Practical Considerations and Difficulties Associated with the Detection of Verocytotoxin‐Producing<i>Escherichia coli</i>(VTEC) in Foods

Baylis, C.L.; Heuvelink, Annet; Boer, E de; Hofstra, H.

doi:10.1002/9780470385098.ch4

Cited by 8 publications

(10 citation statements)

References 137 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In foods, VTEC may not be homogeneously distributed and they may be present in low numbers and in the presence of high numbers of closely related competitor organisms including strains of nonpathogenic E. coli. Therefore, the microbiologist is faced with many practical difficulties during detection, isolation and confirmation of VTEC from foods (Baylis et al 2001). Enrichment in a suitable selective medium that facilitates rapid multiplication and enables subsequent detection and isolation is essential.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the microbiologist is faced with many practical difficulties during detection, isolation and confirmation of VTEC from foods (Baylis et al 2001). Enrichment in a suitable selective medium that facilitates rapid multiplication and enables subsequent detection and isolation is essential.…”

Section: Introductionmentioning

confidence: 99%

“…Two popular enrichment broths for E. coli O157 detection are modified tryptone soya broth (mTSB) (Doyle and Schoeni 1987) and E. coli broth (mEC) (Okrend et al 1990). To improve selectivity, when testing samples containing high levels of competitive microflora, these media are commonly supplemented with 20 mg l )1 novobiocin and incubated at an elevated temperature, typically 42°C (Baylis et al 2001). The current European standard method for detection of E. coli O157 (EN ISO 16654) includes enrichment in mTSB supplemented with 20 mg l )1 novobiocin and incubation at 41AE5 ± 1°C (Anon, 2001).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Growth of pure cultures of Verocytotoxin-producingEscherichia coliin a range of enrichment media

Baylis

2008

Journal of Applied Microbiology

View full text Add to dashboard Cite

Aims: This study compared the growth of different strains of Verocytotoxin‐producing Escherichia coli (VTEC) in a range of selective enrichment media. Methods and Results: Turbidometric and impedance methods were used to determine the growth of VTEC in pure culture in different enrichment media. Ten strains failed to grow in buffered peptone water + vancomycin, cefsulodin, cefixime at 42°C and some failed to grow, or grew poorly in E. coli (EC) medium supplemented with 20 mg l−1 novobiocin and modified EC supplemented with 20 mg l−1 novobiocin at 37°C and 42°C. Individual VTEC strains were sensitive to the selective agents in some media. Statistical analysis of the conductance detection times of 10 strains showed no overall effect of temperature alone (P = 0·66) but there were significant (P < 0·001) effects as a result of the combination of medium and temperature and these two factors were influenced by strain. Conclusions: Growth of VTEC during enrichment is dependent on different factors alone or in combination. These include medium type, presence of certain selective agents or antibiotics, incubation temperature and the initial population of VTEC. Sensitivity to these conditions can be strain related. Significance and Impact of the Study: This study highlighted differences in the ability of some enrichment media to support the growth of VTEC, making them unsuitable for the isolation of VTEC, especially low numbers of non‐O157 strains.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Growth of pure cultures of Verocytotoxin-producingEscherichia coliin a range of enrichment media

Baylis

2008

Journal of Applied Microbiology

View full text Add to dashboard Cite

show abstract

“…2000). The most widely employed agar is sorbitol MacConkey agar (SMAC) with or without the addition of cefixime and tellurite (Baylsis et al. 2001; Chapman 2001).…”

Section: Introductionmentioning

confidence: 99%

“…Similarly, a range of media has been used in the isolation of E. coli O157:H7 from bovine faeces and/or hide include BPW (Tutenel et al 2003) TSB (Barkocy-Gallagher et al 2002) and sterile brilliant green bile 2% (Elder et al 2000). The most widely employed agar is sorbitol MacConkey agar (SMAC) with or without the addition of cefixime and tellurite (Baylsis et al 2001;Chapman 2001). While cultural techniques for E. coli O157:H7 have been subject to considerable investigation over the last number of years, few papers present information on detection limits or the scale of statistical error associated with these techniques.…”

Section: Introductionmentioning

confidence: 99%

Detection and recovery rates achieved using direct plate and enrichment/immunomagnetic separation methods for Escherichia coli O157:H7 in minced beef and on bovine hide

