Shiga Toxigenic Escherichia Coli O157 Research Articles

Antimicrobial Profiles and Conventional PCR Assay of Shiga Toxigenic Escherichia coli O157:H7 (STEC) Isolated from Cattle Slaughtered at Bedele Municipal Abattoir, South West Ethiopia.

Shiga toxin producing Escherichia coli O157:H7 (STEC) is considered the most prevalent food borne pathogen that has gained increasing attention worldwide in recent years. A cross-sectional study was carried out at Bedele Municipal abattoir on cattle that were reported healthy from detailed ante-mortem inspections and having various body conditions scores. A total of 516 samples were collected and examined after enriched in modified peptone water. Following an enrichment, the samples were plated onto MacConkey agar and then onto Eosin methylene blue agar. Finally after a few similar procedures, 14 E. coli O157:H7 (STEC) isolates were confirmed through latex agglutination test. The collected data were analyzed using SPSS version 20 statistical software. This study finding revealed that the overall prevalence of E. coli O157:H7 out of 516 samples was found to be 2.7%. However, on sample type basis, the prevalence of E. coli O157:H7 from feacal samples, carcass swabs, butcher hand swabs and knife swabs were 4.7%, 3.3%, 1.1% and 1.1%, respectively. It was also found that that the prevalence of E. coli O157:H7 was significantly affected by age groups of slaughtered cattle (p<0.05). Moreover, in vitro antimicrobial susceptibility test result on average showed that almost all of E. coli O157:H7 isolates were highly susceptible to kanamycin and no resistance was shown to ciprofloxacin and gentamicin. Finally, the conventional PCR detection of stx1, st2 and hylA genes revealed that only 21.4% and 14.3% were found to contain stx1 and hylA genes respectively. To wrap up, this study showed that Shiga toxin producing E. coli O157:H7 (STEC) isolates were found with almost low overall prevalence rate from all sample sources in this study site. Therefore, improving abattoir facilities and slaughter house workers' personal hygiene are recommended to curtail E. coli O157:H7 meat contamination in this abattoir.

Differential Survival of Non-O157 Shiga Toxigenic Escherichia coli in Simulated Cattle Feedlot Runoff.

Environmental survival time is important when evaluating adverse health outcomes from foodborne pathogens. Although outbreaks associated with manure-impacted irrigation or runoff water are relatively infrequent, their broad scope, regulatory importance, and severe health outcomes highlight the need to better understand the environmental survival of manure-borne pathogens. Shiga toxigenic Escherichia coli (STEC) are excreted in feces and persist in the environment until they die or recolonize a new host. Surface waters contaminated with manure-borne STEC can infect humans through drinking and recreational water use or irrigated crops that are minimally cooked. In this study, manure-impacted water microcosms mimicking beef cattle feedlot runoff were used to assess survival of STEC strains representing seven STEC serotypes (O26, O45, O103, O111, O121, O145, and O157) and persistence of target O antigen genes. Microcosms were sampled over the course of 1 year, and the entire experiment was repeated in a second year. Culture and polymerase chain reaction (PCR)-based techniques were used for detection and enumeration. Serotype-specific survival results were observed. Both STEC O26 and O45 declined slowly and remained culturable at 24 months. In contrast, STEC O121 and O145 decreased rapidly (-0.84 and -1.99 log10 abundance per month, respectively) and were unculturable by months 4 and 5, but detectable by PCR for a mean of 4.5 and 8.3 months, respectively. STEC O103, O111, and O157 remained culturable for a mean of 11.6, 5.5, and 15 months and detectable by PCR for a mean of 12, 13.8, and 18.6 months after inoculation, respectively. Results document that some STEC serotypes have the biological potential to survive in manure-impacted waters for extended periods of time when competing microflora are eliminated. Serotype-specific differences in survival of target bacteria and persistence of target genes were observed in this sample set, with STEC O26 and O45 strains appearing the most robust in these microcosm studies.

Effectiveness of Bacteriophages Against Biofilm-Forming Shiga-Toxigenic Escherichia coli on Leafy Greens and Cucumbers.

