Characterization of verocytotoxin-producing Escherichia coli O157 isolates from patients with haemolytic uraemic syndrome in Western Europe

Domestic cats are potential reservoirs of multidrug-resistant human enteropathogenic E. coli strains in Bangladesh

Companion animals serve as our best friends, confidants, and family members. Thus, disease and antibiotic resistance gene transmission in pets and humans must be sought out. The study aimed to identify the common pathogenic Escherichia coli (E.coli) in pet cats and the antibiotic resistance patterns and resistant gene distribution. Samples (n = 210) were collected from different veterinary clinics in Bangladesh's cities of Mymensingh and Dhaka. Pathogenic E. coli was identified using conventional and molecular approaches. The disc diffusion method assessed the resistance profile against 12 antibiotics, and PCR was used to identify the beta-lactam resistance genes. The prevalence of the stx-1 gene was found to be 2.86%, whereas the rfbO157 prevalence was found to be 1.90% in cats. The stx-1 gene (n = 6) was 100% resistant to erythromycin and imipenem, whereas 100% sensitive to chloramphenicol. In turn, the rfbO157 gene (n = 4) exhibited 100% resistance to erythromycin, imipenem, cefixime, and azithromycin. In addtion, we identified genes that exhibit resistance to beta-lactam antibiotics (100% blaTEM, 40% blaCTX-M, 40% blaSHV2). This study found shiga-toxin producing and extended-spectrum beta-lactamase (ESBL) producing E. coli for the first time in pet cats of Bangladesh. Furthermore, the antimicrobial resistance (AMR) profile of the isolated strains refers to the occurrence of multidrug, which concerns cats and their owners. The existence of these genes in non-diarrheic pet animal isolates indicates that domestic pets may serve as a reservoir for human infection. Thus, one health strategy comprising animal and human health sectors, governments, together with stakeholders is needed to confront multidrug-resistant E. coli infections in Bangladesh.

ESBL Producing Escherichia coli in Faecal Sludge Treatment Plants: An Invisible Threat to Public Health in Rohingya Camps, Cox's Bazar, Bangladesh

Introduction: Human faecal sludge contains diverse harmful microorganisms, making it hazardous to the environment and public health if it is discharged untreated. Faecal sludge is one of the major sources of E. coli that can produce extended-spectrum β-lactamases (ESBLs).

Objective: This study aimed to investigate the prevalence and molecular characterization of ESBL-producing E. coli in faecal sludge samples collected from faecal sludge treatment plants (FSTPs) in Rohingya camps, Bangladesh.

Methods: ESBL producing E. coli were screened by cultural as well as molecular methods and further characterized for their major ESBL genes, plasmid profiles, pathotypes, antibiotic resistance patterns, conjugation ability, and genetic similarity.

Results: Of 296 isolates, 180 were phenotypically positive for ESBL. All the isolates, except one, contained at least one ESBL gene that was tested (bla_CTX−M−1, bla_CTX−M−2, bla_CTX−M−8, bla_CTX−M−9, bla_CTX−M−15, bla_CTX−M−25, bla_TEM, and bla_SHV). From plasmid profiling, it was observed that plasmids of 1–211 MDa were found in 84% (151/180) of the isolates. Besides, 13% (24/180) of the isolates possessed diarrhoeagenic virulence genes. From the remaining isolates, around 51% (79/156) harbored at least one virulence gene that is associated with the extraintestinal pathogenicity of E. coli. Moreover, 4% (3/156) of the isolates were detected to be potential extraintestinal pathogenic E. coli (ExPEC) strains. Additionally, all the diarrhoeagenic and ExPEC strains showed resistance to three or more antibiotic groups which indicate their multidrug-resistant potential. ERIC-PCR differentiated these pathogenic isolates into seven clusters. In addition to this, 16 out of 35 tested isolates transferred plasmids of 32–112 MDa to E. coli J53 recipient strain.

Conclusion: The present study implies that the faecal sludge samples examined here could be a potential origin for spreading MDR pathogenic ESBL-producing E. coli. The exposure of Rohingya individuals, living in overcrowded camps, to these organisms poses a severe threat to their health.

Processed ready-to-eat (RTE) foods sold in Yenagoa Nigeria were colonized by diarrheagenic Escherichia coli which constitute a probable hazard to human health

The study aimed to recover diarrheagenic Escherichia coli strains from processed ready-to-eat (RTE) foods in Yenagoa, Nigeria and characterize them using culture-based and molecular methods. Three hundred RTE food samples were collected randomly from different food outlets between February 2021 and August 2021 and assessed for the occurrence of E. coli using standard bacteriological procedures. The virulence factor formation and antibiotic susceptibility profile of the isolates was carried out using standard microbiological procedures. Polymerase chain reaction (PCR) was used to confirm the identity of the isolates via specific primers and further used to assay the diarrheagenic determinants of the E. coli isolates. The prevalence of E. coli positive samples based on the proliferation of E. coli on Chromocult coliform agar forming purple to violet colonies was 80(26.7%). The population density of E. coli from the RTE foods ranged from 0–4.3 × 10⁴ ± 1.47 CFU/g. The recovered E. coli isolates (n = 62) were resistant to antibiotics in different proportions such as ampicillin 62(100%), aztreonam 47(75.81%) and chloramphenicol 43(69.35%). All the recovered E. coli isolates were resistant to ≥ 2 antibiotics. The multiple antibiotic-resistant index (MARI) ranged from 0.13–0.94 with 47(75.8%) of isolates having MARI >2. A total of 48(77.4%) of the isolates were multidrug-resistant (MDR). The proportion of extracellular virulence factor formation is as follows: protease 12(19.35%), curli 39(62.9%), cellulose 21(33.89%), ornithine decarboxylase 19(30.65%) and aesculin hydrolysis 14(22.58%). The overall proportion of diarrheagenic E. coli was 33/62(53.2%). The distributions of typical diarrheagenic E. coli includes: tETEC 9(14.5%), tEPEC 13(20.9%), tEAEC 6(9.7%), tEIEC 2(3.2%) and tEHEC 3(4.8%). The proportions of atypical strains include aETEC 10(16.1%), aEAEC 5(8.1%), aEPEC 1(1.6%) and aEIEC 3(4.8%). This study demonstrated that some RTE foods sold in Yenagoa, Nigeria, are contaminated and constitute a probable human health hazard. Thus, there is a need for intensive surveillance of this isolate in RTE foods variety to spot evolving AMR phenotypes and avert food-borne infections.

Molecular detection and analysis of virulence genes in multi-drug resistant Escherichia coli from infected broilers

Escherichia coli associated infections are major threats in poultry industry owing to severe economic losses each year. This study was conducted to identify E. coli isolates, to evaluate their antibiotic sensitivity and to find out their virulence patterns from infected broilers of Sylhet city in Bangladesh. Using polymerase chain reaction, a total 20 isolates were identified as E. coli from 11 chickens, exhibiting symptoms like colibacillosis and/or diarrhea. All isolates were positive for type-1 fimbrial adhesion (fimH), followed by putative avian hemolysin (hlyF) in 17 isolates; while none of the isolates was amplified with intimin (eaeA). Among 10 tested antibiotics, 100% of the isolates (n = 20) showed resistance to ampicillin, amoxicillin and tetra-cycline; but they were 100% sensitive to gentamicin. Organ specific correlations of antibiotic sensitivity were obtained among the isolates through principal component analysis (PCA) and Agglomerative Hierarchical Clustering (AHC). The 16S rRNA data of two multi-drug resistant isolates revealed closed clustering with clinical E. coli strains which could be indication of their zoonotic potential. In conclusion, the results depict higher prevalence of fimH and hlyF genes and drug resistance patterns of E. coli isolates from broilers in Sylhet city of Bangladesh.

Molecular diversity survey on diarrheagenic Escherichia coli isolates among children with gastroenteritis in Fars, Iran

Aim: To differentiate Escherichia coli isolates from diarrheal pediatric patients in clinical laboratories. Materials & methods: Patients with watery diarrhea were selected for sampling and tested for diarrheagenic E. coli (DEC) by API kit. DEC isolates were tested for phylotyping, pathotyping and presence of determined virulence-encoding genes by specific molecular methods. Results: About 50% of isolates were detected as DECs (>55 and >31% were categorized B2 and D phylotypes respectively). Enterotoxigenic E. coli was the most and enteroinvasive E. coli was the lowest prevalent pathotypes. csg and fim genes were the most present virulence factors. Conclusion: Typing of E. coli isolates from stool specimens will help to determine the diversity of diarrheal pathogens and take proper decisions to reduce the health burden of diarrheal diseases.

First report on Cryptosporidium parvum, Escherichia coli K99, rotavirus and coronavirus in neonatal lambs from north-center region, Algeria

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The etiology of neonatal diarrhea is multifactorial and remains one of the biggest problems in ruminant livestock farming. This study represent the first report in Algeria on Cryptosporidium parvum, Escherichia coli K99, rotavirus and coronavirus in the etiology of neonatal diarrhea in lambs.

