Katherine D. Greene

Non-O157 Shiga Toxin–Producing Escherichia coli Infections in the United States, 1983–2002

BACKGROUND Shiga toxin-producing Escherichia coli (STEC) O157:H7 is a well-recognized cause of bloody diarrhea and hemolytic-uremic syndrome (HUS). Non-O157 STEC contribute to this burden of illness but have been underrecognized as a result of diagnostic limitations and inadequate surveillance. METHODS Between 1983 and 2002, 43 state public health laboratories submitted 940 human non-O157 STEC isolates from persons with sporadic illnesses to the Centers for Diseases Control and Prevention reference laboratory for confirmation and serotyping. RESULTS The most common serogroups were O26 (22%), O111 (16%), O103 (12%), O121 (8%), O45 (7%), and O145 (5%). Non-O157 STEC infections were most frequent during the summer and among young persons (median age, 12 years; interquartile range, 3-37 years). Virulence gene profiles were as follows: 61% stx(1) but not stx(2); 22% stx(2) but not stx(1); 17% both stx(1) and stx(2); 84% intimin (eae); and 86% enterohemolysin (E-hly). stx(2) was strongly associated with an increased risk of HUS, and eae was strongly associated with an increased risk of bloody diarrhea. STEC O111 accounted for most cases of HUS and was also the cause of 3 of 7 non-O157 STEC outbreaks reported in the United States. CONCLUSIONS Non-O157 STEC can cause severe illness that is comparable to the illness caused by STEC O157. Strains that produce Shiga toxin 2 are much more likely to cause HUS than are those that produce Shiga toxin 1 alone. Improving surveillance will more fully elucidate the incidence and pathological spectrum of these emerging agents. These efforts require increased clinical suspicion, improved clinical laboratory isolation, and continued serotyping of isolates in public health laboratories.

Illnesses Associated with Escherichia coli 0157:H7 Infections: A Broad Clinical Spectrum

STUDY OBJECTIVE To describe the spectrum of illnesses associated with Escherichia coli O157:H7 infections. DESIGN Described an outbreak that showed the broad spectrum of these infections. Reviewed the clinical findings in the other eight major outbreaks reported between 1982 and 1986. Also reviewed reports of sporadic cases. SETTING Outbreaks in communities, nursing homes, a day care center, and a kindergarten. CASES Persons identified in outbreaks of E. coli O157:H7 infections. RESULTS Escherichia coli O157:H7 infection causes bloody diarrhea (hemorrhagic colitis), nonbloody diarrhea, the hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura. Infection can be asymptomatic, can involve extraintestinal sites, and can be fatal. Bloody diarrhea is the commonest symptom. Most patients have severe abdominal cramps; fever is documented in less than half. Findings from fecal leukocyte examinations often suggest a noninfectious cause. Results of radiologic and colonoscopic examinations can be consistent with a diagnosis of inflammatory bowel disease or ischemic colitis. Patients at the extremes of age are at increased risk for E. coli O157:H7-associated diarrhea, the hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, and death. Antimicrobial agents have not been shown to modify the illness, but there are few data on individual agents. CONCLUSION Infection with E. coli O157:H7 should be considered in all patients with bloody diarrhea, the hemolytic uremic syndrome, or thrombotic thrombocytopenic purpura because the infection can masquerade as gastrointestinal bleeding of noninfectious cause, the antecedent diarrhea may be resolved and forgotten by the time the hemolytic uremic syndrome or thrombotic thrombocytopenic purpura is diagnosed, and the detection of E. coli O157:H7 requires specific stool culture techniques.

