RESUMEN
BACKGROUND AND PURPOSE: The purpose of this study was to assess cerebral perfusion changes following systemic administration of the recreational drug 3,4-methylendioxymethamphetamine (MDMA 'ecstasy') to rats. EXPERIMENTAL APPROACH: Cerebral perfusion was quantified using bolus-tracking arterial spin labelling (btASL) MRI. Rats received MDMA (20 mg·kg(-1); i.p.) and were assessed 1, 3 or 24 h later. Rats received MDMA (5 or 20 mg·kg(-1); i.p.) and were assessed 3 h later. In addition, rats received MDMA (5 or 10 mg·kg(-1); i.p.) or saline four times daily over 2 consecutive days and were assessed 8 weeks later. Perfusion-weighted images were generated in a 7 tesla (7T) MRI scanner and experimental data was fitted to a quantitative model of cerebral perfusion to generate mean transit time (MTT), capillary transit time (CTT) and signal amplitude. KEY RESULTS: MDMA reduces MTT and CTT and increases amplitude in somatosensory and motor cortex 1 and 3 h following administration, indicative of an increase in perfusion. Prior exposure to MDMA provoked a long-term reduction in cortical 5-HT concentration, but did not produce a sustained effect on cerebral cortical perfusion. The response to acute MDMA challenge (20 mg·kg(-1); i.p.) was attenuated in these animals indicating adaptation in response to prior MDMA exposure. CONCLUSIONS AND IMPLICATIONS: MDMA provokes changes in cortical perfusion, which are quantifiable by btASL MRI, a neuroimaging tool with translational potential. Future studies are directed towards elucidation of the mechanisms involved and correlating changes in cerebrovascular function with potential behavioural deficits associated with drug use.
Asunto(s)
Corteza Cerebral/efectos de los fármacos , Circulación Cerebrovascular/efectos de los fármacos , Alucinógenos/farmacología , N-Metil-3,4-metilenodioxianfetamina/farmacología , Serotoninérgicos/farmacología , Animales , Volumen Sanguíneo/efectos de los fármacos , Temperatura Corporal/efectos de los fármacos , Corteza Cerebral/irrigación sanguínea , Corteza Cerebral/metabolismo , Corteza Cerebral/fisiopatología , Ácido Hidroxiindolacético/metabolismo , Imagen por Resonancia Magnética/métodos , Masculino , Ratas Wistar , Serotonina/metabolismo , Marcadores de SpinRESUMEN
Human campylobacteriosis exhibits a distinctive seasonality in temperate regions. This paper aims to identify the origins of this seasonality. Clinical isolates [typed by multi-locus sequence typing (MLST)] and epidemiological data were collected from Scotland. Young rural children were found to have an increased burden of disease in the late spring due to strains of non-chicken origin (e.g. ruminant and wild bird strains from environmental sources). In contrast the adult population had an extended summer peak associated with chicken strains. Travel abroad and UK mainland travel were associated with up to 17% and 18% of cases, respectively. International strains were associated with chicken, had a higher diversity than indigenous strains and a different spectrum of MLST types representative of these countries. Integrating empirical epidemiology and molecular subtyping can successfully elucidate the seasonal components of human campylobacteriosis. The findings will enable public health officials to focus strategies to reduce the disease burden.
