Sab, a Novel Autotransporter of Locus of Enterocyte Effacement-Negative Shiga-Toxigenic Escherichia coli O113:H21, Contributes to Adherence and Biofilm Formation

Research Centre for Infectious Diseases, University of Adelaide, South Australia.
Infection and immunity (Impact Factor: 3.73). 07/2009; 77(8):3234-43. DOI: 10.1128/IAI.00031-09
Source: PubMed


Shiga-toxigenic Escherichia coli (STEC) strains cause serious gastrointestinal disease, which can lead to potentially life-threatening systemic complications
such as hemolytic-uremic syndrome. Although the production of Shiga toxin has been considered to be the main virulence trait
of STEC for many years, the capacity to colonize the host intestinal epithelium is a crucial step in pathogenesis. In this
study, we have characterized a novel megaplasmid-encoded outer membrane protein in locus of enterocyte effacement (LEE)-negative
O113:H21 STEC strain 98NK2, termed Sab (for STEC autotransporter [AT] contributing to biofilm formation). The 4,296-bp sab gene encodes a 1,431-amino-acid protein with the features of members of the AT protein family. When expressed in E. coli JM109, Sab contributed to the diffuse adherence to human epithelial (HEp-2) cells and promoted biofilm formation on polystyrene
surfaces. A 98NK2 sab deletion mutant was also defective in biofilm formation relative to its otherwise isogenic wild-type parent, and this was
complemented by transformation with a sab-carrying plasmid. Interestingly, an unrelated O113:H21 STEC isolate that had a naturally occurring deletion in sab was similarly defective in biofilm formation. PCR analysis indicated that sab is present in LEE-negative STEC strains belonging to serotypes/groups O113:H21, O23, and O82:H8. These findings raise the
possibility that Sab may contribute to colonization in a subset of LEE-negative STEC strains.

Download full-text


Available from: James C Paton
  • Source
    • "It increases the adherence of E. coli O157 : H7 strains to the intestine of calves (Dziva et al., 2007), but may also downregulate the human complement system by cleavage of C3/C3b and C5 (Orth et al., 2010). The STEC autotransporter mediating biofilm formation (Sab) is encoded by the sab gene located on a megaplasmid that is present in LEEnegative non-O157 STEC (Herold et al., 2009). It mediates adherence to human epithelial cells as well as biofilm formation on polystyrene beads, but its prevalence in food isolates is low (Buvens & Piérard, 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The ability of bacteria to bind different compounds and to adhere to biotic and abiotic surfaces provides them with a range of advantages, such as colonization of various tissues, internalisation, avoidance of an immune response and survival and persistence in the environment. A variety of bacterial surface structures are involved in this process and these promote bacterial adhesion in a more or less specific manner. In this review, we will focus on those surface adhesins and exopolymers in selected foodborne pathogens that are involved mainly in primary adhesion. Their role in biofilm development will also be considered when appropriate. Both the clinical impact and implications for food safety of such adhesion will be discussed.
    Full-text · Article · Sep 2014 · Microbiology
  • Source
    • "Screens in STEC strains have identified 9 autotransporter genes: chromosome encoded agn43, cah, ehaA, ehaB, ehaD, ehaG, saa, and sab and plasmid-encoded espP (Torres et al., 2002; Wells et al., 2008, 2009; Herold et al., 2009; Puttamreddy et al., 2010). The protein products of each of these genes have been associated with biofilm formation (Torres et al., 2002; Wells et al., 2008, 2009; Herold et al., 2009; Puttamreddy et al., 2010). A comparative study of three autotransporter genes (agn43, cah, and ehaA) among 51 STEC strains found that the presence of autotransporter genes within the genome was variable among STEC serotypes (Biscola et al., 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Escherichia coli is a heterogeneous species that can be part of the normal flora of humans but also include strains of medical importance. Among pathogenic members, Shiga-toxin producing E. coli (STEC) are some of the more prominent pathogenic E. coli within the public sphere. STEC disease outbreaks are typically associated with contaminated beef, contaminated drinking water, and contaminated fresh produce. These water- and food-borne pathogens usually colonize cattle asymptomatically; cows will shed STEC in their feces and the subsequent fecal contamination of the environment and processing plants is a major concern for food and public safety. This is especially important because STEC can survive for prolonged periods of time outside its host in environments such as water, produce, and farm soil. Biofilms are hypothesized to be important for survival in the environment especially on produce, in rivers, and in processing plants. Several factors involved in biofilm formation such as curli, cellulose, poly-N-acetyl glucosamine, and colanic acid are involved in plant colonization and adherence to different surfaces often found in meat processing plants. In food processing plants, contamination of beef carcasses occurs at different stages of processing and this is often caused by the formation of STEC biofilms on the surface of several pieces of equipment associated with slaughtering and processing. Biofilms protect bacteria against several challenges, including biocides used in industrial processes. STEC biofilms are less sensitive than planktonic cells to several chemical sanitizers such as quaternary ammonium compounds, peroxyacetic acid, and chlorine compounds. Increased resistance to sanitizers by STEC growing in a biofilm is likely to be a source of contamination in the processing plant. This review focuses on the role of biofilm formation by STEC as a means of persistence outside their animal host and factors associated with biofilm formation.
    Full-text · Article · Jul 2014 · Frontiers in Microbiology
  • Source
    • "The subAB operon from the positive strains was typed using the primer pairs SubAF/ RTsubABR (Michelacci et al., 2013; Paton et al., 2004) and subA_startF/RTsubABR (Michelacci et al., 2013; Paton et al., 2004), able to specifically detect the prototype subAB 1 or the allelic variant subAB 2 , respectively. The presence of saa, tia and sab was tested as previously described (Herold et al., 2009; Tozzoli et al., 2010). The identification of stx1 and stx2 subtypes was performed using a recently developed PCR-based method (Scheutz et al., 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Subtilase cytotoxin (SubAB) is an AB5 toxin produced by Shiga toxin (Stx)-producing Escherichia coli (STEC) strains usually lacking the eae gene product intimin. Two allelic variants of SubAB encoding genes have been described: subAB1, located on a plasmid, and subAB2, located on a pathogenicity island (PAI) together with tia gene. While subAB1 has been reported to be more frequent among bovine strains, subAB2 has been mainly associated with strains from small ruminants. We investigated the presence of the two variants of subAB among 59 eae-negative STEC from large game animals (deer and wild boar) and their meat and meat products in order to assess the role of other species in the epidemiology of subAB-positive, eae-negative STEC. For this approach, the strains were PCR-screened for the presence of subAB, including the specific detection of both allelic variants, for the presence of saa, tia and sab, and for stx subtyping. Overall, subAB genes were detected in 71.2% of the strains: 84.1% of the strains from deer and 33.3% of the strains from wild boar. Most of them (97.6%) possessed subAB2 and most of these subAB2-positive strains (92.7%) were also positive for tia and negative for saa, suggesting the presence of the subAB2-harbouring PAI. Subtype stx2b was present in most of the strains (67.8%) and a statistically significant association could be established between subAB2 and stx2b. Our results suggest that large game animals, mainly deer, may represent an important animal reservoir of subAB2-positive, eae-negative STEC, and also highlight the risk of human infection posed by the consumption of large game meat and meat products.
    Full-text · Article · Jul 2013 · Veterinary Microbiology
Show more