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Faecal samples from 559 neonatal lambs aged less than 30 days from 30 sheepfolds were screened with pathogen-specific antigen ELISA for C. parvum, E. coli K99, rotavirus, and coronavirus.

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The prevalence of C. parvum was the highest compared to other enteric pathogens.

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In various combinations, mixed infections were detected only with C. parvum.

The etiology of neonatal diarrhea is multifactorial and remains one of the greatest health problems in sheep livestock farming. Faecal samples from 559 neonatal lambs aged less than 30 days from 30 sheepfolds located in the north-center region of Algeria were screened with pathogen-specific antigen ELISA for Cryptosporidium parvum, Escherichia coli K99, rotavirus, and coronavirus. Of the 559 lambs, 312 (58.81 %), 155 (27.72 %), 72 (12.88 %) and 20 (3.57 %) were positives for C. parvum, E. coli K99, rotavirus and coronavirus antigens, respectively. The prevalence of C. parvum was the highest (p < 0.0001). C. parvum, E. coli K99, rotavirus and coronavirus were observed in 23 (76.66 %), 17 (56.66 %), 9 (30 %) and 3 (10 %) sheepfolds, respectively. Compared to age, the prevalence of C. parvum was highest during the second and third week of age (p < 0.001). In contrast, other pathogens were found to be more frequent in lambs aged ≤7 days (p < 0.001). The number of lambs with diarrhea was 280 (50.09 %) of which 280 (100 %), 127 (45.35 %), 52 (18.57 %) and 10 (3.57 %) were found to be infected with C. parvum, E. coli K99, rotavirus and coronavirus, respectively (p < 0.0001). In various combinations, mixed infections were detected only with C. parvum. This is the first report of C. parvum, E. coli K99, rotavirus, and coronavirus in ≤30-days old neonatal lambs in Algeria. Special attention should be given to the first colostrum feeding, hygiene of the farm, prevention and control measures for a better prevention of neonatal diarrhea in lambs.

Extended-Spectrum Beta-Lactamase-Producing Escherichia coli in Drinking Water Samples From a Forcibly Displaced, Densely Populated Community Setting in Bangladesh

Introduction: Community-acquired infections due to extended-spectrum beta-lactamase (ESBL) producing Escherichia coli are rising worldwide, resulting in increased morbidity, mortality, and healthcare costs, especially where poor sanitation and inadequate hygienic practices are very common.

Objective: This study was conducted to investigate the prevalence and characterization of multidrug-resistant (MDR) and ESBL-producing E. coli in drinking water samples collected from Rohingya camps, Bangladesh.

Methods: A total of 384 E. coli isolates were analyzed in this study, of which 203 were from household or point-of-use (POU) water samples, and 181 were from source water samples. The isolates were tested for virulence genes, ESBL-producing genes, antimicrobial susceptibility by VITEK 2 assay, plasmid profiling, and conjugal transfer of AMR genes.

Results: Of the 384 E. coli isolates tested, 17% (66/384) were found to be ESBL producers. The abundance of ESBL-producers in source water contaminated with E. coli was observed to be 14% (27/181), whereas, 19% (39/203) ESBL producers was found in household POU water samples contaminated with E. coli. We detected 71% (47/66) ESBL-E. coli to be MDR. Among these 47 MDR isolates, 20 were resistant to three classes, and 27 were resistant to four different classes of antibiotics. Sixty-four percent (42/66) of the ESBL producing E. coli carried 1 to 7 plasmids ranging from 1 to 103 MDa. Only large plasmids with antibiotic resistance properties were found transferrable via conjugation. Moreover, around 7% (29/384) of E. coli isolates harbored at least one of 10 virulence factors belonging to different E. coli pathotypes.

Conclusions: The findings of this study suggest that the drinking water samples analyzed herein could serve as an important source for exposure and dissemination of MDR, ESBL-producing and pathogenic E. coli lineages, which therewith pose a health risk to the displaced Rohingya people residing in the densely populated camps of Bangladesh.

Comparative genomics reveals structural and functional features specific to the genome of a foodborne Escherichia coli O157:H7

Background

Escherichia coli O157:H7 (O157) has been linked to numerous foodborne disease outbreaks. The ability to rapidly sequence and analyze genomes is important for understanding epidemiology, virulence, survival, and evolution of outbreak strains. In the current study, we performed comparative genomics to determine structural and functional features of the genome of a foodborne O157 isolate NADC 6564 and infer its evolutionary relationship to other O157 strains.

Results

The chromosome of NADC 6564 contained 5466 kb compared to reference strains Sakai (5498 kb) and EDL933 (5547 kb) and shared 41 of its 43 Linear Conserved Blocks (LCB) with the reference strains. However, 18 of 41 LCB had inverse orientation in NADC 6564 compared to the reference strains. NADC 6564 shared 18 of 19 bacteriophages with reference strains except that the chromosomal positioning of some of the phages differed among these strains. The additional phage (P19) of NADC 6564 was located on a 39-kb insertion element (IE) encoding several hypothetical proteins, an integrase, transposases, transcriptional regulators, an adhesin, and a phosphoethanolamine transferase (PEA). The complete homologs of the 39-kb IE were found in E. coli PCN061 of porcine origin. The IE-encoded PEA showed low homology (32–33%) to four other PEA in NADC 6564 and PEA linked to mobilizable colistin resistance in E. coli but was highly homologous (95%) to a PEA of uropathogenic, avian pathogenic, and enteroaggregative E. coli. NADC 6564 showed slightly higher minimum inhibitory concentration of colistin compared to the reference strains. The 39-kb IE also contained dndBCDE and dptFGH operons encoding DNA S-modification and a restriction pathway, linked to oxidative stress tolerance and self-defense against foreign DNA, respectively. Evolutionary tree analysis grouped NADC 6564 with lineage I O157 strains.

Conclusions

These results indicated that differential phage counts and different chromosomal positioning of many bacteriophages and genomic islands might have resulted in recombination events causing altered chromosomal organization in NADC 6564. Evolutionary analysis grouped NADC 6564 with lineage I strains and suggested its earlier divergence from these strains. The ability to perform S-DNA modification might affect tolerance of NADC 6564 to various stressors.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5568-6) contains supplementary material, which is available to authorized users.

Antibiotic resistance, ESBL genes, integrons, phylogenetic groups and MLVA profiles of Escherichia coli pathotypes isolated from patients with diarrhea and farm animals in south-east of Iran

The aims of this study were to investigate the prevalence, antibiotic resistance, presence of class 1 and 2 integrons, Extended Spectrum β-Lactamases (ESBL) genes, phylogenetic group and epidemiological relationships of EPEC, ETEC and EHEC pathotypes isolated from patients with diarrhea and farm animals in south east region of Iran. A total of 671 diarrheagenic E. coli (DEC) were collected from stool samples of 395 patients with diarrhea and 276 farm cattles and goats. Presence of EPEC, ETEC and EHEC were identified using multiplex-PCR employing primers targeted the shiga toxin (stx), intimin (eae), bundle forming pili (bfp), and enterotoxins (lt and st) genes. The highest proportion of the patients (64%) were children under age 1-15 year (p ≤ 0.05). Among the isolates, atypical EPEC was detected in 26 patients and 14 animal stool samples, while typical EPEC was found in 2 cattles. ETEC isolates were detected in stools of 13 patients and 4 EHEC was identified in 3 goats and one cattle. The isolates were checked for susceptibility to 14 antibiotics. 50% (n = 13) of EPEC and 61.5% (n =8) of ETEC showed multi-drug resistance (MDR) profiles and one EPEC was found to be extensive drug resistant (XDR). In contrast, EHEC isolates were susceptible to the majority of antimicrobial agents. The MDR isolates were positive for bla_TEM and bla_CTX-M ESBL genes and carried class 1 integrons. Further study on the biofilm formation indicated that, 3 out of 4 EHEC isolates showed strong biofilm, while other pathotypes had either moderate, weak or no biofilm activity. Majority of EPEC isolates were belonged to phylogenetic group B1, all except one ETEC were classified as phylogenetic group A and two EHEC were belonged to phylogroup D, respectively. A multilocus variable tandem repeat analysis (MLVA) exhibited 22 distinct patterns. In conclusion, MLVA data showed high clonal diversity. Presence of EHEC in animal origins pose public health concern in this region.

