Growth of Shiga-Toxin producing Escherichia coli (STEC) and bovine feces background microflora in various enrichment protocols

Vimont, A.; Vernozy-Rozand, C.; Montet, M.P.; Bavai, C.; Frémaux, B.; Delignette-Muller, Marie Laure

doi:10.1016/j.vetmic.2007.02.003

Cited by 20 publications

(17 citation statements)

References 18 publications

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“…E2 was degraded to below the detection limit within approximately 9 h in systems directly inoculated with swine manure (system 1), but only 20% of the E2 was degraded within the same incubation period in systems inoculated with TSB pre‐enriched microbial cultures (system 2) despite the higher cell density. The most likely reason for the slower and different (zero‐ vs. pseudo first‐order kinetics) degradation pattern in system 2 is that the TSB pre‐enrichment disfavored the bacteria that were responsible for the rapid degradation in system 1 (Vimont et al, 2007). The relative degradation rates of E2, testosterone, and progesterone observed in system 1 (E2 > progesterone > testosterone) are in contrast to results obtained from studies conducted with soils, biosolids, and swine manure‐applied soils, broiler litter, and composted chicken ( Gallus gallus ) manure (Casey et al, 2004; Ermawati et al, 2007; Hakk et al, 2005; Hemmings and Hartel, 2006; Jacobsen et al, 2005; Lee et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

Degradation Kinetics of Testosterone by Manure‐Borne Bacteria: Influence of Temperature, pH, Glucose Amendments, and Dissolved Oxygen

et al. 2010

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Land application of manure may contribute endocrine disrupting compounds (EDCs) such as steroid hormones to the environment. Little attention has been paid to the potential for degradation of steroid hormones by manure-borne bacteria and their degradation kinetics and pathways. In a laboratory study, the potential for biodegradation of testosterone, 17beta-estradiol (E2) and progesterone by swine (Sus scrofa) manure-borne bacteria was examined. In addition, the impact of temperature, pH (6, 7, and 7.5), glucose amendments (0, 3, and 22 mmol L(-1)), and presence of oxygen on testosterone degradation kinetics was determined. Testosterone, 17beta-estradiol and progesterone were biodegraded within 25 h of reaction initiation under aerobic conditions. The degradation of testosterone followed pseudo first-order and zero-order reaction kinetics under aerobic and anaerobic conditions, respectively, in tryptic soy broth (TSB) pre-enriched systems. The half-life (t1/2) for the degradation of testosterone under anaerobic conditions was six times longer than aerobic conditions. Testosterone degradation was found to significantly increase (- 17%) when incubated at 37 degrees C vs. 22 degrees C. The impact of pH (t1/2 ranged from 4.4-4.9 h) and glucose amendments (t1/2 ranged from 4.6-5.1 h) on the testosterone degradation rate were found to be small. Testosterone was transformed to dehydrotestosterone (DHT) (major degradation product), androstenedione (AD), and androstadienedione (ADD) under aerobic conditions as revealed by liquid chromatography-time-of-flight mass spectrometry (LC/TOF-MS). These results indicate that testosterone is rapidly degraded by manure-borne bacteria under a wide range of environmentally relevant conditions. However, the formed degradation products are still of potential concern due to their endocrine disrupting potential.

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Section: Discussionmentioning

confidence: 99%

Degradation Kinetics of Testosterone by Manure‐Borne Bacteria: Influence of Temperature, pH, Glucose Amendments, and Dissolved Oxygen

et al. 2010

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“…IMS appears to be less sensitive for detection than RT-PCR (4,72). Even though detection and strain isolation are not comparable, it must be emphasized that STEC isolation methods are substantially less sensitive than molecular methods for detecting these pathogens (52).…”

Section: Discussionmentioning

confidence: 97%

Novel Real-Time PCR Method To Detect Escherichia coli O157:H7 in Raw Milk Cheese and Raw Ground Meat

