[Transplantation of hematopoietic stem cells from umbilical cord blood]

Detection and antibiogram profile of diarrheagenic Escherichia coli isolated from two abattoir settings in northwest Ethiopia: a one health perspective

BACKGROUND

Diarrheagenic Escherichia coli (E. coli) is a zoonotic pathogen that contaminates abattoir workers, slaughter environments, slaughter equipment, and carcasses during abattoir processing. Infection with E. coli is associated with the consumption of contaminated food and water, and it is a potential threat to the health and welfare of both humans and animals. Hence, this study aimed to detect diarrheagenic E. coli and assess its antibiogram profile in two abattoir settings, in one health lens.

METHODS

A cross-sectional study in one health approach was conducted from December 2020 to June 2021. A total of 384 samples from abattoir workers' hands, carcasses, knives, cattle feces, abattoir water and effluents were collected. Bacterial culture and biochemical tests were conducted to isolate E. coli, while conventional polymerase chain reaction was performed to identify virulence genes. The antibiogram of diarrheagenic E. coli was tested against nine antimicrobials using the Kirby Bauer disk diffusion method.

RESULTS

A total of 115 (29.95%) E. coli were isolated from the 384 samples, and from these isolates, about 17 (14.8%) were confirmed to be diarrheagenic E. coli (DEC). Among the DEC pathotypes, nine (52.94%), five (29.4%), and three (17.65%) were Shiga toxin-producing, enterohemorrhagic, and enterotoxigenic E. coli, respectively. While 14 (82.35%) DEC isolates harbored the stx2 gene, five (29.41%) the eae gene, five (29.41%) the hlyA gene and three (17.65%) harbored the st gene. All the DEC isolates were resistant to erythromycin and vancomycin; whereas, they were susceptible to ampicillin, nalidixic acid and norfloxacin. Furthermore, 64.7% of DEC isolates showed resistance to both ceftazidime and kanamycin and 88.24% of the isolates showed multidrug resistance.

CONCLUSION

This study detected DEC isolates having different virulence genes, which showed single and multiple antimicrobial resistance. Given the existing poor hygienic and sanitary practices along the abattoir-to-table food chain, coupled with the habit of raw meat consumption, this result indicates a potential public and animal health risk from the pathogen and antimicrobial resistance.

Molecular detection and antibiogram of Shiga toxin-producing Escherichia coli (STEC) from raw milk in and around Bahir Dar town dairy farms, Ethiopia

Illnesses associated with consuming infected milk and milk products are a widespread problem in low and middle-income countries. Shiga toxin-producing Escherichia coli (STEC) is a bacterium commonly found in raw milk and causes foodborne diseases ranging from mild diarrhea to severe hemorrhagic colitis and hemolytic uremic syndrome. This study aimed to investigate the virulence gene and antimicrobial resistance profiles of Shiga toxin-producing E. coli strains isolated from raw milk in dairy farms in and around Bahir Dar town. Raw milk samples (n = 128) collected from December 2021 to July 2022 were cultured, and E. coli strains were isolated using standard methods. Shiga toxin-producing E. coli strains were identified genotypically by the presence of the virulence markers using a single-plex polymerase chain reaction. The antibiotic susceptibility testing of Shiga toxin-producing E. coli isolates was done by the agar disk diffusion method. In total, 32 E. coli isolates were recovered from milk samples from lactating animals. PCR screening of these isolates resulted in 19 (59.3%) positives for Shiga toxin-producing E. coli. The stx2 gene was detected in 53% of cases, followed by stx1 (31%) and eae (16%. The STEC isolates were highly sensitive to ciprofloxacin (94.7%) and kanamycin (89.5%), while exhibiting significant resistance to amoxicillin (89.5%) and streptomycin (73.7%). The present study points out the occurrence of virulent and antibiotic-resistant Shiga toxin-producing E. coli strains in raw milk that could pose a potential risk to public health. Further analysis by whole genome sequencing is necessary for an in-depth assessment and understanding of their virulence and resistance factors. Moreover, large-scale studies are needed to identify the prevalence and potential risk factors and to prevent the spread of antibiotic-resistant STEC strains in the milk production chain.

Occurrence of Escherichia coli Pathotypes in Diarrheic Calves in a Low-Income Setting

Different E. coli pathotypes are common zoonotic agents. Some of these pathotypes cause recurrent and widespread calf diarrhea and contribute to significant economic losses in the livestock sector worldwide in addition to putting humans at risk. Here, we investigated the occurrence of E. coli pathotypes in diarrheic calves in Ethiopia kept under various calf management practices. One hundred fecal samples were collected from diarrheic calves in 98 different farms. E. coli was isolated in the samples from 99 of the diarrheic calves, and virulence genes were detected in 80% of the samples. The occurrence of E. coli pathotypes in the samples was 32% ETEC, 23% STEC, 18% STEC/ETEC, 3% EPEC, 2% EAEC, and 1% EHEC. No diarrheic calves were positive for the EIEC and DAEC pathotypes. The occurrence of pathotypes was positively associated with female calves (EPEC, p = 0.006), aged less than 2 weeks (STEC, p = 0.059), and calves fed colostrum via the hand method (STEC, p = 0.008 and EAEC, p = 0.003). This study revealed that several E. coli pathotypes occurred among calves affected with diarrhea. Moreover, the presence of a mixed STEC/ETEC pathotypes infection was present in the studied low-income setting. These findings indicate a considerable risk for the zoonotic transmission from calves to humans and the options to provide the better management for younger calves in order to reduce the economic loss.

Molecular Epidemiology of Antimicrobial Resistance and Virulence Profiles of Escherichia coli, Salmonella spp., and Vibrio spp. Isolated from Coastal Seawater for Aquaculture

The occurrence of waterborne antimicrobial-resistant (AMR) bacteria in areas of high-density oyster cultivation is an ongoing environmental and public health threat given the popularity of shellfish consumption, water-related human recreation throughout coastal Thailand, and the geographical expansion of Thailand's shellfish industry. This study characterized the association of phenotypic and genotypic AMR, including extended-spectrum β-lactamase (ESBL) production, and virulence genes isolated from waterborne Escherichia coli (E. coli) (n = 84), Salmonella enterica (S. enterica) subsp. enterica (n = 12), Vibrio parahaemolyticus (V. parahaemolyticus) (n = 249), and Vibrio cholerae (V. cholerae) (n = 39) from Thailand's coastal aquaculture regions. All Salmonella (100.0%) and half of V. cholerae (51.3%) isolates harbored their unique virulence gene, invA and ompW, respectively. The majority of isolates of V. parahaemolyticus and E. coli, ~25% of S. enterica subsp. enterica, and ~12% of V. cholerae, exhibited phenotypic AMR to multiple antimicrobials, with 8.9% of all coastal water isolates exhibiting multidrug resistance (MDR). Taken together, we recommend that coastal water quality surveillance programs include monitoring for bacterial AMR for food safety and recreational water exposure to water for Thailand's coastal water resources.

A systematic review and meta-analysis of published literature on prevalence of non-O157 Shiga toxin-producing Escherichia coli serogroups (O26, O45, O103, O111, O121, and O145) and virulence genes in feces, hides, and carcasses of pre- and peri-harvest cattle worldwide

OBJECTIVE

The objective of this study was to summarize peer-reviewed literature on the prevalence and concentration of non-O157 STEC (O26, O45, O103, O111, O121, and O145) serogroups and virulence genes (stx and eae) in fecal, hide, and carcass samples in pre- and peri-harvest cattle worldwide, using a systematic review of the literature and meta-analyses.

