Investigation of diarrhoeic faecal samples for enterotoxigenic, Shiga toxin-producing and typical or atypical enteropathogenic Escherichia coli in Kashmir, India

Antimicrobial resistance in food-borne pathogens at the human-animal interface: Results from a large surveillance study in India

Background

The burden of foodborne diseases and antimicrobial resistance carried by key foodborne pathogens in India is unknown due to a lack of an integrated surveillance system at the human-animal interface.

Methods

We present data from the WHO-AGISAR (Advisory Group on Integrated Surveillance of Antimicrobial Resistance), India project. Concurrent human and animal sampling was done across a large area across north India. Community-acquired diarrhea cases (n = 1968) of all age groups were included. Cross-sectional sampling of stool/ intestinal contents (n = 487) and meat samples (n = 419) from food-producing animals was done at farms, retail shops, and slaughterhouses. Pathogens were cultured and identified, and antimicrobial susceptibility was performed.

Results

Over 80% of diarrhoeal samples were obtained from moderate to severe diarrhea patients, which yielded EAEC (5%), ETEC (4.84%), EPEC (4.32%), and Campylobacter spp. (2%). A high carriage of EPEC (32.11%) and Campylobacter spp. (24.72%) was noted in food animals, but the prevalence of ETEC (2%) and EAEC (1%) was low. Atypical EPEC (aEPEC, 84.52%, p ≤0.0001) were predominant and caused milder diarrhea. All EPEC from animal/poultry were aEPEC. Overall, a very high level of resistance was observed, and the MDR rate ranged from 29.2% in Campylobacter spp., 53.6% in EPEC, and 59.8% in ETEC. Resistance to piperacillin-tazobactam, cefepime, ceftriaxone, and co-trimoxazole was significantly higher in human strains. In contrast, resistance to ciprofloxacin, aminoglycosides, and tetracycline was higher in animal strains, reflecting the corresponding usage in human and animal sectors. ESBL production was commoner in animal isolates than in humans, indicating high use of third-generation cephalosporins in the animal sector. C. hyointestinalis is an emerging zoonotic pathogen, first time reported from India.

Conclusion

In one of the most extensive studies from India, a high burden of key foodborne pathogens with MDR and ESBL phenotypes was found in livestock, poultry, and retail meat.

Typical and atypical enteropathogenic Escherichia coli in children with acute diarrhoea: Changing trend in East Delhi

Background

Worldwide around 2 million deaths occur every year due to diarrhoeal illnesses among children less than 5 years of age. Among diarrhoeagenic Escherichia coli, Enteropathogenic E. coli (EPEC) is highly prevalent in both community and hospital settings and is one of the main causes of persistent diarrhea in children in developing countries. EPEC remains underdiagnosed in India due to lack of conventional tools for identification.

Methods

We in this study investigated the prevalence and regional variation of EPEC in paediatric population suffering from diarrhoea in East Delhi, India. Two hundred stool samples were collected from children, aged between 0.5 and 5 years, with acute diarrhoea. E. coli were identified by conventional tests and PCR.

Results

We observed 7% atypical EPEC (aEPEC) and 2.5% typical EPEC (tEPEC), with an overall 9.5% EPEC prevalence amongst total samples. E. coli phylogenetic group A was the predominant. The most common age group affected was 6–23 months with common symptoms being vomiting, watery diarrhoea and severe dehydration. High drug resistance pattern was observed in EPEC isolates.

Conclusion

The study depicts a changing trend of aEPEC over tEPEC in children less than 5 years with diarrhoea, an emerging drug resistant enteropathogen and a public health concern demanding monitoring and surveillance.