House Flies in the Confined Cattle Environment Carry Non-O157 Shiga Toxin-Producing Escherichia coli

Cattle manure is one of the primary larval developmental habitats of house flies, Musca domestica (L.). Cattle serve as asymptomatic reservoirs of Shiga toxin-producing Escherichia coli (STEC), and bacteria are released into the environment in cattle feces. The USDA-FSIS declared seven STEC serogroups (O157, O26, O45, O103, O145, O121, and O111) as adulterants in beef products. In addition, the serogroup O104 was a culprit of a large outbreak in Germany in 2011. Our study aimed to assess the prevalence of seven non-O157 STEC (O26, O45, O145, O103, O121, O111, and O104) serogroups in adult house flies. Flies (n = 463) were collected from nine feedlots and three dairy farms in six states in the United States and individually processed. This involved a culturing approach with immunomagnetic separation followed by multiplex polymerase chain reactions for detection of individual serogroups and virulence traits. The concentration of bacteria on modified Possé agar ranged between 1.0 × 101 and 7.0 × 107 (mean: 1.5 ± 0.3 × 106) CFU/fly. Out of 463 house flies, 159 (34.3%) carried one or more of six E. coli serogroups of interest. However, STEC was found in 1.5% of house flies from feedlots only. These were E. coli O103 and O104 harboring stx1 and ehxA and E. coli O45 with stx1, eae, and ehxA. This is the first study reporting the isolation of non-O157 STEC in house flies from the confined cattle environment and indicating a potential role of this insect as a vector and reservoir of non-O157 STEC in confined beef cattle.

Molecular characterization, genetic diversity and antibacterial susceptibility of Escherichia coli encoding Shiga toxin 2f in domestic pigeons

This study aimed to evaluate prevalence, characteristics, genotypic diversity and antibacterial susceptibility of Escherichia coli encoding Shiga toxin 2f in domestic pigeons in different provinces of Iran. A total of 117 faecal samples were collected from pigeons and were subjected to molecular detection of stx2f. In total, 20, 25·8, 21·4 and 9% of pigeons from Tehran, Ferdows, Garmsar and Babol cities carried stx2f+ isolates, respectively. Of the 460 E. coli isolates examined, 43 were stx2f+ and most also carried eae (95·3%) and astA (97·7%) genes. Some of the stx2f+ isolates harboured cnf (9·3%), but all were negative for stx1, stx2 (other subtypes) and ehly. Most Strains (90%) were assigned to B1 phylogroup and possessed Intimin-β. Fingerprinting of the stx2f+ isolates using either enterobacterial repetitive intergenic consensus sequences (ERIC) or random amplified polymorphic DNA (RAPD)-polymerase chain reaction revealed seven distinct profiles by each method, with one prevailing (65·1 and 46·5%, respectively). By the combination of methods, 10 profiles were recognized. Ten isolates from different profiles were shown to belong to O20, O78 and O115 serogroups, and eight were 100% identical in the stx2f gene sequence. The strains were consistently resistant to amoxicillin and lincospectin and commonly resistant to tetracycline (88·4%) and doxycycline (74·4%). Overall, the results indicate a limited degree of genetic diversity in stx2f-harbouring E. coli from pigeons. Significance and impact of the study: Carriage of stx2f gene tends to be underreported in pigeon Escherichia coli isolates because most routine genetic and phenotypic tests cannot efficiently target this gene or detect the toxin. Nevertheless, pigeons frequently carry E. coli strains that are stx2f-positive, and this situation is not limited to any distinct geographical area. The current results suggest that genetic background of stx2f-encoding E. coli is distinct from most Shiga toxin-producing E. coli strains. However, the factors that contribute to host preferences and pathogenicity remain unclear. These findings have public health significance that should be addressed in future research.

Virulence factors, serogroups and antimicrobial resistance properties of Escherichia coli strains in fermented dairy products

Background

From a clinical perspective, it is essential to know the microbial safety of fermented dairy products. Doogh and kashk are fermented dairies. These products are used by millions of people but their microbial qualities are unknown. Shiga toxin producing Escherichia coli (STEC) is one of the most commonly detected pathogens in the cases of food poisoning and food-borne illnesses. The present investigation was carried out in order to study the molecular characterization and antimicrobial resistance properties of STEC strains isolated from fermented dairy products.

Methods

Six hundred fermented dairy samples were collected and immediately transferred to the laboratory. All samples were cultured immediately and those that were E. coli-positive were analyzed for the presence of O157 , O26, O103, O111, O145, O45, O91, O113, O121 and O128 STEC serogroups, tetA, tetB, blaSHV, CITM, cmlA, cat1, aadA1, dfrA1, qnr, aac (3)-IV, sul1 and ereA antibiotic resistance genes and stx1, stx2, eaeA, ehly, cnf1, cnf2, iutA, cdtB, papA, traT, sfaS and fyuA virulence factors using PCR. Antimicrobial susceptibility testing was performed also using disk diffusion methodology with Mueller–Hinton agar.

Results

Fifty out of 600 (8.33%) dairy samples harbored E. coli. In addition, yoghurt was the most commonly contaminated dairy. O157 (26%) and O26 (12%) were the most commonly detected serogroups. A significant difference was found between the frequency of Attaching and Effacing E. coli and Enterohaemorrhagic E. coli (P <0.05). Stx1 (44%), eae (36%), papA (32%) stx2 (30%), and ehly (28%) were the most commonly detected virulence factors. The genes encode resistance against tetracycline (tetA and tetB) (76% and 70%, respectively), cephalothin (blaSHV) (38%), ampicillin (CITM) (36%) and gentamicin (aac (3)-IV) (32%) were the most commonly detected. High resistance levels to tetracycline (84%), penicillin (46%), ampicillin (38%) and streptomycin (36%) were observed.

Conclusion

Fermented dairy products can easily become contaminated by antibiotic resistant STEC strains. Our findings should raise awareness about antibiotic resistance in Iran. Clinicians should exercise caution when prescribing antibiotics, especially in veterinary treatments.

Shiga toxin production and translocation during microaerobic human colonic infection with Shiga toxin-producing E. coli O157:H7 and O104:H4

Haemolytic uraemic syndrome caused by Shiga toxin-producing E. coli (STEC) is dependent on release of Shiga toxins (Stxs) during intestinal infection and subsequent absorption into the bloodstream. An understanding of Stx-related events in the human gut is limited due to lack of suitable experimental models. In this study, we have used a vertical diffusion chamber system with polarized human colon carcinoma cells to simulate the microaerobic (MA) environment in the human intestine and investigate its influence on Stx release and translocation during STEC O157:H7 and O104:H4 infection. Stx2 was the major toxin type released during infection. Whereas microaerobiosis significantly reduced bacterial growth as well as Stx production and release into the medium, Stx translocation across the epithelial monolayer was enhanced under MA versus aerobic conditions. Increased Stx transport was dependent on STEC infection and occurred via a transcellular pathway other than macropinocytosis. While MA conditions had a similar general effect on Stx release and absorption during infection with STEC O157:H7 and O104:H4, both serotypes showed considerable differences in colonization, Stx production, and Stx translocation which suggest alternative virulence strategies. Taken together, our study suggests that the MA environment in the human colon may modulate Stx-related events and enhance Stx absorption during STEC infection.

Serogroups, virulence genes and antibiotic resistance in Shiga toxin-producing Escherichia coli isolated from diarrheic and non-diarrheic pediatric patients in Iran

Background

From a clinical perspective, it is important to know which serogroups, virulence genes and antibiotic resistance patterns are present in Shiga toxin-producing Escherichia coli strains in pediatric patients suffering from diarrheic and non-diarrheic infections. This is the first study in Iran that has comprehensively investigated the Shiga toxin-producing Escherichia coli -related infection characteristics in diarrheic and non-diarrheic pediatric patients of 0–60 months of age.

Methods

Two-hundred and twenty four diarrheic and 84 non-diarrheic stool specimens were collected from the Baqiyatallah hospital of Tehran, Iran. The stool samples were cultured immediately and those that were E. coli-positive were analyzed for the presence of antibiotic resistance genes and bacterial virulence factors using PCR. Antimicrobial susceptibility testing was performed using disk diffusion method.

Results

One-hundred and fifty four out of 224 (68.75%) diarrheic stools and 31 out of 84 (36.90%) non-diarrheic stools harbored E. coli. In addition, children in 13–24 month-old age group had the highest incidence of infection with this bacterium (77.63%). A significant difference was found between the frequency of Attaching and Effacing Escherichia coli and Enterohaemorrhagic Escherichia coli (P =0.045). The genes encoding Shiga toxins and intimin were the most commonly detected virulence factors. Among all serogroups studied, O26 (27.04%) and O111 (18.85%) had the highest incidences in the diarrheic and non-diarrheic patients. The incidence of genes encoding resistance against sulfonamide (sul1), gentamicin (aac(3)-IV), trimethoprim (aadA1), cephalothin (blaSHV) and tetracycline (tetA) were 82.78%, 68.03%, 60.65%, 56.55% and 51.63%, respectively. High resistance levels against penicillin (100%), tetracycline (86.88%), gentamicin (62.29%) and streptomycin (54.91%) were observed. Marked seasonality in the serogroup distributions was evident, while STEC infections were more common in summer (P =0.041).

