Enterotoxigenic Escherichia coli and Reovirus-like agent in rural Bangladesh.
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Biomedical subjects
Publications and source records attributed to J G Wells.
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During 1970 and 1971, a large increase in the number of isolations of Shigella organisms (90% S sonnei) occurred among patients of Grady Memorial Hospital in Atlanta. Examination of strains isolated during this outbreak showed a marked decline in the frequency of antibiotic resistance, especially multiple resistance, from that which had been observed during the preceding three years, in spite of continued heavy usage of antibiotics. These findings are contrary to most recently reported experience, which has indicated a rapidly increasing incidence of antibiotic resistance, especially to ampicillin.
Symptomatic infection with Salmonella heidelberg developed in 55 children after their admission to the pediatric wards of two adjacent hospiatls in San Juan, Puerto Rico. Many of these children had been hospitalized for the treatment of diarrhea of unidentified etiology. In 25 of these patients, Salmonella bacteremia was documented. Five had clinically unsuspected and untreated bacteremia with no evidence of complications during the follow-up period of four and a half months. The remaining 30 had "standard" symptomatic infection due to S. heidelberg. Eight children died; four of these proved to be bacteremic. The index patient, who also introduced the infection into one of the hospitals, was identified. Person to person spread perpetuated the outbreak within and between the two hospitals for nearly four months. Although neonates with salmonellosis had a higher rate of bacteremia than other children, no other specific predisposing factors for Salmonella bacteremia were identified. Laboratory studies of the epidemic strain revealed neither invasive nor enterotoxic properties of the organisms, nor enhanced virulence in laboratory mice. Cohort nursing and isolation of patients with positive cultures halted the epidemic. Nontyphoid Salmonella bacteremia, sometimes clinically unsuspected and self-limited, should be recognized as a frequent accompaniment of Salmonella enteritis in young hospitalized children.
A laboratory investigation was conducted on cultures collected from travelers before, during, and after a trip to Mexico to characterize the etiology of traveler's diarrhea. Four laboratory methods for detecting enterotoxigenicity of Escherichia coli were evaluated: the infant mouse assay, the Chinese hamster ovary (CHO) cell assay, the Y1 adrenal cell assay, and the rabbit ileal loop. Although a number of common enteric pathogens were identified as a cause of traveler's diarrhea, including six serotypes of Salmonella, two serotypes of Shigella, Vibrio parahaemolyticus, Giardia lamblia, and Entamoeba histolytica, enterotoxigenic Escherichia coli was most commonly isolated. Strains were identified that produced only heat-labile enterotoxin (LT), only heat-stable enterotoxin (ST), or both LT and ST. The infant mouse assay yielded results falling into two distinct groups, providing a clear separation of positive and negative cultures. The CHO assay also formed two groups, with positive cultures producing 11% or more of the elongated cells. There was good agreement between the CHO and the Y1 adrenal cell assays for detection of LT. The adrenal cell system for detection of LT was more suitable than the CHO assay for processing large numbers of specimens because of the miniculture modification of this method utilized in this study. The infant mouse method was a simple and reliable method for detecting ST.
Five patients who developed acute watery diarrhoea while travelling in Mexico in October, 1974, were found to have enterotoxigenic Escherichia coli in their stool which produced heat-stable enterotoxin (S.T.) without producing heat-labile enterotoxin (L.T.). These S.T.-only E. coli, which have previously been described as causing diseases in animals, must now be regarded as pathogenic for humans as well.
Medical logs of 2,445 cruises taken by 38 vessels over a 20-month period beginning Jan 1, 1972, were reviewed. On 92% of the cruises, the recorded incidence of gastrointestinal illness was 1% or less; on 2% of cruises, it was 5% or greater. The actual incidence of gastrointestinal illness determined by a questionnaire survey of passengers sailing on nine cruises was found to be at least four times as high as that recorded in the medical logs. Although the cause of the illnesses was not known, there was evidence that transmission took place aboard ship. A survey of food-handling practices and water systems aboard selected ships demonstrated a significant potential for transmission of foodborne and waterborne disease.
In September, 1973, diarrhoea caused by Salmonella typhimurium developed in 32 people in a Maine hospital. Both epidemiological and microbiological evidence indicated that raw egg beaten in milk ("egg-nog") was responsible for the infection. However, 6 patients and 8 employees had not had egg-nog, and their illness developed after the source of infection had been recognised and removed. Most of these people had had direct contact with an infected patient, and presumably acquired the infection by person-to-person spread. It is concluded that person-to-person spread of S. typhimurium can occur in hospitals and can be a hazard to patients and staff.
Between June 23 and June 30, 1973, 90% of 650 passengers and at least 35% of 299 crew members experienced a diarrheal illness during a 7-day Caribbean cruise aboard a passenger cruise liner. Symptoms were consistent with shigellosis, and Shigella flexneri 6, Boyd 88 biotype, was isolated from rectal swabs taken from 8 to 35 ill passengers and 33 of 294 crew members. Epidemiologic evidence incriminated the ship's water, including ice, as the probable vehicle of transmission, and elevated coliform counts were found in potable water samples obtained aboard the vessel at the peak of the outbreak. Potential sources of contamination of the vessel's potable water supply were investigated, and improvements in the loading and chlorination of potable water were recommended.
