Shigatoxigenic and atypical enteropathogenic Escherichia coli in fish for human consumption

Atwill E, Jeamsripong S. Antimicrobial resistance, virulence profile, and genetic analysis of ESBL-producing Escherichia coli isolated from Nile tilapia in fresh markets and supermarkets in Thailand

This study investigated the prevalence and antimicrobial resistance (AMR) of Escherichia coli (E. coli) in Nile tilapia from fresh markets and supermarkets. A total of samples (n = 828) were collected from Nile tilapia including fish flesh (n = 276), liver and kidney (n = 276), and intestine (n = 276). Overall prevalence of fecal coliforms (61.6%) and E. coli (53.0%) were observed. High prevalence of E. coli was found in the intestine (71.4%), followed by the liver and kidney (45.7%). The highest prevalence of resistance was commonly found against tetracycline (78.5%), ampicillin (72.8%), and sulfamethoxazole (45.6%) with resistance to only tetracycline (15.2%) as the most common antibiogram. The prevalence of multidrug resistance (MDR) (54.4%) and Extended-spectrum beta-lactamases (ESBLs) (5.7%) were examined. The predominant virulence genes (n = 158) were st (14.6%), followed by eaeA (0.6%). The blaTEM (73.4%), tetA (65.2%), and qnrS (57.6%). There is statistical significance between Nile tilapia from fresh markets and supermarkets. Based on logistic regression analysis, ampicillin-resistant E. coli was statistically associated with the phenotypic resistance to tetracycline and trimethoprim, and the presence of blaTEM and tetA (p < 0.05). Further investigation of AMR transference and their mechanisms is needed for AMR control.

Prevalence and co-infections of pathogenic bacteria in Nile tilapia broodstock farms: implications for aquaculture management in Togo

This study aimed to evaluate the prevalence of E. coli, Pseudomonas spp., and Enterococcus spp. in Nile tilapia broodstock farms in Togo and their association with fish diseases. In total, 60 samples were collected from two tilapia broodstock farms, including 40 broodstock tilapia and 20 water samples. Each farm had concrete tanks supplied with water from two drills. Of the 40 fish samples, 20 were healthy, and the other 20 were diseased. Microbiological analysis of samples was conducted using standardized methods. The study revealed significant contamination in all collected water samples, detecting multiple bacterial populations. Bacterial infections were more prevalent in symptomatic fish, with 85% exhibiting co-infections (df = 1, χ2 = 7.03, p = 0.008). Contamination levels varied among sample types, with higher counts observed in wastewater (E. coli: 0-300 CFU/mL, Pseudomonas spp.: 3-300 CFU/mL, Enterococcus spp.: 0-55 × 102 CFU/mL) compared to drilling water (Pseudomonas spp.: 0-300 CFU/mL, E. coli: 3-400 CFU/mL, Enterococcus spp.: 0-14 × 102 CFU/mL), and intestinal samples (E. coli: 0-120 × 102 CFU/mL, Enterococcus spp.: 0-170 × 102 CFU/mL, Pseudomonas spp.: 0-60 × 102 CFU/mL) (df = 21, χ2 = 59.31, p < 0.000). Our findings emphasize the significant prevalence of pathogenic bacteria in Nile tilapia broodstock farms in Togo, highlighting the importance of water quality management and infection control strategies. Further studies are required to develop appropriate prevention strategies.

Phenotypic and genotypic characterization of pathogenic Escherichia coli identified in resistance mapping of β-lactam drug-resistant isolates from seafood along Tuticorin coast

The ubiquity of pathogenic E. coli isolate possessing antimicrobial resistance was investigated in seafood samples procured from major seafood supply chain markets established for export and domestic consumption along Tuticorin coast. Out of 63 seafood samples examined, 29 (46%) were found to be contaminated by pathogenic E. coli harbouring one or more genes of virulent potential. Based on virulome profiling, 9.55% of isolates belonged to enterotoxigenic E. coli (ETEC), 8.08% to enteroaggregative E. coli (EAEC), 7.35% to enterohemorrhagic E. coli (EHEC), 2.20% to enteropathogenic E. coli (EPEC), and 2.20% to uropathogenic E. coli (UPEC). All the 34 virulome positive and haemolytic pathogenic E. coli have been serogrouped as O119, O76, O18, O134, O149, O120, O114, O25, O55, O127, O6, O78, O83, O17 and clinically significant O111, O121, O84, O26, O103, and O104 (non-O157 STEC) serotypes in this study. Multi-drug resistance (MDR) (≥ 3 antibiotic classes/sub-classes) was exhibited in 38.23% of the pathogenic E. coli, and 17.64% were extensive drug resistant (XDR). Extended spectrum of β-lactamase (ESBL) genotypes were confirmed in 32.35% isolates and 20.63% isolates harboured ampC gene. One sample (Penaeus semisulcatus) collected from landing centre (L1) harboured all ESBL genotypes bla_CTX-M, bla_SHV, bla_TEM, and ampC genes. Hierarchical clustering of isolates revealed the separation of ESBL isolates into three clusters and non-ESBL isolates into three clusters based on phenotypic and genotypic variations. Based on dendrogram analysis on antibiotic efficacy pattern, carbapenems and β-lactam inhibitor drugs are the best available treatment for ESBL and non-ESBL infections. This study emphasizes the significance of comprehensive surveillance of pathogenic E. coli serogroups that pose serious threat to public health and compliance of AMR antimicrobial resistant genes in seafood that hinder seafood supply chain.