Conclusions

Our findings should raise awareness about antibiotic resistance in diarrheic pediatric patients in Iran. Clinicians should exercise caution when prescribing antibiotics, especially during the warmer months of the year.

Molecular epidemiology ofEscherichia colidiarrhoea in children in Tehran

From July to December 2003, four categories of diarrhoeagenic Escherichia coli were investigated in Tehranian children with acute diarrhoea. Stool specimens of children under 5 years of age with diarrhoea (n=200) and matched controls (n=200) without diarrhoea were studied for the presence of entero-aggregative (EAEC), enteropathogenic (EPEC), enterotoxigenic (ETEC) and Shiga toxin-producing (STEC) E. coli by PCR identification of six different genes of diarrhoeagenic E. coli. STEC isolates were typed by O157 and H7 antisera. EAEC was the most prevalent category and was found in 24% of patients with diarrhoea and 8% of controls (p<0.0001). ETEC was isolated in 15.5% of patients with diarrhoea but not in any controls ( p<0.0001), STEC in 15% of patients and 2% of controls (p<0.0001) and EPEC in 6% of patients and 5% of controls. Of 30 STEC isolates from patients with diarrhoea, seven were O157:H7 and 23 were non-O157:H7.

Shiga toxin-producing Escherichia coli isolated from chicken meat in Iran: serogroups, virulence factors, and antimicrobial resistance properties

The aim of the current study was to determine the virulence factors, serogroups, and antibiotic resistance properties of Shiga toxin-producing Escherichia coli isolated from chicken meat samples. A total of 422 chicken meat samples were collected from 5 townships of Iran. Specimens were immediately transferred to the laboratory in a cooler with an ice pack. Samples were cultured, and the positive culture samples were analyzed by PCR assays. Finally, the antimicrobial susceptibility test was performed using the disk diffusion method in Mueller-Hinton agar. According to the results, out of 422 samples, 146 (34.59%) were confirmed to be E. coli positive and among E. coli-positive samples, 51 (34.93%) and 31 (21.23%) were from attaching and effacing E. coli (AEEC) and enterohemorrhagic E. coli (EHEC) subgroups, respectively. All of the EHEC-positive samples had all stx1, eaeA, and ehly virulence genes, whereas only 5 (9.80%) of AEEC subgroup had all stx1, stx2, and eaeA genes. As the data revealed, O157 was the most prevalent and O111 was the least prevalent strains in the Shiga toxin-producing E. coli (STEC) population. Among STEC strains, sulI and blaSHV had the highest and lowest incidence rate, respectively. There was a high resistance to tetracycline (76.82%), followed by chloramphenicol (73.17%) and nitrofurantoin (63.41%), but there was low resistance to cephalotine (7.31%) antibiotics in isolated strains. Results shows that the PCR technique has a high performance for detection of serogroups, virulence genes, and antibiotic resistance genes in STEC strains. This study is the first prevalence report of detection of virulence genes, serogroups, and antibiotic resistance properties of STEC strains isolated from chicken meat samples in Iran. Based on the results, chicken meat is one of the main sources of STEC strains and its virulence factors in Iran, so an accurate meat inspection would reduce disease outbreaks.

Incidence of Shiga toxin-producing Escherichia coli serogroups in ruminant's meat

To assess the presences of Escherichia coli, its serogroups, virulence factors and antibiotic resistance properties in ruminant's meat, a total of 820 raw meat samples were collected and then evaluated using culture, PCR and disk diffusion methods. Totally, 238 (29.02%) samples were positive for presence of Escherichia coli. All of the isolates had more than one virulence gene including Stx1, Stx2, eaeA and ehly. All investigated serogroups were found in beef and sheep and all except O145, O121 and O128 were found in goat. The O91, O113, O111, O103, O26 and O157 serogroups were found in camel. Totally, aadA1-blaSHV combination was the most predominant antibiotic resistance gene. The highest resistance of STEC strains was seen against penicillin while resistance to nitrofurantoin and ciprofloxacin was minimal. These findings showed that health care and meat inspection should be reconsidered in Iranian slaughterhouses and butchers.

Prevalence and distribution of different diarrhoeagenic Escherichia coli virulotypes in major water bodies in Bangladesh

Escherichia coli, a prominent waterborne pathogen, causes a variety of gastrointestinal and extraintestinal infections that depend on virulence determinants. To monitor natural aquatic systems for virulence-associated genes of E. coli, multiplex PCR was used in a survey covering 46 major natural water bodies in Bangladesh. DNA was extracted directly from water samples as well as from pre-enriched and enriched cultures during three successive seasons and assessed for E. coli virulotype distribution. From the five virulotypes, genes from the enterotoxigenic (ETEC), enteropathogenic (EPEC), and enterohaemorrhagic (EHEC) virulotypes were detected consistently, but genes from the enteroinvasive (EIEC) and enteroaggregative (EAEC) virulotypes were traced only occasionally. ETEC was the most prevalent virulotype, followed by EPEC. However, EIEC and EAEC virulotypes could not be detected in winter or the rainy season, respectively. Specific regional distribution patterns of different E. coli virulotypes and their temporal fluctuations were identified. These observations may assist with assessing seasonal risk and identifying vulnerable areas of the country prone to E. coli-associated outbreaks.

Evaluation of CHROMagar STEC and STEC O104 chromogenic agar media for detection of Shiga Toxin-producing Escherichia coli in stool specimens

The performance of CHROMagar STEC and CHROMagar STEC O104 (CHROMagar Microbiology, Paris, France) media for the detection of Shiga toxin-producing Escherichia coli (STEC) was assessed with 329 stool specimens collected over 14 months from patients with suspected STEC infections (June 2011 to August 2012). The CHROMagar STEC medium, after an enrichment broth step, allowed the recovery of the STEC strain from 32 of the 39 (82.1%) Shiga toxin-positive stool specimens, whereas the standard procedure involving Drigalski agar allowed the recovery of only three additional STEC strains. The isolates that grew on CHROMagar STEC medium belonged to 15 serotypes, including the prevalent non-sorbitol-fermenting (NSF) O157:H7, O26:H11, and O104:H4 serotypes. The sensitivity, specificity, and positive and negative predictive values for the CHROMagar STEC medium were between 89.1% and 91.4%, 83.7% and 86.7%, 40% and 51.3%, and 98% and 98.8%, respectively, depending on whether or not stx-negative eae-positive E. coli was considered atypical enteropathogenic E. coli (EPEC) or STEC that had lost Shiga toxin genes during infection. In conclusion, the good performance of CHROMagar STEC agar medium, in particular, the high negative predictive value, and its capacity to identify NSF O157:H7 as well as common non-O157 STEC may be useful for clinical bacteriology, public health, and reference laboratories; it could be used in addition to a method targeting Shiga toxins (detection of stx genes by PCR, immunodetection of Shiga toxins in stool specimens, or Vero cell cytotoxicity assay) as an alternative to O157 culture medium. This combined approach should allow rapid visualization of both putative O157 and non-O157 STEC colonies for subsequent characterization, essential for real-time surveillance of STEC infections and investigations of outbreaks.

Shiga toxin-producing Escherichia coli isolated from bovine mastitic milk: serogroups, virulence factors, and antibiotic resistance properties

The aim of this study was to detect the virulence factors, serogroups, and antibiotic resistance properties of Shiga toxin-producing Escherichia coli, by using 268 bovine mastitic milk samples which were diagnosed using California Mastitis Test. After E. coli identification, PCR assays were developed for detection of different virulence genes, serogroups, and antibiotic resistance genes of Escherichia coli. The antibiotic resistance pattern was studied using disk diffusion method. Out of 268 samples, 73 (27.23%) were positive for Escherichia coli, and, out of 73 positive samples, 15 (20.54%) were O26 and 11 (15.06%) were O157 so they were the highest while O111 was not detected in any sample so it was the lowest serogroup. Out of 73 STEC strains, 11 (15.06%) and 36 (49.31%) were EHEC and AEEC, respectively. All of the EHEC strains had stx1, eaeA, and ehly, virulence genes, while in AEEC strains stx1 had the highest prevalence (77.77%), followed by eaeA (55.55%). Totally, aadA1 (65.95%) had the highest while blaSHV (6.38%) had the lowest prevalence of antibiotic resistance genes. The disk diffusion method showed that the STEC strains had the highest resistance to penicillin (100%), followed by tetracycline (57.44%), while resistance to cephalothin (6.38%) was the lowest.

Analysis of an outbreak of puerperal Fever due to group a streptococci by random amplified polymorphic DNA fingerprinting

Objective: Streptococcus pyogenes is the cause of the classical childbed fever and can occur in both sporadic and epidemic form. Once an outbreak is identified on a maternity ward it is not only necessary to place the patients in strict isolation but also identify to the source of the infection. Fast reliable typing methods can aid in infection control.