Mixed Aetiology of Diarrhoea in Infants Attending Clinics in the North-West Province of South Africa: Potential for Sub-Optimal Treatment

Routine diagnostic methods for the aetiologic agents of diarrhoea in most developing countries are usually not sensitive enough, leading to under-diagnosis. Thus, this study investigated possible mixed diarrhoeal aetiology by using cultures and real-time polymerase chain reactions (PCR) in children younger than four years old in the Northwest Province, South Africa. In total, 505 stool samples were collected from symptomatic and asymptomatic children who were attending three clinics and the Brits hospital in Madibeng District, between September 2016 and December 2017. Rotavirus, norovirus, Campylobacter, Arcobacter, and diarrhoeagenic Escherichia coli (DEC) were targeted. Campylobacter spp. (24.6%), Arcobacter (15.8%) and DEC (19.6%) were detected using PCR; only Campylobacter spp. (29.7%) and DEC (26.9%) were detected through the culture. Campylobacter jejuni (36%), Campylobacter coli (28%), Campylobacter upsalensis (12%), and Arcobacter butzleri (15.8%) were the only spp. of Campylobacter and Arcobacter identified. The eaeA gene (31.4%) of enteropathogenic E. coli/enterohaemorrhagic E. coli (EPEC/EHEC) was the most prevalent DEC virulence gene (VG) identified. Rotavirus and norovirus were detected at 23.4% and 20%, respectively. Mixed viral aetiology (7.3%) and the co-infection of A. butzleri and Campylobacter (49%) were recorded. A mixed bacterial-viral aetiology was observed in 0.6% of the specimens. Sensitive diagnostic procedures like PCR should be considered to provide the best treatment to children experiencing diarrhoea.

Serological diversity, molecular characterisation and antimicrobial sensitivity of avian pathogenic Escherichia coli (APEC) isolates from broiler chickens in Kashmir, India

The present study has determined the serological diversity, virulence-gene profile and in vitro antibiogram of avian pathogenic Escherichia coli (APEC) isolates from broiler chickens in India suspected to have died of colibacillosis. The virulence-gene profile of APEC was compared with that of the Escherichia coli isolates from faeces of apparently healthy chickens, called avian faecal E. coli (AFEC). In total, 90 representative isolates of APEC and 63 isolates of AFEC were investigated in the present study. The APEC were typed into 19 serogroups, while some isolates were rough and could not be typed. Most prevalent serogroup was O2 (24.44%). Among the eight virulence genes studied, the prevalence of seven genes (iss, iucD, tsh, cva/cvi, irp2, papC and vat) was significantly higher in APEC than in AFEC isolates. However, there was no significant difference between APEC and AFEC isolates for possession of astA gene. The most frequent gene detected among the two groups of organisms was iss, which was present in 98.88% and 44.44% of APEC and AFEC isolates respectively. The in vitro antibiogram showed that the majority (96.6%) of APEC isolates were resistant to tetracycline, while 82.2% were resistant to cephalexin, 78.8% to cotrimoxazole, 68.8% to streptomycin and 63.3% to ampicillin. However, most of them (84.45%) were sensitive to gentamicin. Thus, it is concluded that APEC from the broiler chickens carried putative virulence genes that attributed to their pathogenicity. Furthermore, the majority of APEC isolates were found to be multi-drug resistant, which, in addition to leading treatment failures in poultry, poses a public health threat.

Molecular characterization and antimicrobial profiling of Escherichia coli isolates from diarrheic calves

Diarrhea due to Escherichia coli is one of the major economic concerns of bovine industry in the first few weeks after birth. The present study was carried out for characterization of virulence traits of Escherichia coli associated with diarrhea in calves less than 3 months of age and their antimicrobial profiling. Escherichia coli isolates (700) were recovered in this study, which belonged to 25 different serogroups out of which O2 and O6 were most predominant. The isolates were screened for 7 virulence genes, viz. sta, stx1, stx2, lt, f5, f41 and eae. Out of 700 isolates, 65 (9.2%) carried virulence genes either alone (f5, eae, f41, sta, stx1 and stx2) or in different combinations (f41/sta, sta/lt, stx1/eae and f5/stx2). Based on the presence of virulence factors, these isolates were classified as Shiga-toxin producing E. coli (27), enterotoxigenic E. coli (20), enteropathogenic E. coli (15) and 3 were unclassified. These 65 isolates were resistant to commonly used antibacterial agents like amoxicillin, ceftriaxone, cephalexin, cloxacillin, enrofloxacin and gentamicin. Multidrug resistance was also observed in 84.6% of them.This study reveals that PCR based detection of E. coli virotypes can be used in diagnosis and epidemiological studies. Also increasing multidrug resistance for most of the commonly used antibiotics is a matter of concern.