Asunto(s)
Infecciones por Campylobacter/etiología , Adolescente , Adulto , Factores de Edad , Anciano , Animales , Animales Salvajes/microbiología , Aves/microbiología , Infecciones por Campylobacter/epidemiología , Pollos/microbiología , Niño , Preescolar , Humanos , Incidencia , Persona de Mediana Edad , Epidemiología Molecular/métodos , Tipificación de Secuencias Multilocus , Población Rural/estadística & datos numéricos , Escocia/epidemiología , Estaciones del Año , Viaje , Población Urbana/estadística & datos numéricos , Adulto JovenRESUMEN
E. coli O157 can be transmitted to humans by three primary (foodborne, environmental, waterborne) and one secondary (person-to-person transmission) pathways. A regression model and quantitative microbiological risk assessments (QMRAs) were applied to determine the relative importance of the primary transmission pathways in NE Scotland. Both approaches indicated that waterborne infection was the least important but it was unclear whether food or the environment was the main source of infection. The QMRAs over-predicted the number of cases by a factor of 30 and this could be because all E. coli O157 strains may not be equally infective and/or the level of infectivity in the dose-response model was too high. The efficacy of potential risk mitigation strategies to reduce human exposure to E. coli O157 using QMRAs was simulated. Risk mitigation strategies focusing on food and environment are likely to have the biggest impact on infection figures.
Asunto(s)
Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/microbiología , Escherichia coli O157/aislamiento & purificación , Microbiología de Alimentos , Microbiología del Agua , Animales , Bovinos , Heces/microbiología , Humanos , Carne/microbiología , Factores de Riesgo , Escocia/epidemiología , Ovinos , Factores de TiempoRESUMEN
Campylobacter prevalence from retail liver (chicken, cattle, pig and sheep) was found to be 81%, 69%, 79% and 78% respectively. Molecular source attribution demonstrated that strains from chicken liver were most similar to those found commonly in humans. This provides further evidence of liver being a probable source of human infection.
Asunto(s)
Campylobacter/aislamiento & purificación , Hígado/microbiología , Carne/microbiología , Animales , Bovinos , Pollos , Microbiología de Alimentos , Prevalencia , Ovinos , PorcinosRESUMEN
During a 15-month period in Scotland a small but important number of human Campylobacter cases (3·2%) arose from 91 putative household outbreaks. Of the 26 outbreaks with known strain composition, 89% were composed of the same MLST which supports the potential use of MLST in public health epidemiology. The number of cases associated with household outbreaks is much larger than general outbreaks and there is some evidence to indicate that there may be secondary transmission, although this is relatively rare.
Asunto(s)
Técnicas de Tipificación Bacteriana , Infecciones por Campylobacter/epidemiología , Campylobacter/clasificación , Campylobacter/aislamiento & purificación , Dermatoglifia del ADN , Brotes de Enfermedades , Salud de la Familia , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Campylobacter/genética , Niño , Preescolar , Análisis por Conglomerados , Composición Familiar , Femenino , Genotipo , Humanos , Lactante , Masculino , Persona de Mediana Edad , Escocia/epidemiología , Análisis de Secuencia de ADN , Adulto JovenRESUMEN
AIMS: To assess whether flies and slugs acquire strains of Campylobacter jejuni and Campylobacter coli present in local ruminant faeces. METHODS AND RESULTS: Campylobacter was cultured from flies, slugs and ruminant faeces that were collected from a single farm in Scotland over a 19-week period. The isolates were typed using multi-locus sequence typing (MLST) and compared with isolates from cattle and sheep faeces. Campylobacter jejuni and Camp. coli were isolated from 5·8% (n=155, average of 75 flies per pool) and 13·3% (n=15, average of 8·5 slugs per pool) of pooled fly and slug samples, respectively. The most common sequence type (ST) in flies was Camp. coli ST-962 (approx. 40%) regardless of the prevalence in local cattle (2·3%) or sheep (25·0%) faeces. Two positive slug pools generated the same ST that has not been reported elsewhere. CONCLUSIONS: Despite their low carriage rate, flies are able to acquire Campylobacter STs that are locally present, although the subset carried may be biased when compared to local source. Slugs were shown to carry a previously unreported Campylobacter ST. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has demonstrated that flies carry viable Campylobacter and may contribute to the transfer of STs within and between groups of animals on farms. Further, they may therefore present a risk to human health via their contact with ready-to-eat foods or surfaces.