Miszczycha

Ganet

Dunière

et al. 2012

Journal of Food Protection

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Raw milk, raw milk cheeses, and raw ground meat have been implicated in Escherichia coli O157:H7 outbreaks. Developing methods to detect these bacteria in raw milk and meat products is a major challenge for food safety. The aim of our study was to develop a real-time PCR assay to detect E. coli O157:H7 in raw milk cheeses and raw ground meat. Well-known primers targeting a mutation at position +93 of the uidA gene in E. coli O157:H7 were chosen, and a specific TaqMan-minor groove binder probe was designed. This probe targets another mutation, at position +191 of the uidA gene in E. coli O157:H7. The first step in the study was to evaluate the specificity of this probe with 156 different O157:H7/NM strains and 48 non-O157:H7/NM strains of E. coli. The sensitivity of the method was evaluated by pre- and postinoculation of cheeses and meat enrichments with different E. coli O157:H7 strains. All the E. coli O157:H7 isolates tested were positive, and none of the other bacteria were detected. Our results indicate that this method is sensitive enough to detect 10(2) E. coli O157:H7 isolates per ml of cheese or meat enrichment broth (24 h at 41.5° C) and is more sensitive than the International Organization for Standardization reference method. We can conclude that this new real-time PCR protocol is a useful tool for rapid, specific, and sensitive detection of E. coli O157:H7 in raw milk and raw ground meat products.

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“…The protocol developed to detect E. coli O26 in raw milk cheeses is very efficient and easy to use in routine diagnostic procedures with the added benefit that it could be available to the cheese industry as a bivalent detection approach permitting E. coli O26 and O157 detection from the same enrichment. Indeed, numerous studies have shown that E. coli O157:H7 strains could grow on cefixim–tellurite‐supplemented media (Vimont et al. 2007).…”

Section: Discussionmentioning

confidence: 99%

“…In raw milk cheeses, the presence of high levels of background flora can influence the growth of STEC (Vimont et al. 2007) and make difficult its subsequent detection.…”

Section: Introductionmentioning

confidence: 99%

Optimized enrichment for the detection of Escherichia coli O26 in French raw milk cheeses

Savoye

Rozand

Bouvier

et al. 2011

Letters in Applied Microbiology

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Aims: Our main objective was to optimize the enrichment of Escherichia coli O26 in raw milk cheeses for their subsequent detection with a new automated immunological method. Methods and Results: Ten enrichment broths were tested for the detection of E. coli O26. Two categories of experimentally inoculated raw milk cheeses, semi‐hard uncooked cheese and ‘Camembert’ type cheese, were initially used to investigate the relative efficacy of the different enrichments. The enrichments that were considered optimal for the growth of E. coli O26 in these cheeses were then challenged with other types of raw milk cheeses. Buffered peptone water supplemented with cefixim–tellurite and acriflavin was shown to optimize the growth of E. coli O26 artificially inoculated in the cheeses tested. Despite the low inoculum level (1–10 CFU per 25 g) in the cheeses, E. coli O26 counts reached at least 5·104 CFU ml−1 after 24‐h incubation at 41·5°C in this medium. Conclusions: All the experimentally inoculated cheeses were found positive by the immunological method in the enrichment broth selected. Significance and Impact of the Study: Optimized E. coli O26 enrichment and rapid detection constitute the first steps of a complete procedure that could be used in routine to detect E. coli O26 in raw milk cheeses.

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Growth of Shiga-Toxin producing Escherichia coli (STEC) and bovine feces background microflora in various enrichment protocols

Cited by 20 publications

References 18 publications

Degradation Kinetics of Testosterone by Manure‐Borne Bacteria: Influence of Temperature, pH, Glucose Amendments, and Dissolved Oxygen

Degradation Kinetics of Testosterone by Manure‐Borne Bacteria: Influence of Temperature, pH, Glucose Amendments, and Dissolved Oxygen

Novel Real-Time PCR Method To Detect Escherichia coli O157:H7 in Raw Milk Cheese and Raw Ground Meat

Optimized enrichment for the detection of Escherichia coli O26 in French raw milk cheeses

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