Molecular Epidemiology of Extended-Spectrum β-Lactamase-Producing Escherichia coli Pathotypes in Diarrheal Children from Low Socioeconomic Status Communities in Bihar, India: Emergence of the CTX-M Type

Background

Childhood diarrheal diseases remain highly endemic in India, but the emergence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli among children with diarrhea in Bihar remains elusive. In this study, we determine and characterize ESBL-producing E coli pathotypes among hospitalized diarrheal preschool children living in low socioeconomic level communities in Bihar, India.

Materials and methods

The stool samples were collected everyday throughout the year for 2 consecutive years. In our study, we collected stool samples randomly from every fifth patient. Stool samples were collected from a total of 633 randomly selected diarrheal children (age: 0-60 months) belonging to 17 communities and screened for identification of virulent diarrheagenic E coli (DEC) pathotype (viz, enteropathogenic E coli [EPEC], enteroaggregative E coli [EAEC], enterotoxigenic E coli [ETEC], enteroinvasive E coli [EIEC], and enterohemorrhagic E coli [EHEC]) by a multiplex polymerase chain reaction (PCR) assay. Furthermore, ESBLs were screened by conventional antibiotic resistance pattern testing and later characterized for the presence of β-lactamase (bla) genes by PCR and DNA sequencing.

Results

Diarrheagenic E coli was detected in 191 cases (30.2%) of the total 633 diarrheic children. Maximum occurrence of DEC was found in ≤12 months age group (72.7%) with prevalence of the EAEC pathotype. Most isolates were resistant to ampicillin, ciprofloxacin, piperacillin, levofloxacin, ceftazidime, cefotaxime, ceftriaxone, and gentamicin, whereas over 96% of them were sensitive to amikacin. About 37.6% of total 191 DEC isolates were ESBL producers (n = 72), being prevalent among ETEC (n = 35; 18.32%), followed by EPEC (n = 21; 10.9%), EAEC (n = 13; 6.8%), and EIEC (n = 3; 1.57%). Interestingly, the commonest β-lactamase was CTX-M type (bla_CTX-M) in 86.1% (n = 62) of the ESBL isolates, followed by bla_SHV (n = 49; 68%), bla_TEM (n = 37; 51.8%), and bla_OXA (n = 21; 29.1%) determinants. Resistance of ESBL isolates was mostly related to ampicillin (100%), ceftriaxone (98.1%), cefotaxime (92.4%), gentamicin (74.1%), and levofloxacin (73.2%), whereas best antimicrobial activities were observed for piperacillin-tazobactam, amikacin, meropenem, and imipenem.

Conclusions

This study revealed that EAEC (72.1%) is the predominant pathotype in Bihar, significantly high in ≤12 months age group children (P = .04). Moreover, the widespread prevalence of ESBLs in children, especially the CTX-M type, is of great concern, which requires monitoring of infection control measures through efficient antimicrobial management and detection of ESBL-producing isolates.

Prevalence of multi drug resistant enteropathogenic and enteroinvasive Escherichia coli isolated from children with and without diarrhea in Northeast Indian population

Background

Diarrheagenic Escherichia coli are associated with infantile diarrhea in the developing countries. The present study was conducted to determine the occurrence and antimicrobial resistance pattern of enteropathogenic and enteroinvasive E. coli associated with diarrhoea among the paediatric patients.

Methods

A total of 262 stool samples were collected from children with and without diarrhea from Mizoram, Northeast India. E. coli were isolated and subjected to multiplex PCR to detect virulent genes of EPEC (eaeA and bfpA) and EIEC (ial). Isolates were subjected to antimicrobial sensitivity assay using disc diffusion method. Selected eaeA genes were sequenced for identification and genetic relationship.

Results

A total of 334 E. coli was isolated, of which 17.37% were carrying at least one virulent gene. Altogether, 14.97 and 2.40% isolates were categorized as EPEC and EIEC, respectively. Among the DEC isolates, 4.79% were EPEC and 7.78% were EIEC. A total of 8 (2.40%) isolates were EIEC (ial+), of which 6 (1.80%) and 2 (0.60%) were from diarrhoeic and non-diarrhoeic patients, respectively. A total of 24 (41.40%) DEC isolates were MDR (resistance against ≥5 antimicrobials).