Background: Shiga-toxigenic Escherichia coli (STEC) have caused several produce-associated outbreaks, making it challenging to control these pathogens. Bacteriophages could serve as effective biocontrol. Materials and Methods: Spinach, lettuce, and cucumbers, inoculated with STEC (O157, O26, O45, O103, O111, O121, O145), were treated with lytic bacteriophages and stored at 4°C for 3 days. Surviving STEC were enumerated and observed under scanning electron microscope (SEM), and data analyzed using one-way analysis of variance (ANOVA) (p < 0.05). Results: Bacteriophage treatments significantly reduced STEC populations, compared with the control (p < 0.05). On spinach and romaine, STEC O26, O45, and O103 were reduced to undetectable levels and STEC O157, O111, O121, and O145 by ∼2 logs CFU/cm2. Multiserotype phage cocktail reduced STEC on leafy greens by 1.4 CFU/cm2 and on cucumbers by 1.7 logs CFU/cucumber. Clusters of STEC cells, surrounded by extracellular matrix, were observed under SEM of positive control, whereas phage-treated produce surface showed fewer cells, with cellular damage. Conclusions: Bacteriophages could be utilized as biocontrol against STEC on fresh produce.

Effect of a bacteriophage T5virus on growth of Shiga toxigenic Escherichia coli and Salmonella strains in individual and mixed cultures

A previously isolated a bacteriophage, vB_EcoS_AKFV33 of T5virus, demonstrated great potential in biocontrol of Shiga toxigenic Escherichia coli (STEC) O157. This study further evaluated its potential as a biocontrol agent in broth culture against other important non-O157 serogroups of STEC and Salmonella. AKFV33 was capable of lysing isolates of STEC serogroups O26 (n = 1), O145 (n = 1) and Salmonella enterica serovars (n = 6). In a broth culture microplate system, efficacy of AKFV33 for killing STEC O26:H11, O145:NM and Salmonella was improved (P < 0.05) at a lower multiplicity of infection and sampling time (6–10 h), when STEC O157:H7 was also included in the culture. This phage was able to simultaneously reduce numbers of STEC and Salmonella in mixtures with enhanced activity (P < 0.05) against O157:H7 and O26:H11, offering great promise for control of multiple zoonotic pathogens at both pre and post-harvest.

Phage Predation Shapes the Population Structure of Shiga-Toxigenic Escherichia coli O157:H7 in the UK: An Evolutionary Perspective.

Bacterial–host interactions are non-linear and actually threefold, involving significant selection through predatory lytic bacteriophages in the host environment. In studies of human and animal gut microbiome bacteria, it is important to consider phage in all host–pathogen interactions. We use an important zoonotic pathogen, Shiga toxigenic Escherichia coli (STEC) O157:H7, to investigate this. Our study provides evidence that phage resistance profiles are well maintained at the sub-lineage level with variation in profiles within sub-lineages uncommon. This indicates that phage resistance heterogeneity happened early on in the STEC O157:H7 natural history and that occasional “wobbles” do not often outcompete the stable lineage unless combined with a competitive advantage. We discuss an example of this in the acquisition of stx2a that, while an important virulence factor, also conveys increased phage cross-resistance. We also discuss the role of phage resistance in co-occurrence of the three stable lineages worldwide and whether differing phage resistance is maintaining diversity.

Whole-Genome Sequences of Phages p000v and p000y, Which Infect the Bacterial Pathogen Shiga-Toxigenic Escherichia coli.

ABSTRACTWe report here the genome sequences and morphological characterizations of phages p000v and p000y, which infect the bacterial pathogen Shiga-toxigenic Escherichia coli O157:H7 and which are potential candidates for phage therapy against such pathogens.

An investigation of shedding and super-shedding of Shiga toxigenic Escherichia coli O157 and E.coli O26 in cattle presented for slaughter in the Republic of Ireland.

