5 years ago

Genotypic and phenotypic characteristics in association with biofilm formation in different pathotypes of human clinical Escherichia coli isolates.

Böhm, Weinreich, Ali, Roggenbuck, Burdukiewicz, Nitschke, Schiebel, Schierack, Rödiger
Bacterial biofilm formation is a widespread phenomenon and a complex process requiring a set of genes facilitating the initial adhesion, maturation, production of extracellular polymeric matrix (EPS) and subsequent dispersal of bacteria. Most studies on Escherichia coli (E. coli) biofilm formation have investigated non-pathogenic E. coli K-12 strains. Due to the extensive focus on laboratory strains in most studies, there is poor information regarding biofilm formation by pathogenic E. coli isolates. In this study, we genotypically and phenotypically characterized 187 human clinical E. coli isolates representing various pathotypes (e.g., uropathogenic, enteropathogenic and enteroaggregative E. coli). We investigated the presence of biofilm-associated genes ("genotype") and phenotypically analyzed the isolates for motility, curli and cellulose production ("phenotype"). We developed a new screening method to examine the in vitro biofilm formation ability. In summary, we found a high prevalence of biofilm-associated genes. However, we could not detect a biofilm-associated gene or specific phenotype correlating with the biofilm formation ability. In contrast, we could identify an association of increased biofilm formation with a specific E. coli pathotype. Enteroaggregative E. coli (EAEC) were found to exhibit the highest capacity of biofilm formation. Using our image-based technology for the screening of biofilm formation, we have demonstrated the characteristic biofilm formation pattern of EAEC, consisting of thick bacterial aggregates. In summary, our results highlight the fact that biofilm-promoting factors shown to be critical for biofilm formation in non-pathogenic strains do not reflect their impact in clinical isolates and that the ability of biofilm formation is a defined characteristic for EAEC.IMPORTANCE Bacterial biofilms are ubiquitous and consist of sessile bacterial cells surrounded by a self-produced extracellular polymeric matrix. They cause chronic and device-related infections due to their high resistance to antibiotics and the host immune system. In non-pathogenic E. coli cell surface components playing a pivotal role in biofilm formation are well known. In contrast, there is poor information for their role in biofilm formation of pathogenic isolates. Our study provides insights into the correlation of biofilm-associated genes or specific phenotypes with the biofilm formation ability of commensal and pathogenic E. coli Additionally, we represent a new developed method enabling qualitative biofilm analysis by automated image analysis which is beneficial for high-throughput screenings. Our results help to establish a better understanding of E. coli biofilm formation.

Publisher URL: http://doi.org/10.1128/AEM.01660-17

DOI: 10.1128/AEM.01660-17

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