Methods: An outbreak of puerperal fever due to S. pyogenes was analyzed by random amplified polymorphic DNA (RAPD) analysis.

Results: Identical fingerprint patterns were found in isolates of 3 patients, the throat and infected finger of the delivering obstetrician, 2 of the physician's family members, and from the cervix of a woman who was examined by the physician 7 months after the outbreak. The outbreak was stopped after antimicrobial treatment of the physician and his family members.

Conclusions: RAPD typing appeared to be a fast and reliable tool for epidemiological studies of S. pyogenes and is probably more efficient in strain differentiation than classical M and T serotyping.

Molecular characterization of Shiga toxin-producing Escherichia coli isolated from ruminant and donkey raw milk samples and traditional dairy products in Iran

The aims of the current study were to detect the virulence factors and antibiotic resistance of Shiga toxin-producing E. coli, in animal milk and dairy products in Iran. After E. coli dentification with culture method, PCR assay were developed for detection of pathogenic genes, serotypes and antibiotic resistance genes of E. coli. Results showed that out of 719 samples, 102 (14.18%) were confirmed to be positive for E. coli and out of 102 positive samples, 17.64% were O26 and 13.72% were O157 and 1.96% were O91 and 1.96% were O145 serotypes. Totally, the prevalence of stx1 and papA genes were the highest while the prevalence of sfaS and fyuA were the lowest in the positive samples. PCR results showed that tetA, tetB were the highest (64.70%) and aac(3)-IV were the lowest (27.45%) antibiotic resistant genes in E. coli positive samples. Our study indicated that the isolated E. coli trains in these regions had a highest antibiotic resistance to tetracycline (58.82%) and the lowest to nitrofurantoin (3.92%). tetA gene and E. coli O157 serotype had highest and aac(3)-IV gene, and E. coli O145 serotype had a lowest frequency rates of antibiotics resistance genes, in the region.

Shiga toxin interaction with human intestinal epithelium

After ingestion via contaminated food or water, enterohaemorrhagic E. coli colonises the intestinal mucosa and produces Shiga toxins (Stx). No Stx-specific secretion system has been described so far, and it is assumed that Stx are released into the gut lumen after bacterial lysis. Human intestinal epithelium does not express the Stx receptor Gb3 or other Stx binding sites, and it remains unknown how Stx cross the intestinal epithelial barrier and gain access to the systemic circulation. This review summarises current knowledge about the influence of the intestinal environment on Stx production and release, Stx interaction with intestinal epithelial cells and intracellular uptake, and toxin translocation into underlying tissues. Furthermore, it highlights gaps in understanding that need to be addressed by future research.

Verotoxigenic Escherichia coli O157:H7 from Swedish cattle; isolates from prevalence studies versus strains linked to human infections--a retrospective study

Background

Several cases of human infection caused by verotoxin-producing Escherichia coli (VTEC) O157:H7 in Sweden have been connected with cattle farm visits. Between 1996 and 2002, 18 farms were classified as the source of human cases with isolation of EHEC (Enterohaemorrhagic Escherichia coli) after VTEC O157:H7 had been isolated from cattle on those farms.

Results

Characterization by phage typing and molecular methods of the strains isolated from these 18 farms, including PCR for virulence genes (vtx₁, vtx₂ and variants thereof, eaeA and EHEC-hlyA) and Pulsed-Field Gel Electrophoresis (PFGE), demonstrated a cluster of very similar strains from 16 farms. All were of phage type 4, carried the genes encoding the verotoxins VT2 and VT2c, intimin, EHEC-haemolysin and flagellin H7 as shown by PCR, and had identical or very similar PFGE patterns. When analysing strains in a prevalence study of VTEC O157:H7 from cattle at slaughter as well as from an on-farm prevalence study of dairy cattle, using the same typing methods, a rather wide variation was observed among the isolated VTEC O157:H7 strains.

Conclusions

In Sweden, a limited group of genetically similar and highly pathogenic VTEC O157:H7 strains seem to predominate in direct or indirect transmission from cattle to man.

Molecular Screening, Isolation, and Characterization of Enterohemorrhagic Escherichia coli O157:H7 from Retail Shrimp

Foodborne outbreaks attributed to the contamination of foods with enterohemorrhagic Escherichia coli (EHEC) O157:H7 are a growing global concern. Fish and shrimp samples obtained from different retail fish markets in Cochin, India, were screened by direct PCR assays targeting three important virulence markers of EHEC, the intimin protein (eaeA gene), enterohemolysin (hlyA gene), and Shiga toxin (stx gene). One shrimp (Fenneropenaeus indicus) sample was positive for all these virulence markers, and seven typical E. coli O157:H7 isolates were recovered from the marker-positive shrimp sample. This is the first report of recovery of typical E. coli O157:H7 from fish or shellfish in India. All the typical EHEC isolates had a characteristic reaction in eosin methylene blue agar and belonged to IMViC (indole, methyl red, Voges Proskauer, Simmons citrate reactions) biotype I. These isolates also were negative for sorbitol and methylumbelliferyl-β -glucuronide and exhibited β-hemolytic activity. One isolate showed self-agglutination for E. coli O157 antisera and produced a false-positive reaction with CHROMagar O157. These typical EHEC isolates belonged to a restricted biotype group and had a very low multiple antibiotic resistance index. Isolation of E. coli O157:H7 in fish and shellfish indicates that strict adherence to hygienic handling methods and proper cooking or processing is needed before consumption of these products.

Prevalence, characterisation and clinical profiles of Shiga toxin-producing Escherichia coli in The Netherlands

Detection of Shiga toxin-producing Escherichia coli (STEC) in The Netherlands is traditionally limited to serogroup O157. To assess the relative importance of STEC, including non-O157 serogroups, stool samples submitted nationwide for investigation of enteric pathogens or diarrhoea were screened with real-time PCR for the presence of the Shiga toxin genes. Patients were selected if their stool contained blood upon macroscopic examination, if they had a history of bloody diarrhoea, were diagnosed with haemolytic uraemic syndrome, or were aged <6 years (irrespective of the bloody aspect of the stool). PCR-positive stools were forwarded to a central laboratory for STEC isolation and typing. In total, 4069 stools were examined, with 68 (1.7%) positive PCR results. The highest prevalence was for stools containing macroscopic blood (3.5%), followed by stools from patients with a history of bloody diarrhoea (2.4%). Among young children, the prevalence (1.0%) was not significantly higher than among random, non-bloody, stool samples from diarrhoeal patients (1.4%). STEC strains were isolated from 25 (38%) PCR-positive stools. Eleven O-serogroups were detected, including five STEC O157 strains. As serogroup O157 represented only 20% of the STEC isolates, laboratories should be encouraged to use techniques enabling them to detect non-O157 serogroups, in parallel with culture, for isolation and subsequent characterisation of STEC strains for public health surveillance and detection of outbreaks.

Shiga toxin-producing Escherichia coli isolated from patients with diarrhoea in Bangladesh

The prevalence of Shiga toxin-producing Escherichia coli (STEC) and its characteristics were determined among hospitalized patients with diarrhoea and children with diarrhoea in an urban slum community of Dhaka city using sensitive culture and PCR methods. Stool samples were collected from 410 patients with diarrhoea enrolled in the 2% surveillance system (every 50th patient attending the hospital with diarrhoeal disease is included) at the ICDDR,B hospital and from 160 children of 2-5 years of age with diarrhoea living in an urban slum in Dhaka, between September 2004 and April 2005. Shiga toxin genes (stx) were detected by multiplex PCR in the enrichment broth of nine samples (2.2%) from hospitalized patients and 11 samples (6.9%) from the community patients. STEC was isolated from five stool samples with positive PCR results using a colony patch technique. All five isolates were positive in the Vero cell assay and PCR fragments of stx genes were confirmed by sequencing. Two isolates were positive for the E. coli attaching-and-effacing (eae) gene and four were positive for the enterohaemolysin (hlyEHEC) gene and enterohaemolysin production. The five isolates belonged to five different serotypes:O32:H25, O2:H45, O76:H19, ONT:H25 and ONT:H19. It can be concluded that STEC is not a common pathogen in Bangladesh among hospitalized patients with diarrhoea nor among mild cases of diarrhoea in the community.

