Characterization of Non-O157 Escherichia coli from Cattle Faecal Samples in the North-West Province of South Africa

Abstract

Escherichia coli are commensal bacteria in the gastrointestinal tract of mammals, but some strains have acquired Shiga-toxins and can cause enterohemorrhagic diarrhoea and kidney failure in humans. Shiga-toxigenic E. coli (STEC) strains such as E. coli O157:H7 and some non-O157 strains also contain other virulence traits, some of which contribute to their ability to form biofilms. This study characterized non-O157 E. coli from South African cattle faecal samples for their virulence potential, antimicrobial resistance (AMR), biofilm-forming ability, and genetic relatedness using culture-based methods, pulsed-field gel electrophoresis (PFGE), and whole genome sequencing (WGS). Of 80 isolates screened, 77.5% (62/80) possessed Shiga-toxins genes. Of 18 antimicrobials tested, phenotypic resistance was detected against seven antimicrobials. Resistance ranged from 1.3% (1/80) for ampicillin-sulbactam to 20% (16/80) for tetracycline. Antimicrobial resistance genes were infrequently detected except for tetA, which was found in 31.3% (25/80) and tetB detected in 11.3% (9/80) of isolates. Eight biofilm-forming associated genes were detected in STEC isolates (n = 62) and two non-STEC strains. Prevalence of biofilm genes ranged from 31.3% (20/64) for ehaAβ passenger to 100% for curli structural subunit (csgA) and curli regulators (csgA and crl). Of the 64 STEC and multi-drug resistant isolates, 70.3% (45/64) and 37.5% (24/64) formed strong biofilms on polystyrene at 22 and 37 °C, respectively. Of 59 isolates screened by PFGE, 37 showed unique patterns and the remaining isolates were grouped into five clusters with a ≥90% relatedness. In silico serotyping following WGS on a subset of 24 non-O157 STEC isolates predicted 20 serotypes comprising three novel serotypes, indicating their diversity as potential pathogens. These findings show that North West South African cattle harbour genetically diverse, virulent, antimicrobial-resistant and biofilm-forming non-O157 E. coli. Biofilm-forming ability may increase the likelihood of persistence of these pathogens in the environment and facilitate their dissemination, increasing the risk of cross contamination or establishment of infections in hosts.

Biofilm formation by South African non-O157 Shiga toxigenic Escherichia coli on stainless steel coupons

“…In our previous study (Bumunang et al 2019), we detected biofilm forming genes via PCR and in silico whole genome sequencing of these isolates (supplementary Table S1 1 ). Molecular responses are known to play essential roles in biofilm-forming ability of non-O157 STEC in different environmental conditions (Farfan and Torres 2012).…”

“…The STEC strains used in this study were selected among isolates from a previous study (Bumunang et al 2019) based on novelty (wzx-Onovel5:H19), multidrug resistance (streptomycin, tetracycline, ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, nalidixic acid, and norfloxacin; O154:H10), and ability to form intermediate to strong biofilm on polystyrene at 22 and 37°C (O26:H11, O116:H21, O129:H21, and O129:H23). These cultures were stored as glycerol stocks at -80°C.…”

“…The bacterial isolates selected in the present study comprised those isolated from cattle faeces collected in North West Province of South Africa (Bumunang et al 2019). Additionally, the potential effects of biofilmassociated genes for these isolates previously screened via PCR and predicted using in silico whole genome sequence analysis are discussed.…”

Interactions of Shiga toxin-producing Escherichia coli with leafy green vegetables

“…Different adhesive structures account for the capacity of STEC to bind to several surfaces, and autotransporters are important factors related to adherence and biofilm formation of non-O157 STEC [25]. A high occurrence of flu genes has been described among non-O157 STEC strains, but its presence was not statistically related to biofilm formation [26,27]. In this study, it was shown that the adherence of O105:H18 to rocket leaves significantly decreased when genes related to Sab were deleted, confirming previous observations on the participation of this AT in the adherence ability of non-O157 isolates [6].…”

Activity of Bacteriophage and Complex Tannins against Biofilm-Forming Shiga Toxin-Producing Escherichia coli from Canada and South Africa

“…Food products contaminated with Shiga toxin-producing Escherichia coli (STEC) have caused serious outbreaks in humans for decades [2][3][4]. For example, STEC serotype O113:H21, which has been associated with human illness [5,6] and O154:H10, which has the ability to colonize and form biofilms on food contact surfaces under different environmental conditions, also poses a health risk [7,8]. The persistence of STEC biofilms on food contact surfaces is a contributing factor to the contamination of food products [9,10].…”