DATA SYNTHESIS

Seventy articles were eligible for meta-analysis inclusion; data from 65 articles were subjected to random-effects meta-analysis models to yield fecal prevalence estimates. Meta-regression models were built to explore variables contributing to the between-study heterogeneity.

RESULTS

Worldwide pooled non-O157 serogroup, STEC, and EHEC fecal prevalence estimates (95% confidence interval) were 4.7% (3.4-6.3%), 0.7% (0.5-0.8%), and 1.0% (0.8-1.1%), respectively. Fecal prevalence estimates significantly differed by geographic region (P < 0.01) for each outcome classification. Meta-regression analyses identified region, cattle type, and specimen type as factors that contribute to heterogeneity for worldwide fecal prevalence estimates.

CONCLUSIONS

The prevalence of these global foodborne pathogens in the cattle reservoir is widespread and highly variable by region. The scarcity of prevalence and concentration data for hide and carcass matrices identifies a large data gap in the literature as these are the closest proxies for potential beef contamination at harvest.

Seasonal effect on Salmonella, Shiga toxin-producing E. coli O157:H7 and non-O157 in the beef industry in Colombia, South America

This research investigated the variations in the occurrence of Salmonella, STEC O157:H7 and non-O157 in the beef production chain in Colombia affected by seasons, hypothesizing that pathogen prevalence will be highest in the rainy season owing to soil moisture promoting bacteria multiplication and transfer between animals. To test this hypothesis, samples were obtained from five abattoirs, which represent 50% of the beef production in this country. A total of 1017 samples were collected, from which 606 were bovine feces, 206 were hide swabs, and 205 corresponded to carcass post-intervention. From the 1017 samples, 49.9% (n = 507) were collected during dry season, while 50.1% (n = 510) during rainy season. All samples (n = 1017) underwent screening for E. coli O157:H7 and Salmonella, while only a proportion of fecal samples (n = 339) were screened for the big six STEC serogroups and their virulence markers. The effect of season, age of animal and sex of animal were correlated with the prevalence results. A total of 84.7% of fecal samples carried virulence genes associated to STEC (stx or eae), suggesting that testing and control should be increased for the big-six STEC compared to E. coli O157:H7. Pathogen prevalence in feces was found to be 8.3%, 5.0%, and 51.0% for Salmonella, E. coli O157:H7 and STEC non-O157, respectively. Hides had a prevalence of 15.0% and 6.8% of Salmonella and E. coli O157:H7, respectively. Carcasses post-intervention were found to have 4.4% and 2.5% prevalence of Salmonella and E. coli O157:H7, respectively. A seasonal effect was found for fecal samples. E. coli O157 and non-O157 STEC shedding were significantly higher (P ≤ 0.05) during rainy season compared to dry season. In contrast, hides and carcasses were more likely to present lower incidence of pathogens during rainy months compared to dry season; however, it was significant only for Salmonella on carcasses with estimated odds of detection almost six times higher in the dry season relative to the rainy season (OR = 5.90, 95% CI 1.18-29.57).

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

Background and Aim:

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

Materials and Methods:

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

Results:

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

Conclusion:

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

Pathotyping of Escherichia coli isolated from community toilet wastewater and stored drinking water in a slum in Bangladesh

This study investigated the occurrence of Escherichia coli pathotypes in sanitary wastewater and drinking water in a Bangladeshi urban slum and the potential associations between these sources. We examined 621 E. coli isolates from sanitary wastewater and stored drinking water by multiplex PCR and dual-index sequencing, classifying them into eight pathotypes based on 14 virulence genes and additionally evaluating the possession of the human-specific E. coli genetic biomarker H8. The proportions of pathogenic E. coli were significantly different (P < 0·001) between wastewater (18·6%) and drinking water (1·7%). StIb-positive enterotoxigenic E. coli (ETEC) were predominant in wastewater, indicating that people in the site carried ETEC. In contrast, no ETEC was present in drinking water and the proportion of H8-positive isolates was significantly smaller (7·8%) than that in wastewater (16·3%) (P = 0·001). Our findings indicate that sanitary wastewater from the slum was heavily contaminated with pathogenic E. coli, posing a great health risk. Furthermore, E. coli contamination of drinking water could be derived from not only human but also other sources.

SIGNIFICANCE AND IMPACT OF THE STUDY

Sanitary wastewater from an urban slum was heavily contaminated with pathogenic Escherichia coli. It is worth noting a great health risk of accidental exposure to pathogenically contaminated wastewater improperly discharged in and around urban slums. The distinct difference in pathotypes between wastewater and drinking water and the significantly smaller positive proportion of the human-specific E. coli genetic biomarker (H8) in drinking water indicate that drinking water contamination could be derived from not only human but also other sources. This highlights that pathotyping in association with the H8 marker provides an indication of pathogen contamination sources of environmental transmission media.

Detection and drug resistance profile of Escherichia coli from subclinical mastitis cows and water supply in dairy farms in Saraburi Province, Thailand

Subclinical mastitis is a persistent problem in dairy farms worldwide. Environmental Escherichia coli is the bacterium predominantly responsible for this condition. In Thailand, subclinical mastitis in dairy cows is usually treated with various antibiotics, which could lead to antibiotic resistance in bacteria. E. coli is also a reservoir of many antibiotic resistance genes, which can be conveyed to other bacteria. In this study, the presence of E. coli in milk and water samples was reported, among which enteropathogenic E. coli was predominant, followed by enteroaggregative E. coli and enterohemorrhagic E. coli, which was found only in milk samples. Twenty-one patterns of antibiotic resistance were identified in this study. Ampicillin- and carbenicillin-resistant E. coli was the most common among the bacterial isolates from water samples. Meanwhile, resistance to ampicillin, carbenicillin, and sulfamethoxazole-trimethoprim was the pattern found most commonly in the E. coli from milk samples. Notably, only the E. coli from water samples possessed ESBL phenotype and carried antibiotic resistance genes, bla_TEM and bla_CMY-2. This indicates that pathogenic E. coli in dairy farms is also exposed to antibiotics and could potentially transfer these genes to other pathogenic bacteria under certain conditions.

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

Background and Aim:

Shiga toxin-producing Escherichia coli (STEC) are important pathogens of global significance. STEC are responsible for numerous food-borne outbreaks worldwide and their presence in food is a potential health hazard. The objective of the present study was to determine the incidence of STEC in fresh seafood in Mumbai, India, and to characterize STEC with respect to their virulence determinants.

Materials and Methods:

A total of 368 E. coli were isolated from 39 fresh seafood samples (18 finfish and 21 shellfish) using culture-based methods. The isolates were screened by polymerase chain reaction (PCR) for the genes commonly associated with STEC. The variant Shiga toxin genes were confirmed by Southern blotting and hybridization followed by DNA sequencing.

Results:

One or more Shiga toxins genes were detected in 61 isolates. Of 39 samples analyzed, 10 (25.64%) samples harbored STEC. Other virulence genes, namely, eaeA (coding for an intimin) and hlyA (hemolysin A) were detected in 43 and 15 seafood isolates, respectively. The variant stx1 genes from 6 isolates were sequenced, five of which were found to be stx1d variants, while one sequence varied considerably from known stx1 sequences. Southern hybridization and DNA sequence analysis suggested putative Shiga toxin variant genes (stx2) in at least 3 other isolates.

Conclusion:

The results of this study showed the occurrence of STEC in seafood harboring one or more Shiga toxin genes. The detection of STEC by PCR may be hampered due to the presence of variant genes such as the stx1d in STEC. This is the first report of stx1d gene in STEC isolated from Indian seafood.

