Massive outbreak of Escherichia coli O157:H7 infection in schoolchildren in Sakai City, Japan, associated with consumption of white radish sprouts

Escherichia coli O157:H7

E. coli O157:H7 can cause potentially lethal illness in hosts of all ages. These patients often are evaluated and treated by gastroenterologists. The treating physician should administer adequate hydration, usually parenterally, and avoid the use of antibiotics and antimotility agents. The physician needs to notify immediately the appropriate public health authorities of the diagnosis and to ensure that the isolate is recovered by the microbiologist and forwarded for molecular linkage analyses.

Immunomagnetic separation of Escherichia coli O26, O111 and O157 from vegetables

AIMS

Raw fruits and vegetables have been increasingly associated with human infections caused by Shiga toxin-producing Escherichia coli. This study evaluates the isolation and detection of E. coli O26, O111 and O157 from vegetable samples using immunomagnetic particles.

METHODS AND RESULTS

Standard cultivation and immunomagnetic separation (IMS) procedures were compared. It was found that immunomagnetic particles could efficiently concentrate E. coli cells, detecting significantly more bacteria than with standard cultivation procedures.

CONCLUSION

Bacteria were detected in 93-100% of the inoculated samples using the IMS procedure, but only 36-93% samples tested by standard cultivation procedures were found to be positive.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results indicate that E. coli O26, O111 and O157 immunomagnetic particles can be a very useful and efficient tool for the detection of E. coli strains in raw vegetables, and could probably be used with samples of animal origin.

Escherichia coli O157:H7 in faeces from cattle, sheep and pigs in the southwest part of Norway during 1998 and 1999

During a 2-year period from January 1998 to December 1999, intestinal content from 1541 cattle, 665 sheep and 1976 pigs were analysed for Escherichia coli O157:H7 using the immunomagnetic separation procedure. The animals originated from 848, 605 and 832 herds from the southwest part of Norway, respectively. E. coli O157:H7 was present in three samples from cattle from different herds, giving a herd prevalence of 0.35% and an animal prevalence of 0.19%. From pigs, E. coli O157:H7 was isolated from two pigs from different herds, giving a herd prevalence of 0.24% and an animal prevalence of 0.1%. A follow-up study revealed another positive testing pig from one of these herds. E. coli O157:H7 was not found from any of the 665 investigated sheep. By PCR analysis, all six E. coli O157:H7 isolates were shown to contain the genes encoding Shiga toxin 2 (stx2), the intimin protein (eae) and the H7 flagellum (fliC-H7). One of the cattle isolates also harboured the Shiga toxin 1 encoding (stx1) gene. The six isolates were differentiated into three pulse-field gel electrophoresis profiles. The results indicate that the occurrence of E. coli O157:H7 in cattle, sheep and pigs in the southwest part of Norway is low compared to other European countries.

Type 1 fimbriation and its phase switching in diarrheagenic Escherichia coli strains

Type 1 fimbriae can be expressed by most Escherichia coli strains and mediate mannose-sensitive (MS) adherence to mammalian epithelial cells. However, the role of type 1 fimbriae in enteric pathogenesis has been unclear. Expression of type 1 fimbriae in E. coli is phase variable and is associated with the inversion of a short DNA element (fim switch). Forty-six strains of diarrheagenic E. coli were examined for the expression of type 1 fimbriae. Only four of these strains were originally type 1 fimbriated. Seventeen strains, originally nonfimbriated, expressed type 1 fimbriae in association with off-to-on inversion of the fim switch, after serial passages in static culture. The switching frequencies of these strains, from fimbriate to nonfimbriate, were greater than that of the laboratory strain E. coli K-12. None of the 16 strains of serovar O157:H7 or O157:H(-) expressed type 1 fimbriae after serial passages in static culture. The nucleotide sequence analysis of the fim switch region revealed that all of the O157:H7 and O157:H(-) strains had a 16-bp deletion in the invertible element, and the fim switch was locked in the "off" orientation. The results suggest that expression of type 1 fimbriae may be regulated differently in different E. coli pathogens causing enteric infections.