Asunto(s)
Campylobacter coli/clasificación , Campylobacter jejuni/clasificación , Dípteros/microbiología , Heces/microbiología , Gastrópodos/microbiología , Animales , Campylobacter coli/genética , Campylobacter coli/aislamiento & purificación , Campylobacter jejuni/genética , Campylobacter jejuni/aislamiento & purificación , Bovinos , Tipificación de Secuencias Multilocus , Escocia , Ovinos/microbiologíaRESUMEN
An outbreak of campylobacteriosis affected approximately one-half of 165 people attending an annual farmers' dance in Montrose, Scotland, in November 2005. Epidemiological investigations, including a cohort study (n = 164), identified chicken liver paté as the most likely vehicle of infection. Paté preparation involved deliberate undercooking of chicken livers by flash-frying, followed by mechanical homogenization. Typing of 32 Campylobacter strains (isolated from submitted stools) by multilocus sequence typing identified four distinct clades of Campylobacter jejuni. There was good agreement when isolates were typed by Penner serotyping, pulsed-field gel electrophoresis, and flaA short variable region sequencing but poorer agreement with phage and antibiotic susceptibility testing. At least three attendees were coinfected with two Campylobacter strains each. The outbreak was probably due to several livers contributing Campylobacter strains that survived undercooking and were dispersed throughout the paté. The study highlights improper culinary procedures as a potential human health risk and provides a striking counterexample to the "dominant outbreak strain" view of point source outbreaks of food-borne infections. It also demonstrates that previous exposure to biologically plausible sources of Campylobacter may confer protection against subsequent infection.
Asunto(s)
Infecciones por Campylobacter/epidemiología , Infecciones por Campylobacter/inmunología , Campylobacter jejuni/inmunología , Campylobacter jejuni/aislamiento & purificación , Brotes de Enfermedades , Técnicas de Tipificación Bacteriana , Tipificación de Bacteriófagos , Infecciones por Campylobacter/microbiología , Campylobacter jejuni/clasificación , Análisis por Conglomerados , Dermatoglifia del ADN , ADN Bacteriano/genética , Electroforesis en Gel de Campo Pulsado , Heces/microbiología , Flagelina/genética , Genotipo , Humanos , Productos de la Carne/microbiología , Pruebas de Sensibilidad Microbiana , Escocia/epidemiología , Análisis de Secuencia de ADN , SerotipificaciónRESUMEN
AIMS: To perform a longitudinal study of the diversity of Escherichia coli O157 from a ruminant pasture/stream environment using multiple-locus variable-number tandem-repeat analysis (MLVA). METHODS AND RESULTS: Samples of faecal droppings from grazing ruminants and from an adjacent stream were tested longitudinally for E. coli O157 by enrichment and immunomagnetic separation (IMS). Using MLVA, 24 different profiles were identified from a total of 231 E. coli O157 isolates, of which 80 were included in a similarity analysis. Four main clusters with several subclusters were observed. Although there was close contact between sheep and cattle during the study period, E. coli O157 was surprisingly not detected from cattle faeces. CONCLUSIONS: The cluster analysis indicated both unrelated and closely related E. coli O157 strains. The choice of loci to target in MLVA is important for the subtyping result, as loci with high diversities are essential for discriminating between closely related isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: There is a lack of data available on the use of MLVA to describe E. coli O157 diversity and changes over time in the animal reservoirs and the environment. Such data are needed in order to further develop MLVA as a typing method.
Asunto(s)
Enfermedades de los Bovinos/microbiología , Infecciones por Escherichia coli/microbiología , Escherichia coli O157/clasificación , Heces/microbiología , Variación Genética , Secuencias Repetidas en Tándem/genética , Animales , Bovinos , Análisis por Conglomerados , ADN Bacteriano/aislamiento & purificación , Infecciones por Escherichia coli/veterinaria , Escherichia coli O157/genética , Escherichia coli O157/aislamiento & purificación , Estudios Longitudinales , Microbiología del AguaRESUMEN
Sexual dimorphism in infectious diseases whereby disease incidence is more prevalent in one gender has been reported repeatedly in the scientific literature. Both behavioural and physiological differences have been suggested as a cause of this gender bias but there is a paucity of data to support either of these viewpoints. Here it is hypothesized that for campylobacteriosis physiological factors play an important role in the higher incidence in males. We demonstrate in the human population (from several countries in three continents) that this bias exists in young children (<1 year) where behavioural differences between genders are likely to be minimal. Further we demonstrate this difference in an animal model where both infection rates and shedding rates of the organism are greater in male mice.
