Isolation of Shiga toxin-producing Escherichia coli harboring variant Shiga toxin genes from seafood

Sanitary status and water quality of some drinking water sources and antibiogram of Shiga toxin-producing Escherichia coli O157:H7 isolated from Shika, Zaria, Nigeria

This study assessed the sanitary condition and quality of selected wells and boreholes in Shika, Zaria Nigeria. Fifty samples each were collected during the dry and wet seasons. This involved sanitary survey, water quality assessment, isolation and characterization of Shiga toxin-producing Escherichia coli O157:H7 (STEC) and, antibiogram assay. Based on the risk of contamination, wells (72%) had a high risk of contamination, while boreholes (44%) had low risk of contamination. Their physicochemical quality varied with season and location, and mean total coliform (TC) and faecal coliform (FC) were significantly lower in the dry season (p < 0.05). STEC were isolated from only wells with a prevalence of 4%, and exhibited a multidrug resistance pattern (amoxicillin, erythromycin and tetracycline). There was a strong positive correlation between sanitary status and water quality. The high- and very high-risk categories (wells) were strongly correlated with TC, FC, BOD, phosphate, turbidity and pH.              .

Prevalence and Implications of Shiga Toxin-Producing E. coli in Farm and Wild Ruminants

Shiga-toxin-producing Escherichia coli (STEC) is a food-borne pathogen that causes human gastrointestinal infections across the globe, leading to kidney failure or even death in severe cases. E. coli are commensal members of humans and animals' (cattle, bison, and pigs) guts, however, may acquire Shiga-toxin-encoded phages. This acquisition or colonization by STEC may lead to dysbiosis in the intestinal microbial community of the host. Wildlife and livestock animals can be asymptomatically colonized by STEC, leading to pathogen shedding and transmission. Furthermore, there has been a steady uptick in new STEC variants representing various serotypes. These, along with hybrids of other pathogenic E. coli (UPEC and ExPEC), are of serious concern, especially when they possess enhanced antimicrobial resistance, biofilm formation, etc. Recent studies have reported these in the livestock and food industry with minimal focus on wildlife. Disturbed natural habitats and changing climates are increasingly creating wildlife reservoirs of these pathogens, leading to a rise in zoonotic infections. Therefore, this review comprehensively surveyed studies on STEC prevalence in livestock and wildlife hosts. We further present important microbial and environmental factors contributing to STEC spread as well as infections. Finally, we delve into potential strategies for limiting STEC shedding and transmission.

Virulence and antimicrobial-resistance of shiga toxin-producing E. coli (STEC) Isolated from edible shellfish and its public health significance

Shiga toxin-producing E. coli (STEC) are an important cause of foodborne illness in humans with infections ranging from mild non-bloody diarrhea to bloody diarrhea (BD) and hemolytic uremic syndrome (HUS). This study aimed to investigate the distribution of STEC in shellfish from coastal shores of Lake Timsah in Ismailia Governorate, Egypt and its probable hazard to seafood consumers. Samples from the external surface and tissues of shrimp (n = 45), crabs (n = 45), and oysters (n = 45) batches were examined bacteriologically for the presence of STEC and tested for their antibiotic sensitivity. Moreover, occurrence of virulence genes was determined via detection of stx1, stx2 and eaeA genes using PCR. Overall, E. coli and presumptive STEC isolates (from CHROMagar) were identified from the surface (55.6 and 5.9%) and tissues (42.2 and 8.9%) of the examined shellfish batches, respectively. Five STEC isolates had been confirmed and found belonging to O26:H11, O125:H6, O146:H21, and O159 serogroups, those were 4 isolates from tissues of the three shellfish species and one isolate from the crab surface. The STEC isolates were multi-drug resistant, showing complete resistance to; penicillins, amoxycillin/clavulanic acid, colistin, fosfomycin, ceftriaxone, ciprofloxacin, and tetracycline, however, they were sensitive to gentamycin except O159 serogroup. The current study revealed low level of contamination of shellfish from coastal shores of Lake Timsah with STEC, however, it also highlights the extreme level of antimicrobial resistance exhibited by the presumptive and confirmed STEC isolates which is very hazardous for seafood consumers in the study area.