Characterization of Shiga Toxigenic Escherichia coli O157 and Non-O157 Isolates from Ruminant Feces in Malaysia

Shiga toxigenic Escherichia coli (STEC) O157 and several other serogroups of non-O157 STEC are causative agents of severe disease in humans world-wide. The present study was conducted to characterize STEC O157 and non-O157 serogroups O26, O103, O111, O121, O45, and O145 in ruminants in Malaysia. A total of 136 ruminant feces samples were collected from 6 different farms in Peninsular Malaysia. Immunomagnetic beads were used to isolate E. coli O157 and non-O157 serogroups, while PCR was used for the detection and subtyping of STEC isolates. STEC O157:H7 was isolated from 6 (4%) feces samples and all isolates obtained carried stx 2c, eaeA-γ1, and ehxA. Non-O157 STEC was isolated from 2 (1.5%) feces samples with one isolate carrying stx 1a, stx 2a, stx 2c, and ehxA and the other carrying stx 1a alone. The presence of STEC O157 and non-O157 in a small percentage of ruminants in this study together with their virulence characteristics suggests that they may have limited impact on public health.

An epidemiological and environmental study of Shiga toxin-producing Escherichia coli in India

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens of worldwide importance, but a shortage of data exists for STEC isolation from India. Therefore, an epidemiological and environmental study that covers a large geographic area in north India was conducted. Ruminant stool samples (n=650) were collected from 59 dairies. Meat samples (n=450) were collected from local abattoirs and the main slaughterhouse of the region. Additionally, 600 human cases of diarrhea and hemolytic uremic syndrome were screened for STEC. Isolates were characterized for the virulence gene profiles and for the serogroups and were submitted to molecular typing by the multilocus variable-number tandem-repeat analysis (MLVA). Overall, 12.3% of animal stool samples and 6.3% of mutton samples (n=160) were positive for STEC. Additionally, STEC were isolated from 1.7% and 1.6% of watery (n=290) and bloody (n=310) stool specimens, respectively. Animal stool isolates were significantly more prevalent in hilly areas (p<0.05) than in plain areas. Polymerase chain reaction demonstrated the presence of stx1, stx2, hly, espP, saa, toxB, and iha genes in 117 (83.5%), 94 (67.1%), 77 (55%), 33 (23%), 62 (44.2%), 29 (20.7%), and 51 (36%) of the isolates, respectively. Five new serogroups (O55, O33, O173, O165, and O136) are being reported for the first time from India. Four isolates from serogroup O103 were found in mutton and stool specimens of cattle and humans (n=160). One isolate from serogroup O104 was isolated from a mutton sample. MLVA suggested the potential transmission of STEC from contaminated meat and bovine sources. This study confirms the frequent contamination of mutton samples (24%), whereas chicken and pork samples were negative for STEC. This study demonstrates the presence of STEC that carry a large repertoire of virulence genes and the potential transmission of STEC from contaminated mutton and animal stools in north India.

Molecular characterization of Shiga-toxigenic Escherichia coli isolated from diverse sources from India by multi-locus variable number tandem repeat analysis (MLVA)

In a first study from India, a diverse collection of 140 environmental and clinical non-O157 Shiga-toxigenic Escherichia coli strains from a large geographical area in north India was typed by multi-locus variable number tandem repeat analysis (MLVA). The distribution of major virulence genes stx1, stx2 and eae was found to be 78%, 70% and 10%, respectively; 15 isolates were enterohaemorrhagic E. coli (stx1 +/stx2 + and eae +). By MLVA analysis, 44 different alleles were obtained. Dendrogram analysis revealed 104 different genotypes and 19 MLVA-type complexes divided into two main lineages, i.e. mutton and animal stool. Human isolates presented a statistically significant greater odds ratio for clustering with mutton samples compared to animal stool isolates. Five human isolates clustered with animal stool strains suggesting that some of the human infections may be from cattle, perhaps through milk, contact or the environment. Further epidemiological studies are required to explore these sources in context with occurrence of human cases.

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.

Isolation, molecular characterization and antibiotic resistance of Shiga Toxin-Producing Escherichia coli (STEC) from buffalo in India

In total, 363 Escherichia coli were isolated from 165 faecal samples of healthy buffaloes in West Bengal, India. Twenty-four of these isolates (6·61%) were found to carry at least one gene characteristic for Shiga toxin-producing Escherichia coli (STEC). These STEC strains belonged to 13 different O-serogroups. The stx1 gene was present in 23 (95·8%) of total STEC isolates, whereas 20 (83·3%) STEC isolates carried the gene stx2. Twelve strains of E. coli (50% of total STEC isolates) possessed enterohaemolysin (ehxA) gene in combination with others. Fourteen (58·33%) isolates found to possess saa gene. However, no E. coli was detected harbouring gene for intimin protein (eaeA). Of 23 stx1 -positive isolates, seven (30·43%) were positive for genes of the stx1C subtype. Of the 20 isolates with the stx2 gene, 25% (5/20) possessed stx2C and 10% (2/20) possessed stx2d gene. The phylogenetic analysis after RAPD of STEC strains revealed six major clusters. The isolated STEC strains were resistant most frequently to erythromycin (95·83%), cephalothin (62·5%), amikacin (54·17%), kanamycin (45·83%) and gentamicin (41·67%) group of antibiotics. No ESBL-producing (blaCTXM , blaTEM , blaSHV ) or quinolone resistance gene (qnrA) was detected in the STEC isolates.

Prevalence, biogenesis, and functionality of the serine protease autotransporter EspP

Enterohemorrhagic E. coli (EHEC) causes severe diseases in humans worldwide. One of its virulence factors is EspP, which belongs to the serine protease autotransporters of Enterobacteriaceae (SPATE) family. In this review we recapitulate the current data on prevalence, biogenesis, structural properties and functionality. EspP has been used to investigate mechanistic details of autotransport, and recent studies indicate that this transport mechanism is not autonomous but rather dependent on additional factors. Currently, five subtypes have been identified (EspPα-EspPε), with EspPα being associated with highly virulent EHEC serotypes and isolates from patients with severe disease. EspPα has been shown to degrade major proteins of the complement cascade, namely C3 and C5 and probably interferes with hemostasis by cleavage of coagulation factor V. Furthermore, EspPα is believed to contribute to biofilm formation perhaps by polymerization to rope-like structures. Together with the proteolytic activity, EspPα might ameliorate host colonization and interfere with host response.

Detection of Shiga toxin variants among Shiga toxin-forming Escherichia coli isolates from animal stool, meat and human stool samples in India

AIM

To study the prevalence and distribution of various variants in the stx gene of Shiga toxin-producing Escherichia coli (STEC) isolated from diverse environmental sources (animal stool, meat) and human illness, from a large geographic area in India, and to understand the association between variants, serotype distribution and human disease.

METHODS AND RESULTS

A surveillance for STEC was conducted in the semi-urban and rural areas of Punjab, Himachal, Haryana and Chandigarh. Shiga toxin-producing Escherichia coli isolates (80 animal stool, 39 meat, 21 human stool from diarrhoea and HUS cases) were characterized for stx variants by PCR. Shiga-like toxin (Stx) was detected using Ridascreen-EIA assay. Variant stx2c was the most common (25·1%), followed by stx1d (13%), stx1c (10·7%) and stx2d (9·2%), whereas stx2e, stx2f and stx2g were absent. Only 8/21 (38%) human isolates harboured stx variants, of which stx2c and stx2d were found in 2 and 1 isolates, respectively. The low frequency of carriage of these potentially more pathogenic variants may explain the low severity of human illness seen in India. Shiga-like toxin was detected in only 42 of the isolates positive for the stx genes probably due to the low levels of toxins produced. Serogroup distribution was found to be diverse, suggesting the lack of any predominant circulating type.