A Waterborne Outbreak in Missouri of Escherichia coli O157:H7 Associated with Bloody Diarrhea and Death

OBJECTIVE To describe and determine the source of a large outbreak of Escherichia coli O157:H7 (ECO157) infections in Missouri. DESIGN A case-control study and a household survey. SETTING A small city in a rural Missouri township that had an unchlorinated water supply. PATIENTS Case patients were residents of or visitors to Burdine Township with bloody diarrhea or diarrhea and abdominal cramps occurring between 15 December 1989 and 20 January 1990. MEASUREMENTS Escherichia coli O157 was isolated from 21 stool specimens. All isolates were resistant to sulfisoxazole, tetracycline, and streptomycin; produced Shiga-like toxins I and II; and had one 60-megadalton plasmid. RESULTS Among the 243 case patients, 86 had bloody stools, 32 were hospitalized, 4 died, and 2 had the hemolytic uremic syndrome. In the case-control study, no food was associated with illness, but ill persons had drunk more municipal water than had controls (P = 0.04). The survey showed that, during the peak of the outbreak, bloody diarrhea was 18.2 times more likely to occur in persons living inside the city and using municipal water than in persons living outside the city and using private well water (P = 0.001). Shortly before the peak of the outbreak, 45 water meters were replaced, and two water mains ruptured. The number of new cases declined rapidly after residents were ordered to boil water and after chlorination of the water supply. CONCLUSIONS This was the largest outbreak of ECO157 infections, the first due to a multiply resistant organism, and the first shown to be transmitted by water. System-wide chlorination as well as hyperchlorination during repairs might have prevented this outbreak. Both bloody and nonbloody diarrhea may be common manifestations of this infection, which is probably underdiagnosed because of the failure of routine stool cultures to identify the organism. Cities with deteriorating water systems using untreated water risk widespread illness from contaminated drinking water.

The United States National Prospective Hemolytic Uremic Syndrome Study: Microbiologic, Serologic, Clinical, and Epidemiologic Findings

The frequency of Shiga toxin-producing Escherichia coli (STEC) serotypes associated with postdiarrheal hemolytic uremic syndrome (HUS) cases among children and adults in the United States and the proportion with IgM or IgG lipopolysaccharide antibodies to E. coli O157 were determined by use of a nationwide sample from January 1987 through December 1991. Among 83 patients, STEC were isolated from 30 (43%) of 70 whose stool cultures yielded bacterial growth (25 E. coli O157 isolates and 5 non-O157 STEC isolates). Fifty-three (80%) of 66 patients with serum samples had positive O157 lipopolysaccharide antibody titers. Of the 83 patients, 60 (72%) had evidence of STEC infection, including 6 of 8 adults whose illnesses also met criteria for thrombotic thrombocytopenic purpura. Data from a subset of patients suggest that E. coli O157 was the cause of > or = 80% of the STEC infections. All 3 women who were postpartum had evidence of E. coli O157 infection. STEC infection should be considered the likely cause for all persons with postdiarrheal HUS.

Hemolytic-uremic syndrome during an outbreak of Escherichia coli O157:H7 infections in institutions for mentally retarded persons: Clinical and epidemiologic observations

PURPOSE To describe an outbreak of Escherichia coli O175:H7 infection resulting in a high rate of progression to hemolytic-uremic syndrome, and to attempt to identify predictors of and risk factors for progression. DESIGN Case-control study among employees and comparison of daily clinical features in two groups: infected residents with subsequent development of HUS and those who had no complications. SETTING Two institutions for retarded persons in Utah. PATIENTS Twenty residents with E. coli O157:H7 infection (13 culture confirmed, 2 probable, and 5 possible); HUS developed in 8, and 4 died. Thirty-one infected employees (3 with culture-confirmed, 6 with probable, and 22 with possible infection). MEASUREMENTS AND MAIN RESULTS In a case-control study among employees, infection was independently associated with eating ground beef from a single lot prepared at several barbecues and with close contact with a resident who had diarrhea. Five of eight residents in whom HUS developed had received trimethoprim-sulfamethoxazole, compared with none of seven who had no subsequent complications (p = 0.026); this finding may reflect antimicrobial treatment of patients with more severe illness. Compared with infected residents without complications, persons with HUS were younger (median age 13 vs 27 years, p = 0.043) and, by the third day of illness, had higher leukocyte counts (median 23.7 X 10(9)/L vs 9.1 X 10(9)/L, p = 0.018) and temperature (median 38.5 degrees C vs 37.0 degrees C, p = 0.016). Leukocytosis peaked on day 4, more than 24 hours before signs of HUS appeared. CONCLUSIONS Food-borne outbreaks of E. coli O157:H7 in institutions may have devastating effects. Leukocytosis and fever may precede and predict HUS in patients with E. coli O157:H7 infection.

