Unusually high illness severity and short incubation periods in two foodborne outbreaks of Salmonella Heidelberg infections with potential coincident Staphylococcus aureus intoxication.

We describe the investigation of two temporally coincident illness clusters involving salmonella and Staphylococcus aureus in two states. Cases were defined as gastrointestinal illness following two meal events. Investigators interviewed ill persons. Stool, food and environmental samples underwent pathogen testing. Alabama: Eighty cases were identified. Median time from meal to illness was 5·8 h. Salmonella Heidelberg was identified from 27 of 28 stool specimens tested, and coagulase-positive S. aureus was isolated from three of 16 ill persons. Environmental investigation indicated that food handling deficiencies occurred. Colorado: Seven cases were identified. Median time from meal to illness was 4·5 h. Five persons were hospitalised, four of whom were admitted to the intensive care unit. Salmonella Heidelberg was identified in six of seven stool specimens and coagulase-positive S. aureus in three of six tested. No single food item was implicated in either outbreak. These two outbreaks were linked to infection with Salmonella Heidelberg, but additional factors, such as dual aetiology that included S. aureus or the dose of salmonella ingested may have contributed to the short incubation periods and high illness severity. The outbreaks underscore the importance of measures to prevent foodborne illness through appropriate washing, handling, preparation and storage of food.

Vibriosis, not cholera: toxigenic Vibrio cholerae non-O1, non-O139 infections in the United States, 1984-2014.

Toxigenic strains of Vibrio cholerae serogroups O1 and O139 have caused cholera epidemics, but other serogroups - such as O75 or O141 - can also produce cholera toxin and cause severe watery diarrhoea similar to cholera. We describe 31 years of surveillance for toxigenic non-O1, non-O139 infections in the United States and map these infections to the state where the exposure probably originated. While serogroups O75 and O141 are closely related pathogens, they differ in how and where they infect people. Oysters were the main vehicle for O75 infection. The vehicles for O141 infection include oysters, clams, and freshwater in lakes and rivers. The patients infected with serogroup O75 who had food traceback information available ate raw oysters from Florida. Patients infected with O141 ate oysters from Florida and clams from New Jersey, and those who only reported being exposed to freshwater were exposed in Arizona, Michigan, Missouri, and Texas. Improving the safety of oysters, specifically, should help prevent future illnesses from these toxigenic strains and similar pathogenic Vibrio species. Post-harvest processing of raw oysters, such as individual quick freezing, heat-cool pasteurization, and high hydrostatic pressurization, should be considered.

Outbreaks of non-O157 Shiga toxin-producing Escherichia coli infection: USA.

Non-O157 Shiga toxin-producing Escherichia coli (STEC) infections are increasingly detected, but sources are not well established. We summarize outbreaks to 2010 in the USA. Single-aetiology outbreaks were defined as ⩾2 epidemiologically linked culture-confirmed non-O157 STEC infections; multiple-aetiology outbreaks also had laboratory evidence of ⩾2 infections caused by another enteric pathogen. Twenty-six states reported 46 outbreaks with 1727 illnesses and 144 hospitalizations. Of 38 single-aetiology outbreaks, 66% were caused by STEC O111 (n = 14) or O26 (n = 11), and 84% were transmitted through food (n = 17) or person-to-person spread (n = 15); food vehicles included dairy products, produce, and meats; childcare centres were the most common setting for person-to-person spread. Of single-aetiology outbreaks, a greater percentage of persons infected by Shiga toxin 2-positive strains had haemolytic uraemic syndrome compared with persons infected by Shiga toxin 1-only positive strains (7% vs. 0·8%). Compared with single-aetiology outbreaks, multiple-aetiology outbreaks were more frequently transmitted through water or animal contact.

Cholera in the United States, 1995-2000: trends at the end of the twentieth century.

