Detection in Escherichia coli of the genes encoding the major virulence factors, the genes defining the O157:H7 serotype, and components of the type 2 Shiga toxin family by multiplex PCR

Neem (Azadirachta indica A. Juss) Oil to Tackle Enteropathogenic Escherichia coli

Neem (Azadirachta indica A. Juss) oil (NO) was assayed against forty-eight isolates of Escherichia coli by standardised disc diffusion test and microdilution test. By molecular biology characterization, fourteen isolates resulted in diarrheagenic E. coli with sixteen primer pairs that specifically amplify unique sequences of virulence genes and of 16S rRNA. The NO showed biological activity against all isolates. The bacterial growth inhibition zone by disc diffusion method (100 µL NO) ranged between 9.50 ± 0.70 and 30.00 ± 1.00 mm. The antibacterial activity was furthermore determined at lower NO concentrations (1 : 10–1 : 10,000). The percent of growth reduction ranged between 23.71 ± 1.00 and 99.70 ± 1.53. The highest bacterial growth reduction was 1 : 10 NO concentration with 50 µL of bacterial suspension (ca. 1 × 10⁶ CFU/mL). There is significant difference between the antibacterial activities against pathogenic and nonpathogenic E. coli, as well as NO and ciprofloxacin activities. Viable cells after the different NO concentration treatments were checked by molecular biology assay using PMA dye. On the basis of the obtained results, NO counteracts E. coli and also influences the virulence of E. coli viable cells after NO treatment. The NO metabolomic composition was obtained using fingerprint HPTLC.

Detection of E. coli O157:H7 and Shigella dysenteriae toxins in clinical samples by PCR-ELISA

Shiga toxin producing bacteria are potential causes of serious human disease such as hemorrhagic colitis, severe inflammations of ileocolonic regions of gastrointestinal tract, thrombocytopenia, septicemia, malignant disorders in urinary ducts, hemolytic uremic syndrome (HUS). Shiga toxin 1 (stx1), shiga toxin 2 (stx2), or a combination of both are responsible for most clinical symptoms of these diseases. A lot of methods have been developed so far to detect shiga toxins such as cell culture, ELISA, and RFPLA, but due to high costs and labor time in addition to low sensitivity, they have not received much attention. In this study, PCR-ELISA method was used to detect genes encoding shiga toxins1 and 2 (stx1 and stx2). To detect stx1 and stx2 genes, two primer pairs were designed for Multiplex-PCR then PCR-ELISA. PCR products (490 and 275, respectively) were subsequently verified by sequencing. Sensitivity and specificity of PCR-ELISA method were determined by using genome serial dilution and Enterobacteria strains. PCR-ELISA method used in this study proved to be a rapid and precise approach to detect different types of shiga toxins and can be used to detect bacterial genes encoding shiga toxins.

Synchronization ofE. coliO157 shedding in a grass-fed beef herd: a longitudinal study

This study aims to describe in detail the temporal dynamics ofE. coliO157 shedding and risk factors for shedding in a grass-fed beef herd. During a 9-month period, 23 beef cows were sampled twice a week (58 sampling points) andE. coliO157 was enumerated from faecal samples. Isolates were screened by PCR for presence ofrfbE,stx1andstx2. The prevalence per sampling day ranged from 0% to 57%. This study demonstrates that many members of the herd were concurrently sheddingE. coliO157. Occurrence of rainfall (P< 0·01), feeding silage (P< 0·01) and lactating (P< 0·01) were found to be predictors of shedding. Moving cattle to a new paddock had a negative effect on shedding. This approach, based on short-interval sampling, confirms the known variability of shedding within a herd and highlights that high shedding events are rare.

Comparison of recto-anal mucosal swab and faecal culture for the detection of Escherichia coli O157 and identification of super-shedding in a mob of Merino sheep

We compared the use of recto-anal mucosal swab (RAMS) culture and faecal culture for the detection of E. coli O157 in a mob of Merino sheep. Fifty Merino wethers and maiden ewes housed in indoor pens were sampled on five occasions. We detected E coli O157 in 32% (16/50) of sheep, with weekly prevalence ranging from 4% (2/50) to 16% (8/50). Overall, 12·5% (2/16) were detected by RAMS culture only, and 37·5% (6/16) were detected by faecal culture only. The level of agreement between the two sampling methods was moderate [kappa statistic = 0·583, 95% confidence interval (CI) 0·460-0·707]. The relative sensitivities of RAMS and faecal culture were 67% (95% CI 41-86) and 57% (95% CI 34-77), respectively. We identified four super-shedding sheep using direct faecal culture. Although the majority of culture-positive sheep were detected at one sampling point only, 3/4 super-shedding sheep were culture-positive at two sampling points, and 1/4 was culture-positive at four sampling points. Persistent culture positivity may indicate sheep that could be considered 'super-shedders' at some point. The use of immunomagnetic separation further improved the rate of detection of E. coli O157, which was isolated from 1/34 animals that were previously negative by enrichment culture alone. A significant difference between sampling weeks was detected for both faecal (P = 0·021) and RAMS (P = 0·006), with the prevalence at the mid-point of sampling (week 4) significantly (P < 0·05) higher than at the beginning or end of the study. Study conditions (penned sheep) might have been responsible for the high prevalence and the epidemic pattern of infection observed, and could serve as a future model for studies of E. coli O157 transmission, shedding and super-shedding in sheep.