Escherichia coli O157: H7 Diarrhea in the United States: Clinical and Epidemiologic Features

Escherichia coli O157:H7 was first recognized as a human pathogen in 1982 [1], and it is increasingly recognized as an important cause of sporadic and outbreak-associated bloody diarrhea [2]. Strains of E. coli O157:H7 are characterized by their ability to produce moderate or large amounts of two types of Shiga toxin. These toxins are important factors in the pathogenesis of postdiarrheal hemolytic uremic syndrome, and E. coli O157:H7 infection is the major cause of this syndrome in children in the United States and Canada [3-6]. Outbreaks of E. coli O157:H7 have involved communities [7-9] and such institutions as nursing homes [10, 11], schools [12], and day care facilities [13, 14]. Routine stool cultures do not identify E. coli O157:H7. Unlike 80% of E. coli serotypes, however, E. coli O157:H7 does not rapidly ferment D-sorbitol and therefore appears colorless on sorbitol-MacConkey agar culture plates read at 24 hours [15, 16]. These sorbitol-negative colonies can then be screened for agglutination in O157 antiserum. Relatively little information is available about the frequency of isolation of E. coli O157:H7 from ill persons in the United States; most U.S. laboratories do not routinely culture for this organism [17]. In single-center studies in the United States in which all stool specimens were cultured for this organism, isolation rates ranged from 0.08% to 0.5% [18-20]. Recent information suggests that E. coli O157:H7 has been isolated from patients in most states [21], but the frequency of this isolation compared with that of other enteric pathogens in different geographic areas during similar time periods has not been described. The reported clinical signs and symptoms of E. coli O157:H7 infection include bloody or nonbloody diarrhea, abdominal cramps, and lack of reported fever [22, 23]. However, this information was derived from relatively few persons in outbreak settings, and few studies have examined the clinical presentation of illness due to E. coli O157:H7 infection compared with the clinical presentation of illness due to other bacterial enteric pathogens. We therefore sought to determine 1) the frequency of isolation of E. coli O157:H7 and 2) the clinical and epidemiologic features of infections with E. coli O157:H7 compared with those of Campylobacter, Salmonella, and Shigella species at 10 hospitals located throughout the United States. Using standard microbiological methods, we assessed the ways in which time of year, geographic location, and the demographic and clinical features of patients affected the likelihood of isolation of these enteric pathogens. Methods Study Sample Our study was announced and participation was requested in a newsletter that was sent to hospitals in the National Nosocomial Infections Surveillance system [24]. Five hospitals in this system and five other hospitals were chosen on the basis of geographic location, willingness to participate, receipt of specimens in a primary care setting, and the expectation that an adequate number of outpatient stool cultures would be done each year. All four census divisions of the United States were represented. Nine hospitals served general patient populations that included all age groups, and one served a primarily pediatric population. All served both inpatients and outpatients. The average annual number of stool specimens screened by each hospital ranged from 400 to 4000 (median, 1300). Four of the hospitals were university hospitals, and six were community hospitals. At each hospital, all of the specimens studied were fecal samples from inpatients and outpatients of all ages that were submitted to the clinical microbiology laboratory for routine pathogen identification. The study was conducted from October 1990 through October 1992. Collection and Handling of Specimens All sites agreed to use the following methods for the collection and handling of specimens. Swabs were transported in Cary-Blair transport medium, Amies transport medium, or Stuart transport medium and were streaked immediately onto plating media or were kept at 4 C for no more than 24 hours. If whole stool specimens were not examined within 1 hour of receipt by the laboratory, a swab of the stool was placed in transport medium, refrigerated, and examined within 24 hours. Specimens were visually inspected for gross blood, and the presence of occult blood was determined by using the hemoccult test. The presence of fecal leukocytes was determined by placing a bit of stool in a drop of methylene blue on a slide or by doing a Gram stain and examining the specimen using the high-power microscope objective. Specimens were graded as having 0, 1 to 4, 5 to 9, or 10 or more leukocytes per high-power field. Standard methods were used to isolate and identify Campylobacter, Salmonella, and Shigella species. Other assays, such as those for Clostridium difficile or rotavirus, were not part of the protocol and were done