Genotypic and Phenotypic Characteristics Associated with Biofilm Formation by Human Clinical Escherichia coli Isolates of Different Pathotypes

Abstract

Bacterial biofilm formation is a widespread phenomenon and a complex process requiring a set of genes facilitating the initial adhesion, maturation, and production of the extracellular polymeric matrix and subsequent dispersal of bacteria. Most studies on biofilm formation have investigated nonpathogenic K-12 strains. Due to the extensive focus on laboratory strains in most studies, there is poor information regarding biofilm formation by pathogenic isolates. In this study, we genotypically and phenotypically characterized 187 human clinical isolates representing various pathotypes (e.g., uropathogenic, enteropathogenic, and enteroaggregative ). We investigated the presence of biofilm-associated genes ("genotype") and phenotypically analyzed the isolates for motility and curli and cellulose production ("phenotype"). We developed a new screening method to examine the 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 did identify an association of increased biofilm formation with a specific pathotype. Enteroaggregative (EAEC) was found to exhibit the highest capacity for biofilm formation. Using our image-based technology for the screening of biofilm formation, we 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 nonpathogenic strains do not reflect their impact in clinical isolates and that the ability of biofilm formation is a defined characteristic of EAEC. 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 nonpathogenic , 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 Additionally, we describe a newly 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 biofilm formation.

Biofilm forming properties of quinolone resistant Escherichia coli from the broiler production chain and their dynamics in mixed biofilms

“…Previous studies have shown variations in the ability of different E. coli strains to produce biofilm under conditions relevant for the food production chain [14,15]. E. coli strains also display variations in biofilm matrix composition which can be visualized when grown on agar plates with Congo Red and Coomassie Blue dyes (CR agar plates) [16,17].…”

Non-pathogenic Escherichia coli biofilms: effects of growth conditions and surface properties on structure and curli gene expression

“…We studied and optimised biofilm formation on different surfaces and under different growth conditions. Biofilm formation differs in different E. coli strains, shown both in the literature (for example, (Schiebel et al 2017)) and in this study, therefore, such studies on different strains are important. In addition, many studies focus on pathogenic E. coli strains, thus studies on non-pathogenic strains offer an interesting comparison.…”

The Role of Functional Amyloids in Bacterial Virulence

“…The curli genes occur in most commensal as well as human and animal pathogenic E. coli isolates and Salmonella enterica serovars [73] , [74] . However, although the csg genes are present, their expression pattern can vary considerably depending on the lifestyle of the bacterium or the infection site, even within a species.…”

“…However, although the csg genes are present, their expression pattern can vary considerably depending on the lifestyle of the bacterium or the infection site, even within a species. While curli were originally thought to be expressed mainly at ambient temperatures [8] , [75] , it now seems that depending on the growth medium, commensal E. coli as well as enteropathogenic E. coli , enterotoxigenic E. coli , uropathogenic E. coli (UPEC), enteroaggregative E. coli , avian pathogenic E. coli and E. coli isolates causing sepsis can express curli at 37 °C [74] , [76] , [77] , [78] , [79] , [80] . Strikingly, in enteroinvasive E. coli , Shigella spp.…”