Conclusions

A high frequency of EPEC pathotypes associated with paediatric diarrhea was observed in Mizoram, Northeast India and majority of the isolates are resistant to antibiotics with a high frequency of MDR, which is a matter of concern to the public health. This also raises an alarm to the world communities to monitor the resistance pattern and analyse in a global scale to combat the problems of resistance development.

Epidemiology, Antimicrobial Resistance and β-lactamase Genotypic Features of Enteropathogenic Escherichia coli Isolated from Children with Diarrhea in Southern China

The main objective of this study was to investigate the epidemiology, drug resistance and β-lactamase genotype distribution of enteropathogenic Escherichia coli (EPEC) isolated from pediatric patients with diarrhea in southern China. The prevalence of EPEC in children with diarrhea was 3.53%. The commonest serotypes were O55:K59 and O126:K71, and the typical EPEC were more prevalent than atypical EPEC (51 vs 7). Isolates from this region were most commonly found to be resistant to ampicillin and cotrimoxazole, followed by chloramphenicol, ceftriaxone, and ceftazidime. More than 96% of the strains were susceptible to cefoperazone/sulbactam and imipenem. The most common β-lactamase genotypes identified in 58 strains were blaCTX-M-1 (60.3%), blaTEM (56.9%), blaCTX-M-9 (27.6%), and blaSHV (15.5%). Among 58 isolates, 22 strains were found to harbor one β-lactamase gene, and the proportions of resistance to ampicillin, cotrimoxazole, chloramphenicol, ceftriaxone, and ceftazidime, were 81.8%, 63.6%, 40.9%, 18.2%, and 9.1%, respectively. A further 30 strains carrying multiple β-lactamase genes had increased resistance to the above antimicrobial agents (100%, 83.3%, 70.0%, 60.0%, and 30.0%, respectively). In contrast, antibiotic resistance in the last 6 strains without a detectable β-lactamase gene was substantially reduced. Drug resistance may be associated with the β-lactamase gene number, with a greater the number of β-lactamase genes resulting in higher antibiotic resistance.

Prevalence and characteristics of intimin-producing Escherichia coli strains isolated from healthy chickens in Korea

Virulent Escherichia coli strains have commonly been associated with diarrheal illness in humans and animals. Typical enteropathogenic Escherichia coli (EPEC) with intimin gene (eaeA) and E. coli adherence factor plasmid, or atypical EPEC with only eaeA have been implicated in human cases. In the present study, we investigated the prevalence of virulence-associated genes including eaeA in the E. coli strains isolated from cloacal specimens of 184 chicken flocks in 7 provinces in Korea between 2009 and 2010. When 7 virulence genes (VT1, VT2, LT, and ST for enterotoxigenic E. coli; eaeA and bfpA for enteropathogenic E. coli; and aggR for enteroaggregative E. coli) were screened by multiplex PCR, a total of 30 E. coli strains carrying only the eaeA gene were detected from 184 flocks that were identified as atypical enteropathogenic Escherichia coli (aEPEC). The aEPEC strains were analyzed by eae subtyping, phylogenetic grouping PCR, and serotyping. Twelve (40%) of 30 aEPEC strains possessed an eae-β subtype, followed by θ (30%), ε (16.7%), and β1 (13.3%). Eight (26.7%) of 30 aEPEC strains were designated into the phylogenetic group A. Two (6.7%) and 3 (10%) aEPEC strains were classified into the phylogenetic group B2 and D, respectively. A total of 15 (50%) aEPEC strains were serotyped to groups O24, O25, O26, O71, O80, O103, and O157, and the remaining strains were nontypeable. In analyzing the genetic diversity among the 30 aEPEC isolates by the pulsed-field gel electrophoresis method with XbaI-digestion, the pulsed-field gel electrophoresis profiling produced 20 different patterns, but isolates within the same group did not show clear geographic or breed relationships. Our data indicate that healthy chickens may constitute an important natural reservoir of aEPEC strains, and suggest that transmission to humans could not be excluded.

