Epidemiological studies on Escherichia coli O157:H7 in Egyptian sheep

Detection of multidrug-resistant Shiga toxin-producing Escherichia coli in some food products and cattle faeces in Al-Sharkia, Egypt: one health menace

BACKGROUND

Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathogen, that is transmitted from a variety of animals, especially cattle to humans via contaminated food, water, feaces or contact with infected environment or animals. The ability of STEC strains to cause gastrointestinal complications in human is due to the production of Shiga toxins (sxt). However, the transmission of multidrug-resistance STEC strains are linked with a severity of disease outcomes and horizontal spread of resistance genes in other pathogens. The result of this has emerged as a significant threat to public health, animal health, food safety, and the environment. Therefore, the purpose of this study is to investigate the antibiogram profile of enteric E. coli O157 isolated from food products and cattle faeces samples in Zagazig City, Al-Sharkia, Egypt, and to reveal the presence of Shiga toxin genes stx1 and stx2 as virulence factors in multidrug-resistant isolates. In addition to this, the partial 16S rRNA sequencing was used for the identification and genetic recoding of the obtained STEC isolates.

RESULTS

There was a total of sixty-five samples collected from different geographical regions at Zagazig City, Al-Sharkia-Egypt, which were divided into: 15 chicken meat (C), 10 luncheon (L), 10 hamburgers (H), and 30 cattle faeces (CF). From the sixty-five samples, only 10 samples (one from H, and 9 from CF) were identified as suspicious E. coli O157 with colourless colonies on sorbitol MacConkey agar media with Cefixime- Telurite supplement at the last step of most probable number (MPN) technique. Eight isolates (all from CF) were identified as multidrug-resistant (MDR) as they showed resistance to three antibiotics with multiple antibiotic resistance (MAR) index ≥ 0.23, which were assessed by standard Kirby-Bauer disc diffusion method. These eight isolates demonstrated complete resistance (100%) against amoxicillin/clavulanic acid, and high frequencies of resistance (90%, 70%, 60%,60%, and 40%) against cefoxitin, polymixin, erythromycin, ceftazidime, and piperacillin, respectively. Those eight MDR E. coli O157 underwent serological assay to confirm their serotype. Only two isolates (CF8, and CF13), both from CF, were showed strong agglutination with antisera O157 and H7, as well as resistance against 8 out of 13 of the used antibiotics with the highest MAR index (0.62). The presence of virulence genes Shiga toxins (stx1 and stx2) was assessed by PCR technique. CF8 was confirmed for carrying stx2, while CF13 was carrying both genes stx1, and stx2. Both isolates were identified by partial molecular 16S rRNA sequencing and have an accession number (Acc. No.) of LC666912, and LC666913 on gene bank. Phylogenetic analysis showed that CF8, and CF13 were highly homologous (98%) to E. coli H7 strain, and (100%) to E. coli DH7, respectively.

CONCLUSION

The results of this study provides evidence for the occurrence of E. coli O157:H7 that carries Shiga toxins stx1 and/or stx2, with a high frequency of resistance to antibiotics commonly used in human and veterinary medicine, in Zagazig City, Al-Sharkia, Egypt. This has a high extent of public health risk posed by animal reservoirs and food products with respect to easy transmission causing outbreaks and transfer resistance genes to other pathogens in animal, human, and plants. Therefore, environmental, animal husbandry, and food product surveillance, as well as, clinical infection control, must be strengthened to avoid the extra spread of MDR pathogens, especially MDR STEC strains.

Molecular characterization of enterohemorrhagic Escherichia coli isolated from diarrhea samples from human, livestock, and ground beef in North Jordan

Background and Aim:

Enterohemorrhagic Escherichia coli (EHEC) is an important foodborne pathogen with worldwide distribution. Data regarding its presence, distribution, virulence, and antimicrobial susceptibility among various animal species and humans in Jordan are lacking. Therefore, the objectives of this study were to isolate and characterize EHEC from human and animal diarrhea fecal samples and ground beef samples.

Materials and Methods:

A total of 100 and 270 diarrhea fecal samples from humans and animals, respectively, were collected. In addition, 40 ground beef meat samples were collected from retail markets. EHEC was positively identified by detecting Shiga toxins (stx1 and stx2) genes using multiplex polymerase chain reaction (PCR). Antimicrobial susceptibility patterns were determined using the disk diffusion test. Beta-lactamase production was detected using the double disk diffusion test and the extended-spectrum beta-lactamases (ESBLs) were identified by detection of bla_TEM, bla_SHV, and OXA-1 genes using multiplex PCR. Pulsed-field gel electrophoresis (PFGE) was used to investigate the relatedness of EHEC isolates from different sources.

Results:

Out of 410 samples, 194 E. coli isolates were positively identified, of which 57 isolates (29%) were classified as EHEC. Thirty-five (61%) of EHEC isolates were serotyped as O157 (19: O157:H7 and 16: O157:NM). The stx1 gene was detected only among the sheep and goats isolates at a rate of 7.6% and 5.2%, respectively, while the stx2 gene was detected in only one ground beef meat sample. EHEC isolates showed high resistance patterns against amoxicillin, gentamycin, cephalexin, and doxycycline. Twenty-four out of 32 EHEC isolates were determined as ESBL producers, among which 14 isolates expressed the bla_SHVgene and 19 isolates expressed the bla_TEM while four expressed both genes. PFGE analysis revealed two clusters with high similarity (92%) originated from ground beef meat and cattle fecal samples. No similarities were found between human and animal E. coli isolates.