Asunto(s)
Infecciones por Campylobacter/epidemiología , Adolescente , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Animales , Niño , Preescolar , Recuento de Colonia Microbiana , Heces/microbiología , Femenino , Humanos , Incidencia , Lactante , Recién Nacido , Masculino , Ratones , Persona de Mediana Edad , Factores SexualesRESUMEN
The infectivity of pathogenic microorganisms is a key factor in the transmission of an infectious disease in a susceptible population. Microbial infectivity is generally estimated from dose-response studies in human volunteers. This can only be done with mildly pathogenic organisms. Here a hierarchical Beta-Poisson dose-response model is developed utilizing data from human outbreaks. On the lowest level each outbreak is modelled separately and these are then combined at a second level to produce a group dose-response relation. The distribution of foodborne pathogens often shows strong heterogeneity and this is incorporated by introducing an additional parameter to the dose-response model, accounting for the degree of overdispersion relative to Poisson distribution. It was found that heterogeneity considerably influences the shape of the dose-response relationship and increases uncertainty in predicted risk. This uncertainty is greater than previously reported surrogate and outbreak models using a single level of analysis. Monte Carlo parameter samples (alpha, beta of the Beta-Poisson model) can be readily incorporated in risk assessment models built using tools such as S-plus and @ Risk.
Asunto(s)
Brotes de Enfermedades , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/transmisión , Escherichia coli O157/aislamiento & purificación , Escherichia coli O157/fisiología , Interacciones Huésped-Patógeno , Modelos Estadísticos , Adulto , Niño , Infecciones por Escherichia coli/microbiología , Humanos , Japón/epidemiología , Método de Montecarlo , Medición de Riesgo , Reino Unido/epidemiología , Estados Unidos/epidemiologíaRESUMEN
AIMS: To determine if contamination levels of Escherichia coli O157 and generic E. coli in retail-minced meat products are greater in rural shops compared with urban shops in Grampian, NE Scotland. We also investigated whether meat from supermarkets and meat from local butcher shops had a similar bacteriological quality. METHODS AND RESULTS: Minced beef and minced lamb were tested from November 2004 to August 2006. Escheichia coli O157 was found at low levels in four samples out of 530 tested samples (0.75%). Generic E. coli were present in 11% of the samples tested, of which 67% came from supermarkets. We observed no significant difference in the prevalence of generic E. coli between rural and urban areas. CONCLUSIONS: Low levels of contamination with E. coli O157 and generic E. coli in retail meat suggest that meat is not a major route of infection in NE Scotland. SIGNIFICANCE AND IMPACT OF THE STUDY: The study does not suggest that the high incidence of E. coli O157 human infection in the rural areas of Grampian is because of meat consumption--this provides further evidence of contact with animals or water being the routes of infection. Hence, risk mitigation should be focussed more on environmental pathways of infection.
Asunto(s)
Microbiología Ambiental , Infecciones por Escherichia coli/transmisión , Escherichia coli O157/aislamiento & purificación , Contaminación de Alimentos , Carne/microbiología , Animales , Bovinos , Recuento de Colonia Microbiana , Seguridad de Productos para el Consumidor , Brotes de Enfermedades , Escherichia coli/aislamiento & purificación , Manipulación de Alimentos/métodos , Humanos , Prevalencia , Salud Rural , Escocia , OvinosRESUMEN
The presence of campylobacters in broiler chickens and throughout the broiler water delivery systems of 12 farms in northeastern Scotland was investigated by sensitive enrichment methods and large-volume filtration. Campylobacter presence was independent of the water source and whether the water was treated. The genotypes of Campylobacter jejuni isolates recovered from chickens and various locations within the water delivery systems were compared by multilocus sequence typing. Matching strains in shed header tanks and birds were found at 1 of the 12 farms investigated. However, the sequence of contamination or whether the source was within or outside the shed was not determined. Nevertheless, these data provide evidence that drinking water could be associated with broiler infection by campylobacters.
