How important is patient-to-patient transmission in extended-spectrum beta-lactamase Escherichia coli acquisition

BACKGROUND

Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli is an emerging pathogen. The causal role of antibiotic selective pressure versus patient-to-patient transmission has not been assessed. The objective of this study was to quantify the amount of patient-to-patient transmission among patients who acquire an ESBL-producing E coli infection using perianal surveillance cultures in an intensive care unit (ICU) population.

METHODS

A prospective cohort of patients admitted between September 1, 2001, and September 1, 2004, to the medical and surgical ICUs at a tertiary care hospital was studied. Patients had perianal cultures on admission, weekly, and upon discharge. Strain typing by pulsed-field gel electrophoresis (PFGE) and epidemiologic criteria were used to quantify the amount of patient-to-patient transmission.

RESULTS

There were 1806 patients admitted to the ICUs. There were 74 patients who had ESBL-producing E coli on admission to the ICU and 23 patients who acquired ESBL-producing E coli. Among these 23 patients, there were 14 PFGE types, and 3 (13%) patient acquisitions were defined as patient-to-patient transmission by similar PFGE type and overlapping time in the hospital.

CONCLUSION

Our data suggest that patient-to-patient transmission is not an important cause of the acquisition of ESBL-producing E coli colonization in the ICU setting.

Environmental change and infectious disease: how new roads affect the transmission of diarrheal pathogens in rural Ecuador

Environmental change plays a large role in the emergence of infectious disease. The construction of a new road in a previously roadless area of northern coastal Ecuador provides a valuable natural experiment to examine how changes in the social and natural environment, mediated by road construction, affect the epidemiology of diarrheal diseases. Twenty-one villages were randomly selected to capture the full distribution of village population size and distance from a main road (remoteness), and these were compared with the major population center of the region, Borbón, that lies on the road. Estimates of enteric pathogen infection rates were obtained from case-control studies at the village level. Higher rates of infection were found in nonremote vs. remote villages [pathogenic Escherichia coli: odds ratio (OR) = 8.4, confidence interval (CI) 1.6, 43.5; rotavirus: OR = 4.0, CI 1.3, 12.1; and Giardia: OR = 1.9, CI 1.3, 2.7]. Higher rates of all-cause diarrhea were found in Borbón compared with the 21 villages (RR = 2.0, CI 1.5, 2.8), as well as when comparing nonremote and remote villages (OR = 2.7, CI 1.5, 4.8). Social network data collected in parallel offered a causal link between remoteness and disease. The significant and consistent trends across viral, bacterial, and protozoan pathogens suggest the importance of considering a broad range of pathogens with differing epidemiological patterns when assessing the environmental impact of new roads. This study provides insight into the initial health impacts that roads have on communities and into the social and environmental processes that create these impacts.

Host specificity of septicemic Escherichia coli: human and avian pathogens

Extraintestinal pathogenic Escherichia coli (ExPEC) strains are the cause of a diverse spectrum of invasive human and animal infections, often leading to septicemia. ExPEC strains contain virulence factors that enable them to survive in the host blood and tissues. Most of these virulence factors are distributed in ExPEC strains in a host-independent fashion. Genomic analyses of these strains provide evidence for numerous recombinational events and horizontal gene transfer, as well as for a high diversity of virulence factors. In studies of human and avian septicemic strains of serotypes O2 and O78 it appears that there is a positive correlation between virulence, invasiveness and clonal origin. Yet, it is clear that clonal division in these strains, as well as distribution of virulence factors, is independent of the host and closely related clones reside in different hosts. Although the possibility exists that ExPEC strains do have a certain degree of host specificity, which is not obvious from genomic studies, it is clear that the similarity of virulence factors presents a significant zoonotic risk.