Shiga toxigenic Escherichia coli (STEC) are an important group of pathogens and can be transmitted to humans from direct or indirect contact with cattle faeces. This study investigated the shedding of E.coli O157 and O26 in cattle at the time of slaughter and factors associated with super-shedding (SS) animals. Rectoanal mucosal swab (RAMS) samples were collected from cattle (n=1,317) at three large Irish commercial beef abattoirs over an 18month period, and metadata were collected at the time of sampling regarding farm of origin, animal age, breed and gender. RAMS swabs were examined for the presence and numbers of E.coli O157 and O26 using a previously developed quantitative real-time PCR protocol. Samples positive by PCR were culturally examined and isolates analysed for the presence of stx subtypes, eae and phylogroup. Any samples with counts >104 CFU/swab of STEC O157 or O26 were deemed to be super-shedders. Overall, 4.18% (55/1,317) of RAMS samples were positive for STEC O157, and 2.13% (28/1,317) were classified as STEC O157 SS. For STEC O26, 0.76% (10/1,317) of cattle were positive for STEC O26, and 0.23% (3/1,317) were classified as super-shedders. Fewer STEC shedders and SS were noted among older animals (>37months). There was a seasonal trend observed for STEC O157, with the highest prevalence of shedding and SS events in the autumn (August to October). The majority of E.coli O157 (50/55) isolates had stx2 and were eae positive, with no significant difference between SS and low shedders (LS). Interestingly, all STEC O26 (n=10) were eae negative and had varied stx profiles. This study demonstrates that, while the overall shedding rates are relatively low in cattle at slaughter, among positive animals there is a high level of SS, which may pose a higher risk of cross-contamination during slaughter.

Comparative Effect of Heat Shock on Survival of O157:H7 and Non-O157 Shiga Toxigenic Escherichia coli and Salmonella in Lean Beef with or without Moisture-Enhancing Ingredients

Thermal tolerance of pathogenic bacteria has been shown to increase after exposure to sublethal elevated temperatures, or heat shock. We evaluated the effect of heat shock at 48°C on thermal tolerance (D55°C) of cocktails of O157 and non-O157 Shiga toxigenic Escherichia coli (STEC) and Salmonella in lean ground beef with or without moisture-enhancing ingredients. Beef was moisture enhanced to 110% (w) with a 5% NaCl-2.5% sodium tripolyphosphate (w/w) brine. Meat, with or without added brine, was inoculated (∼108 CFU/g) and heat shocked at 48°C for 0, 5, or 30 min, followed by isothermal heating at 55°C. Inoculated control samples were unenhanced and were not subject to heat shock. From the linear portion of the log CFU per gram surviving cells over time plots, D55°C-values (minutes) were calculated. D55°C was 20.43, 28.78, and 21.15 min for O157, non-O157, and Salmonella controls, respectively. Overall, heat shock significantly increased D55°C, regardless of pathogen (P < 0.05). After 30 min of heat shock, D55°C increased 89 and 160% for O157 STEC, 32 and 49% for non-O157 STEC, and 29 and 57% for Salmonella, in unenhanced and enhanced samples, respectively, relative to the pathogen control. D55°C for Salmonella was the same or significantly less than for O157 and non-O157 STEC, regardless of heat shock, and was significantly less than for O157 and non-O157 STEC in all trials with moisture-enhanced meat (P < 0.05). Moisture-enhancing ingredients significantly increased D55°C, regardless of pathogen (P < 0.05). We suggest that thermal processes validated against Salmonella may not prove effective against STEC in all cases and that regulators of the beef industry should focus attention on STEC in nonintact moisture-enhanced beef products.

Presence of Staphylococcus aureus and Shiga Toxigenic Escherichia coli O157:H7 in Raw Meat in Ağrı, Turkey

Presence of Staphylococcus aureus and Shiga Toxigenic Escherichia coli O157:H7 in Raw Meat in Ağrı, Turkey

Presence of Staphylococcus aureus and Shiga Toxigenic Escherichia coli O157:H7 in Raw Meat in Ağrı, Turkey