Carbapenem-resistant Escherichia coli from shrimp and salmon available for purchase by consumers in Canada: a risk profile using the Codex framework

Resistance to carbapenems in human pathogens is a growing clinical and public health concern. The carbapenems are in an antimicrobial class considered last-resort, they are used to treat human infections caused by multidrug-resistant Enterobacterales, and they are classified by the World Health Organization as 'High Priority Critically Important Antimicrobials'. The presence of carbapenem-resistant Enterobacterales (CREs) of animal-origin is of concern because targeted studies of Canadian retail seafood revealed the presence of carbapenem resistance in a small number of Enterobacterales isolates. To further investigate this issue, a risk profile was developed examining shrimp and salmon, the two most important seafood commodities consumed by Canadians and Escherichia coli, a member of the Enterobacterales order. Carbapenem-resistant E. coli (CREc) isolates have been identified in shrimp and other seafood products. Although carbapenem use in aquaculture has not been reported, several classes of antimicrobials are utilised globally and co-selection of antimicrobial-resistant microorganisms in an aquaculture setting is also of concern. CREs have been identified in retail seafood purchased in Canada and are currently thought to be uncommon. However, data concerning CRE or CREc occurrence and distribution in seafood are limited, and argue for implementation of ongoing or periodic surveillance.

Survival of the blaNDM-harbouring Escherichia coli in tropical seawater and conjugative transfer of resistance markers

Anthropogenic contamination of coastal-marine water is responsible for introducing multidrug-resistant bacteria such as the pNDM-harbouring Escherichia coli into the seafood chain. This study was conducted to understand the survivability of a multidrug-resistant, the New Delhi Metallo-β-lactamase-producing E. coli (AS-EC121) in tropical seawater at room temperature (28-32 °C) compared to E. coli K12 strain. The experimental and control strains were inoculated at 6 log CFU/ml level into seawater. After an initial sharp decline in counts, AS-EC121 and K12 strains showed a gradual loss of viability after week-1 of inoculation. AS-EC121 was undetectable after day-56, while K12 colonies disappeared a week later, from day-63. The conjugation experiment revealed that pNDM was transferable to a recipient E. coli strain in seawater. This study suggests that the multidrug-resistant, pNDM-harbouring E. coli is able to survive in seawater for over 2 months stably maintaining the resistance plasmid. The resistance genotypes do not seem to compromise the survivability of MDR E. coli and the stability of plasmid provides ample opportunities for dissemination of plasmids among co-inhabiting bacteria in the coastal-marine environments.

E. coli Is a Poor End-Product Criterion for Assessing the General Microbial Risk Posed From Consuming Norovirus Contaminated Shellfish

The fecal indicator organism (FIO) Escherichia coli is frequently used as a general indicator of sewage contamination and for evaluating the success of shellfish cleaning (depuration) processes. To evaluate the robustness of this approach, the accumulation, retention, and depuration of non-pathogenic E. coli, pathogenic E. coli O157:H7 and norovirus GII (NoV GII) RNA were evaluated using a combination of culture-based (E. coli) and molecular methods (E. coli, NoV GII) after exposure of mussels (Mytilus edulis) to water contaminated with human feces. We simulated water contamination after a point-source release from a combined sewer overflow (CSO) where untreated wastewater is released directly into the coastal zone. All three microbiological indicators accumulated rapidly in the mussels, reaching close to maximum concentration within 3 h of exposure, demonstrating that short CSO discharges pose an immediate threat to shellfish harvesting areas. Depuration (72 h) in clean water proved partially successful at removing both pathogenic and non-pathogenic E. coli from shellfish tissue, but failed to eradicate NoV GII RNA. We conclude that current EU standards for evaluating microbiological risk in shellfish are inadequate for protecting consumers against exposure to human norovirus GII found in polluted marine waters.