Prevalence and characterization of diarrheagenic Escherichia coli isolated from adults and children in Mangalore, India

Background:

Diarrheal diseases are a major cause of morbidity and mortality in resource-limited countries. Among the bacterial pathogens, diarrheagenic E. coli (DEC) are most frequently implicated in cases of epidemic and endemic diarrhea worldwide. The objective of this study was to determine the prevalence of DEC in stool specimens from patients with acute diarrhea using polymerase chain reaction (PCR).

Materials and Methods:

Escherichia coli stool samples were collected from 115 hospitalized children and adults with acute diarrhea in Mangalore, a coastal city, in southern India. PCR amplification of eae, bfp, stx, ehx genes were used for detection of enteropathogenic (EPEC) and shigatoxigenic E. coli (STEC), lt and st genes were used for enterotoxigenic E. coli (ETEC) and astA gene for enteroaggregative E. coli (EAEC).

Results:

During the 24 month study period, of the 115 stool samples, DEC type was detected in 20 (17.4%) using the PCR method. The most prevalent DEC was atypical EPEC accounting for 12 (10.4%) cases followed by 4 cases of EAEC (3.4%) and 4 of STEC (3.4%). No ETEC strains were isolated from any of the examined stool samples.

Conclusion:

This study suggests that the atypical EPEC are the newly emerging group among DEC stains in Southern India. Further studies are needed to evaluate the epidemiology and virulence properties of atypical EPEC strains.

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.

Isolation of atypical enteropathogenic Escherichia coli and Shiga toxin 1 and 2f-producing Escherichia coli from avian species in India

AIMS

To study the prevalence and characterize atypical enteropathogenic Escherichia coli (EPEC) and Shiga toxin producing E. coli (STEC) in avian species in India.

METHODS AND RESULTS

Two hundred and twelve faecal samples collected from 62 chickens, 50 ducks and 100 pigeons were investigated for the presence of stx(1), stx(2), eae and ehxA virulence genes by multiplex PCR. In all, 42 E. coli isolates (25 chicken, 2 duck and 15 pigeon) possessed at least one virulence gene. Out of these, nine (4.24%) isolates were STEC and 33 (15.56%) were EPEC. All isolates from duck and chicken were EPEC while among 15 pigeon isolates nine (60%) were STEC and six (40%) were EPEC. Among the STEC isolates four each carried stx(1) or stx(2) and one possessed both stx(1) and stx(2). Subtype analysis of stx revealed the presence of stx(2f) in four STEC isolates. None of the STEC isolates carried stx(1c), stx(2c), stx(2d) or stx(2e). Isolates carrying stx(2f) demonstrated vero cell toxicity. One each belonged to serogroup O17 and O78, while one was rough and the other untypeable. All EPEC isolates were atypical as they lacked bfpA. This appears to be the first report of detection of stx(2f) from India.

CONCLUSIONS

The study established the presence of stx(1) and stx(2f) containing E. coli in pigeons and atypical EPEC in poultry in India. Pigeons might serve as vectors for transmission of STEC to environment and humans.

SIGNIFICANCE AND IMPACT OF THE STUDY

Taking into account the close contact between fanciers and pigeons, these findings warrant a more critical appraisal of these zoonotic pathogens in pigeons and humans.

Association of diarrheagenic Escherichia coli Pathotypes with infection and diarrhea among Mexican children and association of atypical Enteropathogenic E. coli with acute diarrhea