Interactions of Shiga-like toxin with human peripheral blood monocytes

The cytotoxic effect of Shiga-like toxin (Stx; produced by certain Escherichia coli strains) plays a central role in typical hemolytic uremic syndrome (HUS). It damages the renal endothelium by inhibiting the cellular protein synthesis. Also, the monocyte has a specific receptor for Stx but is not sensitive for the cytotoxic effect. In this work, monocytes were studied as a potential transporter for Stx to the renal endothelium. Coincubation of isolated human monocytes loaded with Stx and target cells (vero cells and human umbilical vascular endothelial cells) were performed. Transfer was determined by measuring the protein synthesis of target cells and by flow cytometry. Furthermore, the effect of a temperature shift on loaded monocytes was investigated. Stx-loaded monocytes reduced the protein synthesis of target cells. After adding an antibody against Stx, incomplete recovery occurred. Also, adding only the supernatant of coincubation was followed by protein synthesis inhibition. Stx detached from its receptor on the monocyte after a change in temperature, and no release was detected without this temperature shift. Although the monocyte plays an important role in the pathogenesis of HUS, it has no role in the transfer of Stx.

Phage types, virulence genes and PFGE profiles of Shiga toxin-producing Escherichia coli O157:H7 isolated from raw beef, soft cheese and vegetables in Lima (Peru)

The present study was conducted in Lima Metropolitana to evaluate the prevalence of Shiga toxin-producing Escherichia coli (STEC) O157:H7 in raw beef, raw ground beef, soft cheese and fresh vegetables, sampled at different markets in the city. Between October 2000 and February 2001, 407 food samples were collected from different markets in the 42 districts of Lima Metropolitana. Samples were assayed for E. coli O157 by selective enrichment in modified Tryptic Soy Broth containing novobiocin, followed by immunomagnetic separation (IMS) and plating onto sorbitol MacConkey agar supplemented with cefixime and potassium tellurite. Fifty (12.3%) of 407 food samples resulted positive for E. coli O157 isolation (23 of 102 ground beef; 15 of 102 beef meat; eight of 102 soft cheese and four of 101 fresh vegetables). Thirty-five E. coli O157 isolates were further analysed for the presence of virulence genes. All 35 were positive by PCR for O157 rfbE, fliCh7, eae-gamma1 and ehxA genes. In addition, genes encoding Shiga toxins were detected in 33 of 35 isolates, five isolates (14%) encoded stx(1), stx(2), and 28 (80%) stx2 only. The isolates were of seven different phage types (PT4, PT8, PT14, PT21, PT34, PT54, and PT87) with three phage types accounting for 80% of isolates: PT4 (15 isolates), PT14 (8 isolates), and PT21 (5 isolates). Interestingly, the majority (31 of 35; 89%) of E. coli O157:H7 isolates characterized in this study belonged mainly to the phage types previously found in STEC O157:H7 strains associated with severe human disease in Europe and Canada. Pulsed-field gel electrophoresis (PFGE) of 32 isolates revealed 14 XbaI-PFGE groups (I to XIV) of similarity >85%, with 23 (72%) isolates grouped in five clusters. Some isolates from different districts presented a high clonal relatedness. Thus, PFGE group VIII clustered eleven strains from nine different districts. The broad range of PFGE subtypes found in this study demonstrates the natural occurrence of many genetic variants among STEC O157:H7 spread in Lima.

Phenotypic and genotypic characterization of sorbitol-negative or slow-fermenting (suspected O157) Escherichia coli isolated from milk samples in Lombardy region

AIMS

To investigate phenotypic and genotypic aspects of sorbitol-negative or slow-fermenting Escherichia coli, suspected to belong to O157 serogroup, isolated in Italy.

METHODS AND RESULTS

Milk samples originating from goats and cows were screened for the presence of E. coli O157 with cultural methods. Sorbitol-negative or slow-fermenting strains were subjected to phenotypic characterization, antibiotic resistance profiles, PCR reactions for detection of toxins (stx(1) and stx(2)) and intimin (eae(GEN) and eae(O157)) genes and clustering by pulsed field gel electrophoresis (PFGE). Only one strain revealed to be O157. Susceptibility to 11 antibiotics highlighted the high resistance to tetracycline (50%), sulfonamide and streptomycin (33%). The stx(2) gene was detected in two strains; only the strain identified as O157 exhibited an amplicon for both eae genes. PFGE identified seven distinct XbaI macrorestriction patterns at a similarity level of 41%.

CONCLUSIONS

The use of sorbitol fermentation as cultural method is not sufficient for STEC discrimination while PCR assay proved to be a valuable method.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study reports presence of Shiga toxin-producing E. coli in raw milk, signalling a potential risk for humans.

Description of a 111-kb pathogenicity island (PAI) encoding various virulence features in the enterohemorrhagic E. coli (EHEC) strain RW1374 (O103:H2) and detection of a similar PAI in other EHEC strains of serotype 0103:H2

Human infections with enterohemorrhagic E. coli (EHEC) strains of serotype O103:H2 are of increasing importance in Germany. As bovines are the principal EHEC reservoir behind the occurrence of human infections, we analyzed a pathogenicity island (PAI I(RW1374)) of bovine O103:H2 strain RW1374 to identify putative virulence features. This PAI I(RW1374) harbors a functional 34-kb locus of enterocyte effacement (LEE) core region and has a total length of 111 kb. About 43 kb upstream of the LEE core a gene cassette consisting of efa1/lifA gene and flanking IS elements suggests another putative transposon within the PAI(IRW1374). In addition, the ent gene, encoding a Shigella ShET-2 enterotoxin homologue, is present about 57 kb upstream of the LEE core. This PAI is therefore a complex assembly of various virulence determinants including the efa1/lifA and the ent gene resembling O157:H7 PAI OI-122/SpLE3 as well as the LEE core region. An integrase gene on the very left end of PAI I(Rw1374) is disrupted by an IS629 homologue. In an attempt to mobilize the LEE core we performed conjugation, transformation and transduction experiments. We were, however, unable to mobilize the whole or even single regions of PAI I(RW1374). Comparative studies with other strains of serotype O103:H2 isolated from humans, bovines and food showed that they all harbored a similar phe V-inserted PAI including the virulence genes ent and lifA/efa1 as well as the large virulence-associated plasmid encoding the EHEC hemolysin. This combination of several virulence factors confirms the complex virulence of O103:H2 EHEC and may at least partly explain the high virulence of this EHEC serotype in humans.

Molecular characteristics of Escherichia coli serogroup O78 strains isolated from diarrheal cases in bovines urge further investigations on their zoonotic potential

We investigated the virulence properties and clonal relationship of 21 Escherichia coli strains of serogroup O78 isolated from diarrhoeic cattle and calves. Isolates were screened for 18 genes representing virulence features of different Escherichia coli pathotypes. None of the strains harboured enterotoxin-genes estIa/Ib, eltIa/Ib, or Shiga toxin (stx) genes, genes involved in adhesion (eae, f5, f41) hemolysin gene hlyA or invasion gene ipaC. With a high prevalence we detected enterotoxin astA (61.9%), genes involved in iron acquisition, like fyuA, irp (each 57.1%) and iucD (81.0%), and the operon sequence of Colicin V plasmids (38.1%). Some strains possessed toxin genes cdt-IIIB and cnf1/2 (both 14.3%), the invasion gene tia (23.8%), and the serine protease encoding gene espP (23.8%). Moreover, we could show that E. coli O78 strains under investigation were able to adhere to and invade MDBK-cells with varying efficiencies. The results indicate that the closely related O78 strains, constituting two major PFGE-clusters, harbor various virulence features for bovine intestinal disease but cannot be grouped into one of the common E. coli intestinal pathogenic or other pathotypes according to their virulence gene pattern. Nevertheless, the ability to adhere, invade or harbor toxin genes lets us suggest that O78 strains isolated from diarrheal cases in bovines urges further investigations on the zoonotic potential of these strains.

Phage types and genotypes of shiga toxin-producing Escherichia coli O157:H7 isolates from humans and animals in spain: identification and characterization of two predominating phage types (PT2 and PT8)

Phage typing and DNA macrorestriction fragment analysis by pulsed-field electrophoresis (PFGE) were used for the epidemiological subtyping of a collection of Shiga toxin-producing Escherichia coli (STEC) O157:H7 strains isolated in Spain between 1980 and 1999. Phage typing distinguished a total of 18 phage types among 171 strains isolated from different sources (67 humans, 82 bovines, 12 ovines, and 10 beef products). However, five phage types, phage type 2 (PT2; 42 strains), PT8 (33 strains), PT14 (14 strains), PT21/28 (11 strains), and PT54 (16 strains), accounted for 68% of the study isolates. PT2 and PT8 were the most frequently found among strains from both humans (51%) and bovines (46%). Interestingly, we detected a significant association between PT2 and PT14 and the presence of acute pathologies. A group of 108 of the 171 strains were analyzed by PFGE, and 53 distinct XbaI macrorestriction patterns were identified, with 38 strains exhibiting unique PFGE patterns. In contrast, phage typing identified 15 different phage types. A total of 66 phage type-PFGE subtype combinations were identified among the 108 strains. PFGE subtyping differentiated between unrelated strains that exhibited the same phage type. The most common phage type-PFGE pattern combinations were PT2-PFGE type 1 (1 human and 11 bovine strains), PT8-PFGE type 8 (2 human, 6 bovine, and 1 beef product strains), PT2-PFGE subtype 4A (1 human, 3 bovine, and 1 beef product strains). Nine (29%) of 31 human strains showed phage type-PFGE pattern combinations that were detected among the bovine strains included in this study, and 26 (38%) of 68 bovine strains produced phage type-PFGE pattern combinations observed among human strains included in this study, confirming that cattle are a major reservoir of strains pathogenic for humans. PT2 and PT8 strains formed two groups which differed from each other in their motilities, stx genotypes, PFGE patterns, and the severity of the illnesses that they caused.