according to the routines of the individual site laboratories and the physicians ordering the tests. Isolation of Escherichia coli O157:H7 Before the study began, each laboratory received control strains of E. coli O157:H7 and instructions about the isolation and identification of this organism. To identify E. coli O157:H7, fecal specimens were plated onto sorbitol-MacConkey agar and the plates were incubated at 37 C for 24 hours. Three sorbitol-negative colonies were tested for agglutination with O157 latex reagents (Pro-Lab, Inc., Round Rock, Texas). The O157-positive colonies were sent to the Centers for Disease Control and Prevention for biochemical identification and serotyping [25]. Isolates confirmed as E. coli O157:H7 or O157:NM (nonmotile) were tested for production of Shiga toxin 1 and 2 (formerly called Shiga-like toxins I and II [26]) and for the presence of Shiga toxin genes by hybridization with oligonucleotide probes [27]. Isolates were tested by using the disk diffusion technique [28] for susceptibility to a standard panel of antimicrobial agents [28]. Data Collection For each fecal specimen received, data were entered on a standard line list; only the first specimen from each patient was included. The information collected for each specimen included date obtained, date plated, source (whole stool or swab), presence of visible or occult blood, presence and quantity of fecal leukocytes, and presence of pathogens. After permission was obtained from the relevant health care provider, a clinical data form was completed through retrospective chart review for all patients from whom Campylobacter, Salmonella, or Shigella species or E. coli O157:H7 were isolated and from every 25th patient from whom no pathogen was isolated. Information obtained included age, sex, date of the onset of illness, inpatient or outpatient status, symptoms (including presence and date of onset of diarrhea, bloody stools, abdominal pain, vomiting, and fever in the previous 2 weeks), abdominal tenderness, largest number of bowel movements in a 24-hour period, maximum body temperature on the day of culture (as measured by a health practitioner), peripheral blood leukocyte count, and whether the patient was admitted to the hospital. If a patient had a body temperature of at least 37.8 C, he or she was considered to have fever. Data Analysis Salmonella, Shigella, and Campylobacter species and E. coli O157:H7 were considered to be major bacterial enteric pathogens. Isolates that were identified as O157:H7 or O157:NM and that produced Shiga toxin were considered to be strains of E. coli O157:H7. An isolation proportion for a pathogen was defined as the proportion of all fecal specimens that yielded that pathogen. To estimate the age-specific isolation proportion of pathogens from stool specimens, we divided the number of persons in each age group for whom a specific pathogen was isolated by the sum of all persons (both culture-positive and culture-negative) in that age group. We estimated the total number of culture-negative persons in each age group by extrapolating the age group distribution frequency from the sample of culture-negative persons for whom age was known to all culture-negative persons. For the analysis of clinical features associated with infection, patients whose stool cultures yielded more than one bacterial pathogen were excluded. Differences in proportions were analyzed using a chi-square test or the Fisher exact test. For normally distributed data, differences in means were compared using the Student t-test; for nonparametric data, differences in medians were compared using the Wilcoxon two-sample test. Logistic regression analysis was done using generalized estimating equations to assess factors independently associated with E. coli O157:H7 infection while controlling for study site. For all statistical tests, a two-tailed P value less than 0.05 was considered significant. Results Isolation of Pathogens During the study period, fecal specimens from 30 463 persons were examined. A source was specified for 29 355 of these specimens; 63% were from whole stools and 37% were from swabs. Overall, 1708 of the specimens (5.6%) yielded at least one of the four major bacterial enteric pathogens; for 27 902 specimens (91.6%), no pathogen was isolated. Eleven patients had dual infections: Six had Shigella species and Campylobacter species infections, 3 had Salmonella species and Campylobacter species infections, and 2 had Shigella species and Salmonella species infections. The highest isolation proportions from fecal specimens for E. coli O157:H7 were seen in hospitals in Maine and Wisconsin; the lowest proportion was seen in Virginia (Table 1). Of the four bacterial pathogens, E. coli O157:H7 was the second most frequently isolated in Maine, the third most frequently isolated (ahead of Shigella species) in Washington and Wisconsin, and the third most frequently isolated (tied with Shigella species) in Michigan. In the hospitals in northern states (Maine, Michigan, New