Development of a monoclonal sandwich ELISA for the detection of animal and human Escherichia coli O157 strains

AIMS

Production of a monoclonal antibody (MAb) to Escherichia coli O157 to develop a rapid test using a sandwich ELISA (sELISA) format.

METHODS AND RESULTS

A MAb (7A6) was developed to the long-chain lipopolysaccharide of E. coli O157. A sELISA developed with the MAb reacted with 28 bovine and seven human enterohaemorrhagic E. coli (EHEC) O157 strains and also with two enterotoxigenic E. coli O157 strains. Cross-reaction to a rabbit diarrhoeal E.coli O15, Citrobacter freundii, Salmonella urbana and Vibrio cholerae O1 Inaba was detected.

CONCLUSION

A MAb-based sELISA to detect E. coli O157 was produced. Its application to field samples is required to fully determine its prospective use for the detection of EHEC O157, to evaluate the non-specific interference of the cross-reacting strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

The assay produced is not wholly specific to EHEC O157, but has the potential to be used as a rapid method for screening large numbers of samples for E. coli O157.

Effect of bicozamycin on the eradication of Shiga toxin-producing Escherichia coli in calves

Fifty-nine calves, aged 11 days to 9 months, from three farms breeding Japanese Black beef cattle in Miyazaki Prefecture, Japan, were examined for the presence of Shiga toxin-producing Escherichia coli (STEC). A high prevalence of STEC was detected among calves, with 45 (76.3%) animals carrying STEC including different serogroups (O26, O74, O111, O114, O119, O127, O153, O157, and ONT) and toxin types. The number of STEC in the feces was estimated by a combined method involving enumeration of colony-forming units by a plate-most-probable-number (plate-MPN) technique and polymerase chain reaction for the detection of Shiga toxin genes. Fecal shedding ranged from 10(1) to 10(10) MPN/g feces. To evaluate the safety and efficacy of bicozamycin (BCM: previously named as bicyclomycin) in eradicating STEC, 30 calves carrying STEC with or without diarrhea were examined. Fifteen calves were treated orally with BCM (10 mg/kg/day) once daily for 5 days, and the other 15 were untreated. Twenty-four hours after the last dose, fecal specimens were collected from both groups to compare the number of coliforms and STEC with those before treatment. BCM-treated animals had a significantly lower number of coliforms and STEC compared to the untreated calves. The STEC eradication rate was 86.6% (13/15) in the BCM-treated group, compared to 0% (0/15) in the control group. The corresponding cure rates for diarrhea were 87.5 (7/8) and 0% (0/3), respectively. No adverse reactions were observed in the calves during treatment. It is concluded that BCM is an effective agent for the eradication of STEC in calves with or without diarrhea.

Enteropathogenic and enterohaemorrhagic Escherichia coli and diarrhoea

Enteropathogenic and enterohaemorrhagic Escherichia coli are important causes of bacterial gastroenteritis with the potential for progression to more serious syndromes, especially in the case of enterohaemorrhagic E. coli. Consequently, recent developments in molecular epidemiology and treatment regimens have focused on enterohaemorrhagic E. coli, while the similar initial pathogenic mechanisms of both enterohaemorrhagic and enteropathogenic E. coli continue to be investigated in detail. The carriage of most E. coli virulence determinants on pathogenicity islands, plasmids or phages allows the rapid evolution of these pathotypes, which need to be monitored closely.

Risk factors in causing outbreaks of food-borne illness originating in schoollunch facilities in Japan

We reviewed records of all outbreaks of food-borne illnesses due to schoollunch in Japan from 1987 through 1996 to determine the risk factors causing these outbreaks. Major hazards in 269 outbreaks were Salmonella spp., Campylobacter jejuni, Escherichia coli and Staphylococcus aureus. Foods including uncooked or partially cooked items, salad or egg products presented a high risk in 62 outbreaks with confirmed food sources. Contaminated food items were involved in 29 incidents (46.8%); storage of foods for an extended period before serving in 29 incidents (46.8%), inadequate cooking and cross contamination in 21 incidents (33.9%) each; infected employees in nine incidents (14.5%).