To evaluate recent trends in cholera in the United States, surveillance data from all cases of laboratory-confirmed toxigenic Vibrio cholerae O1 and O139 infection reported to the Centers for Disease Control and Prevention between 1995 and 2000 were reviewed. Sixty-one cases of cholera, all caused by V. cholerae O1, were reported. There was 1 death, and 35 (57%) of the patients were hospitalized. Thirty-seven (61%) infections were acquired outside the United States; 14 (23%) were acquired through undercooked seafood consumed in the United States, 2 (3%) were acquired through sliced cantaloupe contaminated by an asymptomatically infected food handler, and no source was identified for 8 (13%) infections. The proportion of travel-associated infections resistant to trimethoprim-sulfamethoxazole, sulfisoxazole, streptomycin, and furazolidone increased from 7 (8%) of 88 in 1990-1994 to 11 (31%) of 35 in 1995-2000. Foreign travel and undercooked seafood continue to account for most US cholera cases. Antimicrobial resistance has increased among V. cholerae O1 strains isolated from ill travelers.

Outbreaks of enterotoxigenic Escherichia coli infection in American adults: a clinical and epidemiologic profile.

Because enterotoxigenic Escherichia coli (ETEC) is not identified by routine stool culture methods, ETEC outbreaks may go unrecognized, and opportunities for treatment and prevention may be missed. To improve recognition of adult ETEC outbreaks, we compared them with reported outbreaks of viral gastroenteritis. During 1975-95, we identified 14 ETEC outbreaks in the United States and 7 on cruise ships, caused by 17 different serotypes and affecting 5683 persons. Median symptom prevalences were: diarrhoea 99%, abdominal cramps 82%, nausea 49%, fever 22%, vomiting 14%. The median incubation period was 42 h, and for 8 of 10 outbreaks, the mean or median duration of illness was > 72 h (range 24-264). For 17 (81%) ETEC outbreaks, but for only 2 (8%) viral outbreaks, the prevalence of diarrhoea was > or = 2.5 times the prevalence of vomiting. ETEC outbreaks may be differentiated from viral gastroenteritis outbreaks by a diarrhoea-to-vomiting prevalence ratio of > or = 2.5 and a longer duration of illness.

Clinical features of infections due to Escherichia coli producing heat-stable toxin during an outbreak in Wisconsin: a rarely suspected cause of diarrhea in the United States.

In September 1994, a foodborne outbreak of enterotoxigenic Escherichia coli (ETEC) infection occurred in attendees of a banquet in Milwaukee. E. coli was isolated from stool specimens from 13 patients that were comprehensively tested; isolates from five patients were positive for E. coli producing heat-stable toxin, were biochemically identified and serotyped as E. coli O153:H45, and were all resistant to tetracycline, ampicillin, sulfisoxazole, and streptomycin. Diarrhea (100%) and abdominal cramps (83%) were the most prevalent symptoms in 205 cases; vomiting (13%) and fever (19%) were less common. The median duration of diarrhea and abdominal cramps was 6 days and 5 days, respectively. In the United States, health care providers rarely consider ETEC as a possible cause of diarrhea in their patients, and few laboratories offer testing to identify ETEC. Hence, outbreaks of ETEC infection may be underdiagnosed and underreported. As in this outbreak, the relatively high prevalence of diarrhea and cramps lasting > or = 4 days and the low prevalence of vomiting and fever can help distinguish ETEC infection from Norwalk-like virus infection and gastroenteritis due to other causes with incubation times of > or = 15 hours and can provide direction for confirmatory laboratory testing.

Etiology of bloody diarrhea in Bolivian children: implications for empiric therapy. Bolivian Dysentery Study Group.

In Bolivia, few data are available to guide empiric therapy for bloody diarrhea. A study was conducted between December 1994 and April 1995 to identify organisms causing bloody diarrhea in Bolivian children. Rectal swabs from children <5 years old with bloody diarrhea were examined for Salmonella, Shigella, and Campylobacter organisms; fecal specimens were examined for Entamoeba histolytica. A bacterial pathogen was identified in specimens from 55 patients (41%). Shigella organisms were found in 39 specimens (29%); 37 isolates (95%) were resistant to ampicillin, 35 (90%) to trimethoprim-sulfamethoxazole, and 24 (62%) to chloramphenicol, but all were susceptible to nalidixic acid. Only 1 of 133 stool specimens contained E. histolytica trophozoites. Multidrug-resistant Shigella species are a frequent cause of bloody diarrhea in Bolivian children; E. histolytica is uncommon. Clinical predictors described in this study may help identify patients most likely to have Shigella infection. Laboratory surveillance is essential to monitor antimicrobial resistance and guide empiric treatment.