In November 1972 an outbreak of gastrointestinal illness occurred at a public school in Stockport, Iowa. One hundred ninety-four (72%) of 269 pupils and 14 (16%) of 23 staff members were affected. The etiologic agent was a strain of Shigella sonnei resistant to multiple antimicrobials. Waterborne transmission of shigellosis was documented epidemiologically and by isolation of the organism from the school water system. Ninety-seven (14%) of 698 of the students' household contacts developed diarrhea, and possible secondary cases also occurred in 3 (9%) of 32 household contacts of school staff.
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Two methods for isolating Salmonella and Arizona organisms from turtles, blending and excretion, were evaluated, and the percentage of isolates obtained by each method was compared with the percentage of isolates obtained by culture of turtle organs. The blending and excretion methods were equally effective in detecting the overall incidence of Salmonella and Arizona infections in turtles. The percentage of isolates obtained by specific organ culture, however, was less than the percentage obtained by the other two methods. The blending method detected a greater number of turtles with Arizona infections than did the excretion method, but there was no difference in the number of Salmonella infections detected by the two methods. The frequency of isolation of Arizona organisms from organs other than the small intestine and colon was higher than that of Salmonella.
The colicin typing method for differentiating epidemic strains of Shigella sonnei was evaluated. Forty percent of the strains were untypable, but the method divides 60% of the strains into 15 established colicin types. The method has reasonably good reproducibility, but should not be interpreted with the same degree of confidence as some other characteristics such as serotypes. For this reason, known type strains should be included as controls in each analysis to ensure uniformity of results.
We compared the relative advantages of using glass test tubes and plastic multi-well plates in the serological identification of Salmonella cultures by the Spicer-Edwards method, and we conclude that the advantages of multi-well plates outweigh those of test tubes.
The use of a cotton gauze swab and subsequent culture of the swab was found to be a more sensitive method for isolating Salmonella from liquid milk than the revised procedure of North. The swab method was found to be as sensitive as the North procedure for recovering Salmonella when incubated at 37 C but more sensitive when incubated at 43 C. Incubation of the swab cultures at the elevated temperature of 43 C gave good results when Salmonella was present at levels as low as one per liter. Swabs exposed to milk contaminated with 100 Salmonella per liter remained positive even when subsequently washed for 2 hr in noncontaminated milk. Bismuth sulfite agar and Brilliant Green sulfadiazine agar were equally effective for isolating Salmonella from broth cultures; use of both media resulted in maximal isolations.
A polyvalent OH conjugate for Salmonella O groups A through I, K, L, and O was prepared and tested against pure cultures of salmonellae, nonsalmonellae, and a variety of food, fecal, and environmental specimens. Examination of pure cultures revealed that the conjugate gave negligible staining with representative strains of Shigella, Proteus, Providence, Serratia, and Pseudomonas. However, it stained 12% of the Escherichia coli and Citrobacter freundii strains and 36% of the Arizona strains. Over 1,200 specimens of various types were examined by both fluorescent-antibody (FA) and cultural procedures. Results indicate that, when used with discretion, FA screening can be a useful tool for rapid presumptive indication of the presence of salmonellae. The need for careful selection of strains used for preparing antisera and the importance of adequate evaluation of Salmonella FA reagents are discussed.
Previous studies have shown that Menhaden fish meal, a common ingredient of animal feeds, is frequently contaminated with salmonellae. Animals that eat contaminated feed may become infected. If they, in turn, are eaten by humans, they may be a means by which salmonellae are introduced into the human population. Epidemiological studies of the fish-meal industry were carried out to determine the sources of salmonellae in fish meal and the factors affecting the persistence and survival of salmonellae during the processing of fish meal. Examination of 190 fish immediately after they came from the Gulf of Mexico revealed no salmonellae, but salmonellae were frequently isolated from samples of fish taken from the boats when they arrived at the plants. Salmonellae were also frequently isolated from dockside water at each of the plants. Approximately 50% of the samples taken in the raw fish processing areas were contaminated with salmonellae. The percentage of samples yielding salmonellae decreased progressively through the various sequences of processing, but more than 15% of the samples taken from the finished products were also positive. Salmonellae were isolated from the raw area of the plant most frequently while the plant was operating and less frequently when the plant was idle, whereas in the processing area of the plant the reverse was true. Salmonellae appeared to survive and multiply in the processing area of the plant while the plant was idle, which resulted in contamination of the first portion of each day's production. Salmonellae in the processed fish meal were reduced to nondetectable levels by reprocessing the first 45 min of each day's production.
Bacteriological examination of 1,427 samples from a poultry-processing plant over a 2-year period yielded 202 (14.2%) cultures positive for salmonellae. The results indicate that contamination is reduced by washing procedures within the plant but that recontamination of the carcasses occurred in at least two different stages of processing, i.e., during evisceration and chilling. There was evidence of spread of salmonellae from flock to flock during the serial processing of flocks, but the spread was usually not extensive. The serotypes of salmonellae isolated in this study were similar to those of chicken origin reported from other areas of the country.
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