CONCLUSIONS

The presence of stx variants 1c, 1d, 2c and stx2d in diverse environmental and human sources in India was demonstrated. The prevalence of the most common subtype stx2c found in this study in animal isolates may pose a threat to the public health. We report the subtyping of human STEC isolates and report the presence of stx1d subtype for the first time from India.

SIGNIFICANCE AND IMPACT OF THE STUDY

We demonstrated the presence of potentially pathogenic subtypes in the environmental specimens which may act as a reservoir for human infections. Serogroups new to India were also reported.

Pathotypes of diarrheagenic Escherichia coli in children attending a tertiary care hospital in South India

The prevalence of diarrheagenic Escherichia coli (DEC) in children under 5 years was studied in children with diarrhea and controls in South India. Four polymerase chain reaction (PCR) "schemes" were used to detect genes of the 6 pathotypes of DEC. In 394 children with diarrhea, 203 (52%) DEC infections were found. Among the 198 controls, 126 (63%) DEC infections were found. Enteroaggregative E. coli was the most common pathotype by multiplex PCR both in cases (58, 14.7%) and controls (47, 23.7%), followed by enteropathogenic E. coli seen in 10% cases and 8% of controls. Enterotoxigenic E. coli (ETEC), enterohemorrhagic E. coli (EHEC), enteroinvasive E. coli (EIEC), and diffusely adherent E. coli (DAEC) were found in 4.1%, 2.0%, 1.0%, and 0.5% of cases, respectively. ETEC was found in 2.5% of controls, but EHEC, EIEC, and DAEC were not detected. Overall, no single assay worked well, but by discounting genes with a pathogenicity index of less than 1, it was possible to use the PCR assays to identify DEC in 75/394 (19%) cases and 12/198 (6.1%) controls, while mixed infection could be identified in 8/394 (2%) cases and 2/198 (1%) controls.

Isolation of atypical enteropathogenic Escherichia coli from children with and without diarrhoea in Delhi and the National Capital Region, India

A total of 17 typical and atypical enteropathogenic Escherichia coli (EPEC) were isolated from 396 children with and without diarrhoea. Out of 12 EPEC isolates from patients with diarrhoea, 3 (25 %) were atypical EPEC while 9 (75 %) were typical EPEC. It was observed that atypical EPEC strains had colonized the intestines of healthy children and its isolation rates were higher in healthy children than in children with diarrhoea. Interestingly all of the atypical EPEC isolates carried a megaplasmid, mostly comparable with the size of EPEC adherence factor (EAF) encoding gene but no virulence gene was detected in this megaplasmid. Studies also indicated that multidrug resistance EPEC are emerging and all the atypical EPEC strains showed significantly less resistance to all antimicrobial agents used in this study than typical EPEC. This study also supports the opinion that Shiga toxin-producing E. coli does not pose a major threat to human health in India. Subtyping analysis reveals that eae-α1, eae-β2 and eae-λ could be common EPEC subtypes prevalent in children with diarrhoea in Delhi. The present study is believed to be the first report of the detection of atypical EPEC from children without diarrhoea and records of isolation of eae-γ1, eae-γ2 and the rare eae-λ subtype in India. The data also indicated that typical EPEC are a common cause of diarrhoea and atypical EPEC are emerging as colonizers of the intestine of children with and without diarrhoea in Delhi and the National Capital Region, India.

Pathogenic potential of Aeromonas hydrophila isolated from surface waters in Kolkata, India

Members of the genus Aeromonas (family Aeromonadaceae) are medically important, Gram-negative, rod-shaped micro-organisms and are ubiquitous in aquatic environments. Aeromonas species are increasingly recognized as enteric pathogens; they possess several virulence factors associated with human disease, and represent a serious public health concern. In the present study, putative virulence traits of Aeromonas hydrophila isolates collected from different natural surface waters of Kolkata, India, were compared with a group of clinical isolates from the same geographical area using tissue culture and PCR assays. Enteropathogenic potential was investigated in the mouse model. Of the 21 environmental isolates tested, the majority showed cytotoxicity to HeLa cells (81 %), haemolysin production (71 %) and serum resistance properties (90 %), and they all exhibited multi-drug resistance. Some of the isolates induced fluid accumulation (FA ratio≥100), damage to the gut and an inflammatory reaction in the mouse intestine; these effects were comparable to those of clinical strains of A. hydrophila and toxigenic Vibrio cholerae. Interestingly, two of the isolates evoked a cell vacuolation effect in HeLa cells, and were also able to induce FA. These findings demonstrate the presence of potentially pathogenic and multi-drug-resistant A. hydrophila in the surface waters, thereby indicating a significant risk to public health. Continuous monitoring of surface waters is important to identify potential water-borne pathogens and to reduce the health risk caused by the genus Aeromonas.

Comparison of enrichment procedures for shiga toxin-producing Escherichia coli in wastes from commercial swine farms

Three methods for enrichment of Shiga toxin-producing Escherichia coli (STEC) were compared using waste pit samples from swine production facilities housing 50 to 3,000 animals. The STEC gene stx2 was detected in 5 of 17 pooled samples using a U.S. Department of Agriculture (USDA) enrichment procedure, 6 of 17 samples using a U.S. Food and Drug Administration (FDA) enrichment procedure, and 8 of 17 samples using an experimental acid enrichment. All isolates were non-O157 and 5 of 6 were positive for enterotoxigenic E. coli-associated heat stable toxins a and b. The three enrichment procedures were also tested for their ability to support growth of 31 strains of STEC. The acid enrichment media supported growth of 100% of the strains, the FDA medium supported 77% of the strains, and the USDA medium supported 16% of the strains.

Serogroup distribution and virulence characteristics of sorbitol-negative Escherichia coli from food and cattle stool

AIMS

To (i) study the serogroup distribution and virulence characteristics of non-sorbitol-fermenting Escherichia coli isolates from foods of animal origin and cattle faeces and (ii) re-examine the true sorbitol and beta-D-glucuronidase (GUD) reactions of sorbitol-negative (Sor(-)) strains from MacConkey sorbitol agar (SMAC) to assess their phenotypic similarity with E. coli O157.

METHODS AND RESULTS

One hundred and thirty Sor(-)E. coli were isolated from 556 food samples and 177 cattle stool samples using cefixime tellurite-supplemented SMAC (CT-SMAC) and chromogenic HiCrome MS.O157 agar respectively. Based on typing of somatic antigen, the isolates were classified into 38 serogroups. PCR results identified about 40% strains, belonging to O5, O8, O20, O28, O48, O60, O78, O82, O84, O101, O110, O123, O132, O156, O157, O-rough and OUT as Shiga toxigenic. Majority of O5, O84, O101, O105, O123, O157, O-rough and OUT strains were enterohaemolytic. Further, 39.2% and 63.1% of Sor(-) isolates from CT-SMAC fermented sorbitol in phenol red broth and hydrolysed 4-methylumbelliferyl-beta-D-glucuronide (MUG) respectively. Members of serogroups O5, O28, O32, O81, O82, O84, O101, O-rough lacked both the sorbitol fermentation (broth test) and GUD activity and might create confusion in phenotypic identification of E. coli O157.