Rates of mutation and host transmission for an Escherichia coli clone over 3 years

Although over 50 complete Escherichia coli/Shigella genome sequences are available, it is only for closely related strains, for example the O55:H7 and O157:H7 clones of E. coli, that we can assign differences to individual evolutionary events along specific lineages. Here we sequence the genomes of 14 isolates of a uropathogenic E. coli clone that persisted for 3 years within a household, including a dog, causing a urinary tract infection (UTI) in the dog after 2 years. The 20 mutations observed fit a single tree that allows us to estimate the mutation rate to be about 1.1 per genome per year, with minimal evidence for adaptive change, including in relation to the UTI episode. The host data also imply at least 6 host transfer events over the 3 years, with 2 lineages present over much of that period. To our knowledge, these are the first direct measurements for a clone in a well-defined host community that includes rates of mutation and host transmission. There is a concentration of non-synonymous mutations associated with 2 transfers to the dog, suggesting some selection pressure from the change of host. However, there are no changes to which we can attribute the UTI event in the dog, which suggests that this occurrence after 2 years of the clone being in the household may have been due to chance, or some unknown change in the host or environment. The ability of a UTI strain to persist for 2 years and also to transfer readily within a household has implications for epidemiology, diagnosis, and clinical intervention.

Emerging enterohaemorrhagic Escherichia coli, causes and effects of the rise of a human pathogen

Shiga toxin (Stx) [Verotoxin (VT)]-producing Escherichia coli (STEC), also called enterohaemorrhagic E. coli or VTEC are emerging zoonotic agents and became most important as human pathogens, particularly in the industrialized countries. Production of cytotoxins, also called Stx or VT, is the major pathogenicity determinant of STEC, which can cause life-threatening haemorrhagic diseases in humans. The spectrum of STEC phenotypes is diverse and domestic and wildlife animals constitute important reservoirs for these bacteria. STEC are spread from animal faeces to the environment, water and food. Ingestion of contaminated foodstuff and water, as well as contact with the environment, STEC-excreting animals or humans are the major sources of human infection. Economical changes in animal and food production, alteration of consumer habits and lack of specific immune response, particularly in urbanized populations, have contributed to the recent spread of STEC as a zoonotic agent. Supranational surveillance networks as well as national reference laboratories as sentinels play an important role in the prevention and control of STEC infections in humans. Development of new vaccines and probiotics may serve as future tools to control the spread of STEC in animals and humans.

Detection, isolation, and molecular subtyping of Escherichia coli O157:H7 and Campylobacter jejuni associated with a large waterborne outbreak

The largest reported outbreak of waterborne Escherichia coli O157:H7 in the United States occurred in upstate New York following a county fair in August 1999. Culture methods were used to isolate E. coli O157:H7 from specimens from 128 of 775 patients with suspected infections. Campylobacter jejuni was also isolated from stools of 44 persons who developed diarrheal illness after attending this fair. There was one case of a confirmed coinfection with E. coli O157:H7 and C. jejuni. Molecular detection of stx(1) and stx(2) Shiga toxin genes, immunomagnetic separation (IMS), and selective culture enrichment were utilized to detect and isolate E. coli O157:H7 from an unchlorinated well and its distribution points, a dry well, and a nearby septic tank. PCR for stx(1) and stx(2) was shown to provide a useful screen for toxin-producing E. coli O157:H7, and IMS subculture improved recovery. Pulsed-field gel electrophoresis (PFGE) was used to compare patient and environmental E. coli O157:H7 isolates. Among patient isolates, 117 of 128 (91.5%) were type 1 or 1a (three or fewer bands different). Among the water distribution system isolates, 13 of 19 (68%) were type 1 or 1a. Additionally, PFGE of C. jejuni isolates revealed that 29 of 35 (83%) had indistinguishable PFGE patterns. The PFGE results implicated the water distribution system as the main source of the E. coli O157:H7 outbreak. This investigation demonstrates the potential for outbreaks involving more than one pathogen and the importance of analyzing isolates from multiple patients and environmental samples to develop a better understanding of bacterial transmission during an outbreak.

Uropathogenic Escherichia coli are more likely than commensal E. coli to be shared between heterosexual sex partners

Because uropathogenic Escherichia coli are better adapted than other E. coli to the urethra, periurethra, and vagina, the authors reasoned that uropathogenic E. coli would be more likely than commensal E. coli to be shared between sex partners. In this 1996-1999 Michigan study, the genetic identity of E. coli isolated from 166 women with E. coli urinary tract infection (UTI) and 94 women without UTI and their sex partners was determined by pulsed-field gel electrophoresis. Rectal isolates were considered uropathogenic E. coli if genetically identical to the urinary isolate causing UTI. All eight urinary isolates from men with UTI partners were identical to the E. coli found in the urine or vagina of their sex partner. When the 550 unique rectal E. coli isolates from couples were considered the unit of analysis, E. coli that caused UTI were nine times (odds ratio (OR) = 8.87, 95% confidence interval (CI): 5.41, 14.54) more likely than other E. coli to be shared between sex partners. Sharing occurred twice as frequently (OR = 1.87, 95% CI: 1.13, 3.08) if the E. coli had P pili or if the couples engaged in oral sex (OR = 2.09, 95% CI: 1.09, 4.00). Uropathogenic E. coli are more likely than commensal E. coli to be shared with a current heterosexual sex partner. Both sexual behaviors and a bacterial virulence factor, P pili, modified sharing.

