Biofilm-Forming Abilities of Shiga Toxin-Producing Escherichia coli Isolates Associated with Human Infections

Abstract

bForming biofilms may be a survival strategy of Shiga toxin-producing Escherichia coli to enable it to persist in the environment and the food industry. Here, we evaluate and characterize the biofilm-forming ability of 39 isolates of Shiga toxin-producing Escherichia coli isolates recovered from human infection and belonging to seropathotypes A, B, or C. The presence and/or production of biofilm factors such as curli, cellulose, autotransporter, and fimbriae were investigated. The polymeric matrix of these biofilms was analyzed by confocal microscopy and by enzymatic digestion. Cell viability and matrix integrity were examined after sanitizer treatments. Isolates of the seropathotype A (O157:H7 and O157:NM), which have the highest relative incidence of human infection, had a greater ability to form biofilms than isolates of seropathotype B or C. Seropathotype A isolates were unique in their ability to produce cellulose and poly-N-acetylglucosamine. The integrity of the biofilms was dependent on proteins. Two autotransporter genes, ehaB and espP, and two fimbrial genes, z1538 and lpf2, were identified as potential genetic determinants for biofilm formation. Interestingly, the ability of several isolates from seropathotype A to form biofilms was associated with their ability to agglutinate yeast in a mannose-independent manner. We consider this an unidentified biofilmassociated factor produced by those isolates. Treatment with sanitizers reduced the viability of Shiga toxin-producing Escherichia coli but did not completely remove the biofilm matrix. Overall, our data indicate that biofilm formation could contribute to the persistence of Shiga toxin-producing Escherichia coli and specifically seropathotype A isolates in the environment. Shiga toxin-producing Escherichia coli (STEC) strains, including enterohemorrhagic E. coli (EHEC), are food-borne and waterborne human enteric pathogens responsible for infections. They are associated with important public health concerns in developed countries. Symptoms associated with STEC infections range from abdominal cramps and bloody diarrhea to postinfectious complications, such as hemolytic-uremic syndrome (HUS). HUS, a life-threatening complication of STEC infections, is a consequence of Shiga toxin production. According to the Public Health Agency of Canada (PHAC), more than 30,000 cases of STEC infections occur each year in Canada (1). Environmentally, the main reservoir for STEC is cattle. Transmission of STEC to humans typically is associated with the consumption of contaminated food such as undercooked beef, fresh produce, unpasteurized milk, or contaminated drinking water (2), but these pathogens also can be transmitted from person to person or via direct contact with animals or their feces.The 2003 Karmali seropathotype model classifies STEC into seropathotypes based on their reported incidence in human disease, outbreaks, and/or association with the development of severe symptoms in humans (3). Serotypes frequently responsible for hemorrhagic colitis (HC) and HUS, ...

Autotransporter Adhesins in Escherichia coli Pathogenesis

“…[90] In addition to imparting these phenotypes, both EhaA and EhaB were associated with the formation of biofilms. [90,92] A role of EhaB in biofilm formation is consistent with the same function for UpaC which is its positional orthologue in UPEC CFT073. [52] Much less is known with regards to both EhaC and EhaD.…”

“…EhaA was further found to be able to self‐associate, which conferred an aggregation phenotype to E. coli . In addition to imparting these phenotypes, both EhaA and EhaB were associated with the formation of biofilms . A role of EhaB in biofilm formation is consistent with the same function for UpaC which is its positional orthologue in UPEC CFT073 …”

The Helicobacter pylori biofilm involves a multi-gene stress-biased response including a structural role for flagella

“…To further characterize the EPS that composed the SS1 biofilm matrix, BOBO-3 and FilmTracer SYPRO Ruby biofilm matrix stains were used to stain extracellular DNA (eDNA) and extracellular proteins, respectively as described previously (29,30). Both of these molecules extensively stained the biofilm EPS, consistent with the idea that the H. pylori SS1 biofilm matrix contains significant amount of eDNA and extracellular proteins (Fig.…”

Escherichia coliO157:H7 responds to phosphate starvation by modifying LPS involved in biofilm formation

“…The biofilm formation was investigated as described previously (49) with modifications. Overnight cultures at 37°C in LB media were diluted (1:100) in 5 ml of morpholine propanesulfonic acid (MOPS) minimal medium (Teknova) containing 0.2% (wt/vol) glycerol, thiamine (0.1 μg/mL), and 1.32 mM (MOPS high Pi) KH 2 PO 4 or in M9 medium with 0.2% (wt/vol) glycerol and minerals (1.16 mM MgSO 4 , 2 µM FeCl 3 , 8 µM CaCl 2 , and 16 µM MnCl 2 ) and incubated for 24 h at 37°C with antibiotics when required.…”

“…Stained biofilms were visualized by confocal laser scanning microscopy at 40X (CLSM; FV1000 IX81; Olympus, Markham, ON, Canada) as previously described (49).…”