The biofilm on the glass was stained with SYTO® 9 solution and propidium iodide, according to the manufacturer’s protocol (Filmtracer™; Invitrogen, Carlsbad, California, USA), and then observed with an epi-fluorescence microscope (Axio Scope.A1; ZEISS, Oberkochen, Germany).…”