Seventy-six children < or =2 years old were prospectively followed for 1 year in a peri-urban community of Mexico City to determine asymptomatic infection and acute diarrhea associated with diarrheagenic Escherichia coli pathotypes (DEPs). By use of a pathogen-specific multiplex PCR, DEPs were sought in 795 stool samples, of which 125 (16%) were positive for DEP; of these, 4 represented shedding episodes and 4 parasite coinfections. Most single-DEP infections (85/117) were asymptomatic (P < 0.001), and of the 32 DEP diarrhea episodes, 41% were associated with atypical enteropathogenic E. coli (aEPEC), 37.5% with enterotoxigenic E. coli, 9% with typical EPEC, 9% with enteroinvasive E. coli, and 3% with Shiga toxin-producing E. coli strains. Among the 76 children, 54 had at least one stool positive for DEP, of which 23 experienced a DEP-associated diarrhea episode. In the last group of children, DEP infection was significantly associated with a diarrhea episode (relative risk [RR] = 2.5; 95% confidence interval [CI], 1.79 to 3.57; P < 0.001), with ETEC (RR = 2.30; 95% CI, 1.49 to 3.54; P = 0.003) and aEPEC (RR = 1.92; 95% CI, 1.23 to 3.0; P = 0.019) being the pathotypes associated with diarrhea. aEPEC-associated diarrhea episodes were frequently in the <12-month age group (RR = 2.57; 95% CI, 1.05 to 6.27; P = 0.04). aEPEC infections were distributed all year round, but associated diarrheal episodes were identified from April to October, with a May-June peak (rainy season). Most ETEC infections and diarrhea episodes characteristically occurred during the summer (rainy season), with a diarrhea peak in August. Of all DEPs, only aEPEC was associated with acute diarrhea episodes lasting 7 to 12 days (P = 0.019). DEPs are important causes of community-acquired enteric infection and diarrhea in Mexican children.

Closing the diarrhoea diagnostic gap in Indian children by the application of molecular techniques

A large proportion of diarrhoeal illnesses in children in developing countries are ascribed to an unknown aetiology because the only available methods, such as microscopy and culture, have low sensitivity. This study was aimed at decreasing the diagnostic gap in diarrhoeal disease by the application of molecular techniques. Faecal samples from 158 children with and 99 children without diarrhoea in a hospital in South India were tested for enteric pathogens using conventional diagnostic methods (culture, microscopy and enzyme immunoassays) and molecular methods (six PCR-based assays). The additional use of molecular techniques increased identification to at least one aetiological agent in 76.5 % of diarrhoeal specimens, compared with 40.5 % using conventional methods. Rotavirus (43.3 %), enteropathogenic Escherichia coli (15.8 %), norovirus (15.8 %) and Cryptosporidium spp. (15.2 %) are currently the most common causes of diarrhoea in hospitalized children in Vellore, in contrast to a study conducted two decades earlier in the same hospital, where bacterial pathogens such as Shigella spp., Campylobacter spp. and enterotoxigenic E. coli were more prevalent. Molecular techniques significantly increased the detection rates of pathogens in children with diarrhoea, but a more intensive study, testing for a wider range of infectious agents and including more information on non-infectious causes of diarrhoea, is required to close the diagnostic gap in diarrhoeal disease.

Detection of Escherichia coli, Salmonella spp., Shigella spp., Yersinia enterocolitica, Vibrio cholerae, and Campylobacter spp. enteropathogens by 3-reaction multiplex polymerase chain reaction

The magnitude of bacterial diarrhea in developing countries is largely unknown because affordable detection methods are not available. We have developed a polymerase chain reaction (PCR)-based assay for use in areas with limited resources to screen for diarrheogenic strains from clinical isolates. To simplify the assay and minimize reagents, our method implemented the use of plasmids rather than bacteria as template controls and the use of bacterial suspensions or crude DNA preparations rather than purified genomic DNA as template DNA. The assay consisted of 3 PCR reactions using 3 groups of 5 to 6 primer pairs to identify the 11 most common bacterial diarrheogenic pathogens. The 3-reaction multiplex PCR amplifies DNA targets specific for each 1 of the 6 Escherichia coli diarrheogenic strains and the 5 non-E. coli diarrheogenic strains, including Salmonella spp., Shigella spp., Campylobacter spp., Yersinia enterocolitica, and Vibrio cholerae. The assay may provide an important epidemiologic tool to investigate the role of diarrheogenic bacterial pathogens in areas of the world with limited resources.