CONCLUSIONS

Sor(-)E. coli isolates from raw meat, milk, shrimp and cattle stool belonged to 38 serogroups, with E. coli O157 constituting only 14.6% of the isolates. Many of these nonclinical Sor(-) strains were potentially pathogenic. Nearly 39% of these Sor(-)E. coli from CT-SMAC fermented sorbitol in broth, indicating the need for confirmation of sorbitol reaction in broth.

SIGNIFICANCE AND IMPACTS OF THE STUDY

Classical sorbitol utilization and GUD tests are not likely definitive tests for E. coli O157. Further improvement of differential media based on these phenotypic properties is necessary for detection of pathogenic serotypes from foods and environmental samples.

Microbiological quality of finfish and shellfish with special reference to shiga toxin-producing Escherichia coli O157

The objective of this study was to determine the microbiological quality of fish and shellfish from Kolkata, India, with special emphasis on E. coli O157. Fresh and ice-preserved Labeo rohita, Catla catla, Cirrhinus mrigala, Oreochromis mossambica, Heteropneustesfossilis, Clarias batrachus, and Penaeus monodon were examined for total heterotrophic bacteria and coliform loads and presence of E. coli and E. coli serotype O157 by culture method. While the total plate count of bacteria was within acceptable or marginally acceptable limits for most samples, fishes were contaminated with coliforms, including E. coli, indicating poor hygiene and sanitary conditions. Although E. coli O157 could not be detected, a few samples were contaminated with non-O157 serotypes of enterohaemolysin- and Shiga toxin-producing E. coli, raising public health concern.

Putative virulence traits and pathogenicity of Vibrio cholerae Non-O1, Non-O139 isolates from surface waters in Kolkata, India

Vibrio cholerae non-O1, non-O139 was isolated from natural surface waters from different sites sampled in diarrhea endemic zones in Kolkata, India. Twenty-one of these isolates were randomly selected and included in the characterization. The multiserogroup isolates were compared by their virulence traits with a group of clinical non-O1, non-O139 isolates from the same geographic area. Of the 21 environmental isolates, 6 and 14 strains belonged to Heiberg groups I and II, respectively. Three of the environmental isolates showed resistance to 2,2-diamine-6,7-diisopropylpteridine phosphate. All of the non-O1, non-O139 strains were positive for toxR, and except for one environmental isolate, none of them were positive for tcpA in the PCR assay. None of the isolates were positive for genes encoding cholera toxin (ctxA), heat-stable toxin (est), heat-labile toxin (elt), and Shiga toxin variants (stx) of Escherichia coli. Additionally, except for one environmental isolate (PC32), all were positive for the gene encoding El Tor hemolysin (hly). The culture supernatants of 86% (18 of 21) of the environmental isolates showed a distinct cytotoxic effect on HeLa cells, and some of these strains also produced cell-rounding factor. The lipase, protease, and cell-associated hemagglutination activities and serum resistance properties of the environmental and clinical isolates did not differ much. However, seven environmental isolates exhibited very high hemolytic activities (80 to 100%), while none of the clinical strains belonged to this group. The environmental isolates manifested three adherence patterns, namely, carpet-like, diffuse, and aggregative adherence, and the clinical isolates showed diffuse adherence on HeLa cells. Of the 11 environmental isolates tested for enteropathogenic potential, 8 (73%) induced positive fluid accumulation (>/=100) in a mouse model, and the reactivities of these isolates were comparable to those of clinical strains of non-O1, non-O139 and toxigenic O139 V. cholerae. Comparison of the counts of the colonized environmental and clinical strains in the mouse intestine showed that the organisms of both groups had similar colonizing efficiencies. These findings indicate the presence of potentially pathogenic V. cholerae non-O1, non-O139 strains in surface waters of the studied sites in Kolkata.

Backpacking in Yosemite and Kings Canyon National Parks and neighboring wilderness areas: how safe is the water to drink?

OBJECTIVE

The objective of this study was to determine the risk of acquiring disease from popular Sierra Nevada wilderness area lakes and streams. This study examines the relative risk factors for harmful waterborne microorganisms using coliforms as an indicator.

METHODS

Water was collected in the backcountry Yosemite and Kings Canyon National Parks and neighboring wilderness areas. A total of 72 sites from lakes or streams were selected to statistically differentiate the risk categories: (1) natural areas rarely visited by humans or domestic animals; (2) human day use-only areas; (3) high use by backpackers; (4) high use by pack animals; and (5) cattle- and sheep-grazing tracts. Water was collected in sterile test tubes and Millipore coliform samplers during the summer of 2006. Water was analyzed at the university microbiology lab, where bacteria were harvested and then subjected to analysis using standardized techniques. Statistical analysis to compare site categories was performed using Fisher's exact test.

RESULTS

Coliforms were found in none of the 13 wild sites, none of the 12 day hike sites, and only 3 of 18 backpacker sites (17%). In contrast, 14 of 20 sites (70%) with pack animal traffic yielded coliforms, and all 9 sites (100%) below the cattle-grazing areas grew coliforms. Differences between backpacker versus cattle or pack areas were significant, p <or= 0.05. All samples grew normal aquatic bacteria. Sites below cattle grazing and pack animal use tended to have more total heterotrophic bacteria.

CONCLUSIONS

Alpine wilderness water below cattle areas used by pack animals is at risk for containing coliform organisms. Water from wild, day hike, or backpack areas showed far less risk for coliforms.

Serogroups, atypical biochemical characters, colicinogeny and antibiotic resistance pattern of Shiga toxin-producing Escherichia coli isolated from diarrhoeic calves in Gujarat, India

This study was designed to investigate the antibiotic resistance, colicinogeny, serotyping and atypical biochemical characteristics of 41 Shiga toxin-producing Escherichia coli (STEC) strains detected using polymerase chain reaction from 90 E. coli strains isolated from 46 diarrhoeic calves. The STEC strains belonged to 14 different serogroups. Seventeen per cent of the STEC strains carried the eaeA gene while 14.28% of the 49 non-STEC strains were eaeA positive. Twenty eight (68.29%) of the 41 STEC strains were rhamnose non-fermentors. All the STEC strains revealed resistance to at least three of the antibiotics tested. 100% resistance was found against kanamycin and cephalexin followed by cephaloridine, enrofloxacin, amikacin, ampicillin, tetracycline, ceftiofur, ciprofloxacin, colistin and co-trimoxazole. Eighteen (44%) of the STEC strains produced colicin and all these colicinogenic strains were resistant to three or more antibiotics. Eleven STEC strains (26.82%) showed urease activity. The results of this study suggest that diarrhoeic calves are an important reservoir of STEC strains that are potentially pathogenic for farm animals and humans. Moreover, rhamnose fermentation, colicinogeny and atypical biochemical behaviour, such as urease activity, may serve as important markers or diagnostic tools for epidemiological surveys to trace the source of infection in disease 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.