Human Escherichia coli O157:H7 infection associated with the consumption of unpasteurized goat's milk

A cluster of four cases of haemolytic uraemic syndrome in children occurred in Northern Bohemia, Czech Republic, between 15 June and 7 July, 1995. All the cases had significantly elevated titres of anti-O157 lipopolysaccharide (LPS) antibodies as detected by the indirect haemagglutination assay. All but one of them had drunk unpasteurized goat's milk from the same farm within the week before the disease. Evidence of E. coli O157 infection was subsequently found in 5 of 15 regular drinkers of the farm's raw goat's milk; four of them were asymptomatic, 1 had mild diarrhoea at the end of June. Verocytotoxin 2-producing E. coli O157:H7 strains of phage type 2 and of identical pulsed-field gel electrophoresis patterns were isolated from 1 of 2 farm goats and from 1 of the asymptomatic goat's milk drinkers. The frequency of anti-O157 LPS antibodies found among regular drinkers of the farm's raw goat's milk (33%; 5 of 15) was significantly higher than that found in control population (0%; none of 45) (P = 0.0005; Fisher's exact test). Our findings indicate that goats may be a reservoir of E. coli O157:H7 and a source of the infection for humans; raw goat's milk may serve as a vehicle of the pathogen transmission.

Sharing of virulent Escherichia coli clones among household members of a woman with acute cystitis

BACKGROUND

Within-household transmission of extraintestinal pathogenic Escherichia coli (ExPEC) may contribute to the pathogenesis of urinary tract infection (UTI), but this is poorly understood.

METHODS

A woman with acute UTI, 4 human household members who cohabited with her, and the family's pet dog underwent prospective longitudinal surveillance for colonizing E. coli for 7-9 weeks after the woman's UTI episode. Unique clones were resolved by random amplified polymorphic DNA and pulsed-field gel electrophoresis analysis. Virulence genes, phylogenetic group, and O types were defined by PCR. Comparisons with reference strains were made using random amplified polymorphic DNA profiling.

RESULTS

Serial fecal and urine samples from the 6 household members yielded 7 unique E. coli clones (4 of which were ExPEC and 3 of which were non-ExPEC). For 3 clones, extensive among-host sharing was evident in patterns suggesting host-to-host transmission. The mother's UTI clone, which represented E. coli O1:K1:H7, was the clone that was most extensively shared (in 5 hosts, including the dog) and most frequently recovered (in 45% of samples and at all 3 time points). The other 3 ExPEC clones corresponded with E. coli O6:K2:H1, O1:K1:H7, and O2:F10,F48.

CONCLUSIONS

E. coli clones, including ExPEC, can be extensively shared among human and animal household members in the absence of sexual contact and in patterns suggesting host-to-host transmission.

Intermittent and persistent shedding of Escherichia coli O157 in cohorts of naturally infected calves

AIMS

We conducted two short-term studies of cohorts of naturally infected calves to determine the prevalence and concentrations of Escherichia coli O157 shed in faeces.

METHODS AND RESULTS

Two cohorts of calves were sampled; in the first study 14 calves were sampled up to five times a day for 5 days; in the second study a group of 16 separate calves were sampled once or twice a day for 15 days. All cattle within the two cohorts shed E. coli O157 at some point during the respective studies. In 18% of samples, E. coli O157 could only be isolated using immunomagnetic separation after an enrichment period, suggesting concentrations <250 CFU g(-1). The highest concentrations recorded were 6.7 x 10(5) and 1.6 x 10(6) CFU g(-1) for studies 1 and 2 respectively.

CONCLUSIONS

Persistent, high shedders (shedding >10(3) CFU g(-1)) were evident in both studies but, in the majority of calves, the pathogen was isolated intermittently.

SIGNIFICANCE AND IMPACT OF THE STUDY

The variable patterns of shedding have important implications for the design of appropriate sampling protocols and for gaining meaningful estimates of parameters used in mathematical models of transmission.