Molecular characterization and antibiotic susceptibility pattern of caprine Shiga toxin producing-Escherichia coli (STEC) isolates from India

The present study was conducted to detect the occurrence, serotype, genotype, phylogenetic relationship and antimicrobial resistance pattern of STEC from healthy goats of West Bengal, India. From the 125 faecal samples collected from healthy goats, 245 isolates were identified as Escherichia coli. The E. coli harbouring any gene for Shiga toxins (stx 1/stx 2) was detected in 36 (14.7%) of the 245 E. coli isolates. These STEC strains belonged to 22 different serogroups (O2, O5, O20, O21, O22, O25, O41, O44, O45, O60, O71, O76, O84, O85, O87, O91, O103, O112, O113, O120, O156, and O158) and three were untypeable. The stx 1 and stx 2 was detected in 26 (72.2%) and 21 (58.3%) of Shiga toxin producing-E. coli (STEC) isolates, respectively. Further, E. coli harbouring eaeA only (Enteropathogenic E. coli) and ehxA was detected in 22 (61.1%) and 28 (77.7%) isolates, respectively. Whereas the saa was present in 8 (22.2%) E. coli isolates. The subtyping of the 26 E. coli strains possessing stx 1 showed that 73.% (19/26) of these isolates were positive for stx 1C subtype. Of the 21 isolates with the stx 2 gene, 42.8% (9/21) were positive for stx 2C, and 38.1% (8/21) were positive for stx 2d gene. The phylogenetic analysis of STEC strains after RAPD reveals eight major clusters. However, no serogroup specific cluster was observed. Resistance was observed most frequently to erythromycin (80.5%), amikacin (52.7%), cephalothin (50%), kanamycin (41.6%), neomycin (36.1%) and gentamycin (36.1%) and less frequently to norfloxacin (2.7%), enrofloxacin (2.7%), and ciprofloxacin (2.7%). Multidrug resistance was observed in eleven STEC isolates.

Virulence and antimicrobial resistance of Escherichia coli isolated from Tigris River and children diarrhea

Objective

To investigate the virulence factors including hemolysin production, β-lactamase production, and biofilm formation. Antimicrobial resistance and plasmid content of 20 Escherichia coli isolates obtained from feces and Tigris water were screened.

Methods

Ten clinical and ten environmental E. coli isolates were collected from children diarrhea and swim areas on Tigris River in Baghdad city, Iraq, respectively. The bacterial isolates were identified by cultural characteristics, Gram stain, biochemical tests, and screened for the presence of E. coli O157:H7 serotype. Bacterial E. coli isolates were investigated for hemolysin production, biofilm formation, and β-lactamase production. Antibiotics susceptibility and plasmid content were determined.

Results

A total of ten clinical and ten water E. coli isolates were studied. Results showed that all E. coli isolates give negative results for latex O157:H7. Virulence factors analysis showed that 6/10 water isolates and 2/10 clinical isolates were hemolytic, 5/10 water isolates and 3/10 clinical isolates were biofilm formation, and 7/10 water isolates and 4/10 clinical isolates were β-lactamase producer. Antibiotics profile showed that all bacterial isolates were multidrug resistant. All E. coli isolates (100%) were resistant to carbenicillin, cefodizime, imipenem, and piperacillin. The plasmid DNA analysis showed that all E. coli isolates contained plasmid with molecular weight range between 4.507 kbp and 5.07 kbp, but clinical isolates contained multiple small and mega plasmids.

Conclusion

Our study revealed that E. coli isolates from river water exhibit a higher level of hemolysin production, β-lactamase production, and biofilm formation than feces isolates may be due to long adaptation. On the other hand, clinical E. coli isolates from feces showed higher level of antibiotic resistance and have multiple plasmids.

Multilocus genotypic characterization of Escherichia coli O157:H7 recovered from food sources

Escherichia coli O157:H7 strains (n = 33) recovered from different food sources in Egypt were characterized using molecular assays to identify strain genotypes associated with various levels of pathogenic potential. Genotypic characterization included: lineage-specific polymorphism assay (LSPA-6), Shiga-toxin-encoding bacteriophage insertion site assay (SBI), clade 8 typing, Tir (A255 T) polymorphism, and variant analysis of Shiga toxin 2 gene (Stx 2a and Stx 2c), and anti-terminator Q genes (Q 933 and Q 21). Genotypes LI/II (76%), SBI 1 (60·6%), clade 8 (69·7%), Tir (255 T) (72·7%) and Stx 2c (45·5%) were found to be significantly more frequent compared to other genetic markers in the strains analysed. Multivariable analysis revealed a significant association between LPSA-6 and clade types as well as Tir (A255 T). To the best of our knowledge, this is the first study to report the characterization of these genetic markers in E. coli O157:H7 strains in the Middle East and Africa.

Genetic diversity of Shiga toxin-producing Escherichia coli O157 : H7 recovered from human and food sources

The aim of this study was to identify an epidemiological association between Shiga toxin-producing Escherichia coli O157 : H7 strains associated with human infection and with food sources. Frequency distributions of different genetic markers of E. coli O157 : H7 strains recovered from human and food sources were compared using molecular assays to identify E. coli O157 : H7 genotypes associated with variation in pathogenic potential and host specificity. Genotypic characterization included: lineage-specific polymorphism assay (LSPA-6), clade typing, tir (A255T) polymorphism, Shiga toxin-encoding bacteriophage insertion site analysis and variant analysis of Shiga toxin 2 gene (stx2a and stx2c) and antiterminator Q genes (Q933 and Q21). The intermediate lineage (LI/II) dominated among both food and human strains. Compared to other clades, clades 7 and 8 were more frequent among food and human strains, respectively. The tir (255T) polymorphism occurred more frequently among human strains than food strains. Q21 and Q933 + Q21 were found at significantly higher frequencies among food and human strains, respectively. Moreover, stx2a and stx2a+c were detected at significantly higher frequencies among human strains compared to food strains. Bivariate analysis revealed significant concordance (P<0.05) between the LSPA-6 assay and the other typing methods. Multivariable regression analysis suggested that tir (255T) was the most distinctive genotype that can be used to detect bacterial clones with potential risk for human illness from food sources. This study supported previous reports of the existence of diversity in genetic markers among different isolation sources by including E. coli O157 : H7 strains from both food and human sources. This might enable tracking genotypes with potential risk for human illness from food sources.