Development of a simple latex agglutination assay for detection of shiga toxin-producing Escherichia coli (STEC) by using polyclonal antibody against STEC

Rabbit antiserum raised against the whole-cell antigen of Shiga toxin-producing Escherichia coli (STEC) strain VT3 (stx1+ stx2+ eae+) was repeatedly adsorbed with heat-killed cells of different non-STEC strains and other enteric bacteria. Thus, the antiserum obtained was designated VT3 antiserum. VT3 antiserum reacted with intimin type gamma. We assessed the reactivity of VT3 antiserum to whole-cell lysates of 87 strains of E. coli and other enteric bacteria by immunoblotting. The antiserum recognized the 97-kDa protein in whole-cell lysate from strain VT3, and 36 (83.7%) of the 43 STEC strains were positive for the STEC antigen. None of the non-STEC strains or strains of other species examined tested positive by immunoblotting. Based on this result, we developed a latex agglutination assay for the detection of STEC strains. Thirty-five (81.4%) of the 43 STEC strains tested positive for the STEC antigen by the latex agglutination assay. One (3.3%) of the 30 non-STEC strains and none of the strains of the other enteric bacteria included in this study tested positive by the latex agglutination assay. The corresponding specificity of the latex agglutination assay was approximately 98%. Results of this study showed the production of STEC antiserum and the generation of a simple, cost-effective, sensitive, and specific latex agglutination assay for establishing an etiological diagnosis of STEC.

Prevalence and pathogenicity of Shiga toxin-producing Escherichia coli in beef cattle and their products1,2

During the past 23 yr, a large number of human illness outbreaks have been traced worldwide to consumption of undercooked ground beef and other beef products contaminated with Shiga toxin-producing Escherichia coli (STEC). Although several routes exist for human infection with STEC, beef remains a main source. Thus, beef cattle are considered reservoirs of O157 and nonO157 STEC. Because of the global nature of the food supply, safety concerns with beef will continue, and the challenges facing the beef industry will increase at the production and processing levels. To be prepared to address these concerns and challenges, it is critical to assess the beef cattle role in human infection with STEC. Because most STEC outbreaks in the United States were traced to beef containing E. coli O157:H7, the epidemiological studies have focused on the prevalence of this serotype in beef and beef cattle. Worldwide, however, additional STEC serotypes (e.g., members of the O26, O91, O103, O111, O118, O145, and O166 serogroups) have been isolated from beef and caused human illnesses ranging from bloody diarrhea and hemorrhagic colitis to the life-threatening hemolytic uremic syndrome (HUS). To provide a global assessment of the STEC problem, published reports on beef and beef cattle in the past 3 decades were evaluated. The prevalence rates of E. coli O157 ranged from 0.1 to 54.2% in ground beef, from 0.1 to 4.4% in sausage, from 1.1 to 36.0% in various retail cuts, and from 0.01 to 43.4% in whole carcasses. The corresponding prevalence rates of nonO157 STEC were 2.4 to 30.0%, 17.0 to 49.2%, 11.4 to 49.6%, and 1.7 to 58.0%, respectively. Of the 162 STEC serotypes isolated from beef products, 43 were detected in HUS patients and 36 are known to cause other human illnesses. With regard to beef cattle, the prevalence rates of E. coli O157 ranged from 0.3 to 19.7% in feedlots and from 0.7 to 27.3% on pasture. The corresponding prevalence rates of nonO157 STEC were 4.6 to 55.9% and 4.7 to 44.8%, respectively. Of the 373 STEC serotypes isolated from cattle feces or hides, 65 were detected in HUS patients and 62 are known to cause other human illnesses. The results indicated the prevalence of a large number of pathogenic STEC in beef and beef cattle at high rates and emphasized the critical need for control measures to assure beef safety.

Serotypes, virulence genes and intimin types of Shiga toxin (verocytotoxin)-producing Escherichia coli isolates from minced beef in Lugo (Spain) from 1995 through 2003

Background

Shiga toxin-producing Escherichia coli (STEC) have emerged as pathogens that can cause food-borne infections and severe and potentially fatal illnesses in humans, such as haemorrhagic colitis (HC) and haemolytic uraemic syndrome (HUS). In Spain, like in many other countries, STEC strains have been frequently isolated from ruminants, and represent a significant cause of sporadic cases of human infection. In view of the lack of data on STEC isolated from food in Spain, the objectives of this study were to determine the level of microbiological contamination and the prevalence of STEC O157:H7 and non-O157 in a large sampling of minced beef collected from 30 local stores in Lugo city between 1995 and 2003. Also to establish if those STEC isolated from food possessed the same virulence profiles as STEC strains causing human infections.

Results

STEC were detected in 95 (12%) of the 785 minced beef samples tested. STEC O157:H7 was isolated from eight (1.0%) samples and non-O157 STEC from 90 (11%) samples. Ninety-six STEC isolates were further characterized by PCR and serotyping. PCR showed that 28 (29%) isolates carried stx₁ genes, 49 (51%) possessed stx₂ genes, and 19 (20%) both stx₁ and stx₂. Enterohemolysin (ehxA) and intimin (eae) virulence genes were detected in 43 (45%) and in 25 (26%) of the isolates, respectively. Typing of the eae variants detected four types: γ1 (nine isolates), β1 (eight isolates), ε1 (three isolates), and θ (two isolates). The majority (68%) of STEC isolates belonged to serotypes previously detected in human STEC and 38% to serotypes associated with STEC isolated from patients with HUS. Ten new serotypes not previously described in raw beef products were also detected. The highly virulent seropathotypes O26:H11 stx₁ eae-β1, O157:H7 stx₁stx₂ eae-γ1 and O157:H7 stx₂eae-γ1, which are the most frequently observed among STEC causing human infections in Spain, were detected in 10 of the 96 STEC isolates. Furthermore, phage typing of STEC O157:H7 isolates showed that the majority (seven of eight isolates) belonged to the main phage types previously detected in STEC O157:H7 strains associated with severe human illnesses.

Conclusion

The results of this study do not differ greatly from those reported in other countries with regard to prevalence of O157 and non-O157 STEC in minced beef. As we suspected, serotypes different from O157:H7 also play an important role in food contamination in Spain, including the highly virulent seropathotype O26:H11 stx₁ eae-β1. Thus, our data confirm minced beef in the city of Lugo as vehicles of highly pathogenic STEC. This requires that control measures to be introduced and implemented to increase the safety of minced beef.

Isolation of potentially pathogenic Escherichia coli O157:H7 from the Ganges River

Escherichia coli serotype O157:H7 was detected among bacteria collected from the Ganges River. O157:H7 isolates tested positive for stx(1), stx(2), and eae gene sequences. Identification of potentially pathogenic isolates from extensively used source water indicates that O157:H7 may be a significant but as yet underacknowledged public health concern in India.

Occurrence, virulence characteristics and antimicrobial resistance of Escherichia coli O157 in slaughtered cattle and diarrhoeic calves in West Bengal, India

AIMS

(i) To study the occurrence of Escherichia coli serotype O157 in cattle stool in West Bengal, India, and (ii) the virulence properties and antimicrobial resistance of the E. coli isolates.

METHODS AND RESULTS

Following enrichment in modified EC broth and plating onto HiCrome MS.O157 agar, a total of 14 strains of E. coli serotype O157 was isolated from faecal samples from two (2.04%) slaughtered cattle and six (7.59%) diarrhoeic calves. By multiplex PCR, Shiga toxin genes were detected in all the isolates. The enterohaemolysin phenotype was found in all, but one strain. Among 14 strains, ten were resistant to at least one of the antimicrobial agents tested. Multiple antibiotic resistance was frequent.

CONCLUSIONS

The study showed that occurrence of Shiga toxin-producing and multiple antibiotic-resistant E. coli O157 among cattle population in this region of India is significant.

SIGNIFICANCE AND IMPACT OF THE STUDY

Considering routine human contacts with cattle, a large human population in this region may be at risk for exposure to Shiga toxin-producing E. coli O157.

Shiga toxin-producing Escherichia coli and enteropathogenic Escherichia coli in healthy goats in India: occurrence and virulence properties

AIMS

To describe the occurrence and virulence gene pattern of shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) in healthy goats of Jammu and Kashmir, India.