Background: Staphylococcus aureus and Shiga toxin producing Escherichia coli O157:H7 (EHEC) are significant foodborne pathogens worldwide. While S. aureus can cause mild superficial skin infections or life-threatening bacteremia and endocarditis, as well as toxininduced cases such as toxic shock syndrome; E. coli O157:H7 can cause symptoms from mild diarrhea to severe hemorrhagic colitis (HC), hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP). Objectives: The objectives of this study were to find out the prevalence and seasonal distribution of S. aureus in 214 frozen raw meat (turkey, chicken and beef) and the prevalence of E. coli O157:H7 in 70 raw beef with the characterization of the E. coli O157:H7 isolate by multiplex polymerase chain reaction (PCR). Materials and Methods: For the detection of S. aureus, a total of 214 frozen raw meat samples including 74 turkey meat, 70 chicken meat and 70 beef cuts (approximately 2 × 3 cm cubic parts); and for the detection of E. coli O157:H7, a total of 70 frozen raw beef samples that all were produced from national companies and consumed in Agri, Turkey were analyzed. Results: Out of 214 meat samples, 25.7 % (18/70) of the beef, 11.4 % (8/74) of the chicken meat, and 5.4 % (4/70) of the turkey meat samples were contaminated with S. aureus. Out of 70 frozen raw beef samples, only 1 (1.4%) was identified as both Shiga toxin 1 and 2producing E. coli O157:H7 by the detection of stx1, stx2, eaeA, hly, and fliCh7 according to multiplex PCR analysis. Conclusion: Our findings demonstrate that occurrence frequency of S. aureus was higher in frozen raw beef than in raw chicken and turkey meat samples. Although the prevalence of E. coli O157:H7 was low in beef, the presence of virulence genes, especially toxin genesrema in a significant public health concern.

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.

Thermal Tolerance of O157 and non-O157 Shiga Toxigenic Strains of Escherichia coli, Salmonella, and Potential Pathogen Surrogates, in Frankfurter Batter and Ground Beef of Varying Fat Levels

The non-O157 Shiga toxigenic Escherichia coli (STEC) serogroups most commonly associated with illness are O26, O45, O103, O111, O121, and O145. We compared the thermal tolerance (D55°C) of three or more strains of each of these six non-O157 STEC serogroups with five strains of O157:H7 STEC in 7% fat ground beef. D55°C was also determined for at least one heat-tolerant STEC strain per serogroup in 15 and 27% fat ground beef. D55°C of single-pathogen cocktails of O157 and non-O157 STEC, Salmonella, and potential pathogen surrogates, Pediococcus acidilactici and Staphylococcus carnosus, was determined in 7, 15, and 27% fat ground beef and in frankfurter batter. Samples (25 g) were heated for up to 120 min at 55°C, survivors were enumerated, and log CFU per gram was plotted versus time. There were significant differences in D55°C across all STEC strains heated in 7% fat ground beef (P < 0.05), but no non-O157 STEC strain had D55°C greater than the range observed for O157 STEC. D55°C was significantly different for strains within serogroups O45, O145, and O157 (P < 0.05). D55°C for non-O157 STEC strains in 15 and 27% fat ground beef were less than or equal to the range of D55°C for O157. D55°C for pathogen cocktails was not significantly different when measured in 7, 15, and 27% fat ground beef (P ≥ 0.05). D55°C of Salmonella in frankfurter batter was significantly less than for O157 and non-O157 STEC (P < 0.05). Thermal tolerance of pathogen cocktails in ground beef (7, 15, or 27% fat) and frankfurter batter was significantly less than for potential pathogen surrogates (P < 0.05). Results suggest that thermal processes in beef validated against E. coli O157:H7 have adequate lethality against non-O157 STEC, that thermal processes that target Salmonella destruction may not be adequate against STEC in some situations, and that the use of pathogen surrogates P. acidilactici and S. carnosus to validate thermal processing interventions in ground beef and frankfurter batter would be of limited utility to processors.