Occurrence of virulence genes associated with diarrheagenic Escherichia coli isolated from raw cow's milk from two commercial dairy farms in the Eastern Cape Province, South Africa

Escherichia coli remains a public health concern worldwide as an organism that causes diarrhea and its reservoir in raw milk may play an important role in the survival and transport of pathogenic strains. Diarrheagenic E. coli strains are diverse food-borne pathogens and causes diarrhea with varying virulence in humans. We investigated the prevalence of pathogenic E. coli in raw milk from two commercial dairy farms. Four hundred raw milk samples, 200 from each dairy farm, were screened for the presence of fliCH7, eagR, ial, eagg, lt, and papC genes. In dairy farm A, 100 E. coli were identified based on culture, oxidase and Gram staining, while 88 isolates from dairy farm B were identified in the same manner. Gene detection showed fliCH7 27 (54%) to be the highest gene detected from farm A and lt 2 (4%) to be the lowest. The highest gene detected in dairy farm B was fliCH7 16 (43.2%) and papC 1 (2.7%) was the least. The amplification of pathogenic genes associated with diarrheagenic E. coli from cows' raw milk demonstrates that potentially virulent E. coli strains are widely distributed in raw milk and may be a cause of concern for human health.

Prevalence of enteropathogenic bacteria in common quail (Coturnix coturnix)

The study was aimed at evaluating the prevalence of enteropathogenic bacteria (i.e. Campylobacter spp., shigatoxin-producing Escherichia coli, Salmonella spp.) in common quail (Coturnix coturnix). To achieve this goal, 70 common quails were collected during the hunting season in the Campania region (southern Italy). From each bird, cloacal swab samples were collected and subjected to culture methods, polymerase chain reaction and serotyping. The results of the present study showed a prevalence of 21.4% and 5.7% for Campylobacter spp. and shigatoxin-producing E. coli, respectively. In contrast, no Salmonella spp. was isolated. These findings show that common quail, as migratory birds, may constitute an environmental carrier of these pathogens representing a source of infection for other birds, livestock and humans.

Dual labeled Ag@SiO₂ core-shell nanoparticle based optical immunosensor for sensitive detection of E. coli

An optical nanobiosensor is presented using a fluorescent dye and anti-E. coli McAb anchored Ag@Silica core shell nanoparticles, for rapid and sensitive Escherichia coli detection in environmental samples. The synthesized dual labeled core shell (DLCS) nanoparticle shows intense fluorescence at 620 nm in solution, having a narrow emission with full width at half maxima (FWHM) of 10 nm, as a prerequisite to develop a sensitive detection platform for various biosensing applications. The specific E. coli was captured using an anti-E. coli antibody functionalized quartz glass, followed by a treatment with DLCS, where the photoluminescence spectroscopy was used to detect the target pathogen. The fabrication of the quartz glass based optical-immunosensor was monitored, and the results show changes in the photoluminescent patterns, which substantiate that varied species were immobilized on the surface of the antibody modified quartz glass. Consequently, the optical immunosensor demonstrated specificity and improved sensitivity, as compared to the customary methods, and was able to detect as low as 5CFU/mL. The developed DLCS based optical immunosensor was evaluated with environmental water samples, which showed acceptable precision, reproducibility and stability, and could be readily applied to the routine monitoring of pathogenic microorganisms in the environmental samples, and most importantly, demonstrate the potential of a prototype development of a simple and inexpensive diagnostic technique.

Comparison of extended spectrum β-lactamases-producing Escherichia coli with non-ESBLs-producing E.coli: drug-resistance and virulence

BACKGROUND

The virulent factors of Escherichia coli (E.coli) play an important role in the process of pathopoiesis. The study aimed to compare drug-resistant genes and virulence genes between extended spectrum β-lactamases (ESBLs)-producing E.coli and non-ESBLs-producing E.coli to provide a reference for physicians in management of hospital infection.

METHODS

From October 2010 to August 2011, 96 drug-resistant strains of E.coli isolated were collected from the specimens in Qingdao Municipal Hospital, Qingdao, China. These bacteria strains were divided into a ESBLs-producing group and a non-ESBLs-producing group. Drug sensitivity tests were performed using the Kirby-Bauer (K-B) method. Disinfectant gene, qacEΔ1-sull and 8 virulence genes (CNF2, hlyA, eaeA, VT1, est, bfpA, elt, and CNF1) were tested by polymerase chain reaction (PCR).

RESULTS

Among the 96 E.coli isolates, the ESBLs-producing E.coli comprised 46 (47.9%) strains and the non-ESBLs-producing E.coli consisted of 50 (52.1%) strains. The detection rates of multiple drug-resistant strain, qacEΔ1-sull, CNF2, hlyA, eaeA,VT1, est, bfpA, elt, and CNF1 in 46 ESBLs-producing E.coli isolates were 89.1%, 76.1%, 6.5%, 69.6%, 69.6%, 89.1%, 10.9%, 26.1%, 8.7%, and 19.6%, respectively. In the non-ESBLs-producing E.coli strains, the positive rates of multiple drug-resistant strain, qacEΔ1-sull, CNF2, hlyA, eaeA, VT1, est, bfpA, elt, and CNF1 were 62.0%, 80.0%, 16.0%, 28.0%, 64.0%, 38.0%, 6.0%, 34.0%, 10.0%, and 24.0%, respectively. The difference in the detection rates of multiple drug-resistant strain, hlyA and VT1 between the ESBLs-producing E.coli strains and the non-ESBLs-producing E.coli strains was statistically significant (P<0.05).

CONCLUSION

The positive rate of multiple drug-resistant strains is higher in the ESBLs-producing strains than in the non-ESBLs-producing strains. The expression of some virulence genes hlyA and VT1 varies between the ESBLs-producing strains and the non-ESBLs-producing strains. Increased awareness of clinicians and enhanced testing by laboratories are required to reduce treatment failures and prevent the spread of multiple drug-resistant strains.