METHODS AND RESULTS

A total of 220 E. coli strains belonging to 60 different 'O' serogroups was isolated from 206 local (nonmigratory) and 69 migratory goats. All the 220 strains were screened for the presence of stx(1), stx(2), eaeA and hlyA genes. Twenty-eight E. coli (75.6%) strains from local and nine (24.3%) strains from migratory goats belonging to 18 different serogroups showed at least presence of one virulence gene studied. Twenty-eight strains (16.47%) (belonging to 13 different serogroups) from local goats carried stx(1) gene alone or in combination with stx(2) gene, while as only one strain (2%) from migratory goats possessed stx(2) gene alone. Interestingly in the present study none of the STEC strains carried eaeA gene. Similarly, none of the strains from local goats possessed eaeA and none of the migratory goats possessed stx(1) gene. Eight strains (16%) (belonging to four different serogroups) from migratory goats carried eaeA gene. Twenty-five (14.7%) and seven (14%) strains from local and migratory goats harboured hlyA gene respectively.

CONCLUSIONS

Healthy goats of Jammu and Kashmir state serve as a reservoir of STEC and EPEC. Further studies in this direction are needed to work out whether or not they are transmitted to humans in this part of world.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first report of isolation of STEC and EPEC strains from healthy goats in Jammu and Kashmir State of India, which could be a source of infection to humans.

Comparison of a PCR-restriction fragment length polymorphism (PCR-RFLP) assay to pulsed-field gel electrophoresis to determine the effect of repeated subculture and prolonged storage on RFLP patterns of Shiga toxin-producing Escherichia coli O157:H7

In this study, we compared a recently developed PCR-restriction fragment length polymorphism (PCR-RFLP) assay with pulsed-field gel electrophoresis (PFGE) using three different Shiga toxin-producing Escherichia coli (STEC) strains to understand whether repeated subculture in vitro and prolonged storage at room temperature affect the RFLP patterns of STEC. The PFGE profiles of the STEC strains changed by 1 to 8 fragments after repeated subculture and prolonged storage; one strain was no longer clonal after repeated subculture compared to the original isolate according to the Tenover criteria. In contrast, RFLP patterns obtained by PCR-RFLP were identical after repeated subculture and prolonged storage. These data clearly indicate that the PCR-RFLP assay which is based on the diversity of region V, a regulatory region of Stx-phage, was not affected by repeated subculture and prolonged storage and is a more practical and reliable method for molecular typing of STEC strains.

Intestinal Shiga toxin-producing Escherichia coli bacteria mitigate bovine leukemia virus infection in experimentally infected sheep

Ruminants often carry gastrointestinal Shiga toxin (Stx)-producing Escherichia coli (STEC). Stxs belong to a large family of ribosome-inactivating proteins (RIPs), found in many plants and some bacteria. Plant RIPs, secreted into extracellular spaces, limit the spread of viruses through plant tissues by penetrating and killing virally infected cells. Previously, we showed Stx activity against bovine leukemia virus (BLV)-infected cells in vitro and hypothesized that STEC bacteria have antiviral activity in ruminant hosts. Here, we investigated the impact of STEC on the initial phases of BLV infection in sheep. Sheep were treated with biweekly oral doses of E. coli O157:H7 (an STEC) or an isogenic stx mutant strain. A different group of sheep were similarly treated with five naturally occurring ovine STEC isolates or stx-negative E. coli. Intestinal STEC bacteria were enumerated and identified by standard fecal culture and DNA hybridization. Oral STEC treatment did not always result in carriage of STEC, although many animals consistently presented with >10(4) CFU/g feces. BLV viremia was assessed by spontaneous lymphocyte proliferation (SLP) in cultures of blood mononuclear cells and by syncytium formation in cocultures of the same with F-81 indicator cells. SLP was lower (P < 0.05) and syncytia were fewer (P < 0.05) in STEC-treated sheep than in untreated sheep. Both lower SLP and fewer syncytia positively correlated with fecal STEC numbers. Average weight gain post-BLV challenge was higher in STEC-treated sheep than in untreated sheep (P < 0.05). These results support the hypothesis that in ruminants, intestinal STEC bacteria have antiviral activity and mitigate BLV-induced disease.

Antibiotic resistance and hypermutability of Escherichia coli O157 from feedlot cattle treated with growth-promoting agents

In a longitudinal study (165 days), we investigated the effect of growth-promoting agents (monensin and trenbolone acetate-estradiol) and an antibiotic (oxytetracycline) on the incidence in feedlot steers of Escherichia coli O157, including antibiotic-resistant and hypermutable isolates. Eighty steers in 16 pens were treated with eight combinations of promoters, and each treatment was duplicated. Fecal samples were collected at nine different sampling times for detection of E. coli O157. Overall, 50 E. coli O157 isolates were detected in treated animals, and none were found in untreated animals. Compared with untreated controls, there was a significant association between the utilization of growth-promoting agents or antibiotics and the shedding of E. coli O157 at day 137 (P = 0.03), when a prevalence peak was observed and 50% of the isolates were detected. Multiplex PCR assays were conducted for some virulence genes. PCR results indicated that all except one isolate possessed at least the Shiga toxin gene stx2. MICs for 12 antibiotics were determined, and eight oxytetracycline-resistant E. coli O157 strains were identified. Antibiotic-resistant strains were considered a distinct subpopulation of E. coli O157 by pulsed-field gel electrophoresis typing. Seven of these antibiotic-resistant strains were isolated early in the study (on or before day 25), and among them two were also hypermutable as determined by rifampin mutation frequencies. The proportion of hypermutable strains among E. coli O157 isolates remained relatively constant throughout the study period. These results indicate that the use of growth-promoting agents and antibiotics in beef production may increase the risk of environmental contamination by E. coli O157.

Prevalence of Shiga toxin-producing Escherichia coli in beef cattle

A large number of Shiga toxin-producing Escherichia coli (STEC) strains have caused major outbreaks and sporadic cases of human illnesses, including mild diarrhea, bloody diarrhea, hemorrhagic colitis, and the life-threatening hemolytic uremic syndrome. These illnesses have been traced to both O157 and non-O157 STEC. In a large number of STEC-associated outbreaks, the infections were attributed to consumption of ground beef or other beef products contaminated with cattle feces. Thus, beef cattle are considered reservoirs of STEC and can pose significant health risks to humans. The global nature of the human food supply suggests that safety concerns with beef will continue and the challenges facing the beef industry will increase at the production and processing levels. To be prepared to address these concerns and challenges, it is critical to assess the role of beef cattle in human STEC infections. In this review, published reports on STEC in beef cattle were evaluated to achieve the following specific objectives: (i) assess the prevalence of STEC in beef cattle, and (ii) determine the potential health risks of STEC strains from beef cattle. The latter objective is critically important because many beef STEC isolates are highly virulent. Global testing of beef cattle feces revealed wide ranges of prevalence rates for O157 STEC (i.e., 0.2 to 27.8%) and non-O157 STEC (i.e., 2.1 to 70.1%). Of the 261 STEC serotypes found in beef cattle, 44 cause hemolytic uremic syndrome and 37 cause other illnesses.