Asunto(s)
Infecciones por Campylobacter/microbiología , Campylobacter/genética , Pollos/microbiología , Animales , Técnicas de Tipificación Bacteriana , Campylobacter/clasificación , Campylobacter/aislamiento & purificación , Genotipo , Enfermedades de las Aves de Corral/microbiología , Microbiología del Agua , Abastecimiento de Agua/normasAsunto(s)
Enfermedades de los Bovinos/epidemiología , Reservorios de Enfermedades/veterinaria , Infecciones por Escherichia coli/veterinaria , Escherichia coli O157/aislamiento & purificación , Enfermedades de las Ovejas/epidemiología , Animales , Bovinos , Enfermedades de los Bovinos/prevención & control , Enfermedades de los Bovinos/transmisión , Infecciones por Escherichia coli/epidemiología , Heces/microbiología , Prevalencia , Escocia/epidemiología , Ovinos , Enfermedades de las Ovejas/prevención & control , Enfermedades de las Ovejas/transmisiónRESUMEN
AIMS: To study the presence, numbers and virulence profiles of Escherichia coli O157 in sheep faeces and validate the microbiological methods used to attain these data. METHODS AND RESULTS: Flock level prevalence was found to be 40% (six from 15) and 6.5% of faecal samples tested were found to be positive. Two farms gave samples defined as high shedding (>10(4) CFU g(-1)), one of which comprised 91% positive samples with 13/33 at the high shedding level. CONCLUSIONS: These data confirmed that sheep are an important reservoir of E. coli O157. SIGNIFICANCE AND IMPACT OF THE STUDY: Sheep play a significant role in the maintenance and dispersal of E. coli O157 in the farming environment and are an important source of human infection.
Asunto(s)
Microbiología Ambiental , Infecciones por Escherichia coli/veterinaria , Escherichia coli O157/aislamiento & purificación , Heces/microbiología , Enfermedades de las Ovejas/epidemiología , Animales , Recuento de Colonia Microbiana , Reservorios de Enfermedades , Monitoreo del Ambiente/métodos , Monitoreo Epidemiológico , Infecciones por Escherichia coli/microbiología , Infecciones por Escherichia coli/transmisión , Separación Inmunomagnética , Prevalencia , Escocia/epidemiología , Sensibilidad y Especificidad , Enfermedades de las Ovejas/microbiología , Enfermedades de las Ovejas/transmisión , Oveja Doméstica , Virulencia , ZoonosisRESUMEN
Fourier time-series models were constructed to study regional and national seasonality of human campylobacteriosis in Scotland between 1997 and 2001. Strong seasonality was demonstrated with an annual peak of reported cases in late June to early July. The prominence of this peak varied between regions, which was exemplified for the two major population centres: Lothian, with mixed urban/rural population, had a more prominent peak than Greater Glasgow, which has a predominantly urban population. No significant trend of annual cases of campylobacteriosis was found nationally and Fourier models successfully predicted the seasonal pattern of national and regional cases in 2002. During the period studied, the Fourier model identified >20 bursts of infection (potential outbreaks). Multi-regional bursts were also identified in the summers of 1998 and 2000 - the latter comprising the vast majority of the regions in Scotland, which could suggest a national outbreak.
