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.

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    • "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). "
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    Microbiology 09/2014; 160(Pt_12). DOI:10.1099/mic.0.075887-0 · 2.56 Impact Factor
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    • "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). "
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    Frontiers in Microbiology 07/2014; 5:317. DOI:10.3389/fmicb.2014.00317 · 3.99 Impact Factor
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    • "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). "
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