Association of Putative Enteroaggregative Escherichia coli Virulence Genes and Biofilm Production in Isolates from Travelers to Developing Countries

Abstract

Enteroaggregative Escherichia coli (EAEC) is an emerging enteric pathogen that causes acute and chronic diarrhea among children, human immunodeficiency virus-infected patients, and travelers to developing regions of the world. The pathogenesis of EAEC strains involves the production of biofilm. In this study, we determined the association between presence of putative EAEC virulence genes and biofilm formation in 57 EAEC isolates (as defined by HEp-2 adherence) from travelers with diarrhea and in 18 EAEC isolates from travelers without diarrhea. Twelve nondiarrheagenic E. coli isolates from healthy travelers were used as controls. Biofilm formation was measured by using a microtiter plate assay with the crystal violet staining method, and the presence of the putative EAEC virulence genes aap, aatA, aggR, astA, irp2, pet, set1A, and shf was determined by PCR. EAEC isolates were more likely to produce biofilm than nondiarrheagenic E. coli isolates (P ‫؍‬ 0.027), and the production of biofilm was associated with the virulence genes aggR, set1A, aatA, and irp2, which were found in 16 (40%), 17 (43%), 10 (25%), and 27 (68%) of the biofilm producers versus only 4 (11%), 6 (6%), 2 (6%), and 15 (43%) in non-biofilm producers (P ‫؍‬ 0.008 for aggR, P ‫؍‬ 0.0004 for set1A, P ‫؍‬ 0.029 for aatA, and P ‫؍‬ 0.04 for irp2). Although the proportion of EAEC isolates producing biofilm in patients with diarrhea (51%) was similar to that in patients without diarrhea (61%), biofilm production was related to the carriage of aggR (P ‫؍‬ 0.015), set1A (P ‫؍‬ 0.001), and aatA (P ‫؍‬ 0.025). Since aggR is a master regulator of EAEC, the presence of aap (P ‫؍‬ 0.004), astA (P ‫؍‬ 0.001), irp2 (P ‫؍‬ 0.0006), pet (P ‫؍‬ 0.002), and set1A (P ‫؍‬ 0.014) in an aggR versus an aggR-lacking background was investigated and was also found to be associated with biofilm production. This study suggests that biofilm formation is a common phenomenon among EAEC isolates derived from travelers with or without diarrhea and that multiple genes associated with biofilm formation are regulated by aggR.

Mecanismos de virulencia de Escherichia coli enteropatógena

“…Este patotipo se adhiere a la mucosa intestinal, la coloniza y produce un efecto citotóxico que causa diarrea de tipo acuosa sin fiebre, con secreción de moco 84,85 . Entre las cepas de ECEA existe gran variabilidad en la presencia de factores de patogenicidad; por consiguiente, en los modelos estudiados aún no se ha encontrado relación entre un genotipo o fenotipo específico y el desarrollo de la enfermedad.…”

“…Se han relacionado con la formación de microcolonias otros genes regulados por AggR, entre los que se incluyen una proteína Irp2 involucrada en la expresión de yersiniabactin (sideróforo) encontrada en especies de Yersinia, una enterotoxina de Shigella (ShET1: shigella enterotoxin 1) codificada por el gen set1A 85 , y por úl-timo dos proteínas Fis y YafK junto con un sistema de Figura 4. E. coli enteroagregativa.…”

“…secreción tipo VI 92 . Sin embargo, se ha evidenciado la formación de microcolonias cuando están los factores regulados por AggR y también, cuando ninguno de ellos, incluyendo AggR, está presente, lo que indica la existencia de factores de virulencia aún no descritos 85 . En la adhesión también están involucradas proteínas de la membrana externa como Hra-1 (Hra: heat-resistant agglutinin 1) con actividad aglutinina y adhesina, Hra-2 con actividad adhesina y Tia homóloga de Hra-1 con actividad invasora y adhesina, también relacionada con cepas de ECET 93 .…”

Diarrheagenic Escherichia coli in sub-Saharan Africa: Status, Uncertainties and Necessities

“…Many putative EAEC virulence factors are located on a partially conserved plasmid, pAA, which is marked by the CVD432 locus [191,192,213,214].Although pAA genes have been the focus of much study, they are only partially correlated with EAEC virulence or virulenceassociated phenotypes [135,215,216]. Recent research is beginning to uncover chromosomal loci with promise as epidemiological and virulence markers [217][218][219][220][221].…”

Putative Virulence Genes and Biofilm Production Among Typical Enteroaggregative Escherichia coli Isolates from Diarrhoeic Children in Kashmir and Andhra Pradesh

“…This corroborates with the findings of other workers [17,20] who also observed no correlation between aggR and biofilm formation. However, Mohamed et al [12] observed that isolates carrying aggR alone or in combination with other virulence genes were strongly associated with biofilm formation. Similarly, other virulence genes except set1A were also not associated with biofilm formation in the present study.…”