Conclusion:

Results of this study indicate widespread ESBL EHEC among humans, animals, and ground beef meat samples. These results represent an important alarm that requires the implementation of appropriate preventative measures by both human and animal health sectors to prevent the transmission of this important foodborne pathogen.

Prevalence and Whole-Genome Sequence-Based Analysis of Shiga Toxin-Producing Escherichia coli Isolates from the Recto-Anal Junction of Slaughter-Age Irish Sheep

Shiga toxin-producing Escherichia coli (STEC) organisms are a diverse group of pathogenic bacteria capable of causing serious human illness, and serogroups O157 and O26 are frequently implicated in human disease. Ruminant hosts are the primary STEC reservoir, and small ruminants are important contributors to STEC transmission. This study investigated the prevalence, serotypes, and shedding dynamics of STEC, including the supershedding of serogroups O157 and O26, in Irish sheep. Recto-anal mucosal swab samples (n = 840) were collected over 24 months from two ovine slaughtering facilities. Samples were plated on selective agars and were quantitatively and qualitatively assessed via real-time PCR (RT-PCR) for Shiga toxin prevalence and serogroup. A subset of STEC isolates (n = 199) were selected for whole-genome sequencing and analyzed in silico. In total, 704/840 (83.8%) swab samples were Shiga toxin positive following RT-PCR screening, and 363/704 (51.6%) animals were subsequently culture positive for STEC. Five animals were shedding STEC O157, and three of these were identified as supershedders. No STEC O26 was isolated. Post hoc statistical analysis showed that younger animals are more likely to harbor STEC and that STEC carriage is most prevalent during the summer months. Following sequencing, 178/199 genomes were confirmed as STEC. Thirty-five different serotypes were identified, 15 of which were not yet reported for sheep. Serotype O91:H14 was the most frequently reported. Eight Shiga toxin gene variants were reported, two stx₁ and six stx₂, and three novel Shiga-toxin subunit combinations were observed. Variant stx_1c was the most prevalent, while many strains also harbored stx_2b. IMPORTANCE Shiga toxin-producing Escherichia coli (STEC) bacteria are foodborne, zoonotic pathogens of significant public health concern. All STEC organisms harbor stx, a critical virulence determinant, but it is not expressed in most serotypes. Sheep shed the pathogen via fecal excretion and are increasingly recognized as important contributors to the dissemination of STEC. In this study, we have found that there is high prevalence of STEC circulating within sheep and that prevalence is related to animal age and seasonality. Further, sheep harbor a variety of non-O157 STEC, whose prevalence and contribution to human disease have been underinvestigated for many years. A variety of Stx variants were also observed, some of which are of high clinical importance.

Pathotyping and antimicrobial susceptibility testing of Escherichia coli isolates from neonatal calves

Neonatal calf mortality is a major concern to livestock sector worldwide. Neonatal calf diarrhoea (NCD), an acute severe condition causes morbidity and mortality in calves. Amongst various pathogens involved in NCD, E. coli is considered as one of the major causes. The study was targeted to characterize E. coli isolates from neonatal calves for diarrhoeagenic Escherichia coli (DEC) types (pathotyping), antimicrobial resistance (AMR) profiling and to correlate with epidemiological parameters. From neonates, a total of 113 faecal samples were collected, out of that 308, lactose fermenting colonies were confirmed as E. coli. Pathotypable isolates (12.3%) were represented by STEC (6.1%), EPEC (2.9%), ETEC (1.9%), EAEC (0.9%) and EHEC (0.3%). Occurrence of STEC was more in non-diarrhoeic calves, whereas ETEC was observed more in diarrhoeic calves. EPEC occurrence was observed in both diarrhoeic and non-diarrhoeic calves. Fishers extract test showed no significant association for occurrence of DEC types to type of dairies, health status, species, breed, age and sex of neonatal calves. Two hundred and eighty isolates were tested for antimicrobial susceptibility. The isolates showed maximum resistance towards ampicillin (55.4%) followed by tetracycline (54.3%), while minimum resistance was observed towards meropenem (2.5%). Multidrug resistant E. coli isolates were found to be 139 (49.6%), and Extended-spectrum beta-lactamase (ESBL) producers were 120 (42.9%). DEC pathotypes like STEC, ETEC, EHEC and EAEC that are also multidrug resistant present in neonatal calves have zoonotic potential and hence are of public health significance.