Ocorrência de Escherichia coli O157:H7 e O26 sorbitol negativas em matadouro frigorífico de bovino e suscetibilidade a antimicrobianos

A carne bovina pode ser um meio de transmissão de Escherichia coli O157:H7 e de não-O157 para os humanos, que a ingerem mal cozida, sendo responsáveis por causarem doenças severas, como a síndrome hemolítico urêmica. A resistência bacteriana se tornou preocupante em relação à eficácia nos tratamentos das doenças, e tendo em vista tais aspectos este estudo teve os objetivos de verificar a ocorrência de E. coli O157:H7 e não-O157 em etapas do abate bovino, asssim como de avaliar a suscetibilidade dessas bactérias frente à ação de antimicrobianos. Foram colhidas em abatedouro bovino 21 amostras de superfície de mãos dos manipuladores, 21 de facas e 300 provenientes de 50 animais em seis pontos no fluxograma de abate. O isolamento foi realizado utilizando o ágar CT-SMAC e a caracterização dos sorotipos pela PCR. Houve uma ocorrência maior de E. coli O157:H7 (12,0%) nos animais, e menor ocorrência de E. coli O26 (8,0%) e de O113 (2,0%). E. coli O26 esteve presente em 9,52% das facas. A presença de E. coli não-O157 sorbitol negativa foi um fato inesperado devido ao método de isolamento utilizado. Todos os isolados de E. coli O157:H7 mostraram-se sensíveis à tetraciclina, cefepime, cefoxitina, ciprofloxacina e sulfazotrim, e 78,85% deles foram resistentes à cefalotina e 34,61% à ampicilina. Todas E. coli O26 foram sensíveis ao cefepime, cefoxitina e sulfazotrim, e 88,23% resistentes à tetraciclina e cefalotina e 82,35% à ampicilina. A multirresistência aos antibimicrobianos foi observada em todos os sorotipos, devendo, portanto, haver critérios no uso de antimicrobianos nos tratamentos para não se tornar um problema de saúde pública.

A novel electrochemical DNA biosensor based on HRP-mimicking hemin/G-quadruplex wrapped GOx nanocomposites as tag for detection of Escherichia coli O157:H7

A novel sensitive electrochemical DNA biosensor was developed for amperometric detection of Escherichia coli O157:H7 (E. coli O157:H7). The graphene oxide (GOx) was utilized as nanocarrier to immobilize thionine (Thi) and the Au nanoparticles coated SiO2 nanocomposites (Au-SiO2) by electrostatic adsorption and the adsorption among nanomaterials. Then a large amounts of signal DNA (S2) and G-quadruplex were immobilized on the GOx-Thi-Au@SiO2 nanocomposites. Finally, hemin was intercalated into the G-quadruplex to obtain the hemin/G-quadruplex structure as HRP-mimicking DNAzyme. On the basis of the signal amplification strategy of GOx-Thi-Au@SiO2 nanocomposites and DNAzyme, the developed DNA biosensor could respond to 0.01 nM (S/N=3) with a linear calibration range from 0.02 to 50.0 nM E. coli O157:H7, which could be well accepted for early clinical detection. The studied system provides new opportunities, and might speed up disease diagnosis, treatment and prevention with pathogen.

Isolation and identification of an Enterobacter cloacae strain producing a novel subtype of Shiga toxin type 1

We describe here the isolation and identification of a Shiga toxin 1 (Stx1)-producing Enterobacter cloacae strain, M12X01451, from a human clinical specimen. The bacterial isolate was identified as E. cloacae using a polyphasic approach that included phenotypic, genetic, and proteomic analyses. The M12X01451 stx1 was sequenced, and the holotoxin was found to share only 87% amino acid sequence identity with the nearest Stx1 subtype reference sequence. Sequence analysis of the regions immediately flanking stx1 displayed similarities with bacteriophage-related sequences, suggesting a prophage origin. The stx1 gene was a stable element within the M12X01451 genome, as demonstrated by real-time PCR detection following successive subculturing of the bacterial isolate. Culture supernatant from M12X01451 was cytotoxic to Vero cells but was not neutralized by an anti-Stx1 monoclonal antibody. In addition, Stx1 from M12X01451 demonstrated limited antigenicity with two commercially available lateral flow immunoassays. The M12X01451 Stx represents a new Stx1 subtype based on the degree of sequence dissimilarity with Stx1 subtype reference sequences and its limited reactivity with anti-Stx1 antibodies.

Risk factors for Escherichia coli O157 shedding and super-shedding by dairy heifers at pasture

We undertook a longitudinal study within a cohort of 52 dairy heifers maintained under constant management systems and sampled weekly to investigate a comprehensive range of risk factors which may influence shedding or super-shedding of E. coli O157 (detected by direct faecal culture and immunomagnetic separation). E. coli O157 was detected from 416/933 (44.6%) samples (faeces and recto-anal mucosal swabs) and 32 (3.4%) samples enumerated at >10000 c.f.u./g. Weekly point prevalence ranged from 9.4% to 94.3%. Higher temperature (P < 0.001), rainfall (P = 0.02), relative humidity (P < 0.001), pasture growth (P = 0.013) and body score (P = 0.029) were positively associated with increased shedding. Higher rainfall (P < 0.001), hide contamination (P = 0.002) and increased faecal consistency (P = 0.023) were positively associated with super-shedding. Increased solar exposure had a negative effect on both shedding and super-shedding within bivariate analyses but in the final multivariate model for shedding demonstrated a positive effect (P = 0.017). Results suggest that environmental factors are important in E. coli O157 shedding in cattle.

Sheep as an important source of E. coli O157/O157:H7 in Turkey

Escherichia coli O157:H7 is a globally important foodborne pathogen and has been mainly associated with cattle as the reservoir. However, accumulating data shows the importance of sheep as an E. coli O157:H7 vehicle. The presence of E. coli O157/O157:H7 in recto-anal mucosal swap and carcass sponge samples of 100 sheep brought to the slaughterhouse in Kirikkale were analyzed over a year. Molecular characteristics (stx1, stx2, eaeA, hly, lpfA1-3, espA, eae-α1, eae-α2, eae-β, eae-β1, eae-β2, eae-γ1, eae-γ2/θ, stx1c, stx1d, stx2c, stx2d, stx2e, stx2f, stx2g, blaampC, tet(A), tet(B), tet(C), tet(D), tet(E), tet(G), sul1, sul2, floR, cmlA, strA, strB and aadA) of 79 isolates were determined and minimum inhibitory concentrations of 20 different antibiotics were investigated. E. coli O157/O157:H7 was found in 18% of sheep included in the study and was more prevalent in yearlings than lambs and mature sheep, and male than female sheep, though none of the categories (season, sex or age range) had significant effect on prevalence. Furthermore, Shiga-toxigenic E. coli (STEC) O157:H7 was determined in 2% and 8% of sheep feces and carcasses, respectively. Additionally, lpfA1-3 and eae-γ1 were detected in all isolates. None of the isolates showed resistance against investigated antibiotics, even though 4 sorbitol fermenting E. coli O157 isolates were positive for tet(A), sul1 and aadA. This is the first study in Turkey that reveals the potential public health risk due to the contamination of sheep carcasses with potentially highly pathogenic STEC O157:H7 strains.