Thermal Tolerance Characteristics of Non-O157 Shiga Toxigenic Strains of Escherichia coli (STEC) in a Beef Broth Model System Are Similar to Those of O157:H7 STEC

The non-O157 Shiga toxigenic Escherichia coli (STEC) serogroups most commonly associated with illness are O26, O45, O103, O111, O121, and O145. In the United States, these serogroups are considered adulterants in raw nonintact beef. To begin to understand the behavior of these pathogens in meat systems, we compared the thermal tolerance of acid-adapted cells of non-O157 STEC and O157:H7 STEC in a beef-derived broth. D58°C-values were determined for at least three strains per serogroup, and D54.6°C-values and D63.6°C-values were determined for one strain per serogroup. Each strain was grown to stationary phase in brain heart infusion broth (BHIB; pH 7.0) and inoculated into prewarmed BHIB in a shaking water bath for thermotolerance experiments at 54.6, 58.0, or 63.6°C (three trials per strain). Samples were heated for up to 160 min at 54.6°C, 3 min at 58.0°C, or 45 s at 63.6°C, with periodic sampling followed by rapid cooling and plating on modified Levine's eosin methylene blue agar. For each strain and temperature, the log CFU per milliliter was plotted versus time, and D-values were determined. Across all strains, the least and most heat tolerant STEC serogroups at 58°C were O145 and O157, respectively. D58°C-values in BHIB ranged from 0.44 min for an O145 strain to 1.42 min for an O157:H7 strain. D58°C-values for O157 STEC strains were significantly higher than those for at least one strain in each of the non-O157 STEC serogroups (P < 0.05) except for serogroup O103. At 54.6°C, the most heat-resistant STEC strain belonged to serogroup O103 and was significantly more heat tolerant than the O157:H7 strains (P < 0.05). Grouping the strains, there were no significant differences in heat tolerance between O157 and non-O157 STEC at 63.6°C (P ≥ 0.05). The z-values for non-O157 STEC strains were comparable to those for O157:H7 STEC strains (P ≥ 0.05), ranging from 4.10 to 5.21°C. These results suggest that thermal processing interventions that target destruction of E. coli O157:H7 may have adequate lethality against non-O157 STEC.

Outbreak of Shiga-Toxigenic Escherichia coli O157:H7 Infections Associated with Rodeo Attendance, Utah and Idaho, 2009

In summer 2009, the Utah Department of Health investigated an outbreak of Shiga-toxigenic Escherichia coli (STEC) O157:H7 (O157) illness associated with attendance at multiple rodeos. Patients were interviewed regarding exposures during the week before illness onset. A ground beef traceback investigation was performed. Ground beef samples from patient homes and a grocery store were tested for STEC O157. Rodeo managers were interviewed regarding food vendors present and cattle used at the rodeos. Environmental samples were collected from rodeo grounds. Two-enzyme pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem repeat analysis (MLVA) were performed on isolates. Fourteen patients with primary STEC O157 illness were reported in this outbreak. Isolates from all patients were indistinguishable by PFGE. Isolates from nine patients had identical MLVA patterns (main outbreak strain), and five had minor differences. Thirteen (93%) patients reported ground beef consumption during the week before illness onset. Results of the ground beef traceback investigation and ground beef sampling were negative. Of 12 primary patients asked specifically about rodeo attendance, all reported having attended a rodeo during the week before illness onset; four rodeos were mentioned. All four rodeos had used bulls from the same cattle supplier. An isolate of STEC O157 identified from a dirt sample collected from the bullpens of one of the attended rodeos was indistinguishable by PFGE and MLVA from the main outbreak strain. Recommendations were provided to rodeo management to keep livestock and manure separate from rodeo attendees. This is the first reported STEC O157 outbreak associated with attendance at multiple rodeos. Public health officials should be aware of the potential for rodeo-associated STEC illness.

Changes in cell surface properties of shiga toxigenic Escherichia coli by Quercus infectoria G. Olivier.