Molecular subtyping of toxigenic Vibrio cholerae O139 causing epidemic cholera in India and Bangladesh, 1992-1993.

Since October 1992, > 150,000 cases of cholera have been reported from India and Bangladesh; the great majority of Vibrio cholerae isolates belong to the newly established serogroup O139. To better understand the interaction of genetic and epidemiologic factors responsible for their sudden appearance and rapid spread, representative toxigenic V. cholerae O139 isolates were molecularly characterized and compared with a set of toxigenic V. cholerae O1 and non-O1/non-O139 strains. DNA sequences of the cholera toxin B subunit gene and multilocus enzyme electrophoresis markers of V. cholerae O139 strains were identical to those of V. cholerae O1 isolates of the seventh pandemic. Two distinct ribotypes and four pulsed-field gel electrophoretic patterns were observed for O139 strains. V. cholerae O139 strains were very similar to V. cholerae O1 strains of the seventh pandemic but clearly different from the toxigenic V. cholerae strains of serogroups other than O1 and O139.

Molecular subtyping of Salmonella enteritidis phage type 8 strains from the United States.

Salmonella enteritidis is now the most common serotype of the genus Salmonella reported in the United States. Bacteriophage typing has been helpful for subdividing S. enteritidis strains from different sources in the United States. Most S. enteritidis outbreaks reported were egg related, and the majority of them were caused by strains of phage type 8. To determine whether restriction fragment length polymorphism of the rRNA genes (ribotyping) and of the genomic DNAs from two lysogenic phages from S. enteritidis could be used to discriminate between S. enteritidis phage type 8 strains, we conducted Southern hybridization studies on 24 isolates from different outbreaks and six non-outbreak-associated strains using DNA probes for 16S and 23S rRNA genes and S. enteritidis typing phages 1 and 2 from the Ward typing system (L. R. Ward, J. D. H. de Sa, and B. Rowe, Epidemiol. Infect. 99:291-294, 1987). Of seven restriction endonucleases screened with the probe for rRNA genes, AccI provided the best discrimination between strains; six distinct patterns were observed. AccI ribosomal DNA patterns 1 to 6 were detected among 76.7, 3.3, 6.7, 3.3, 3.3, and 6.7% of isolates tested, respectively. Strains of AccI ribosomal DNA pattern 3 could be further subdivided into two additional patterns by using SmaI. Epidemiologically related strains had identical patterns. No discrimination between strains was achieved by probes for phages 1 and 2. No sequences homologous to the phage I probe were detected among phage type 8 strains, and all strains tested with six restriction enzymes had the same hybridization pattern with the phage 2 probe. These findings demonstrate that ribotyping with AccI and SmaI provides an additional means of discriminating between some phage type 8 strains; however, ribotyping and the phage 2 hybridization results from egg-related outbreak strains support previous findings that these strains are closely related.

The molecular epidemiology of cholera in Latin America.

To explain the sudden appearance and rapid spread of cholera in Latin America in January 1991, molecular techniques were used to define Vibrio cholerae O1 isolates from around the world. Restriction fragment length polymorphisms of rRNA and ctxA genes, DNA sequence of cholera toxin B subunit gene ctxB, and multilocus enzyme electrophoresis data were used to characterize 197 isolates. Worldwide, there are at least four distinct toxigenic El Tor V. cholerae O1 clones: the seventh pandemic (Eastern Hemisphere), US Gulf Coast, Australian, and Latin American. Nontoxigenic V. cholerae O1 previously isolated in Brazil, Mexico, and Peru are unlike current toxigenic isolates. The Latin American clone probably represents an extension of the seventh pandemic into the Western Hemisphere, while the US Gulf Coast clone most likely evolved separately. These data will be useful in monitoring the spread of cholera, determining the origin of outbreaks in both hemispheres, and implicating specific vehicles of transmission.

An outbreak of shigellosis aboard a cruise ship caused by a multiple-antibiotic-resistant strain of Shigella flexneri.