Characterization of Shiga-toxin producing E.coli (STEC) and enteropathogenic E.coli (EPEC) using multiplex Real-Time PCR assays for stx1 , stx2 , eaeA

BACKGROUND AND OBJECTIVE

Diarrheal disease is still a major health problem, especially in developing countries, where it is considered as one of the leading causes of morbidity and mortality especially in children. Studies showed that Diarrheagenic E. coli (DEC) such as STES and EPEC strains are among the most prevalent causative agents in acute diarrhea, particularly in children. Aim of the present study was to investigate the presence and the frequency of STEC and EPEC as etiologic agent of diarrhea in children less than 2 years of age with diarrhea in Shiraz.

MATERIALS AND METHODS

A total of 285 stool samples were collected from patients with diarrhea in Shiraz, in 2012. Diarrheagenic E. coli (DEC) strains were isolated by standard biochemical analysis. In this study, we used multiplex Real time PCR and single PCR to detect the presence of indicator genes stx1 , stx2 and eaeA for STEC and EPEC strains, respectively.

RESULTS

A total of 285 stool samples were tested in which 49 (17%) were identified as contaminated with E. coli by biochemical tests. Out of total samples, 15 STEC (31%) and 13 EPEC (27%) were identified using multiplex Real-Time PCR assay. Among STEC isolates, 2 strains were stx1 (+), 8 isolates stx2 (+), 3 isolates were stx1 (+) , stx2 (+) and 2 isolates were stx1 (+) , stx2 (+), eaeA (+).

CONCLUSION

In this study, we found rather high occurrence of STEC and EPEC virulence genes in children with diarrhea. The results of this study showed that, real time PCR can be used as a replacement for conventional PCR assay in the detecting virulence genes of STEC and EPEC strains. Real-time PCR offers the advantage of being a faster, more robust assay, because it does not require post-PCR procedures to detect amplification products.

PCR and ELISA (VIDAS ECO O157(®)) Escherichia coli O157:H7 identification in Minas Frescal cheese commercialized in Goiânia, GO

Escherichia coli O157:H7 has been incriminated in food poisoning outbreaks and sporadic cases of hemorrhagic colitis and hemolytic uremic syndrome in many countries. Considering the high susceptibility of Minas Frescal cheese to contamination by E. coli O157:H7, the aim of this study was to determine the occurrence of this pathogen through PCR (Polymerase Chain Reaction) and ELISA (VIDAS ECO O157^®, bioMérieux, Lyon, France) test. Thirty cheese samples manufactured by artisan farmhouse producers were collected from open-air markets in Goiânia and thirty from industries under Federal Inspection located in Goiás State which trade their products in supermarkets in Goiânia. E. coli O157:H7 was detected in 6.67% samples collected in open air markets using ELISA, and 23,33% with PCR. The pathogen was not detected in samples from industries under Federal Inspection.

An outbreak of enterotoxigenic Escherichia coli (ETEC) infection in Norway, 2012: a reminder to consider uncommon pathogens in outbreaks involving imported products

We investigated an outbreak of gastroenteritis following a Christmas buffet served on 4–9 December 2012 to ~1300 hotel guests. More than 300 people were reported ill in initial interviews with hotel guests. To identify possible sources of infection we conducted a cohort investigation through which we identified 214 probable cases. Illness was associated with consumption of scrambled eggs (odds ratio 9·07, 95% confidence interval 5·20–15·84). Imported chives added fresh to the scrambled eggs were the suspected source of the outbreak but were unavailable for testing. Enterotoxigenic Escherichia coli (ETEC) infection was eventually confirmed in 40 hotel guests. This outbreak reinforces that ETEC should be considered in non-endemic countries when the clinical picture is consistent and common gastrointestinal pathogens are not found. Following this outbreak, the Norwegian Food Safety Authority recommended that imported fresh herbs should be heat-treated before use in commercial kitchens.

Isolation, prevalence, and risk factors for infection by shiga toxin-producing Escherichia coli (STEC) in dairy cattle

Rectal swabs of 198 Holstein × Gir crossbred beef cattle from 34 milk farms in the central west of Brazil were analyzed from August 2010 to February 2011. Strains of shiga toxin-producing Escherichia coli (STEC) were isolated from 72.73% (144/198) of the animals, on over 97% of the surveyed properties. The molecular characterization indicated the most common toxin gene stx1 in 70.88% of the animals (202/285), followed by 18.95% (54/285) stx1/sxt2, and 10.18% (29/285) stx2. The presence of STEC in animals together with the probable risk factors based on a questionnaire was evaluated in the owners of the evaluated animals. Results showed that the animal category "calves" and production/technification scale "low" of the farm were related to high STEC prevalence in cattle. The season did not significantly affect the presence of STEC in cattle. The STEC strains are considered a major pathogen, causing severe and potentially lethal diseases in humans such as hemorrhagic colitis and hemolytic uremic syndrome. This high prevalence of STEC in dairy cattle poses a significant risk to public health, since these microorganisms can contaminate products intended for human consumption, e.g., water, raw and pasteurized milk, meat products, dairy products, and/or products of plant origin.

Hierarchical cystine flower based electrochemical genosensor for detection of Escherichia coli O157:H7

Synthesis and self-assembly of cystine flowers on gold electrode for biosensing application.