A statewide outbreak of Escherichia coli O157:H7 infections in Washington State

In November 1986, a statewide outbreak of Escherichia coli O157:H7 infections in Washington State was identified after a physician in an eastern Washington community hospitalized three patients with hemorrhagic colitis which progressed to thrombotic thrombocytopenic purpura. Epidemiologic investigation identified 37 cases in this community and linked the illnesses to a local restaurant which had served ground beef that was the suspected initial vehicle of transmission. The plasmid profile and toxin production pattern (Shiga-like toxin II alone) of the outbreak strain provided a unique strain marker. E. coli O157:H7 infections caused by this strain were simultaneously seen in other parts of the state among nursing home residents and in patients with the hemolytic-uremic syndrome, and an increase in sporadic cases of hemorrhagic colitis was noted at a Seattle health maintenance organization. It is suspected that a contaminated product, probably ground beef distributed statewide, was the common source. Tracing of this meat led to farms where rectal swabs from six (1%) of 539 cattle tested yielded E. coli O157:H7, although the plasmids and toxin production patterns of these isolates differed from the human outbreak strain. Introduction of a single strain of E. coli O157:H7 has the potential to cause widespread concurrent outbreaks. Such outbreaks are likely to escape recognition until heightened screening and surveillance for E. coli O157:H7 is established.

Septicemia in the first week of life in a Norwegian national cohort of extremely premature infants

OBJECTIVES

To investigate the incidence, causes, predictors, and outcomes of septicemia in the first week of life in a national cohort of extremely premature infants.

METHODS

A prospective study of survival of all infants with gestational age of <28 weeks or birth weight of <1000 g who were born in Norway in 1999-2000 was performed. Data on the maternal prenatal history, delivery, and neonatal course, including detailed information on episodes of microbiologically verified septicemia, were collected on predefined forms. Septicemia was reported in 2 groups, ie, episodes diagnosed on the day of delivery (ie, very early-onset septicemia [VEOS]) and episodes diagnosed from day 2 to day 7 of life (ie, early-onset septicemia [EOS]). Logistic regression models were used for the selection of variables for predictor analysis in each group.

RESULTS

Of 462 included infants, VEOS occurred for 15 (32.5 per 1000 population) and EOS for 15 (35.5 per 1000 population). The most prevalent bacteria were Escherichia coli in VEOS (n = 9) and staphylococci (coagulase-negative staphylococci and Staphylococcus aureus) (n = 15) in EOS. Case fatality rates were 40% and 13%, respectively. Independent predictive factors for VEOS were clinical chorioamnionitis (odds ratio [OR]: 10.5; 95% confidence interval [CI]: 3.3-33.4) and high maternal age (OR: 1.2; 95% CI: 1.0-1.3), whereas not receiving systemic antibiotic therapy within 2 days of age (OR: 13.6; 95% CI: 3.7-50.2) and receiving nasal continuous positive airway pressure (n-CPAP) support at 24 hours of age (OR: 9.8; 95% CI: 2.5-38.4) independently predicted septicemia after the first day of life.

CONCLUSIONS

Whereas vertically transmitted septicemia was dominated by Gram-negative bacteria, with predictors being exclusively of maternal origin, EOS was dominated by typically nosocomial flora, with n-CPAP treatment at 24 hours of age being a powerful predictor. Early n-CPAP treatment, as opposed to mechanical ventilation, as a powerful predictor of septicemia in the early neonatal period, even with adjustment for early systemic antibiotic treatment, is a new observation among extremely premature infants that warrants additional study.

Swimming-associated haemorrhagic colitis due to Escherichia coli O157:H7 infection: evidence of prolonged contamination of a fresh water lake

We describe an Escherichia coli O157:H7 outbreak associated with a fresh water lake at a county park. Campers were surveyed for diarrhoeal illness within 10 days of their visit, and a case-control study of day visitors was conducted. A confirmed case was a symptomatic person with a stool culture positive for E. coli O157:H7 and a probable case was a person with bloody diarrhoea. Clinical isolates of E. coli O157 were subtyped by pulsed field gel electrophoresis (PFGE). In the camper survey, 12 (38%) of 32 swimmers had a diarrhoeal illness (relative risk [RR] = 12.4; 95% confidence interval [CI] = 1.7-89.7). For the case-control study, the 12 cases were more likely than controls to have purposefully ingested lake water (odds ratio [OR] = 6.9, 95% CI = 0.9-55.8). The PFGE patterns of six clinical isolates were indistinguishable. This report further demonstrates that contaminated fresh-water lakes can be the source of community outbreaks of E. coli O157:H7.