From October 23 to October 27, 1989, an outbreak of gastroenteritis occurred aboard a cruise ship in the Caribbean. The 818 passengers and 518 crew members were surveyed for gastrointestinal symptoms; 72 (14%) of 512 passengers and 12 (3%) of 388 crew members who answered the survey reported having a diarrheal illness. Multiple-antibiotic-resistant Shigella flexneri 4a was isolated from 19 ill passengers and two ill crew members. Thirteen people were hospitalized, and prolonged duration of illness was associated with taking an antibiotic to which the isolated strain of Shigella was resistant. A case-control study of food items implicated German potato salad as the vehicle of transmission. It was prepared and probably infected by a food handler from a country where multiple-antibiotic-resistant Shigella is common. Spread may have been facilitated by the limited availability of toilet facilities for the galley crew. This outbreak demonstrates how antibiotic-resistant strains can be introduced into the United States, where they can pose treatment problems. The continuing problem of foodborne gastrointestinal disease in settings such as cruise ships underscores the need for basic hygienic control for food handlers and food preparation areas. In addition, the availability of adequate working conditions for crew members, including appropriately furnished toilet facilities, may be important issues that must be addressed in order to decrease the frequency of diarrhea outbreaks aboard cruise ships.

The use of plasmid profiles and nucleic acid probes in epidemiologic investigations of foodborne, diarrheal diseases.

The application of nucleic acid analyses to investigations of infectious disease outbreaks has resulted in useful molecular strain markers that distinguish the epidemic clone of a particular pathogen and help identify specific vehicles of infection. We have successfully used plasmid profile analysis, restriction endonuclease digestion of plasmid and whole-cell DNAs, and nucleic acid hybridization to investigate recent outbreaks of foodborne diarrheal illness. Plasmid analysis has been important in identifying epidemic strains of Salmonella enteritidis and Escherichia coli O157:H7. In a culture survey of S. enteritidis isolates from humans and a variety of animals, including chickens and chicken eggs, we identified 16 distinct plasmid profiles and used these to differentiate strains, especially within commonly occurring phage types (Colindale 8 and 13a). HindIII digests of plasmid DNA were useful in distinguishing plasmids of similar mass but dissimilar enzyme target sequences; they clearly distinguished S. enteritidis strains causing systemic infections in children in parts of Africa from U.S. isolates. Investigations of outbreaks of hemorrhagic colitis have also been assisted by plasmid analysis. Restriction endonuclease digests of whole-cell DNA and Southern blot analysis, hybridizing with E. coli 16S and 23S rRNA (ribotyping), have been effective subtyping techniques, especially for plasmidless isolates of Campylobacter jejuni. In five outbreaks of C. jejuni infections, ribotyping of PvuII and ClaI digests distinguished individual epidemic strains within one commonly occurring C. jejuni serotype (Penner 2, Lior 4). Preliminary data show that ribotyping of NcoI digests can also distinguish individual epidemic strains of E. coli O157:H7 and may provide a more stable marker than plasmid profiles. Specific DNA probes derived from cloned virulence genes of E. coli have been invaluable in epidemic investigations and surveys. Using colony hybridization, we found in one survey of stool specimens from 174 dairy cattle that 11% of animals were asymptomatically carrying Shiga-like toxigenic E. coli other than O157:H7. We also found that newly synthesized oligonucleotide probes for the Shiga-like toxins I and II agreed 100% with cloned gene probes in a study of 613 E. coli strains. Future studies of these organisms will include the use of additional synthetic oligonucleotides as primers to amplify the toxin genes directly in patient and animal specimens by the polymerase chain reaction. There is a continuing and expanding role for molecular approaches in epidemiological investigations. The DNA methods described above are not based on the often complex expression of phenotypic characteristics, and, unlike sensitive and specific techniques such as phage typing, a single method can be used to study a variety of Gram-positive and negative bacterial pathogens.

A comparison of alkaline phosphatase and radiolabelled gene probes with bioassays for enterotoxigenic Escherichia coli.