Genomic features and antimicrobial resistance patterns of Shiga toxin-producing Escherichia coli strains isolated from food in Chile

Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathogen that causes severe illness in humans, often associated with foodborne outbreaks. Antimicrobial resistance among foodborne E. coli has increased over the last decades becoming a public health issue. In this study, the presence and features of STEC were investigated in samples of meat, seafood, vegetables and ready-to-eat street-vended food collected in Chile, using a genomic and microbiological approach. Phenotypic and genotypic antimicrobial resistance profiles were determined, and serotype, phylogroup, sequence type (ST) and phylogenomics were predicted using bioinformatic tools. Three thousand three hundred samples collected in 2019 were screened, of which 18 were positive for STEC strains (0.5%), with stx2a (61.1%) being the predominant stx subtype. The presence of the virulence genes lpfA (100%), iha and ehaA (94.4%), and ehxA, hlyA and saa (83.3%) was confirmed among the STEC strains; the Locus of adhesion and autoaggregation (LAA) was predicted in 14 (77.8%) strains. Strains displayed resistance to colistin (100%), and intermediate resistance to enrofloxacin (11.1%) and chloramphenicol (5.6%). In this regard, mutations in the two-component regulatory system genes pmrA (S29G), pmrB (D283G) and phoP (I44L), and the presence of the qnrB19 gene were confirmed. STEC strains belonged to ST11231 (38.9%), ST297 and ST58 (16.7% each), and ST1635, ST11232, ST446, ST442 and ST54 (5.6% each), and the most frequently detected serotypes were O113:H21 (44.4%), O130:H11 and O116:H21 (16.7% each), and O174:H21 (11.1%). Strains belonging to the international ST58 showed genomic relatedness with worldwide strains from human and non-human sources. Our study reports for the first time the genomic profile of STEC strains isolated from food in Chile, highlighting the presence of international clones and sequence types commonly associated with human infections in different geographical regions, as well as the convergence of virulence and resistance in STEC lineages circulating in this country.

Isolation and characterization of Escherichia coli serotype O157:H7 and other verotoxin-producing E. coli in healthy Indian cattle

Background and Aim:

Cattle are the main reservoir of Escherichia coli O157:H7 and other verotoxigenic E. coli (VTEC); therefore, there is an increased risk of infection to humans by either direct or indirect mode of transmissions. However, the prevalence of E. coli O157:H7 in the healthy cattle population of India is yet to be ascertained. This study aimed to screen the dairy cattle in and around Pune, Maharashtra, India, for verotoxin-producing E. coli O157:H7.

Materials and Methods:

A total of 257 rectal swabs were collected from 15 different organized and unorganized dairy farms of Pune during the period, January-March 2015. The screening involved enrichment in EC broth followed by differential identification on MacConkey sorbitol agar. The presumptive positive isolates were further confirmed by multiplex polymerase chain reaction (PCR) using primers specific to rfbE (O157), fliC (H7), VT1 (MK1), and VT2 (MK2). Vero-toxicity and antibiotic sensitivity were examined in PCR confirmed isolates.

Results:

Out of the 257 samples analyzed, 1.9% (2/105) were positive for O157:H7 and 39% (41/105) were positive for VTEC. Two PCR confirmed positive O157:H7 strains and two randomly selected PCR-positive VT strains exhibited in vitro cytopathic effect on Vero cells on day-7 post-inoculation. Antibiotic sensitivity profiling of O157:H7 strains exhibited resistance against penicillin G, kanamycin, ampicillin, tetracycline, gentamycin, cefotaxime, streptomycin, and piperacillin.

Conclusion:

These findings reveal the presence of pathogenic E. coli O157:H7 in the healthy cattle of Pune; in a situation, wherein regular surveillance for O157:H7 is not a norm. Therefore, the findings presented herein warrant routine surveillance and public awareness to prevent the transfer of such pathogens and manage health risks to the public.