Asunto(s)
Infecciones por Campylobacter/epidemiología , Brotes de Enfermedades , Análisis de Fourier , Infecciones por Campylobacter/etiología , Humanos , Incidencia , Factores de Riesgo , Escocia/epidemiología , Estaciones del AñoRESUMEN
AIMS: To compare immunomagnetic separation (IMS) protocols (enrichment media and temperature) for the isolation of Escherichia coli serotypes O26 and O111 from four different foods. METHODS AND RESULTS: Foods (minced beef, cheese, apple juice and pepperoni) spiked with low numbers (<100 g(-1)) of stressed nalidixic mutant E. coli serotypes O26 and O111 were enriched in media based on buffered peptone water (BPW), tryptone soya and EC broths incubated at temperatures of 37 and 42 degrees C to optimize the IMS technique. BPW enrichments gave increased recoveries of both serotypes compared with tryptone soya and EC broths. Elevated temperatures of incubation at 42 degrees C were superior to 37 degrees C. CONCLUSIONS: Positive detection of low numbers of stressed target pathogens in all replicate tests was only possible using BPW enrichments. The majority of tests from alternative enrichments resulted in zero or single colonies recovered post-IMS. SIGNIFICANCE AND IMPACT OF THE STUDY: The optimum IMS protocol would improve isolation rates of E. coli O26 and O111 from foods and lead to increased safety for the consumer. Sub-optimal IMS protocols could lead to foods being incorrectly labelled free from these pathogens.
Asunto(s)
Escherichia coli/aislamiento & purificación , Microbiología de Alimentos , Bebidas , Queso , Separación Inmunomagnética/métodos , Malus , Carne , Sensibilidad y EspecificidadRESUMEN
The concentration and prevalence of Escherichia coli O157 in cattle feces at the time of slaughter was studied over a 9-week period from May to July 2002. Fecal samples (n = 589) were collected from the rectums of slaughtered cattle, and the animal-level prevalence rate was estimated to be 7.5% (95% confidence interval [CI], 5.4 to 9.6%) while the group prevalence was 40.4% (95% CI, 27.7 to 53.2%). Of the 44 infected animals detected, 9% were high shedders that contained E. coli O157 at concentrations of >10(4) CFU g(-1). These 9% represented >96% of the total E. coli O157 produced by all animals tested. All isolates possessed the vt(2) gene, 39 had the eaeA gene, and a further five had the vt(1) gene also. The presence of high-shedding animals at the abattoir increases the potential risk of meat contamination during the slaughtering process and stresses the need for correctly implemented hazard analysis and critical control point procedures.
Asunto(s)
Bovinos/microbiología , Escherichia coli O157/aislamiento & purificación , Mataderos , Adhesinas Bacterianas/genética , Animales , Proteínas Portadoras/genética , Recuento de Colonia Microbiana , Reservorios de Enfermedades , Escherichia coli O157/genética , Escherichia coli O157/patogenicidad , Proteínas de Escherichia coli/genética , Heces/microbiología , Microbiología de Alimentos , Genes Bacterianos , Humanos , Carne/microbiología , Toxina Shiga I/genética , Toxina Shiga II/genética , Reino Unido , Virulencia/genéticaRESUMEN
AIMS: This study monitored survival and growth of Escherichia coli O157 in ovine and bovine abattoir waste. METHODS: Blood and gut contents were inoculated separately with cocktails of E. coli O157. Samples were stored aerophilically and microaerophilically at 5 degrees C, 15 degrees C and 30 degrees C to represent storage at different container depths and at extremes of UK ambient temperature. CONCLUSIONS: Results showed survival of E. coli O157 was irrespective of oxygen content with no significant differences observed between aerophilic and microaerophilic environments. Numbers of E. coli O157 in ovine and bovine gut contents showed no change when stored at 5 degrees C and increased 1-2 log(10) at 15 degrees C and 30 degrees C in 28 h. In ovine and bovine blood, irrespective of storage temperature, there was a 0.5-2 log(10) reduction or no change in numbers except in ovine blood stored at 30 degrees C where the fall in numbers was followed by a 3 log(10) increase. In aged (stored at 4 degrees C for 18 h before spiking) bovine blood there was no significant change in numbers at 5 degrees C while at 15 degrees C there was 2 log(10) rise after 48 h. At 30 degrees C there was an initial 1 log(10) decrease in numbers followed by a 1 log(10) rise over the following 40 h. SIGNIFICANCE AND IMPACT OF STUDY: Abattoir wastes may become contaminated from animals infected with Verocytotoxigenic E. coli O157 and in certain storage conditions these pathogens could significantly increase in numbers. There is need for care in abattoir waste disposal, not only for personnel subject to direct contact, but also in the prevention of cross contamination to adjacent land and water courses which could indirectly infect humans.
