Evaluation of eight agar media for the isolation of shiga toxin—Producing Escherichia coli

Gill, Alexander; Huszczynski, George; Gauthier, Martine; Blais, Burton W.

doi:10.1016/j.mimet.2013.10.022

Cited by 45 publications

(33 citation statements)

References 14 publications

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“…Based on the variability of these organisms, the use of multiple agar media for isolation (as in our study) is recommended (28,33). In the present study, EHEC O157 was the most common serogroup isolated by culture because either it is truly the most prevalent or it is more easily detected because of the greater specificity of the media.…”

Section: Discussionmentioning

confidence: 70%

“…In contrast, culture methods for non-O157 EHEC adulterants have lacked sensitivity and specificity because of the multiplicity of organisms needing to be targeted and the lack of clonality of these organisms, and other than having Shiga toxin and intimin, these organisms lack characteristics that distinguish them from other E. coli (28,38,63,70). FSIS methods for detection and isolation of EHEC from meat products, which involve PCR screening, immunomagnetic separation (IMS), cultural isolation on a chromogenic agar, and confirmatory PCR and agglutination, have been improved through a number of modifications but still are not optimal (67,70).…”

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confidence: 99%

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Prevalence and Level of Enterohemorrhagic Escherichia coli in Culled Dairy Cows at Harvest

Stromberg

Lewis

Aly

et al. 2016

Journal of Food Protection

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The primary objective of this study was to determine the prevalence and level of enterohemorrhagic Escherichia coli (EHEC) O26, O45, O103, O111, O121, and O145 (collectively EHEC-6) plus EHEC O157 in fecal, hide, and preintervention carcass surface samples from culled dairy cows. Matched samples (n =300) were collected from 100 cows at harvest and tested by a culture-based method and two molecular methods: NeoSEEK STEC (NS) and Atlas STEC EG2 Combo. Both the culture and NS methods can be used to discriminate among the seven EHEC types (EHEC-7), from which the cumulative prevalence was inferred, whereas the Atlas method can discriminate only between EHEC O157 and non-O157 EHEC, without discrimination of the serogroup. The EHEC-7 prevalence in feces, hides, and carcass surfaces was 6.5, 15.6, and 1.0%, respectively, with the culture method and 25.9, 64.9, and 7.0%, respectively, with the NS method. With the Atlas method, the prevalence of non-O157 EHEC was 29.1, 38.3, and 28.0% and that of EHEC O157 was 29.1, 57.0, and 3.0% for feces, hides, and carcasses, respectively. Only two samples (a hide sample and a fecal sample) originating from different cows contained quantifiable EHEC. In both samples, the isolates were identified as EHEC O157, with 4.7 CFU/1,000 cm2 in the hide sample and 3.9 log CFU/g in the fecal sample. Moderate agreement was found between culture and NS results for detection of EHEC O26 (κ =0.58, P < 0.001), EHEC O121 (κ = 0.50, P < 0.001), and EHEC O157 (κ = 0.40, P < 0.001). No significant agreement was observed between NS and Atlas results or between culture and Atlas results. Detection of an EHEC serogroup in fecal samples was significantly associated with detection of the same EHEC serogroup in hide samples for EHEC O26 (P =0.001), EHEC O111 (P =0.002), EHEC O121 (P < 0.001), and EHEC-6 (P = 0.029) based on NS detection and for EHEC O121 (P < 0.001) based on detection by culture. This study provides evidence that non-O157 EHEC are ubiquitous on hides of culled dairy cattle and that feces are an important source of non-O157 EHEC hide contamination.

