Studies of Escherichia coli Cultured on RainbowTM Agar O157 with Particular Reference to Enterohaemorrhagic Escherichia coli (EHEC)

Bettelheim, K. A.

doi:10.1111/j.1348-0421.1998.tb02282.x

Cited by 50 publications

(25 citation statements)

References 19 publications

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“…Shortcomings of media for the selective cultivation of E. coli O157:H7 in test samples with heavy background growth such as sewage and river water have been reported by other researchers (Bettelheim, 1998). False-positive laboratory reports can result in delayed consideration of alternative diagnoses or therapeutic interventions.…”

Section: Resultsmentioning

confidence: 99%

Biolog identification of non-sorbitol fermenting bacteria isolated on E. coli O157 selective CT-SMAC agar

Müller¹,

Ehlers²

2007

WSA

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E. coli O157:H7 is recognised as an important human pathogen world-wide and has been associated with diseases such as haemorrhagic colitis (HC), haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopaenic purpura (TTP). Accurate laboratory detection of E. coli O157:H7 is important for diagnostic purposes and to justify epidemiological data on E. coli O157:H7. A well-known phenotypic characteristic of E. coli O157:H7 bacteria is their inability to ferment sorbitol. This characteristic is often used to isolate these organisms from food and water using selective agar medium such as SMAC. However, the high number of false positive results obtained by a number of researchers when selectively screening for E. coli O157: H7 on CT-SMAC has prompted an investigation to determine which other sorbitol-negative bacteria also grow on CT-SMAC. The agar medium used for the investigation consisted of Sorbitol MacConkey agar (SMAC) supplemented with Cefiximetellurite (CT). All sorbitol-negative colonies obtained from CT-SMAC, after selective enrichment and IMS were identified using the Biolog microbial identification system. The majority of sorbitol-negative isolates identified were Burkholderia, Pseudomonas, Vibrio and Aeromonas spp. Only two E. coli O157:H7 isolates were identified with Biolog and confirmed with a polymerase chain reaction (PCR) specific for the shiga toxin 1 (Stx1) genes and with O157 and H7 antisera. The inability of the CT-SMAC agar medium to specifically select for E.coli O157:H7 was confirmed by the results of this study. These observations call for further improvement of affordable methods for the selective isolation of E. coli O157:H7 in the presence of large numbers of interfering bacteria capable of growing on CT-SMAC.

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Section: Resultsmentioning

confidence: 99%

Biolog identification of non-sorbitol fermenting bacteria isolated on E. coli O157 selective CT-SMAC agar

Müller¹,

Ehlers²

2007

WSA

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“…This was followed by a number of more specific media including the Rainbow Agar (Bettelheim 1998a), CHROMagar R (Bettelheim 1998b), and O157:H7 ID agar (O157 H7 ID-F) . When examining any of these media for the presence of O157 STEC, if other typical E. coli-like colonies are selected and subjected to further investigation, it is possible that some may well be non-O157 STEC.…”

Section: Isolation Identification and Characterization Of Non-o157 mentioning

confidence: 99%

“…Soon after the first description of the outbreaks due to the O157 STEC (Riley et al 1983), it was realized that these types were unusual in not being able to ferment the carbohydrate sorbitol and a medium, which had originally been developed to select for certain EPEC (Rappaport and Heng 68 K. A. BETTELHEIM Kudoh et al 1994 1952) was shown to be very effective in selecting O157 STEC from among the other commensal E. coli normally found on primary isolation of fecal specimens (March and Ratnam 1986). As ever-increasing numbers of cases and outbreaks due to O157 STEC were being reported in the world literature and even more effective media for their isolation were available (Bettelheim 1998a(Bettelheim , 1998b, it appeared that the O157 STEC were the only types of STEC of any significance. Although non-O157 STEC had been reported before 1982 (Konowalchuk et al 1977;Wade et al 1979;Wilson and Bettelheim 1980) and have regularly continued to be reported from human cases and outbreaks as well as from animals and environmental sources, very few laboratories look for them.…”

Section: Introductionmentioning

confidence: 99%

The Non-O157 Shiga-Toxigenic (Verocytotoxigenic)Escherichia coli; Under-Rated Pathogens

Bettelheim¹

2007

Critical Reviews in Microbiology

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258

192

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Following a brief review of the ecology of Escherichia coli in general, the role of Shiga-Toxigenic (Verocytotoxigenic) E. coli (STEC) as pathogens is addressed. While STEC belonging to the serogroup O157 have been extensively studied and shown to be involved in many cases and outbreaks of human disease, the importance of STEC belonging to other serogroups has not been recognized as much. This review addresses the problems associated with these pathogens, demonstrating that increasing the awareness of them is a major part of the problem. This review then demonstrates how widespread isolations especially from food animals and human disease have been, discussing in particular STEC belonging to serogroups O8, O26, O103, O111, O113 and O128. The animal host-specificity of these STEC is also reviewed. In conclusion some methods of improving isolation of these pathogens is addressed.