Chloramphenicol-resistant Salmonella newport traced through hamburger to dairy farms. A major persisting source of human salmonellosis in California

Animal-to-human transmission of drug-resistant salmonella and the role of antimicrobial use in food animals in the emergence of these bacteria are controversial subjects. Investigation of a 4.9-fold increase in Salmonella newport isolations from Californians in 1985 showed that 87 percent of the isolates had an unusual antimicrobial-resistance pattern (including chloramphenicol resistance) and a single, identical plasmid. Interviews of 45 patients and 89 matched controls in Los Angeles County showed that illness was associated with penicillin or tetracycline use during the month before onset (P less than 0.001) and with eating ground beef during the week before onset (P = 0.052). The epidemic strain was isolated from hamburger products eaten by cases, abattoirs where the animals from which the meat came were slaughtered, dairies that sent cows for slaughter on days when culture-positive products were processed, and ill dairy cows. Isolation of salmonella from beef carcasses in abattoirs correlated with the proportion of dead or moribund animals received for slaughter (r = 0.60, P less than 0.05). Isolation of chloramphenicol-resistant salmonella from dairy farms was associated with the use of chloramphenicol at those dairies. We conclude that food animals are a major source of antimicrobial-resistant salmonella infections in humans and that these infections are associated with antimicrobial use on farms.

A Nationwide Case-Control Study of Escherichia coli O157:H7 Infection in the United States

Risk factors for Escherichia coli O157:H7 infection were investigated in a case-control study at 10 medical centers throughout the United States. Among 73 case-patients and 142 matched controls, exposures in the 7 days before illness associated with E. coli O157:H7 infection in univariate analysis included consumption of hamburger (matched odds ratio [MOR], 3.8; 95% confidence interval [CI], 1.9-7.9), undercooked hamburger (MOR, 4.5; 95% CI, 1.6-12.2), or hot dogs (MOR, 2.2; 95% CI, 1.1-4.4); eating at a fast-food restaurant (MOR, 2.3; 95% CI, 1.1-4.6); drinking unchlorinated well water (MOR, 2.4; 95% CI, 1.1-5.7); swimming in a pond (MOR, 5.4; 95% CI, 1.1-26.0); and having a household member with diarrhea (MOR, 11.9; 95% CI, 2.7-53.5). In multivariate analysis, only eating undercooked hamburger remained associated with infection. Seven (8%) of 93 patients developed hemolytic uremic syndrome and 1 died. Prevention strategies aimed at modifying risk factors may help to reduce the risk of infection with E. coli O157:H7.

Hospitalization and Antimicrobial Resistance in Salmonella Outbreaks, 1984–2002

Few studies have evaluated the health consequences of antimicrobial-resistant Salmonella strains associated with outbreaks. Among 32 outbreaks occurring in the United States from 1984 to 2002, 22% of 13,286 persons in 10 Salmonella-resistant outbreaks were hospitalized, compared with 8% of 2,194 persons in 22 outbreaks caused by pansusceptible Salmonella strains (p<0.01).

Shiga-like toxin-producing Escherichia coli O111 and associated hemolytic-uremic syndrome : A family outbreak

OBJECTIVE To describe a family cluster of Shiga toxin-producing Escherichia coli O111ac:NM infection. STUDY DESIGN The index case was identified as part of a United States prospective study of hemolytic-uremic syndrome. Epidemiologic investigation was conducted through interviews. E. coli O111:NM infection was characterized through culture and serology. Shiga toxin 1 and 2 gene sequences were determined with oligonucleotide DNA probes. RESULTS All three children and both parents had nonbloody diarrhea, vomiting and abdominal cramps, and one child developed hemolytic-uremic syndrome. Shiga toxin 1- and 2-producing E. coli O111ac:NM was isolated from two children. IgG antibodies to E. coli O111 were detected in all three children. CONCLUSIONS To our knowledge this is the first reported cluster of O111 infection and only the second caused by non-O157 Shiga toxin-producing E. coli in North America.