Asunto(s)
Mataderos , Escherichia coli O157/crecimiento & desarrollo , Residuos , Animales , Sangre/microbiología , Bovinos , Recuento de Colonia Microbiana , Escherichia coli O157/aislamiento & purificación , Intestinos/microbiología , Ovinos , Temperatura , Administración de Residuos/métodosRESUMEN
AIMS: To compare a range of enrichment broths and enrichment temperatures for the isolation of Escherichia coli O157 by immunomagnetic separation (IMS) from sandy, loam and clay soils. METHODS AND RESULTS: Soils were spiked with cocktails of four atoxigenic strains of E. coli O157 and four strains of commensal E. coli. The organisms were stressed by subjecting soils to cycles of freeze/thawing, followed by drying at 20 degrees C for up to 4 days. Nine enrichment broths were trialled based on buffered peptone water, tryptone soya broths and EC broths supplemented with a range of selective additions. Enrichments were incubated for 6 h and assessed by target recovery after IMS on cefixime tellurite sorbitol MacConkey agar (CTSMAC) incubated at 37 degrees C for 24 h. A comparison of enrichment temperatures (37 and 42 degrees C) was also performed. Buffered peptone water (with or without vancomycin) and tryptone soya broth (with or without novobiocin) gave significant increases in recovery of E. coli O157 compared to others tested. In addition, broths incubated at 42 degrees C were superior to those at 37 degrees C for the recovery of E. coli O157. SIGNIFICANCE AND IMPACT OF THE STUDY: This study showed that sub-lethally damaged E. coli O157 surviving in soil can be sensitive to antimicrobial additions. The choice and concentration of these additions is vitally important to optimize target recovery. Some IMS protocols, established for the isolation of E. coli O157, may be unsuitable for the examination of soil samples.
Asunto(s)
Escherichia coli O157/crecimiento & desarrollo , Escherichia coli O157/aislamiento & purificación , Separación Inmunomagnética/métodos , Microbiología del Suelo , Técnicas Bacteriológicas , Recuento de Colonia Microbiana/métodos , Medios de Cultivo/química , Sensibilidad y EspecificidadRESUMEN
AIMS: To monitor the decay of E. coli O157 in soil (loamy sand) on a scout campsite following an outbreak in humans. METHODS AND RESULTS: Samples of soil and sheep faeces were collected from the campsite and tested for the presence of E. coli O157 by immunomagnetic separation (IMS) after enrichment in buffered peptone water + vancomycin at 42 degrees C for 6 h. Enumeration of target was carried out by direct plating onto sorbitol MacConkey agar plates supplemented with cefixime and tellurite (CTSMAC) incubated at 37 degrees C for 24 h. Low numbers (< 100 g(-1)) were estimated by the most probable number (3-tube MPN) technique. CONCLUSIONS: Survival was observed for 15 weeks. SIGNIFICANCE AND IMPACT OF THE STUDY: A number of laboratory studies have followed the decay of E. coli O157 in soil, animal faeces and water. This study follows (for the first time) the decay of the organism in soil after an outbreak associated with sheep. It demonstrates the long-term persistence of the organism in the environment and the results will be potentially important in performing risk assessments for both human and animal infection.