An Overview of Shiga-Toxin Producing Escherichia coli Carriage and Prevalence in the Ovine Meat Production Chain

Shiga-toxin producing Escherichia coli (STEC) are zoonotic foodborne pathogens that are capable of causing serious human illness. Ovine ruminants are recognized as an important source of STEC and a notable contributor to contamination within the food industry. This review examined the prevalence of STEC in the ovine food production chain from farm-to-fork, reporting carriage in sheep herds, during abattoir processing, and in raw and ready-to-eat meats and meat products. Factors affecting the prevalence of STEC, including seasonality and animal age, were also examined. A relative prevalence can be obtained by calculating the mean prevalence observed over multiple surveys, weighted by sample number. A relative mean prevalence was obtained for STEC O157 and all STEC serogroups at multiple points along the ovine production chain by using suitable published surveys. A relative mean prevalence (and range) for STEC O157 was calculated: for feces 4.4% (0.2-28.1%), fleece 7.6% (0.8-12.8%), carcass 2.1% (0.2-9.8%), and raw ovine meat 1.9% (0.2-6.3%). For all STEC independent of serotype, a relative mean prevalence was calculated: for feces 33.3% (0.9-90.0%), carcass 58.7% (2.0-81.6%), and raw ovine meat 15.4% (2.7-35.5%). The prevalence of STEC in ovine fleece was reported in only one earlier survey, which recorded a prevalence of 86.2%. Animal age was reported to affect shedding in many surveys, with younger animals typically reported as having a higher prevalence of the pathogen. The prevalence of STEC decreases significantly along the ovine production chain after the application of postharvest interventions. Ovine products pose a small risk of potential STEC contamination to the food supply chain.

Molecular characterization of pathogenic Escherichia coli isolated from diarrheic and in-contact cattle and buffalo calves

Escherichia coli field isolates from calves were characterized and categorized into the most significant diarrheagenic pathotypes using polymerase chain reaction (PCR) assays with different specific primers. The used PCR systems were designed to detect sequences representing the group-specific virulence genes encoding fimbriae f5 (K99), Shiga toxins (stx₁ and stx₂), heat-stable enterotoxins (st), heat-labile enterotoxins (lt), intimin (eae), hemolysin (hylA), and EAEC heat-stable enterotoxin (astA). In the present work, a total of 150 E. coli field isolates were recovered from 150 fecal swabs collected from 100 diarrheic and 50 apparently healthy in-contact cattle and buffalo calves under 3 months old. Out of these 150 isolated E. coli, 106 isolates from 77 diarrheic and 29 in-contact calves harbored one or more of the investigated virulence genes. The pathotyping of the isolates could classify them into shigatoxigenic E. coli (STEC), enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), and enteroaggregative E. coli (EAEC) with a 30.7, 2.7, 12.7, and 7.3% distribution, respectively. Meanwhile, the detection rates of f5, stx₁, stx₂, st, lt, eae, hylA, and astA genes were 17.3, 27.3, 6.7, 10, 37.3, 17.7, 9.3, and 20.7%, respectively. These virulence genes were found either single or in different combinations, such as stx/eae, stx/st/f5, eae/st/f5, or st/lt/f5. Four attaching-effacing shigatoxigenic E. coli isolates (AE-STEC) harboring stx/eae were retrieved from diarrheic calves. Although none of the stx-or eae-positive isolates was verified as O157:H7, STEC isolates detected in apparently healthy calves have potential pathogenicity to humans highlighting their zoonotic importance as reservoirs. Atypical combinations of ETEC/STEC and ETEC/EPEC were also detected in percentages of 14.7 and 2.7%, respectively. Most of these atypical combinations were found more in buffalo calves than in cattle calves. While STEC and EPEC isolates were detected more in cattle calves than in buffalo calves, ETEC isolates were the same in the two species. The pathogenic E. coli infection in calves was recorded to be higher in the first weeks of life with the largest numbers of virulence factor-positive isolates detected at the age of 4 weeks. Histopathological examination of five intestinal samples collected from four dead buffalo calves revealed typical attaching and effacing (AE) lesion which was correlated with the presence of intimin encoding virulence gene (eae). Other lesions characterized by hemorrhagic enteritis, shortening and fusion of intestinal villi and desquamation of the lining epithelium of intestinal mucosa had also been detected.

Use of Bacteriophages to Control Escherichia coli O157:H7 in Domestic Ruminants, Meat Products, and Fruits and Vegetables

Escherichia coli O157:H7 is an important foodborne pathogen that causes severe bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Ruminant manure is a primary source of E. coli O157:H7 contaminating the environment and food sources. Therefore, effective interventions targeted at reducing the prevalence of fecal excretion of E. coli O157:H7 by cattle and sheep and the elimination of E. coli O157:H7 contamination of meat products as well as fruits and vegetables are required. Bacteriophages offer the prospect of sustainable alternative approaches against bacterial pathogens with the flexibility of being applied therapeutically or for biological control purposes. This article reviews the use of phages administered orally or rectally to ruminants and by spraying or immersion of fruits and vegetables as an antimicrobial strategy for controlling E. coli O157:H7. The few reports available demonstrate the potential of phage therapy to reduce E. coli O157:H7 carriage in cattle and sheep, and preparation of commercial phage products was recently launched into commercial markets. However, a better ecological understanding of the phage E. coli O157:H7 will improve antimicrobial effectiveness of phages for elimination of E. coli O157:H7 in vivo.