Recent Updates on Outbreaks of Shiga Toxin-Producing Escherichia coli and Its Potential Reservoirs

Following infection with certain strains of Shiga toxin-producing Escherichia coli (STEC), particularly enterohemorrhagic ones, patients are at elevated risk for developing life-threatening extraintestinal complications, such as acute renal failure. Hence, these bacteria represent a public health concern in both developed and developing countries. Shiga toxins (Stxs) expressed by STEC are highly cytotoxic class II ribosome-inactivating proteins and primary virulence factors responsible for major clinical signs of Stx-mediated pathogenesis, including bloody diarrhea, hemolytic uremic syndrome (HUS), and neurological complications. Ruminant animals are thought to serve as critical environmental reservoirs of Stx-producing Escherichia coli (STEC), but other emerging or arising reservoirs of the toxin-producing bacteria have been overlooked. In particular, a number of new animal species from wildlife and aquaculture industries have recently been identified as unexpected reservoir or spillover hosts of STEC. Here, we summarize recent findings about reservoirs of STEC and review outbreaks of these bacteria both within and outside the United States. A better understanding of environmental transmission to humans will facilitate the development of novel strategies for preventing zoonotic STEC infection.

High Prevalence of Multiple Antibiotic-Resistant, Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli in Fresh Seafood Sold in Retail Markets of Mumbai, India

In this study, fresh seafood in retail markets was investigated for the antibiotic susceptibility patterns of the faecal indicator Escherichia coli and distribution of important β-lactamase encoding genes. E. coli were isolated from 50 (37 fish and 13 shellfish) fresh seafood samples and studied with respect to the phenotypic and genotypic characters of antibiotic resistance. Of 475 E. coli isolates from fresh seafood, 71.58% exhibited extended-spectrum β-lactamase (ESBL)-positive phenotypes. A high percentage of isolates were resistant to indicator cephalosporins cefotaxime (95%), cefpodoxime (90.88%) and ceftazidime (90.29%). Relatively higher susceptibilities were recorded against imipenem (74.41%), cefoxitin (66.76%) and meropenem (51.18%). The multiple antibiotic resistance (MAR) index of 97.35% of the isolates was above 0.18. The ESBL genes bla_CTX-M, bla_SHV and bla_TEM were detected in 62.37%, 23.35% and 2.6% of E. coli isolates, respectively. The ESBL-producing isolates also harboured the metallo-β-lactamase-encoding genes bla_OXA (7.06%), bla_NDM (4.42%) and bla_VIM (0.88%). This study highlights the risk of dissemination of multidrug resistant E. coli in seafood consumer communities and also the need to improve the hygiene of the coastal waters, landing centres and the retail markets.

Effect of chlorine on cultivability of Shiga toxin producing Escherichia coli (STEC) and β-lactamase genes carrying E. coli and Pseudomonas aeruginosa

The worldwide spread of toxin-producing and multi-drug resistant bacteria in water, food and the environment is considered a major threat to human health. Drinking water quality is controlled by inspection of fecal indicators presence whereby viable contaminants will be efficiently reduced by chlorination which is a common process for disinfection. However, the all-out efficiency is arguable, because bacterial regrowth has been documented after disinfection. In this study, we investigated the stability of Shiga toxin producing Escherichia coli (STEC) and β-lactamase expressing E. coli and Pseudomonas aeruginosa isolates, both equipped with multiple or single β-lactamase resistance genes. The aim of the study was to analyze the efficiency of chlorine (Cl₂) disinfection against shigatoxigenic or β-lactamase producing bacteria. Cl₂ reacts with the bacterial cells after first contact. Counts of antibiotic resistant E. coli were lower after short than upon extended Cl₂ treatment. P. aeruginosa counts decreased moderately upon 15-60 min treatment with 1.2 mg Cl₂/l, while cells adapted to tap water were not cultivable anymore. We assume that the bacterial physiology changed to a temporary non-cultivatable state at first Cl₂ contact followed by resuscitation of some cells at later stages. STEC viability went down continuously at low Cl₂ concentrations and these toxigenic E. coli isolates exhibited slightly increased stability to Cl₂ treatment compared with non-toxigenic E. coli. Controlling the efficiency of disinfection, realistic counts of cultivatable cells are achieved after extended Cl₂ action.