Alkaline phosphatase-conjugated oligonucleotide probes (APO), 32P-labelled oligonucleotide (RO) and cloned polynucleotide (RP) probes were evaluated for their ability to detect enterotoxigenic Escherichia coli (ETEC) as defined by bioassay. These three sets of probes were applied to 301 E. coli strains that had previously been defined by the Y1 adrenal cell assay for heat-labile enterotoxin (LT) and the infant mouse assay for heat-stable enterotoxin (ST). The correlation of the APO probe for LT with the bioassay was 98% with five discrepancies and a positive predictive value (PPV) of 100%. For the APO/ST probe the correlation with the bioassay was 98% with seven discrepancies and a PPV of 96%. The correlation of the RO probe for LT was 99% with four discrepancies and a PPV of 100%, while the overall correlation for the two RO/ST probes was 97% with eight discrepancies and a PPV of 97%. For the RP probes, the correlation for LT was 99% with four discrepancies and a PPV of 100% and for ST was 98% with seven discrepancies and a PPV of 98%. These findings suggest that the APO probes were as sensitive as the RO and RP probes in detecting ETEC by colony hybridization and could be a practical alternative to bioassays and radiolabelled probes for ETEC since they do not require expensive equipment or extensive technical training.

Serotype, antimicrobial resistance, and adherence properties of Escherichia coli strains associated with outbreaks of diarrheal illness in children in the United States.

Since most recorded outbreaks of diarrhea in U.S. infants attributed to Escherichia coli occurred before currently available pathogenicity assays existed, we examined the characteristics of nonenterotoxigenic E. coli strains isolated from 50 outbreaks of diarrheal disease in U.S. infants between 1934 and 1987. We assayed the strains for enteropathogenic E. coli (EPEC) serotype, localized adherence (LA) and diffuse adherence to tissue cultures, the presence of EPEC adherence factor genes, Shiga-like (Vero) toxin production, and antimicrobial resistance. EPEC serotypes were identified in 28 outbreaks (56%). LA to HeLa cells was found in 23 outbreak strains and correlated 100% with the EPEC adherence factor probe. LA was observed in 21 of 28 EPEC and 2 of 22 non-EPEC strains; however, 5 of 23 strains that were LA positive for HeLa cells did not adhere to HEp-2 or HL cells. One strain was diffuse adherence positive, and none was Shiga-like toxin positive. Multiple resistance was common in EPEC (64%), LA-positive (74%), and LA-positive EPEC (76%) strains but not in others (10%). EPEC serotypes or LA was found in 60% (n = 30) of the outbreak strains. The remaining E. coli strains may represent nonpathogenic normal flora, as-yet-undefined pathogens, or pathogens that have lost virulence-associated traits during storage or subculturing.

Chronic diarrhea associated with drinking untreated water.

PURPOSE: To determine the cause of an outbreak of chronic diarrhea and to define the clinical profile of the illness. DESIGN: A case series of patients with chronic diarrhea and case-control and cohort studies to determine the vehicle and cause of the illness. SETTING: Rural Henderson County, Illinois. PATIENTS: Seventy-two patients who had onset of chronic diarrheal illness between May and August 1987. Controls were local residents and eating companions who did not have diarrheal illness. A cohort study included 80 truck drivers from a local firm. METHODS AND MEASUREMENTS: Nonbloody diarrhea was characterized by extreme frequency (median, 12 stools/d), marked urgency, fecal incontinence, and weight loss (mean, 4.5 kg). The median incubation period was 10 days. Nine patients were hospitalized; none died. Diarrhea persisted in 87% of patients after 6 months. Antimicrobial therapy produced no clinical improvement. No bacterial, mycobacterial, viral, or parasitic agents known to be enteropathogenic were detected in stools or implicated water. Three of five small-bowel biopsies showed mild inflammatory changes. Mild inflammation was also seen in two of nine colonic biopsies. Case-control studies implicated a local restaurant (P = 0.0001, odds ratio = 19) and subsequently the untreated well water served in the restaurant (P = 0.04, odds ratio = 9.3) as the vehicle of transmission. CONCLUSIONS: This is the first outbreak of chronic diarrhea linked to drinking untreated water. The causative agent and pathophysiologic mechanism of the illness remain elusive.

Heat-stable-enterotoxin-producing Escherichia coli strains isolated from dogs.