The effects of Quercus infectoria (family Fagaceae) nutgalls on cell surface properties of Shiga toxigenic Escherichia coli (STEC) were investigated with an assay of microbial adhesion to hydrocarbon. The surface of bacterial cells treated with Q. infectoria exhibited a higher level of cell surface hydrophobicity (CSH) toward toluene than did the surface of untreated cells. With 50% ethanolic extract, the CSH of the three strains of STEC O157:H7 treated with 4X MIC of the extract resulted in moderate or strong hydrophobicity, whereas at 2x MIC and MIC, the CSH of only one strain of E. coli O157:H7 was significantly affected. The 95% ethanolic extract had a significant effect on CSH of all three strains at both 4X MIC and 2X MIC but not at the MIC. The effect on bacterial CSH was less pronounced with the other STEC strains. At 4X MIC, the 50% ethanolic extract increased the CSH of all non-O157 STEC strains significantly. At 2X MIC and 4X MIC, the 95% ethanolic extract affected the CSH of E. coli O26:H11 significantly but did not affect E. coli O111 :NM or E. coli O22. Electro microscopic examination revealed the loss of pili in the treated cells. The ability of Q. infectoria extract to modify hydrophobic domains enables this extract to partition the lipids of the bacterial cell membrane, rendering the membrane more permeable and allowing leakage of ions and other cell contents, which leads to cell death. Further studies are required to evaluate the effects of Q. infectoria extract in food systems or in vivo and provide support for the use of this extract as a food additive for control of these STEC pathogens.

The Escherichia coli ycbQRST operon encodes fimbriae with laminin-binding and epithelial cell adherence properties in Shiga-toxigenic E. coli O157:H7.

The human pathogen Shiga-toxigenic Escherichia coli (STEC) O157:H7 contains a ycbQRST fimbrial-like operon, which shares significant homology to the family of F17 fimbrial biogenesis genes f17ADCG found in enterotoxigenic E. coli. We report that growth of STEC O157:H7 strain EDL933 in minimal Minca medium at 37°C and during adherence to epithelial cells led to the production of fine peritrichous fimbriae, which were found to be composed of a major subunit of 18 kDa whose N-terminal amino acid sequence matched the predicted protein product of the ycbQ gene; and showed significant homology to the F17a-A fimbrin. Similar to the F17 fimbriae, the purified STEC fimbriae and the recombinant YcbQ protein fused to a His peptide tag bound laminin, but not fibronectin or collagen. Thus, we propose the name E. coli YcbQ laminin-binding fimbriae (ELF) to designate the fimbriae encoded by the ycbQRST operon. The role of ELF as an adherence factor of STEC to cultured epithelial cells was investigated. We provide compelling evidence demonstrating that ELF contributes to adherence of STEC to human intestinal epithelial cells and to cow and pig gut tissue in vitro. Deletion in the fimbrin subunit gene elfA (or ycbQ) in STEC strain EDL933 led to an isogenic strain, which showed significant reduction (60%) in adherence to HEp-2 cells in comparison with the parental strain. In addition, antibodies against the purified ELF also partially blocked adherence of two STEC O157:H7 strains. These observations suggest that ELF functions as an accessory adherence factor that, along with other known redundant adhesins, contributes to the overall adhesive properties of STEC O157:H7 providing these organisms with ecological advantages to survive in different hosts and in the environment.

A comparative study of biofilm formation by Shiga toxigenic Escherichia coli using epifluorescence microscopy on stainless steel and a microtitre plate method

Attachment of Shiga toxigenic Escherichia coli (STEC) to surfaces and the formation of biofilms may enhance persistence in a food processing environment and present a risk of contaminating products. Seven strains of STEC and three non-STEC strains were selected to compare two biofilm quantification methods; epifluorescence microscopy on stainless steel (SS) and a microtitre plate assay. The influence of prior growth in planktonic (nutrient broth) and sessile (nutrient agar) culture on biofilm production, as well as expression of surface structures and the possession of antigen 43 (encoded by agn43) on biofilm formation were also investigated. Biofilms were produced in diluted nutrient broth at 25 °C for 24 and 48 h. Curli expression was determined using congo red indicator agar, while the presence of agn43 was determined using polymerase chain reaction. No correlation was found between counts for epifluorescence microscopy on SS and the absorbance values obtained with the microtitre plate method for planktonic and sessile grown cultures. Different abilities of individual STEC strains to attach to SS and microtitre plates were found with some strains attaching better to each surface following growth in either planktonic or sessile culture. All O157 STEC strains had low biofilm counts on SS for planktonic and sessile grown cultures; however, one STEC O157:H− strain (EC516) had significantly greater ( p < 0.05) biofilm production on microtitre plates compared to the other O157 STEC strains. EC516 and other STEC (O174:H21 and O91:H21) strains expressing curli fimbriae were found to produce significantly greater ( p < 0.05) biofilms on microtitre plates compared to the non-curli expressing strains. No relationship was found between the production of type-I fimbriae, motility, agn43 and bacterial physicochemical properties (previously determined) and biofilm formation on SS or microtitre plates. Variations between the two biofilm determination methods may suggest that the biofilm production on microtitre plates may not be appropriate to represent other surfaces such as SS and that caution should be taken when selecting a method to quantify biofilm production on a surface.