Isolation and characterization of the Shiga toxin gene (stx)-bearing Escherichia coli O157 and non-O157 from retail meats in Shandong Province, China, and characterization of the O157-derived stx2 phages

Infection by Shiga toxin (Stx)-producing Escherichia coli of non-O157 and O157 serotypes are rare in China, but infection by O157 serotype was found in Shandong Province and three other provinces in China. To understand the reason for these rare infections and to determine the safety of retail meats in Shandong Province, we examined the distribution of Shiga toxin gene (stx)-bearing E. coli in retail meats and characterized the isolated stx-bearing strains. We used hybridization with DNA probes and isolated stx1- and/or stx2-positive E. coli from 31 (58%) of 53 retail meat samples, with beef showing the highest frequency (68%). Of 42 stx-positive isolates, none belonged to O157. Using the O157-specific immunomagnetic bead technique, we isolated E. coli O157 carrying the eae and stx2 genes from eight beef samples (26%). These strains produced little or no Stx2 and carried a unique q gene. Replication of the stx2 phages was detected in these strains, whereas stx2 phage replication was not detected in our previous study in which we examined similar stx2-bearing E. coli O157 strains from other Asian countries. Analysis of E. coli C600 lysogenized with the stx2 phages found in this study suggests that the lack of Stx2 production is due to changes in non-q gene region(s) of the phage genome or chromosomal mutation(s) in the host. Our data and reports by other workers suggest it is necessary to determine if various stx2-bearing E. coli O157 strains producing Stx2 to varying degrees are distributed in meats in various locations in China.

Diarrheagenic Escherichia coli and Shigella strains isolated from children in a hospital case-control study in Hanoi, Vietnam

This case-control study detected and characterized Shigella and diarrheagenic Escherichia coli (DEC) types among Vietnamese children less than 5 years old. In 249 children with diarrhea and 124 controls, Shigella spp. was an important cause of diarrhea (P < 0.05). We used multiplex PCR and DNA probes to detect enteroinvasive E. coli (EIEC), enteroaggregative E. coli (EAggEC), enteropathogenic E. coli (EPEC), attaching and effacing E. coli (A/EEC), verocytotoxin-producing E. coli (VTEC), and enterotoxigenic E. coli (ETEC). The prevalences of DEC in the diarrhea and control groups were 25.7 and 10.5%, respectively. In 62 children with diarrhea, 64 DEC strains included 22 EAggEC (8.8%), 2 EIEC (0.8%), 23 A/EEC (9.2%), 7 EPEC (2.8%), and 10 ETEC strains (4.0%). Among controls, 13 DEC strains included 5 EAggEC strains (4.0%), 7 A/EEC strains (5.6%), and 1 EPEC strain. The characterization of DEC by serotypes, antimicrobial susceptibility patterns, virulence genes, and pulsed-field gel electrophoresis showed the occurrence of many different and highly heterogenic DEC subtypes, but common serotypes were found among ETEC, EIEC and EPEC, respectively. Serotyping was used to distinguish between A/EEC and EPEC. However, A/EEC, EPEC, and EAggEC were isolated at high frequency from both cases and controls. Further in-depth studies are needed to better understand important virulence factors of DEC, especially A/EEC, EPEC, and EAggEC.

Variants of eae and stx genes of atypical enteropathogenic Escherichia coli and non-O157 Shiga toxin-producing Escherichia coli from calves

AIMS

To determine the subtypes of stx and eae genes of Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic Escherichia coli (EPEC) from calves and to ascertain the typical and atypical nature of EPEC.

METHODS AND RESULTS

One hundred and eighty-seven faecal samples from 134 diarrhoeic and 53 healthy calves were investigated for the presence of stx, eae and ehxA virulence genes by polymerase chain reaction and enzyme-linked immunosorbent assay. Subtype analysis of stx(1) exhibited stx(1c) in 13 (31.70%) isolates, while that of stx(2) revealed stx(2c) in eight (24.24%) and stx(2d) in two (6.06%) isolates. Subtyping of eae gene showed the presence of eae-beta, eae-eta and eae-zeta in two, three and four isolates respectively. None of the E. coli isolates possessed stx(2e), stx(2f), eae-alpha, eae-delta, eae-epsilon and eae-xi. All EPEC isolates were atypical.

CONCLUSIONS

stx(1), stx(1c), stx(2), stx(2c), stx(2d), eae-beta, eae-eta and eae-zeta subtypes are prevalent in STEC and EPEC isolates in India.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first subtype analysis of stx(2) and eae genes of animal E. coli isolates in India and emphasizes the need to investigate their transmission to humans.