Five strains of hemolytic Escherichia coli isolated from dogs suffering from diarrhea were shown by radioactive and enzyme-labeled oligonucleotide probes to possess genes coding for heat-stable enterotoxin (STIa). Four of the strains were shown by immunoassay (enzyme-linked immunosorbent assay) and bioassay (infant mouse test) to produce STI in vitro. All five strains, however, were able to induce fluid accumulation in ligated dog intestinal loops. The four STI-producing strains all possessed the K99 fimbrial antigen (F5) and belonged to serotype O42:H37. In these strains, genes encoding STI were located on a 98-megadalton plasmid. In the fifth strain, which produced STI in vitro only after several subcultivations, the STI gene was located on an 80-megadalton plasmid. This strain was nontypable.

Unusual verotoxin-producing Escherichia coli associated with hemorrhagic colitis.

All strains of Escherichia coli isolated from cases of hemorrhagic colitis and sent to the Centers for Disease Control, Atlanta, Ga., over a 3-year period were assayed for toxicity in Vero cell cultures. Strains that produced moderate or high levels of verotoxin were characterized by serotype, biotype, antimicrobial resistance, plasmid profile, and adherence to HeLa cells. Over 200 isolates were typical O157:H7 strains. Six isolates were atypical O157:H7 strains; two were resistant to antimicrobial agents; one was indole negative, two were citrate positive, and one was urea positive. Six isolates were nonmotile O157 strains. All of these isolates were similar to typical O157:H7 strains by plasmid profile and negative or slow sorbitol fermentation. Eleven other verotoxigenic isolates did not possess the O157 antigen, had a variety of plasmid profiles, and were sorbitol positive. Two of the eleven were enteropathogenic serotypes (O111:NM and O26:H11), yet none were adherent to HeLa cells. We conclude that verotoxigenic E. coli associated with hemorrhagic colitis includes atypical O157 strains and other serotypes. Hence, investigators should use current screening methods with caution.

Hemolytic-uremic syndrome--an outbreak in Sacramento, California.

Between July and November 1982, 14 cases of the hemolytic-uremic syndrome occurred in the Sacramento, California, metropolitan area; 9 of the 14 patients lived within a 7.5-mile radius in northeast Sacramento, 10 were female, 12 were white non-Hispanic and 13 were children with a mean age of 3.6 years. Of the 14 patients, 13 were admitted to hospital; 7 required peritoneal dialysis. The 14th child, a 3-month-old white female infant, was found dead in her crib and had renal histopathologic findings consistent with the hemolytic-uremic syndrome. Of the 13 nonfatal cases, 12 patients had diarrhea before being admitted to hospital. A case-control study involving 11 cases and 22 controls did not show any significant differences in exposure to a variety of possible risk factors including restaurants, specific foods and water supply. Stool specimens were negative for enteric bacterial pathogens by culture and for viruses by tissue culture assay, suckling mouse inoculation and immune electron microscopy; no serologic evidence was found for infection due to enteroviruses, respiratory viruses or arenaviruses. Two of four children tested, however, showed serologic evidence of infection by Vero-cytotoxin-producing Escherichia coli. These 14 cases represent one of the largest reported outbreaks of the hemolytic-uremic syndrome in the United States.

In vitro antimicrobial susceptibility, plasmid analysis, and serotyping of epidemic-associated Campylobacter jejuni.

Campylobacter jejuni strains from 11 outbreaks were characterized by antimicrobial susceptibility, plasmid profile, and serotyping by the methods of Lior et al. and Penner and Hennessy. All 31 strains were susceptible to erythromycin, clindamycin, chloramphenicol, kanamycin, tobramycin, streptomycin, and gentamicin. A total of 21 strains from nine outbreaks were resistant to one or more of the following antimicrobial agents: tetracycline, metronidazole, ampicillin, or carbenicillin. Of the 31 strains, 19 possessed plasmid DNA; 4 of the strains containing plasmids were sensitive to all antimicrobial agents tested. All of the strains that were resistant to tetracycline contained a 38-megadalton plasmid, and these plasmids shared common nucleic acid sequences. No other antimicrobial resistance was associated with the presence of plasmid DNA. Eight outbreaks appeared to have been caused by a single serotype, whereas in three outbreaks multiple serotypes were found. In two of the three outbreaks with multiple serotypes, plasmid profiles were also indicative of multiple strains of C. jejuni. Antimicrobial susceptibility and plasmid profile are potentially useful epidemiological markers for C. jejuni and may be used to supplement serotyping.