Interaction of Shiga toxin from Escherichia coli with human intestinal epithelial cell lines and explants: Stx2 induces epithelial damage in organ culture

Shiga toxins (Stx) produced by Escherichia coli are associated with systemic complications such as haemolytic-uraemic syndrome. The mechanism of Stx translocation across the epithelial barrier is unknown as human intestinal epithelium lacks receptor Gb3. In this study, we have examined the interaction of purified Stx1 and 2 with Caco-2 (Gb3+) and T84 (Gb3-) cell lines, and determined the effects of Stx on human intestine using in vitro organ culture (IVOC). Stx exposure caused inhibition of protein synthesis and apoptosis in Caco-2 but not in T84 cells. However, both Stx1 and 2 were transported to the endoplasmic reticulum, and the Stx1 A-subunit was cleaved in a furin-dependent manner in both cell lines. Thus, a Gb3-independent retrograde transport route exists in T84 cells for Stx that does not induce cell damage. IVOC demonstrated increased epithelial cell extrusion in response to exposure to Stx2, but not Stx1, in both small intestine and colon. Pretreatment of Stx2 with Stx2-specific antibody abrogated this effect. Overlaying frozen sections with Stx showed lamina propria, but not epithelial, cell binding that paralleled Gb3 localization, and included endothelium and pericryptal myofibroblasts. This indicates that human intestinal epithelium may evince Stx2-induced damage in the absence of Gb3 receptors, by an as yet unrecognized mechanism.

Occurrence of Shiga toxin-producing Escherichia coli O157 in selected dairy and meat products marketed in the city of Rabat, Morocco

Samples of meat and dairy products taken from the city of Rabat, Morocco, were examined for the presence of Escherichia coli O157 by the selective enrichment procedure followed by plating on cefixime-tellurite-sorbitol MacConkey agar and a latex agglutination test. The ability of isolates to produce Shiga toxins (ST1 or ST2) was also tested by an agglutination test using sensitized latex. Dairy samples (n = 44) included different products commonly consumed in the country. Meat samples (n = 36) were taken from traditional butchers because these products are generally marketed in this way. Random samples were taken from each product during the period of January through May. Of the 80 samples tested, 8 (10%) harbored E. coli O157. Four dairy and four meat samples were contaminated (9.1 and 11.1%, respectively). Of 10 E. coli O157 isolates from contaminated samples demonstrating true antigen-antibody agglutination, 5 (50%) produced either ST2 alone or ST2 plus ST1. Four of the five strains (80%) were meat isolates and produced ST2 with or without ST1, and the fifth was a dairy isolate producing ST2.

DNA-based subtyping of verocytotoxin-producing Escherichia coli (VTEC) O128ab:H2 strains from human and raw meat sources

AIMS

To investigate subtyping methods for verocytotoxin-producing Escherichia coli (VTEC) O128ab:H2.

METHODS AND RESULTS

Eleven human and food strains isolated over a 15-year period were examined. All were intimin (eae)-negative, but all possessed enterohaemolysin and VT1-encoding sequences which in nine strains were vtx1c variant. Ten strains had VT2 genes which were all vtx2d. Plasmid profiles and randomly amplified polymorphic DNA-PCR were not discriminatory. Long-PCR restriction fragment length polymorphism of amplicons bound by the p gene and the VT2A subunit had screening potential. Pulsed field gel electrophoresis (PFGE) using XbaI gave fine discrimination although VT2 sequences were located on a 220 kbp fragment conserved in nine strains and on a 200 kbp fragment in the 10th.

CONCLUSIONS

As a result of apparent clonality, PFGE proved essential for differentiation. Long-PCR has promise for screening but requires further evaluation of inter-strain variable sequences.

SIGNIFICANCE AND IMPACT OF THE STUDY

A combined phenotypic and genotypic screen, and PFGE for selected strains was effective.

Description of a novel intimin variant (type zeta) in the bovine O84:NM verotoxin-producing Escherichia coli strain 537/89 and the diagnostic value of intimin typing

Infections with verotoxin-producing Escherichia coli (VTEC) has resulted in increasing numbers of human illnesses annually. These illnesses usually result from the ability of VTEC to cause the attaching and effacing lesions (AE lesion). The AE phenotype is encoded by the locus of enterocyte effacement (LEE) pathogenicity island. A key adhesion factor involved is the outer membrane protein intimin, encoded by the eae gene within the LEE. Intimin types alpha, beta, gamma, delta, and epsilon have been described previously. Each intimin represents distinct phylogenetic lineages of LEE-positive strains. A new intimin type zeta was identified in a VTEC strain of the serotype O84:NM (nonmotile) that was isolated from a calf with diarrhea. zeta intimin showed the highest similarity (88%) of its amino acid sequence to the alpha intimin. For diagnostic purposes, we established a polymerase chain reaction (PCR) method for diagnosis of the key virulence traits of VTEC (i.e., verotoxins and intimins). This method also distinguishes between the toxins (VT1 and VT2) and the six intimin types. By applying the PCR method, intimin zeta in strains of other VTEC serotypes O84:H2, O92:NM, O119:H25, and O150:NM was identified. Because the intimin types represent distinctive phylogenetic E. coli lineages, application of the intimin subtyping PCR offers significant benefits. These include improving diagnosis of VTEC infection and increasing the understanding of evolution of attaching and effacing VTEC and other LEE-positive bacteria.

Characteristics and association with disease of two major subclones of Shiga toxin (Verocytotoxin)-producing strains of Escherichia coli (STEC) O157 that are present among isolates from patients in Germany

Shiga toxin (Verocytotoxin) producing E. coli (STEC) O157 were isolated from 168 patients living in different parts of Germany. Most isolates were from sporadic cases and seven small outbreaks with STEC O157 were identified. The 168 strains were examined for phenotypic and genotypical traits in order to identify major types of STEC O157 occurring in Germany. Phage typing (PT) revealed PT8 (n = 54) and PT2 (n = 48) strains as most frequent (60.7%) among the isolates. Carriage of the stx(2) gene by STEC O157 was closely associated with hemolytic uremic syndrome (100%) and with bloody diarrhea (61.7%). The stx(2) gene was frequent in PT88, PT47 (both 100%), PT2 (91.5%) and PT4 (87.5%) strains and more rarely (33.3%) found in strains belonging to the other PTs. PT8 and PT2 strains formed two groups which differed from each other in their motility, stx-genotypes and the severity of the illness they caused. Pulsed-field gel electrophoresis of PT2 and PT8 strains and hybridization of XbaI digested DNA with stx(1) and stx(2) specific gene probes revealed similarities among epidemiologically unrelated strains belonging to the same PT. The results indicate that STEC O157 PT2 and PT8 strains form two distinct subclones which are dominating in Germany and other European countries.

The nucleotide sequence of Shiga toxin (Stx) 2e-encoding phage phiP27 is not related to other Stx phage genomes, but the modular genetic structure is conserved

In this study we determined the complete nucleotide sequence of Shiga toxin 2e-encoding bacteriophage phi P27, isolated from the Shiga toxin-producing Escherichia coli patient isolate 2771/97. phi P27 is integrated as a prophage in the chromosomal yecE gene. This integration generates identity segments of attL and attR sites with lengths of 11 nucleotides. The integrated prophage genome has a size of 42,575 bp. We identified 58 open reading frames (ORFs), each with a length of >150 nucleotides. The deduced proteins of 44 ORFs showed significant homologies to other proteins present in sequence databases, whereas 14 putative proteins did not. For 29 proteins, we could deduce a putative function. Most of these are related to the basic phage propagation cycle. The phi P27 genome represents a mosaic composed of genetic elements which are obviously derived from related and unrelated phages. We identified five short linker sequences of 22 to 151 bp in the phi P27 sequence which have also been detected in a couple of other lambdoid phages. These linkers are located between functional modules in the phage genome and are thought to play a role in genetic recombination. Although the overall DNA sequence of phi P27 is not highly related to other known phages, the data obtained demonstrate a typical lambdoid genome structure.