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“…It contains chromogenic substances specific for fJgalactosidase and GUD. Strains of 0157 STEC characteristically produce charcoal grey or steel black colonies, typical non-0157 STEC strains are blue or purple, and most non-STEC E. coli are violet or red (Bettelheim 1998b). The addition of tellurite and novobiocin improves the recovery of E. coli 0157 on Rainbow" Agar 0157 (Stein and Bochner 1998).…”

Section: Enrichment Mediamentioning

confidence: 99%

Methods for the detection and isolation of Shiga toxin-producingEscherichia coli

Boer

Heuvelink

2000

Journal of Applied Microbiology

119

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SUMMARY Shiga toxin‐producing Escherichia coli (STEC) are an important cause of haemorrhagic colitis and the diarrhoea‐associated form of the haemolytic uraemic syndrome. Of the numerous serotypes of E. coli that have been shown to produce Shiga toxin (Stx), E. coli O157:H7 and E. coli O157:NM (non‐motile) are most frequently implicated in human disease. Early recognition of STEC infections is critical for effective treatment of patients. Furthermore, rapid microbiological diagnosis of individual patients enables the prompt notification of outbreaks and implementation of control measures to prevent more cases. Most human infections caused by STEC have been acquired by the consumption of contaminated foods, especially those of bovine origin such as undercooked ground beef and unpasteurized cows' milk, and by person‐to‐person contacts. To identify the reservoirs of STEC and the routes of transmission to man, sensitive methods are needed as these pathogens may only be present in food, environmental and faecal samples in small numbers. In addition, sensitive and rapid detection methods are necessary for the food industry to ensure a safe supply of foods. Sensitive methods are also needed for surveillance programmes in risk assessment studies, and for studies on survival and growth of STEC strains. Cultural methods for the enrichment, isolation and confirmation of O157 STEC are still evolving. Several selective enrichment media have been described, of which modified tryptone soy broth with novobiocin and modified E. coli broth with novobiocin, seem to be the most appropriate. These media are minimally‐selective broths that give a somewhat limited differential specificity favouring isolation of O157 STEC, as opposed to other Gram‐negative bacteria, in the sample. An incubation temperature of 41–42°C further enhances selectivity. The occurrence of heat‐, freeze‐, acid‐ or salt‐stressed STEC in foods means that it is important to be able to detect cells that are in a stressed state, as STEC generally have a very low infectious dose, and injured cells mostly retain their pathogenic properties. For the isolation of stressed O157 STEC, pre‐enrichment in a non‐selective broth is necessary. The most widely used plating medium for the isolation of typical sorbitol‐non‐fermenting strains of STEC of serogroup O157 is sorbitol MacConkey agar with cefixime and tellurite (CT‐SMAC). As some STEC strains are sensitive for tellurite and/or are sorbitol‐fermenting, the use of a second isolation medium, such as one of the newer chromogenic media, is recommended. Immunomagnetic separation (IMS) following selective enrichment, and subsequent spread‐plating of the concentrated target cells onto CT‐SMAC agar, appears to be the most sensitive and cost‐effective method for the isolation of E. coli O157 from raw foods. IMS increases sensitivity by concentrating E. coli O157 relative to background microflora, which may overgrow or mimic O157 STEC cells on selective agars. While cultural isolation of O157 STEC from foods and faeces is time‐consu...

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Studies of Escherichia coli Cultured on Rainbow^TM Agar O157 with Particular Reference to Enterohaemorrhagic Escherichia coli (EHEC)

Cited by 50 publications

References 19 publications

Biolog identification of non-sorbitol fermenting bacteria isolated on <i>E. coli</i> O157 selective CT-SMAC agar

Biolog identification of non-sorbitol fermenting bacteria isolated on <i>E. coli</i> O157 selective CT-SMAC agar

The Non-O157 Shiga-Toxigenic (Verocytotoxigenic)Escherichia coli; Under-Rated Pathogens

Methods for the detection and isolation of Shiga toxin-producingEscherichia coli

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