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Section: Discussionmentioning

confidence: 70%

mentioning

confidence: 99%

Prevalence and Level of Enterohemorrhagic Escherichia coli in Culled Dairy Cows at Harvest

Stromberg

Lewis

Aly

et al. 2016

Journal of Food Protection

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“…A higher level of potassium tellurite may increase the detection rate of STEC through suppression of nontarget organisms. CHROMagar STEC has been evaluated on human stool samples (13) and in pure cultures and beef (12,40). In stool samples, 82% of samples that were Shiga toxin positive were recoverable on CHROMagar STEC (13).…”

Section: Discussionmentioning

confidence: 99%

“…Although non-O157 STEC detection in clinical patients has increased (14), detection of these organisms has remained challenging in food and environmental sources due to their diversity and resemblance to background flora (12). Agar media designed to detect non-O157 STEC have relied on fermentation of specific carbohydrates, b-galactosidase activity, and resistance to antimicrobials (16,27).…”

mentioning

confidence: 99%

Comparison of Agar Media for Detection and Quantification of Shiga Toxin–Producing Escherichia coli in Cattle Feces

Stromberg

Lewis

Moxley

2016

Journal of Food Protection

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The isolation and quantification of non-O157 Shiga toxin-producing Escherichia coli (STEC) from cattle feces are challenging. The primary objective of this study was to evaluate the performance of selected agar media in an attempt to identify an optimal medium for the detection and quantification of non-O157 STEC in cattle feces. Comparison studies were performed using CHROMagar STEC, Possé differential agar (Possé), Possé modified by the reduction or addition of antimicrobials, STEC heart infusion washed blood agar with mitomycin C (SHIBAM), and SHIBAM modified by the addition of antimicrobials. Fourteen STEC strains, two each belonging to serogroups O26, O45, O103, O111, O121, O145, and O157, were used to test detection in inoculated fecal suspensions at concentrations of 10(2) or 10(3) CFU/g. One STEC strain from each of these seven serogroups was used to estimate the concentration of recovered STEC in feces inoculated at 10(3), 10(4), or 10(5) CFU/g. Significantly more suspensions (P < 0.05) were positive for STEC when plated on Possé containing reduced concentrations of novobiocin and potassium tellurite compared with SHIBAM, but not SHIBAM modified by containing these same antimicrobials at the same concentrations. Numerically, more suspensions were positive for STEC by using this same form of modified Possé compared with Possé, but this difference was not statistically significant. More suspensions were positive for STEC cultured on CHROMagar STEC compared with those on Possé (P < 0.05) and on modified Possé (P = 0.05). Most inoculated fecal suspensions below 10(4) CFU/g of feces were underestimated or not quantifiable for the concentration of STEC by using CHROMagar STEC or modified Possé. These results suggest that CHROMagar STEC performs better than Possé or SHIBAM for detection of STEC in bovine feces, but adjustments in the concentrations of novobiocin and potassium tellurite in the latter two media result in significant improvements in their performance.

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“…Though there is no evidence that these selective agents inhibit strains of E. coli O157, their addition to Rainbow Agar O157 does inhibit the growth of some VTEC strains of the serogroups O26, O103, O111 and O145 (Gill et al ., 2014 ). Addition of these selective agents might aid isolation by reducing the amount of background fl ora in enrichment broths from beef trim, but not from ground beef samples (Gill et al ., 2014 ). Rainbow Agar O157 contains chromogenic substrates to detect sorbitol fermentation and β -d -glucuronidase activity.…”

Section: Current Us and Eu Methods Of Sample Testingmentioning

confidence: 99%

Developments in sampling and test methods for pathogens in fresh meat

Gill

2015

Advances in Microbial Food Safety

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Evaluation of eight agar media for the isolation of shiga toxin—Producing Escherichia coli

Cited by 45 publications

References 14 publications

Prevalence and Level of Enterohemorrhagic Escherichia coli in Culled Dairy Cows at Harvest

Prevalence and Level of Enterohemorrhagic Escherichia coli in Culled Dairy Cows at Harvest

Comparison of Agar Media for Detection and Quantification of Shiga Toxin–Producing Escherichia coli in Cattle Feces

Developments in sampling and test methods for pathogens in fresh meat

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