Difficulties in the Modeling of E. coli Spreading from Various Sources in a Coastal Marine Area

Coastal and transitional waters are often used as bathing waters. In many regions, such activities play an important economic role. According to the European Union Bathing Water Directive (2006/7/EC) (BWD) the concentration of Escherichia coli in bathing water exceeding 500 CFU·100 mL⁻¹ poses a high risk for bathers’ health. In order to safeguard public health, microbiological environmental monitoring is carried out, which has recently been supported or replaced by mathematical models detailing the spread of sanitary contamination. This study focuses on the problems and limitations that can be encountered in the process of constructing a mathematical model describing the spread of biological contamination by E. coli bacteria in coastal seawater. This and other studies point to the following problems occurring during the process of building and validating a model: the lack of data on loads of sanitary contamination (often connected with multiple sources of biological contamination inflow) makes the model more complex; E. coli concentrations higher than 250 CFU·100 mL⁻¹ (low hazard for health) are observed very rarely, and are associated with great uncertainty; the impossibility of predicting the time and intensity of precipitation as well as stronger winds and rougher sea, which may be a significant source of E. coli. However, there is universal agreement that such models will be useful in managing bathing water quality and protecting public health, especially during big failures of the wastewater network.

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.

Zoonotic diseases of fish and their prevention and control

Fish and aquatic-derived zoonotic diseases have caused considerable problems in the aquaculture industry and fishery worldwide. In particular, zoonotic diseases can pose widespread threats to humans. With the world’s growing population and potential global trade of aquaculture and fish, the risk of environmental contamination and development of fish and aquatic-derived zoonoses in humans are increasing. The important causes of zoonoses include bacteria, parasites, viruses, and fungi. The zoonotic bacterial agents are divided into two main groups: Gram-positive (Mycobacteriaceae, Streptococcaceae, Erysipelothricaceae families) and Gram-negative (Aeromonadaceae, Vibrionaceae, Pseudomondaceae, Enterobacteriaceae, and Hafniaceae families). The premier parasitic agents include cestodes (tapeworm; e.g. Diphyllobothrium spp.), trematodes (fluke; e.g. Opisthorchis spp.), and nematodes (round worm; e.g. Anisakis spp.). In addition, protozoan organisms such as Cryptosporidium spp. are also considered fish-derived zoonotic pathogens. Two groups of fish-associated fungi causing basidiobolomycosis and sporotrichosis also pose a zoonotic risk for humans. The majority of the fish-derived zoonotic diseases are transmitted to humans mainly via the consumption of improperly cooked or raw fish or fish products. Therefore, the incidence of zoonotic diseases can be reduced by properly processing fish and fish products, e.g. by thermal (heat/freezing) treatment. The prevalence of zoonotic agents in fishes varies seasonally and should be regularly monitored to evaluate the prevalence of pathogens in both wild and cultured fish populations. This review focuses on the fish zoonotic agents/diseases and their control and prevention.

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.

Bacterial Diversity and Antibiotic Susceptibility of Sparus aurata from Aquaculture