O’Brien

Daly

Sheridan

et al. 2005

Lett Appl Microbiol

View full text Add to dashboard Cite

Aims: To assess the detection and recovery rates achieved with commonly used cultural methods for the enumeration and recovery of Escherichia coli O157:H7 from minced beef and bovine hide. Methods and Results: Minced beef and bovine hide were inoculated with varying concentrations (log 10 1AE58-2AE58 CFU g)1 and log 10 2AE42-4AE49 CFU 100 cm 2 respectively) of E. coli O157:H7 and recovered using a direct plate method or an enrichment/immunomagnetic separation (IMS) method and then plated onto SMAC or SMAC-CT in both cases. The direct plate method detected the pathogen consistently from minced beef samples with an average recovery of 69AE2-91AE2%. From faecal material on the bovine hide the recovery of the pathogen ranged from 1AE80 to 64AE5% with fresh faeces depending on the inocula while from dried faeces on hide the results ranged from no recovery at all to 25AE1%. Enrichment/IMS recovered E. coli O157:H7 at all inocula levels tested in minced beef while the pathogen was only detected consistently at an average inocula level of log 10 2AE73 CFU 100 cm 2 from fresh faeces and log 10 4AE49 CFU 100 cm 2 from dried faeces on bovine hide. Conclusions: The direct count enumeration method for E. coli O157:H7 underestimated the numbers of pathogens present. The enrichment/IMS procedure consistently detected the pathogen from minced beef but did not always detect E. coli O157:H7 from faeces on bovine hide. Significance and Impact of the Study: Overall this study highlights that any microbial data, used in either predictive microbiology or risk assessment, must take account of the sensitivity and associated performance of the methods employed, in order to make an accurate reflection of the true microbiology of the examined sample.

show abstract

Optimization of enrichment and plating procedures for the recovery of Escherichia coli O111 and O26 from minced beef

et al. 2003

View full text Add to dashboard Cite

Aim: Optimization of enrichment media and selective agars for the detection of Escherichia coli O26 and O111 from minced beef. Methods and Results:This study compared a number of different enrichment conditions and plating media for the recovery of E. coli O26 and E. coli O111 from minced beef. The optimum enrichment conditions for E. coli O26 was observed in beef samples enriched at 41AE5°C in tryptone soya broth supplemented with cefixime (50 lg l )1 ), vancomycin (40 mg l )1 ) and potassium tellurite (2AE5 mg l )1 ). Similar enrichment conditions were optimal for E. coli O111 with the omission of potassium tellurite. The optimum agar for recovery of E. coli O26 and giving the most effective suppression of contaminants was MacConkey agar [lactose replaced by rhamnose (20 g l )1 )] and supplemented with cefixime (50 lg ml )1 ) and potassium tellurite (2AE5 mg l )1 ). Optimum recovery of E. coli O111 was on chromocult agar, supplemented with cefixime (50 lg ml )1 ), cefsulodin (5 mg l )1 ) and vancomycin (8 mg l )1 ). Minced beef samples were inoculated with a number of strains of E. coli O26 (n ¼ 9) and O111 (n ¼ 8), and the developed enrichment and plating methods, used in combination with immunomagnetic separation, were shown to be an effective method for the recovery of all strains. Conclusions: Routine cultural methods for the recovery of E. coli O26 and O111 from minced beef are described. Significance and Impact of the Study: The optimized enrichment and plating procedure described for the recovery of E. coli O111 and O26 from meat can be used to extend research on these emerging pathogens in beef.

show abstract

Practical Considerations and Difficulties Associated with the Detection of Verocytotoxin‐ProducingEscherichia coli(VTEC) in Foods

Cited by 8 publications

References 137 publications

Growth of pure cultures of Verocytotoxin-producingEscherichia coliin a range of enrichment media

Growth of pure cultures of Verocytotoxin-producingEscherichia coliin a range of enrichment media

Detection and recovery rates achieved using direct plate and enrichment/immunomagnetic separation methods for Escherichia coli O157:H7 in minced beef and on bovine hide

Optimization of enrichment and plating procedures for the recovery of Escherichia coli O111 and O26 from minced beef

Contact Info

Product

Resources

About