Development of a PCR-restriction fragment length polymorphism assay for the epidemiological analysis of Shiga toxin-producing Escherichia coli

Six characteristic regions (I to VI) were identified in Shiga toxin 2 (Stx2) phages (T. Sato, T. Shimizu, M. Watarai, M. Kobayashi, S. Kano, T. Hamabata, Y. Takeda, and S. Yamasaki, Gene 309:35-48, 2003). Region V, which is ca. 10 kb in size and is located in the upstream region of the Stx operons, includes the most distinctive region among six Stx phages whose genome sequences have been determined. In this study, we developed a PCR-restriction fragment length polymorphism (RFLP) assay for the epidemiological analysis of Shiga toxin-producing Escherichia coli (STEC) on the basis of the diversity of region V. When region V was amplified by long and accurate-PCR (LA-PCR) with five control E. coli strains carrying six different Stx phages such as E. coli strains C600 (Stx1 phage), C600 (933W phage), C600 (Stx2 phage-I), C600 (Stx2 phage-II), and O157:H7 Sakai strain RIMD0509952 (VT1-Sakai phage and VT2-Sakai phage), an expected size of the band was obtained. Restriction digest of each PCR product with BglI or EcoRV also gave the expected sizes of banding patterns and discriminated the RFLPs of five control strains. When a total of 204 STEC O157 strains were analyzed by LA-PCR, one to three bands whose sizes ranged from 8.2 to 14 kb were obtained. Two STEC O157 strains, however, did not produce any bands. Subsequent restriction digest of the PCR products with BglI or EcoRV differentiated the RFLPs of 202 STEC O157 strains into 24 groups. The RFLP patterns of pulsed-field gel electrophoresis (PFGE) of representative strains of STEC O157 divided into 24 groups were well correlated with those of PCR-RFLP when STEC O157 strains were isolated in the same time period and in the close geographic area. To evaluate the PCR-RFLP assay developed here, ten strains, each isolated from four different outbreaks in different areas in Japan (Tochigi, Hyogo, Aichi, and Fukuoka prefecture), were examined to determine whether the strains in each group showed the same RFLP patterns in the PCR-RFLP assay. In accordance with the results of PFGE except for strains isolated in an area (Fukuoka), which did not produce any amplicon, ten strains in each group demonstrated the same RFLP pattern. Taken together, these data suggest that the PCR-RFLP based on region V is as useful as PFGE but perhaps more simple and rapid than PFGE for the molecular epidemiological analysis of STEC strains during sporadic and common source outbreaks.

Isolation of shiga toxigenic Escherichia coli from raw beef in Palestine

Shiga toxigenic Escherichia coli (STEC) isolated from raw beef samples in northern Palestine during a 1-year period were characterized for virulence genes by a polymerase chain reaction (PCR) assay and screened for their antibiotic resistance. STEC was identified in 44 (14.7%) of 300 raw beef samples. Twelve (27.3%) of the STEC isolates were serotype O157. Nine of those were isolated during summer. The majority of STEC isolates (70.5%) harbored both stx1 and stx2 genes, while the others harbored either stx1 or stx2. High levels of resistance against different antimicrobial agents were detected. Resistance to at least three drugs was found in 55% of the isolates.

Shiga toxin 1 targets bovine leukemia virus-expressing cells

Direct evidence that Escherichia coli Shiga toxin (Stx) acts against bovine leukemia virus (BLV)-expressing cells was obtained. The active A subunit of Stx type 1 (StxA1) targeted a selected population of permeable cells expressing BLV and inhibited BLV replication in a culture of bovine peripheral blood mononuclear cells. Cells were cultured with and without StxA1, and at various times cells expressing BLV were identified by being stained with MW1 monoclonal antibody specific for the BLV protein gp51. Before culture, permeable cells were tagged by uptake of one of the following: acetoxymethyl of 2',7'-bis-(2-carboxyethyl)-5-(and 6)-carboxyfluorescein (BCECF), BCECF conjugated to 70-kDa dextran, or 70-kDa dextran conjugated to fluorescein. The tagged cells costaining with anti-gp51 were selectively eliminated in StxA1-treated cultures. Electron microscopy analysis of purified B lymphocytes showed sharply reduced numbers of BLV particles in StxA1-treated cultures.

Characterisation of Shiga toxin-producingEscherichia coli(STEC) isolated from seafood and beef

Shiga toxin-producing Escherichia coli (STEC) strains isolated in Mangalore, India, were characterised by bead-enzyme-linked immunosorbent assay (bead-ELISA), Vero cell cytotoxicity assay, PCR and colony hybridisation for the detection of stx1 and stx2 genes. Four strains from seafood, six from beef and one from a clinical case of bloody diarrhoea were positive for Shiga toxins Stx1 and Stx2 and also for stx1and stx2 genes. The seafood isolates produced either Stx2 alone or both Stx1 and Stx2, while the beef isolates produced Stx1 alone. The stx1 gene of all the beef STEC was found to be of recently reported stx1c type. All STEC strains and one non-STEC strain isolated from clam harboured EHEC-hlyA. Interestingly, though all STEC strains were negative for eae gene, two STEC strains isolated from seafood and one from a patient with bloody diarrhoea possessed STEC autoagglutinating adhesion (saa) gene, recently identified as a gene encoding a novel autoagglutinating adhesion.

Isolation and characterization of Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic Escherichia coli (EPEC) from calves and lambs with diarrhoea in India

AIMS

To determine the prevalence and molecular characteristics of Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) in calves and lambs with diarrhoea in India.

METHODS AND RESULTS

Faecal samples originating from 391 calves and 101 lambs which had diarrhoea were screened for presence of E. coli. A total number of 309 (249 bovine and 60 ovine) E. coli strains were isolated. A total of 113 bovine and 15 ovine strains were subjected to multiplex polymerase chain reaction (m-PCR) for detection of stx1, stx2, eaeA and EHEC hlyA genes. STEC and EPEC belonging to different serogpoups were detected in 9.73% of calves studied. Six per cent and 26.66% of lambs studied were carrying STEC and EPEC, respectively. Majority of the STEC serogroups isolated in this study did not belong to those which have been identified earlier to be associated mainly with diarrhoea and enteritis in cattle and sheep outside India. The most frequent serogroup among bovine and ovine EPEC was O26 (40%). One of the most important STEC serogroup O157, known for certain life-threatening infections in humans, was isolated from both bovine and ovine faecal samples.

CONCLUSIONS

A high percentage of STEC and EPEC belonging to different serogroups are prevalent in calves and lambs with diarrhoea in India and could be the cause of disease in them.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study reports, for the first time, the isolation and characterization of STEC and EPEC serogroups associated with diarrhoea in calves and lambs in India. Many STEC and EPEC strains belonged to serogoups known for certain life-threatening diseases in humans.

Emerging water-borne pathogens

Emerging water-borne pathogens constitute a major health hazard in both developed and developing nations. A new dimension to the global epidemiology of cholera-an ancient scourge-was provided by the emergence of Vibrio cholerae O139. Also, water-borne enterohaemorrhagic Escherichia coli ( E. coli O157:H7), although regarded as a problem of the industrialized west, has recently caused outbreaks in Africa. Outbreaks of chlorine-resistant Cryptosporidium have motivated water authorities to reassess the adequacy of current water-quality regulations. Of late, a host of other organisms, such as hepatitis viruses (including hepatitis E virus), Campylobacter jejuni, microsporidia, cyclospora, Yersinia enterocolitica, calciviruses and environmental bacteria like Mycobacterium spp, aeromonads, Legionella pneumophila and multidrug-resistant Pseudomonas aeruginosa have been associated with water-borne illnesses. This review critically examines the potential of these as emerging water-borne pathogens. It also examines the possible reasons, such as an increase in the number of immunocompromised individuals, urbanization and horizontal gene transfer, that may underlie their emergence. Further, measures required to face the challenge posed by these pathogens are also discussed.