SALMONELLOSIS IN THE UNITED STATES RESULTS OF NATIONWIDE SURVEILLANCE

Outbreak ofSalmonella javianaInfection at a Children's Hospital

Objective.

To determine the source of an outbreak of Salmonella javiana infection.

Design.

Case-control study.

Participants.

A total of 101 culture-confirmed cases and 540 epidemiologically linked cases were detected between May 26, 2003, and June 16, 2003, in hospital employees, patients, and visitors. Asymptomatic employees who had eaten in the hospital cafeteria between May 30 and June 4, 2003, and had had no gastroenteritis symptoms after May 1, 2003, were chosen as control subjects.

Setting.

A 235-bed academic tertiary care children's hospital.

Results.

Isolates from 100 of 101 culture-confirmed cases had identical pulsed-field gel electrophoresis patterns. A foodhandler with symptoms of gastroenteritis was the presumed index subject. In multivariate analysis, case subjects were more likely than control subjects to have consumed items from the salad bar (adjusted odds ratio [aOR], 5.3; 95% confidence interval [CI], 2.3-12.1) and to have eaten in the cafeteria on May 28 (aOR, 9.4; 95% CI, 1.8-49.5), May 30 (aOR, 3.6; 95% CI, 1.0-12.7), and/or June 3 (aOR, 4.0; 95% CI, 1.4-11.3).

Conclusions.

Foodhandlers who worked while they had symptoms of gastroenteritis likely contributed to the propagation of the outbreak. This large outbreak was rapidly controlled through the use of an incident command center.

Diarrhea and colitis in mice require the Salmonella pathogenicity island 2-encoded secretion function but not SifA or Spv effectors

We investigated the roles of Salmonella pathogenicity island 2 (SPI-2) and two SPI-2 effectors in Salmonella colitis and diarrhea in genetically resistant BALB/c.D2(Slc11a1) congenic mice with the wild-type Nramp1 locus. Wild-type Salmonella enterica serovar Typhimurium 14028s caused a pan-colitis, and the infected mice developed frank diarrhea with a doubling of the fecal water content. An ssaV mutant caused only a 26% increase in fecal water content, without producing the pathological changes of colitis, and it did not cause weight loss over a 1-week period of observation. However, two SPI-2 effector mutants, the spvB and sifA mutants, and a double spvB sifA mutant caused diarrhea and colitis, even though the sifA mutant was sensitive to killing by bone marrow-derived macrophages from BALB/c.D2 mice and was severely impaired in extraintestinal growth but not in growth in the cecum. These results demonstrate that systemic S. enterica infection and diarrhea/colitis are distinct pathogenic processes and that only the former requires spvB and sifA.

The crucial role of polymorphonuclear leukocytes in resistance to Salmonella dublin infections in genetically susceptible and resistant mice

Macrophages are considered to be the mediators of resistance to extra-intestinal Salmonella infections. Nevertheless, the initial cellular response to Salmonella infections consists primarily of polymorphonuclear leukocytes (PMN). To determine whether PMN serve an important function for the infected host, we made mice neutropenic with the rat mAb to RB6-8C5 and infected them i.v. with approximately 10(3) Salmonella dublin or an isogenic derivative that lacks the virulence plasmid (LD842). We infected BALB/c mice, which have a point mutation in the macrophage-expressed gene Nramp1 that makes them susceptible to Salmonella, and BALB/c.D2 congenic mice, which have the wild-type Nramp1 gene that makes them resistant to Salmonella. Both mouse strains were resistant to LD842, and neutropenia made only the BALB/c strain susceptible to this infection. Neutropenic congenic mice, however, were susceptible only to wild-type S. dublin (plasmid+). These results show a complex interplay between plasmid-virulence genes in Salmonella, host macrophages, and PMN. Mice with normal macrophages need PMN to defend against nontyphoid Salmonella that carry a virulence plasmid but not against Salmonella without virulence plasmids. Mice with a mutant Nramp1 gene need PMN to defend against all Salmonella, even those that lack virulence plasmids. These results, plus the evidence that PMN kill Salmonella efficiently in vitro, suggest that Salmonella have adapted to grow inside macrophages where they are relatively sheltered from PMN. The adaptations that allow Salmonella to survive in macrophages do not protect them from PMN.

Frequency of Salmonella typhimurium the year after a massive outbreak

In 1985, Illinois experienced a large milkborne outbreak of Salmonella typhimurium with over 16,000 cases. During this year, 49.4% of United States and 86.4% of Illinois salmonellae were S. typhimurium. In 1986, 1133 microbiologically confirmed and serotyped cases of salmonellosis were reported in the City of Chicago, comprising 37% of the 3034 cases reported for the State of Illinois. The most frequent serotypes were S. typhimurium (21.3%), Salmonella heidelberg (18.2%), Salmonella enteritidis (10.7%), and Salmonella braenderup (7.7%), similar to the state as a whole. Nationally, excluding Illinois, the most frequent serotypes in 1986 were S. typhimurium (26.1%), S. enteritidis (14.7%), and S. heidelberg (13.0%). S. braenderup comprised 0.9% of the non-Illinois total. Regional variations in the epidemiology of salmonellae are probable and may reflect detected or undetected outbreaks. Within a year of the nation's largest Salmonella outbreak, there was no trace of any effect on the frequency of isolation of Salmonella spp.

Salmonella heidelberg enteritis and bacteremia. An epidemic on two pediatric wards

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.

Salmonella javiana infection in an infant associated with a marsupial, the quokka, Setonix brachyurus, in Western Australia

Salmonella javiana, a serotype rarely isolated in Australia, has been recovered from the faeces of a 14-month-old infant with symptoms of enteritis.The child had been closely associated with a marsupial species, the quokka, during a vacation on Rottnest Island in Western Australia, and S. javiana was isolated from faecal pellets from adult quokkas, and also from a snake collected on the island.Sampling revealed a high incidence of Salmonella infection in the quokkas. In all, 62 out of 87 animals (71%) were found to be infected, and 17 Salmonella and 3 Arizona serotypes were identified from 100 isolations comprising 92 salmonellas and 8 arizonas. Multiple infections were frequently detected and up to four serotypes were recovered from individual animals. S. javiana was isolated from four quokkas.A close parallel was observed between the serotypes isolated from quokkas and sea-gulls on the island, and abattoir effluents, lake waters, bird droppings and reptiles sampled on the adjacent mainland.The epidemiological significance of Salmonella and Arizona infections in the quokka population and their possible association with the seasonal decline in condition and numbers of animals on Rottnest Island is discussed.