Enterohemorrhagic Escherichia coli O157: H7 from healthy dairy cattle in Mid-West Brazil: occurrence and molecular characterization

Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 represents the major Shiga toxin-producing E. coli (STEC) strain related to large outbreaks and severe diseases such as hemorrhagic colitis (HC) and the potentially lethal hemolytic uremic syndrome (HUS). The aim of this study was to report the occurrence and molecular characterization of O157:H7 isolates obtained by rectal swab from 52 healthy dairy cattle belonging to 21 farms in Mid-West of Brazil. Detection of 16SrRNA, stx1, stx2, rfbO157, fliCh7, eae, ehxA, saa, cnf1, chuA, yjaA and TSPE4.C2 genes was performed by PCR. The isolates were further characterized by serotyping. Two hundred and sixty E. coli isolates were obtained, of which 126 were characterized as STEC. Two isolates from the same cow were identified as serotype O157:H7. Both isolates presented the stx2, eae, ehxA, saa and cnf1 virulence factor genes and the chuA gene in the phylogenetic classification (virulent group D), suggesting that they were clones. The prevalence of O157:H7 was found to be 1.92% (1/52 animals), demonstrating that healthy dairy cattle from farms in the Mid-West of Brazil are an important reservoir for highly pathogenic E. coli O157:H7.

Pathotyping bla CTX-M Escherichia coli from Nigeria

BACKGROUND

Escherichia coli have become the enterobacteriaceae species most affected by extended-spectrum β-lactamases (ESBLs) in view of the emergence of CTX-M-type ESBLs. These CTX-M-positive E. coli have been reported in numerous regions worldwide. Virulence determinants of already reported CTX-M-positive E. coli were investigated.

METHODOLOGY

To gain insights into the mechanism underlying this phenomenon, we assessed serogroup, susceptibility pattern and diversity of virulence profiles within a collection of nine bla CTX-M-positive E. coli strains and their virulent determinant using miniaturized DNA microarray techniques. The nine ESBL-positive E. coli isolates were from eight male and one female patient(s) selected for study based on previous work. Virulence potential was inferred by detection of 63 virulence factor (VF) genes.

RESULTS

Four (44.4%) of the 9 E. coli isolates exhibited the same set of core characteristics: serotype O8:Hnt, while all were positive for OXA-1, ciprofloxacin resistance. Five of the isolates exhibited highly similar (91% to 100%) VF profiles.

CONCLUSION

The findings describe a broadly disseminated, bla CTX-M-positive and virulent E. coli serogroup with highly homogeneous virulence genotypes, suggesting recent emergence in this zone. Understanding how this clone has emerged and successfully disseminated within the hospital and community, including across national boundaries, should be a public health priority.

Rapid Categorization of PathogenicEscherichia coliby Multiplex PCR

A one-shot multiplex polymerase chain reaction (PCR) was developed for detecting 12 virulence genes of diarrheagenic Escherichia coli. In order to differentiate between the five categories of diarrheagenic E. coli, we selected the target genes: stx1, stx2, and eaeA for enterohemorrhagic E. coli(EHEC); eaeA, bfpA, and EAF for enteropathogenic E. coli(EPEC); invE for enteroinvasive E. coli(EIEC); elt, estp, and esth for enterotoxigenic E. coli(ETEC); CVD432 and aggR for enteroaggregative E. coli(EAggEC); and astA distributed over the categories of diarrheagenic E. coli. In our multiplex PCR system, all 12 targeted genes (stx1, stx2, eaeA, invE, elt, estp, astA, esth, bfpA, aggR, EAF, and CVD432) were amplified in a single PCR reaction in one tube and detected by electrophoresis. Using our multiplex PCR, the 208 clinically isolated strains of diarrheagenic E. coli in our laboratory were successfully categorized and easily analyzed for the presence of virulence plasmids.

Identification of EnterohemorrhagicEscherichia coliO157-Specific DNA Sequence Obtained from Amplified Fragment Length Polymorphism Analysis

An approximately 1.1 kbp fragment that was commonly observed only in the enterohemorrhagic Escherichia coli (EHEC) O157 strains in an analysis of amplified fragment length polymorphism was found to be a partial gene sequence encoding the locus of toxB and a useful molecular marker for the identification of EHEC O157.

Evolution of a self-inducible cytolethal distending toxin type V-encoding bacteriophage from Escherichia coli O157:H7 to Shigella sonnei

Some cdt genes are located within the genome of inducible or cryptic bacteriophages, but there is little information about the mechanisms of cdt transfer because of the reduced number of inducible Cdt phages described. In this study, a new self-inducible Myoviridae Cdt phage (ΦAA91) was isolated from a nonclinical O157:H7 Shiga toxin-producing Escherichia coli strain and was used to lysogenize a cdt-negative strain of Shigella sonnei. We found that the phage induced from S. sonnei (ΦAA91-ss) was not identical to the original phage. ΦAA91-ss was used to infect a collection of 57 bacterial strains, was infectious in 59.6% of the strains, and was able to lysogenize 22.8% of them. The complete sequence of ΦAA91-ss showed a 33,628-bp genome with characteristics of a P2-like phage with the cdt operon located near the cosR site. We found an IS21 element composed of two open reading frames inserted within the cox gene of the phage, causing gene truncation. Truncation of cox does not affect lytic induction but could contribute to phage recombination and generation of lysogens. The IS21 element was not present in the ΦAA91 phage from E. coli, but it was incorporated into the phage genome after its transduction in Shigella. This study shows empirically the evolution of temperate bacteriophages carrying virulence genes after infecting a new host and the generation of a phage population with better lysogenic abilities that would ultimately lead to the emergence of new pathogenic strains.