Feedstuffs as a vehicle of cattle exposure to Escherichia coli O157:H7 and Salmonella enterica

Feed has been reported as a vehicle for transmission of Salmonella enterica in cattle and several lines of evidence suggest that feed can be a vehicle for transmitting Escherichia coli O157:H7 as well. To show whether microbial contamination of feeds could contribute to the populations of S. enterica and E. coli O157:H7 on a farm, we compared isolates from feed samples to bovine fecal isolates from the same farm using pulsed-field gel electrophoresis (PFGE). Four of 2365 component feed samples (0.2%) and 1 of 226 feed mill samples (0.4%) were positive for E. coli O157:H7. Twenty of 2405 (0.8%) component feed samples and none of 226 feed mill samples were positive for Salmonella. PFGE profiles from E. coli O157:H7 isolated from a component feed sample closely resembled that from a fecal isolate collected later from the same farm, and a similar observation was made of a Salmonella Tyhpimurium isolate from component feed on another farm. There were indistinguishable PFGE profiles from component feed Salmonella Tyhpimurium DT104 isolates and fecal isolates from the same farm. These results provide evidence for a role of cattle feed in transmission of E. coli O157:H7; S. enterica; cattle-bacteria.

Faecal carriage of verocytotoxin-producing Escherichia coli O157 in cattle and sheep at slaughter in Great Britain

A 12-month abattoir survey was conducted between January 1999 and January 2000, to determine the prevalence of faecal carriage of verocytotoxin-producing Escherichia coli O157 (VTEC O157) in cattle and sheep slaughtered for human consumption in Great Britain. Samples of rectum containing faeces were collected from 3939 cattle and 4171 sheep at 118 abattoirs, in numbers proportional to the throughput of the premises. The annual prevalence of faecal carriage of VTEC O157 was 4.7 per cent (95 per cent confidence interval 4.1 to 5.4) for cattle and 1.7 per cent (1.3 to 2.1) for sheep, values which were statistically significantly different from each other (P < 0.001). The organisms were recovered from both cattle and sheep slaughtered throughout the year and at abattoirs in all regions of the country, but the highest prevalence was in the summer. The most frequency recovered VTEC O157 isolates were phage types 2, 8 and 21/28 in cattle and 4 and 32 in sheep, the five most frequently isolated phage types associated with illness in people in Great Britain during the same period.

Recurrent clinical mastitis caused by Escherichia coli in dairy cows

In this study, the occurrence of persistent intramammary infections caused by Escherichia coli with recurrent episodes of clinical mastitis caused by E. coli are described for a cohort of 300 Dutch dairy herds. Calculations on the recurrent episodes were based on data collected by dairy farmers. The genotype of the E. coli strains was determined by means of a polymerase chain reaction using enterobacterial repetitive intergenic consensus (ERIC) primers, resulting in a DNA fingerprint. Quarters in which the same E. coli genotype was found were considered to be persistently infected. In 4.77% of all episodes of clinical mastitis caused by E. coli, persistent intramammary infections caused by the same E. coli genotype were found. Based on the occurrence of the same genotypes, we concluded that, in 2.98% of all episodes, transmission of E. coli strains among quarters within one cow might have occurred. In 13.04% of all episodes of clinical mastitis caused by E. coli in the study, different E. coli genotypes were isolated from recurrent episodes of clinical mastitis within the same cow, indicating that these cows were highly susceptible to recurrent intramammary infections caused by E. coli.

armA and aminoglycoside resistance in Escherichia coli

We report armA in an Escherichia coli pig isolate from Spain. The resistance gene was borne by self-transferable IncN plasmid pMUR050. Molecular analysis of the plasmid and of the armA locus confirmed the spread of this resistance determinant.