Isolation of Salmonella enterica and Shiga-toxigenic Escherichia coli O157 from feces of animals in public contact areas of United States zoological parks.

The fecal prevalence of subclinical Salmonella enterica and Shiga-toxigenic Escherichia coli O157 among animals in human-animal contact exhibits at institutions in the United States accredited by the Association of Zoos and Aquariums was estimated to assess public health risk. The prevalence was less than 0.6% for both zoonotic pathogens among 997 animals sampled at 36 exhibits.

Physicochemical properties of Shiga toxigenic Escherichia coli

To investigate the physicochemical surface properties, such as cellular surface charge, hydrophobicity and electron donor/acceptor potential of a selection of Shiga toxigenic Escherichia coli (STEC) isolates grown in broth and agar culture. Cellular surface charge was determined using zeta potential measurements. Hydrophobicity of the isolates was determined using bacterial adhesion to hydrocarbons assay, hydrophobic interaction chromatography and contact angle measurements. Microbial adhesion to solvents was used to determine the electron donor/acceptor characteristics. No differences of surface charge measurements were found between broth and agar grown cultures. Isolates belonging to serogroup O157 and serotypes O26:H11 and O111:H- were significantly (P < 0.05) less negatively charged than other STEC serotypes tested. All strains were hydrophilic with most methods and demonstrated a lower hydrophobicity in agar culture compared with broth culture. All strains demonstrated a strong microbial adhesion to chloroform indicating that STEC possess an electron donor and basic character. A relationship between serogroup O157 and other STEC serotypes was apparent using principal-component analysis (PCA). Combining the results for physicochemical properties using PCA differentiated between strains belonging to the O157 serogroup and other STEC/non-STEC strains. PCA found similar results for broth and agar grown cultures. Particular serotypes of STEC possess similar physicochemical properties which may play a role in their pathogenicity or potential attachment to various surfaces.

Prevalence of Shiga-toxigenic Escherichia coli O157:H7 in adult dairy cattle.

To describe shiga-toxigenic Escherichia coil O157:H7 (STEC O157:H7) fecal shedding prevalence, seasonal fecal shedding patterns, and site-specific prevalence from the oral cavity, skin, and feces of dairy cattle. Cross-sectional study. Adult dairy cattle from 13 herds in Louisiana. Samples were cultured for STEC O157 by use of sensitive and specific techniques, including selective broth enrichment, immunomagnetic separation, monoclonal antibody-based O:H enzyme immunoassay serotyping, and polymerase chain reaction virulence gene characterization. Point estimates and 95% confidence intervals were calculated for fecal shedding prevalence as well as site-specific prevalence from the oral cavity, skin, and feces. Logistic regression was used to assess seasonal variation and differences at various stages of lactation with respect to fecal shedding of STEC O157 in cattle sampled longitudinally. Summer prevalence in herds in = 13) was 38.5%, with a cow-level prevalence of 6.5%. Among positive herds, prevalence ranged from 3% to 34.6%. Samples from 3 of 5 herds sampled quarterly over 1 year yielded positive results for STEC O157. In herds with STEC O157, an increase in cow-level prevalence was detected during spring (13.3%) and summer (10.5%), compared with values for fall and winter. Site-specific prevalences of STEC O157:H7 from oral cavity, skin, and fecal samples were 0%, 0.7%, and 25.2%, respectively. Our data indicated that STEC O157:H7 was commonly isolated from dairy cows in Louisiana, seasonally shed, and isolated from the skin surface but not the oral cavity of cows.