Virulence gene profiles and population genetic analysis for exploration of pathogenic serogroups of Shiga toxin-producing Escherichia coli

Infection with Shiga toxin (Stx)-producing Escherichia coli (STEC) is a serious public health concern, causing severe diarrhea and hemolytic-uremic syndrome. Patient symptoms are varied among STEC strains, possibly implying the presence of markers for STEC virulence other than Stx. To reveal the genotypic traits responsible for STEC virulence, we investigated 282 strains of various serogroups for the presence of 17 major virulence genes, i.e., stx1, stx2a, stx2c, stx2d, stx2e, stx2f, eae, tir, espB, espD, iha, saa, subA, ehxA, espP, katP, and stcE. Next, we examined the prevalence of virulence genes according to the seropathotypes in which serotypes were classified (seropathotypes A through E) based on the reported frequencies in human illness, as well as known associations with outbreaks and with severe disease. Our results demonstrate that the presence of both katP and stcE in STEC, in addition to the genes located in the locus of enterocyte effacement (LEE), including eae, tir, espB, and espD, may indicate the most pathogenic genotype of STEC. A population structure analysis of the profiles of virulence genes statistically supported the pathogenic genotype and, furthermore, revealed that there are serogroups with potentially higher pathogenicity than previously thought. Some strains in serogroups O26, O145, and O165 may have high virulence equivalent to that of serogroup O157. Several serogroups, including O14, O16, O45, O63, O74, 119, O128, and O untypeable, also may be potentially pathogenic, although rarely in humans.

Predicting the public health benefit of vaccinating cattle against Escherichia coli O157

Identifying the major sources of risk in disease transmission is key to designing effective controls. However, understanding of transmission dynamics across species boundaries is typically poor, making the design and evaluation of controls particularly challenging for zoonotic pathogens. One such global pathogen is Escherichia coli O157, which causes a serious and sometimes fatal gastrointestinal illness. Cattle are the main reservoir for E. coli O157, and vaccines for cattle now exist. However, adoption of vaccines is being delayed by conflicting responsibilities of veterinary and public health agencies, economic drivers, and because clinical trials cannot easily test interventions across species boundaries, lack of information on the public health benefits. Here, we examine transmission risk across the cattle-human species boundary and show three key results. First, supershedding of the pathogen by cattle is associated with the genetic marker stx2. Second, by quantifying the link between shedding density in cattle and human risk, we show that only the relatively rare supershedding events contribute significantly to human risk. Third, we show that this finding has profound consequences for the public health benefits of the cattle vaccine. A naïve evaluation based on efficacy in cattle would suggest a 50% reduction in risk; however, because the vaccine targets the major source of human risk, we predict a reduction in human cases of nearly 85%. By accounting for nonlinearities in transmission across the human-animal interface, we show that adoption of these vaccines by the livestock industry could prevent substantial numbers of human E. coli O157 cases.

Assessments of total and viable Escherichia coli O157:H7 on field and laboratory grown lettuce

Leafy green produce has been associated with numerous outbreaks of foodborne illness caused by strains of Escherichia coli O157:H7. While the amounts of culturable E. coli O157:H7 rapidly decline after introduction onto lettuce in the field, it remains to be determined whether the reduction in cell numbers is due to losses in cell viability, cell injury and a subsequent inability to be detected by standard laboratory culturing methods, or a lack of adherence and hence rapid removal of the organism from the plants during application. To assess which of these options is most relevant for E. coli O157:H7 on leafy green produce, we developed and applied a propidium monoazide (PMA) real-time PCR assay to quantify viable (with PMA) and total (without PMA) E. coli O157:H7 cells on growth chamber and field-grown lettuce. E. coli O157:H7, suspended in 0.1% peptone, was inoculated onto 4-week-old lettuce plants at a level of approximately 10(6) CFU/plant. In the growth chamber at low relative humidity (30%), culturable amounts of the nontoxigenic E. coli O157:H7 strain ATCC 700728 and the virulent strain EC4045 declined 100 to 1000-fold in 24 h. Fewer E. coli O157:H7 cells survived when applied onto plants in droplets with a pipette compared with a fine spray inoculation. Total cells for both strains were equivalent to inoculum levels for 7 days after application, and viable cell quantities determined by PMA real-time PCR were approximately 10(4) greater than found by colony enumeration. Within 2 h after application onto plants in the field, the number of culturable E. coli ATCC 700728 was reduced by up to 1000-fold, whereas PCR-based assessments showed that total cell amounts were equivalent to inoculum levels. These findings show that shortly after inoculation onto plants, the majority of E. coli O157:H7 cells either die or are no longer culturable.

Characterization of Escherichia coli O157:H7 strains isolated from supershedding cattle

Previous reports have indicated that a small proportion of cattle shedding high levels of Escherichia coli O157:H7 is the main source for transmission of this organism between animals. Cattle achieving a fecal shedding status of 10(4) CFU of E. coli O157:H7/gram or greater are now referred to as supershedders. The aim of this study was to investigate the contribution of E. coli O157:H7 strain type to supershedding and to determine if supershedding was restricted to a specific set of E. coli O157:H7 strains. Fecal swabs (n = 5,086) were collected from cattle at feedlots or during harvest. Supershedders constituted 2.0% of the bovine population tested. Supershedder isolates were characterized by pulsed-field gel electrophoresis (PFGE), phage typing, lineage-specific polymorphism assay (LSPA), Stx-associated bacteriophage insertion (SBI) site determination, and variant analysis of Shiga toxin, tir, and antiterminator Q genes. Isolates representing 52 unique PFGE patterns, 19 phage types, and 12 SBI clusters were obtained from supershedding cattle, indicating that there is no clustering to E. coli O157:H7 genotypes responsible for supershedding. While being isolated directly from cattle, this strain set tended to have higher frequencies of traits associated with human clinical isolates than previously collected bovine isolates with respect to lineage and tir allele, but not for SBI cluster and Q type. We conclude that no exclusive genotype was identified that was common to all supershedder isolates.

Comparison of the prevalence of shiga toxin-producing Escherichia coli strains O157 and O26 between beef and dairy cattle in Japan

With the aim of comparing the prevalence of Shiga toxin-producing Escherichia coli (STEC) O157 and O26 between beef and dairy cattle, we collected rectal content samples from 250 beef cattle on 25 beef farms and 250 dairy cows on 25 dairy farms from July through September 2011. STEC O157 was isolated from 16 beef cattle on 7 beef farms, while no STEC O157 was isolated from any dairy farms. This result suggests that the prevalence of STEC O157 is higher in beef cattle than in dairy cattle. STEC O26 was isolated from 1 animal each from beef and dairy cattle herds, and therefore, it was not possible to compare statistically the prevalence of STEC O26 in beef and dairy cattle.