Sensitivity of Shiga toxin-producing Escherichia coli (STEC) strains for colicins under different experimental conditions

Twenty Escherichia coli strains producing well-characterised colicins were tested for their inhibitory activity against five Shiga toxin-producing E. coli (STEC) strains using different media under aerobic and anaerobic conditions. The five STEC strains used were of serotype O26, O111, O128, O145 and O157:H7 which are frequently isolated serotypes associated with disease in humans. The main route of infection for humans is through the eating of badly cooked or handled beef. The major reservoir for STEC strains in cattle is the rumen. To mimic the situation in the rumen of cattle, overlay assays were also performed under anaerobic conditions in the presence of 30% rumen fluid. Colicins E1, E4, E8-J, K and S4 are most active against STEC strains under anaerobic conditions in the absence or presence of rumen fluid. These colicins will be used in future experiments with the aim to eradicate the presence of STEC in cattle.

EPEC, EAEC and STEC in stool specimens: prevalence and molecular epidemiology of isolates

Stool specimens of Finns (n = 695) with (n = 603) and without (n = 92) diarrhea were studied for enteropathogenic (EPEC), enteroaggregative (EAEC) and Shiga toxin-producing (STEC) Escherichia coli by PCR. The specific isolates were subsequently investigated for their O:H serotypes and were genotyped by pulsed-field gel electrophoresis (PFGE). A subset (n = 506) of the diarrheal and all non-diarrheal specimens were also searched for conventional enteric bacterial pathogens by standard methods. Diarrheagenic E. coli were found in 5.5% and other enteric pathogens in 6.7% of the patients with and in 2.2% and 1.1% of the subjects without diarrhea, respectively. Campylobacter (3.8%), EPEC (3.2%) and Salmonella (2.0%) were the most common findings, and were detected in diarrheal patients only. STEC were associated with bloody diarrhea (8/9 isolates), whereas EAEC were equally common (1%) in diarrheal and non-diarrheal subjects. Great genomial heterogeneity was seen among diarrheagenic E. coli, and only one EPEC isolate belonged to the "classic" EPEC serogroup (O55).

Occurrence of Escherichia coli O157 in Finnish cattle

Bovine faecal samples were collected during June-December 1997 at 14 major abattoirs slaughtering cattle in Finland. Escherichia coli O157 was isolated from 19 of the 1448 samples (1.31%) after enrichment and immunomagnetic separation (IMS). The positive faecal isolates originated from 16 farms and eight abattoirs. The occurrence of E. coli O157 was highest in July (8/204; 3.92%) and September (6/244; 2.46%). No E. coli O157 was detected in November and December, nor from the faecal samples from the northernmost region where cattle density is low. All of the isolates carried the eae gene and showed the enterohaemolytic phenotype. All except one were motile and had the flagella antigen H7. Seventeen of the isolates were positive for stx(2) gene and one carried both the stx(1) and stx(2) genes. Of the 17 isolates with stx genes, 16 were verocytotoxin-positive in a reversed passive latex agglutination test after polymyxin extraction but only eight without extraction. The isolates belonged to 10 different pulsed-field gel electrophoresis (PFGE) patterns. The most common PFGE pattern (1.42) was detected in eight isolates (42.1%). Four PFGE patterns (1.1; 1.6; 1.12; 1.14) were identical with those isolated from humans in Finland, suggesting that at least some human E. coli O157 infections may be of bovine origin.

Detection of verocytotoxin bound to circulating polymorphonuclear leukocytes of patients with hemolytic uremic syndrome

The epidemic form of hemolytic uremic syndrome (HUS) is the most common cause of acute renal failure in children and is characterized by a prodromal phase of sometimes bloody diarrhea. The role of verocytotoxin (VT)-producing Escherichia coli has been strongly implicated. Although antibodies against VT have been detected in the serum of patients with HUS, VT itself has never been detected in circulating blood. In this study, VT-2 was detected in the systemic circulation in 9 of 10 patients with the epidemic form of HUS. In those cases, VT-2 was bound exclusively to polymorphonuclear leukocytes (PMN). The detection of VT-2 bound to PMN was associated with the presence of diarrhea at the time the blood samples were obtained. The one patient for whom VT was not detected presented with atypical HUS. For 5 of the 10 patients with HUS who were studied, the time course of VT binding was analyzed; binding decreased in four patients. The finding of VT bound to PMN in the systemic circulation of patients with HUS is important for a clearer understanding of the pathogenesis of HUS and suggests new approaches for treatment in the future.

Phage types and genotypes of Shiga toxin-Producing Escherichia coli O157 in Finland

This study examined Shiga toxin-producing Escherichia coli (STEC) O157, using phage typing, pulsed-field gel electrophoresis, and typing of Shiga toxin variant genes by PCR with restriction fragment length polymorphism in an epidemiological survey of STEC O157 isolated from humans in Finland between 1990 and 1999.

Prevalence of diarrheagenic Escherichia coli in finns with or without diarrhea during a round-the-world trip

The incidence of diarrhea and the prevalence of bacterial enteropathogens, viruses, and parasites in feces of subjects with and without diarrhea were evaluated in 204 Finns traveling round the world (from Finland to China, Malaysia, Australia, Fiji, Chile, and Brazil and back to Finland). Special emphasis was placed on the finding of diarrheagenic Escherichia coli (enterotoxigenic, enteropathogenic, Shiga toxin-producing, and enteroaggregative strains) by PCR from growth on primary culture plates. From the PCR-positive samples, corresponding strains were isolated, confirmed as E. coli, and O serotyped. Of all the subjects, 37% experienced a total of 90 episodes of diarrhea. No adenoviruses or rotaviruses were detected, and findings of parasites were insignificant. In contrast, enteropathogenic bacteria were present in 62% of the 65 diarrheal and in 33% of the 127 nondiarrheal samples (P < 0.001); diarrheagenic E. coli strains were found in 35 and 26% of these, respectively (not statistically significant). As a single pathogen, E. coli was found in 20 and 24% of samples (not significant). Of all diarrheagenic E. coli strains, enteropathogenic strains were the most commonly found independently of the clinical picture of the subjects, whereas Salmonella enterica as a single pathogen was the most common non-E. coli organism found in diarrheal samples. Multiple bacterial pathogens were found 10 times more commonly in diarrheal than in nondiarrheal samples (20 versus 2%; P < 0.001).

Characterization of a shiga toxin 2e-converting bacteriophage from an Escherichia coli strain of human origin

An infectious Shiga toxin (Stx) 2e-converting bacteriophage (phiP27) was isolated from Stx2e-producing Escherichia coli ONT:H(-) isolate 2771/97 originating from a patient with diarrhea. The phage could be transduced to E. coli laboratory strain DH5alpha, and we could show that lysogens were able to produce biologically active toxin in a recA-dependent manner. By DNA sequence analysis of a 6,388-bp HindIII restriction fragment of phiP27, we demonstrated that the stx(2e) gene was located directly downstream of ileZ and argO tRNA genes. Although no analogue of an antiterminator Q encoding gene was present on this fragment, a lysis cassette comprising two holin genes which are related to the holin genes of Pseudomonas aeruginosa phage phiCTX and a gene homologous to the endolysin gene gp19 of phage PS3 were detected. The results of our study demonstrated for the first time that Stx2e can be encoded in the genome of an infectious bacteriophage.

Structural analysis of phage-borne stx genes and their flanking sequences in shiga toxin-producing Escherichia coli and Shigella dysenteriae type 1 strains

The stx-flanking regions of 49 Shiga toxin-producing Escherichia coli strains and nine Shigella dysenteriae serotype 1 strains containing either stx, stx(1), stx(2), or stx(2) variant genes, were examined. We analyzed these regions by PCR using a set of primers with one primer specific for the respective stx gene and a second primer complementary to sequences of Stx phages H-19B and 933W. We further characterized the amplification products by restriction endonuclease digestion and nucleotide sequencing. PCR products of stx(1)-containing E. coli strains of serogroups O157, O26, and 0103 showed the same lengths and similar restriction patterns. However, we failed to amplify the 3' stx-flanking region in stx(1)-harboring E. coli O111:H(-) strains. Stx2-producing E. coli strains revealed amplification products of different lengths and restriction patterns, suggesting greater heterogeneity than in stx(1)-positive strains. We also obtained specific PCR products for two Stx2c-producing and seven Stx2f-producing E. coli strains when they were subjected to PCR analysis. In nine S. dysenteriae type 1 strains, H-19B- and 933W-specific primers amplified only the 3' stx-flanking region. The results of our study demonstrate that the stx genes of all strains investigated are continuous with phage sequences. Whereas almost all strains except E. coli O111:H(-) strains were associated with a S-like gene, association with Q could not be demonstrated in nine S. dysenteriae type 1 strains and three E. coli strains. Furthermore, we showed that the organization of the stx-flanking regions is similar in all strains investigated, whereas fine-structure analysis showed subtle differences among the sequences examined. Our results support the hypothesis that stx genes in E. coli and S. dysenteriae are generally phage-borne.