Temporal and geographical distributions of reported cases of Escherichia coli O157:H7 infection in Ontario

The distribution of 3001 cases of verocytotoxigenic Escherichia coli (VTEC) reported in the Province of Ontario, Canada, were examined to describe the magnitude of this condition geographically and to evaluate the spatial relationship between livestock density and human VTEC incidence using a Geographical Information System. Incidence of VTEC cases had a marked seasonal pattern with peaks in July. Areas with a relatively high incidence of VTEC cases were situated predominantly in areas of mixed agriculture. Spatial models indicated that cattle density had a positive and significant association with VTEC incidence of reported cases (P = 0.000). An elevated risk of VTEC infection in a rural population could be associated with living in areas with high cattle density. Results of this study suggested that the importance of contact with cattle and the consumption of contaminated well water or locally produced food products may have been previously underestimated as risk factors for this condition.

Outbreak of diarrhoea due to Escherichia coli O111:B4 in schoolchildren and adults: association of Vi antigen-like reactivity

During six days in November, 1987, 611 pupils (age range 7-19 years) and 39 adults (23-57) at a school complex in southern Finland had diarrhoea due to Escherichia coli O111:B4. Diarrhoea developed in 137 other household members during the two weeks after the school outbreak. The source of the organism remains unknown. The outbreak strains, when incubated at 22 degrees C or exposed to ampicillin, lost the lipopolysaccharide O antigen and began to react with antisera against Salmonella typhi Vi antigen. The Vi antigen-like reactivity increased the adherence of the organisms to Hep-2 cells. These results indicate that E coli O111:B4, and possibly other enteropathogenic E coli strains, should be considered in the diagnosis of all diarrhoea cases and not only in infantile diarrhoea. Expression of Vi antigen in E coli may play a part in virulence by enhancing adherence to the intestinal epithelium.

Comparative survival of free shiga toxin 2-encoding phages and Escherichia coli strains outside the gut

The behavior outside the gut of seeded Escherichia coli O157:H7, naturally occurring E. coli, somatic coliphages, bacteriophages infecting O157:H7, and Shiga toxin 2 (Stx2)-encoding bacteriophages was studied to determine whether the last persist in the environment more successfully than their host bacteria. The ratios between the numbers of E. coli and those of the different bacteriophages were clearly lower in river water than in sewage of the area, whereas the ratios between the numbers of the different phages were similar. In addition, the numbers of bacteria decreased between 2 and 3 log units in in situ survival experiments performed in river water, whereas the numbers of phages decreased between 1 and 2 log units. Chlorination and pasteurization treatments that reduced by approximately 4 log units the numbers of bacteria reduced by less than 1 log unit the numbers of bacteriophages. Thus, it can be concluded that Stx2-encoding phages persist longer than their host bacteria in the water environment and are more resistant than their host bacteria to chlorination and heat treatment.

Shiga-toxigenic Escherichia coli O157 in agricultural fair livestock, United States

Agricultural fairs exhibiting livestock are increasingly implicated in human Shiga-toxigenic Escherichia coli O157:H7 (STEC O157:H7) outbreaks. To estimate livestock STEC O157:H7 prevalence at US fairs, we collected 2,919 fecal specimens at 29 county fairs in 2 states and at 3 state fairs in 2002. Fly pools were also collected. STEC O157:H7 was isolated from livestock at 31 (96.9%) of 32 fairs, including 11.4% of 1,407 cattle, 1.2% of 1,102 swine, 3.6% of 364 sheep and goats, and 5.2% of 154 fly pools. Cattle, swine, and flies at some fairs shared indistinguishable STEC O157:H7 isolate subtypes. In 2003, a total of 689 ambient environmental samples were collected at 20 fairgrounds 10-11 months after 2002 livestock sampling while fairgrounds were livestock-free. Four beef barn environmental samples at 3 fairgrounds yielded STEC O157:H7. These data suggest that STEC O157 is common and transmissible among livestock displayed at agricultural fairs and persists in the environment after the fair.

Escherichia coli O157:H7 diarrhoea associated with well water and infected cattle on an Ontario farm

A 16-month old female child living on an Ontario dairy farm was taken to hospital suffering from bloody diarrhoea. Escherichia coli O157:H7 was isolated from her stool. Initial tests of well water samples were negative for E. coli by standard methods but culture of selected coliform colonies on sorbitol-MacConkey agar led to isolation of E. coli O157:H7. E. coli O157:H7 was also isolated from 63% of cattle on the farm. The E. coli O157:H7 isolates from the child, the water and the cattle were phage type 14, produced verotoxins 1 and 2, and were highly related on analysis by pulsed field gel electrophoresis. The child did not have known direct contact with the cattle and did not consume unpasteurized milk. Hydrogeological investigation revealed the design and location of the well would allow manure-contaminated surface water to flow into the well. This investigation demonstrates that cattle farm well water is a potential source of E. coli O157:H7 which may not be identified by standard screening for E. coli in water.