Multiplex real-time PCR (MRT-PCR) for diarrheagenic

Diarrheagenic Escherichia coli strains are important causes of diarrhea in children from the developing world and are now being recognized as emerging enteropathogens in the developed world. Current methods of detection are too expensive and labor-intensive for routine detection of these organisms to be practical. We developed a real-time fluorescence-based multiplex PCR for the detection of all six of the currently recognized classes of diarrheagenic E. coli. The primers were designed to specifically amplify eight different virulence genes in the same reaction: aggR for enteroaggregative E. coli (EAEC), stIa/stIb and lt for enterotoxigenic E. coli (ETEC), eaeA for enteropathogenic E. coli (EPEC), stx1 and stx2 for Shiga toxin-producing E. coli (STEC), ipaH for enteroinvasive E. coli (EIEC), and daaD for diffusely adherent E. coli (DAEC).

Simultaneous detection of Salmonella pathogenicity island 2 and its antibiotic resistance genes from seafood

Salmonella enterica serovars are virulent pathogens of humans and animals with many strains possessing multiple drug resistance traits. They have been found to carry resistance to ampicillin, chloramphenicol, florfenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT-resistant). A rapid and sensitive multiplex PCR (mPCR)-based assay was developed for the detection of Salmonella serovars from seafood. Six sets of primers which are one primer pair targeting Salmonella specific gene invA (284 bp), two Salmonella pathogenicity island 2 (SPI-2) genes ssaT (780 bp) and sseF (888 bp) and three antibiotic resistance genes floR (198 bp), sul1 (425 bp), tetG (550 bp) were used for the study. The specificity and sensitivity of the assay were tested by spiking shrimp/fish/clam homogenate with viable cells of Salmonella. This assay allows for the cost effective and reliable detection of pathogenic Salmonella enterica from seafood. The mPCR developed in the present study proved to be a potent analytical tool for the rapid identification of multidrug-resistant Salmonella serovars from seafood.

Genetic characteristics of Shiga toxin-producing E. coli O157, O26, O103, O111 and O145 isolates from humans, food, and cattle in Belgium

In this study, we characterized 272 Shiga toxin-producing Escherichia coli (STEC) isolates from humans, food, and cattle in Belgium [O157 (n = 205), O26 (n = 31), O103 (n = 15), O111 (n = 10), O145 (n = 11)] for their virulence profile, whole genome variations and relationships on different genetic levels. Isolates of O157 displayed a wide variation of stx genotypes, heterogeneously distributed among pulsogroups (80% similarity), but with a concordance at the pulsosubgroup level (90% similarity). Of all serogroups evaluated, the presence of eae was conserved, whereas genes encoded on the large plasmid (ehx, espP, katP) occurred in variable combinations in O26, O103, and O145. The odds of having haemolytic uraemic syndrome was less for all genotypes stx2a, stx2c, stx1/stx2c, and stx1 compared to genotype stx2a/stx2c; and for patients aged >5 years compared to patients aged ≤ 5 years. Based on the genetic typing and by using epidemiological data, we could confirm outbreak isolates and suggest epidemiological relationships between some sporadic cases. Undistinguishable pulsotypes or clones with minor genotypic variations were found in humans, food, and cattle in different years, which demonstrated the important role of cattle as a reservoir of STEC O157, and the circulation and persistence of pathogenic clones.

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.

Quantifying colonization potential of enterohemorrhagic Escherichia coli O157 using bovine in vitro organ culture and immunofluorescent staining

A robust semiquantitative method for measuring the colonization potential of O157 enterohemorrhagic Escherichia coli (EHEC) strains was developed combining an established ex vivo model infection system, bovine in vitro organ culture, with detection of bacteria attached to tissue sections by immunofluorescent assay (bIVOC-IFA) using Quantum dot(®) nanocrystal technology. The method was tested on ten O157 strains chosen to reflect a diversity of genotypes found in New Zealand based on the novel polymerase chain reaction-binary typing (P-BIT) system. High- and low-colonizing EHEC O157 strains were identified using bIVOC-IFA, with the highest colonizing strain belonging to the pulsed-field gel electrophoresis type most commonly identified from New Zealand beef meat. Furthermore, all of the toxigenic O157 strains exhibiting a low-colonizing phenotype were closely related, belonging to the same P-BIT genotype cluster. Future use of this method to characterize EHEC strains could provide valuable information for risk assessment and risk management interventions aimed at improving food safety along the beef farm to fork continuum.

Enteroaggregative Escherichia coli quantification in children stool samples using quantitative PCR

Enteroaggregative Escherichia coli (EAEC) is a common cause of infectious diarrhea, especially in children living in poor-resource countries. In this article, we present a SYBR Green-based real-time polymerase chain reaction (qPCR) method for quantitative detection of EAEC in DNA directly extracted from human stool samples. To test the proposed qPCR system, we examined specificity, sensitivity, repeatability, and also the degree of DNA extraction efficiency using EAEC strain 042 spiked into EAEC-free stool sample. The specificity of this assay was proved using six strains of EAEC, seven strains of other E. coli types, and one strain of Shigella. The detection limit of qPCR was 67 CFU/reaction. In naturally infected stool samples, we found EAEC in quantities varying from 6.7 × 10(5) to 2 × 10(9 ) CFU/g of feces. We could not detect any reduction after stool DNA extraction for the amounts of 10(7) and 10(6) CFU/mL of spiked EAEC. This qPCR assay is simple, rapid, reproducible, sensitive, specific, and allows rapid EAEC quantification to be used in a variety of further EAEC studies. This new quantitative method provides a relatively simple means to quantify EAEC, which will likely be key to understanding the pathophysiology and impact of EAEC infection.