In a world where the population continues to increase and the volume of fishing catches stagnates or even falls, the aquaculture sector has great growth potential. This study aimed to contribute to the depth of knowledge of the diversity of bacterial species found in Sparus aurata collected from a fish farm and to understand which profiles of diminished susceptibility to antibiotics would be found in these bacteria that might be disseminated in the environment. One hundred thirty-six bacterial strains were recovered from the S. aurata samples. These strains belonged to Bacillaceae, Bacillales Family XII. Incertae Sedis, Comamonadaceae, Enterobacteriaceae, Enterococcaceae, Erwiniaceae, Micrococcaceae, Pseudomonadaceae and Staphylococcaceae families. Enterobacter sp. was more frequently found in gills, intestine and skin groups than in muscle groups (p ≤ 0.01). Antibiotic susceptibility tests found that non-susceptibility to phenicols was significantly higher in gills, intestine and skin samples (45%) than in muscle samples (24%) (p ≤ 0.01) and was the most frequently found non-susceptibility in both groups of samples. The group of Enterobacteriaceae from muscles presented less decreased susceptibility to florfenicol (44%) than in the group of gills, intestine and skin samples (76%). We found decreased susceptibilities to β-lactams and glycopeptides in the Bacillaceae family, to quinolones and mupirocin in the Staphylococcaceae family, and mostly to β-lactams, phenicols and quinolones in the Enterobacteriaceae and Pseudomonadaceae families. Seven Enterobacter spp. and five Pseudomonas spp. strains showed non-susceptibility to ertapenem and meropenem, respectively, which is of concern because they are antibiotics used as a last resort in serious clinical infections. To our knowledge, this is the first description of species Exiguobacterium acetylicum, Klebsiella michiganensis, Lelliottia sp. and Pantoea vagans associated with S. aurata (excluding cases where these bacteria are used as probiotics) and of plasmid-mediated quinolone resistance qnrB19-producing Leclercia adecarboxylata strain. The non-synonymous G385T and C402A mutations at parC gene (within quinolone resistance-determining regions) were also identified in a Klebsiella pneumoniae, revealing decreased susceptibility to ciprofloxacin. In this study, we found not only bacteria from the natural microbiota of fish but also pathogenic bacteria associated with fish and humans. Several antibiotics for which decreased susceptibility was found here are integrated into the World Health Organization list of "critically important antimicrobials" and "highly important antimicrobials" for human medicine.

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.

Shiga toxin-producing Escherichia coli in the animal reservoir and food in Brazil

Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathotype associated with human gastrointestinal disease that may progress to severe complications. Ruminants, especially cattle, are the main reservoirs of STEC contaminating the environment and foods of animal or vegetable origin. Besides Shiga toxin, other virulence factors are involved in STEC virulence. O157:H7 remains the most frequent serotype associated with disease. In Brazil, the prevalence of STEC reaches values as high as 90% in cattle and 20% in meat products which may impact the Brazilian food export trade. However, only few reports are related to human disease. The stx1 gene prevails in cattle, whereas the stx2 gene is more frequent in food. Several STEC serotypes have been isolated from cattle and food in Brazil, including the O157:H7, O111:NT, NT:H19 as well as O26 and O103 serogroups. O113: H21 STEC strains are frequent in ruminants and foods but with no report in human disease. The virulence profile of Brazilian STEC strains from cattle and food suggests a pathogenic potential to humans, although some differences with clinical strains have been detected. Further studies, employing recent and more discriminative techniques are in need to better clarify their virulence potential.

Unveiling hákarl: A study of the microbiota of the traditional Icelandic fermented fish

Hákarl is produced by curing of the Greenland shark (Somniosus microcephalus) flesh, which before fermentation is toxic due to the high content of trimethylamine (TMA) or trimethylamine N-oxide (TMAO). Despite its long history of consumption, little knowledge is available on the microbial consortia involved in the fermentation of this fish. In the present study, a polyphasic approach based on both culturing and DNA-based techniques was adopted to gain insight into the microbial species present in ready-to-eat hákarl. To this aim, samples of ready-to-eat hákarl were subjected to viable counting on different selective growth media. The DNA directly extracted from the samples was further subjected to Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) and 16S amplicon-based sequencing. Moreover, the presence of Shiga toxin-producing Escherichia coli (STEC) and Pseudomonas aeruginosa was assessed via qualitative real-time PCR assays. pH values measured in the analyzed samples ranged from between 8.07 ± 0.06 and 8.76 ± 0.00. Viable counts revealed the presence of total mesophilic aerobes, lactic acid bacteria and Pseudomonadaceae. Regarding bacteria, PCR-DGGE analysis highlighted the dominance of close relatives of Tissierella creatinophila. For amplicon sequencing, the main operational taxonomic units (OTUs) shared among the data set were Tissierella, Pseudomonas, Oceanobacillus, Abyssivirga and Lactococcus. The presence of Pseudomonas in the analyzed samples supports the hypothesis of a possible role of this microorganism on the detoxification of shark meat from TMAO or TMA during fermentation. Several minor OTUs (<1%) were also detected, including Alkalibacterium, Staphylococcus, Proteiniclasticum, Acinetobacter, Erysipelothrix, Anaerobacillus, Ochrobactrum, Listeria and Photobacterium. Analysis of the yeast and filamentous fungi community composition by PCR-DGGE revealed the presence of close relatives of Candida tropicalis, Candida glabrata, Candida parapsilosis, Candida zeylanoides, Saccharomyces cerevisiae, Debaryomyces, Torulaspora, Yamadazyma, Sporobolomyces, Alternaria, Cladosporium tenuissimum, Moristroma quercinum and Phoma/Epicoccum, and some of these species probably play key roles in the development of the sensory qualities of the end product. Finally, qualitative real-time PCR assays revealed the absence of STEC and Pseudomonas aeruginosa in all of the analyzed samples.