Enteric pathogens in Mexican sauces of popular restaurants in Guadalajara, Mexico, and Houston, Texas

BACKGROUND

The transmission of traveler's diarrhea is primarily foodborne.

OBJECTIVE

To examine the level of microbial contamination of tabletop sauces found in Mexican-style restaurants.

DESIGN

Cross-sectional study of Mexican sauces.

SETTING

Mexican restaurants in Guadalajara, Mexico, and Houston, Texas, during the summer of 1998.

MEASUREMENTS

71 sauces from Guadalajara and 25 sauces from Houston were examined. The number of sauces contaminated with Escherichia coli, the median number of E. coli colonies per gram of sauce, and enteropathogens were identified.

RESULTS

47 of 71 sauces from Guadalajara were contaminated with E. coli versus 10 of 25 sauces from Houston (P = 0.03); the median number of E. coli colonies per gram of sauce was 1000 in the Guadalajara sauces versus 0.0 in the Houston sauces (P = 0.007). Among sauces from Guadalajara tested for diarrheogenic E. coli, 4 of 43 sauces contained enterotoxigenic E. coli and 14 of 32 contained enteroaggregative E. coli.

CONCLUSIONS

Contamination with E. coli was common in samples of Mexican tabletop sauces from Guadalajara restaurants. These sauces commonly contained enteric pathogens.

Fecal Escherichia coli O157:H7 shedding patterns of orally inoculated calves

To assess the duration of fecal shedding upon initial infection, the duration of shedding after subsequent re-infection and the effects of dietary restriction and antibiotic treatment on shedding recrudescence, four, one-week-old calves were orally inoculated on three separate occasions with 5x10(8) cfu of Escherichia coli O157:H7 strain 86-24 Nal-R. Fecal shedding was followed by serial culture three times weekly. Following the first inoculation, the calves shed E. coli O157:H7 in their feces for a mean of 30 days, with a range of 20 to 43 days. Following the second and third inoculations, the calves shed E. coli O157:H7 in their feces for 3-8 days. In each of the three inoculations, feed was withheld from the calves for 24 h after they had become fecal culture negative. Two calves resumed shedding, one for 1 day and the other for 4 days, after food was withheld after the third inoculation, but not in the first two inoculations. In the third inoculation, one calf resumed shedding for one day after treatment with oxytetracycline. No E. coli O157:H7 strain 86-24 Nal-R was found in the calves at necropsy. These calves did not exhibit persistent low-level shedding, and did not appear to be persistently colonized with E. coli O157:H7.

Transmission of Escherichia coli O157:H7 to cattle by house flies

The main reservoir of Escherichia coli O157:H7 is the digestive tract of cattle; however, the ecology of this food-borne pathogen is poorly understood. House flies (Musca domestica L.) might play a role in dissemination of this pathogen in the cattle environment. In our study, eight calves were individually exposed to house flies that were orally inoculated with a mixture of four strains of nalidixic acid-resistant E. coli O157:H7 (Nal(R)EcO157) for 48h. Another eight calves were individually exposed to uninoculated flies and served as the control. Fresh cattle feces (rectal sampling) and drinking water were periodically sampled and screened for Nal(R)EcO157 up to 19 days after the exposure. At the end of the experiment, all calves were euthanized and the lumen contents of rumen, cecum, colon, and rectum as well as swab samples of gall-bladder mucosa and the recto-anal mucosa were screened for Nal(R)EcO157. On day 1 after the exposure, fecal samples of all eight calves and drinking-water samples of five of eight calves exposed to inoculated flies tested positive for Nal(R)EcO157. The concentration of Nal(R)EcO157 in feces ranged over time from detectable only by enrichment (<10(2)) to up to 1.1 x 10(6)CFU/g. Feces of all calves remained positive for Nal(R)EcO157 up to 11 days after the exposure and 62% were positive until the end of experiment. Contamination of drinking water was more variable and all samples were negative on day 19. At necropsy, the highest prevalence of Nal(R)EcO157 was in the recto-anal mucosa region, followed by rectal and colonic contents.