Virulence of Salmonella enterica serotype Enteritidis aflagellate and afimbriate mutants in a day-old chick model.
(17/802)
Certain fimbriae and the flagellae of Salmonella enterica serovar Typhimurium have been shown to contribute to attachment and invasion of gut epithelium in the murine typhoid infection model and to contribute to pathogenesis in the chick. However, little is known of the role these organelles play in Enteritidis poultry infections and, to study this, day-old chicks were dosed orally in separate experiments with defined multiply afimbriate and/or aflagellate mutant strains of Enteritidis. The colonization and invasion characteristics of each mutant were compared with those of the isogenic wild type strain by the determination of the number of bacteria recovered from livers and spleens at known time points post infection. Compared with wild type Enteritidis, a mutant unable to express flagella but retaining the genetic potential to express fimbriae was recovered post mortem from livers and spleens in significantly reduced numbers compared to the isogenic wild-type at all time points post infection (P < 0.001). Conversely, a flagellate but multiply afimbriate mutant (defective for the elaboration of five different fimbrial types) and a flagellate but non-motile 'paralysed' mutant were recovered from livers and spleens in similar numbers to the wild-type. The data suggested that Enteritidis flagella, but not fimbriae, played an important role in pathogenesis in the chick model and that the flagellar apparatus itself and not motility per se contributed significantly to this role. (+info)
Efficacy of electrolyzed oxidizing water for inactivating Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes.
(18/802)
The efficacy of electrolyzed oxidizing water for inactivating Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes was evaluated. A five-strain mixture of E. coli O157:H7, S. enteritidis, or L. monocytogenes of approximately 10(8) CFU/ml was inoculated in 9 ml of electrolyzed oxidizing water (treatment) or 9 ml of sterile, deionized water (control) and incubated at 4 or 23 degrees C for 0, 5, 10, and 15 min; at 35 degrees C for 0, 2, 4, and 6 min; or at 45 degrees C for 0, 1, 3, and 5 min. The surviving population of each pathogen at each sampling time was determined on tryptic soy agar. At 4 or 23 degrees C, an exposure time of 5 min reduced the populations of all three pathogens in the treatment samples by approximately 7 log CFU/ml, with complete inactivation by 10 min of exposure. A reduction of >/=7 log CFU/ml in the levels of the three pathogens occurred in the treatment samples incubated for 1 min at 45 degrees C or for 2 min at 35 degrees C. The bacterial counts of all three pathogens in control samples remained the same throughout the incubation at all four temperatures. Results indicate that electrolyzed oxidizing water may be a useful disinfectant, but appropriate applications need to be validated. (+info)
Oral administration of lipopolysaccharide exacerbates collagen-induced arthritis in mice.
(19/802)
We investigated whether oral administration of LPS exacerbated collagen-induced arthritis (CIA) in mice, which was an experimental model of autoimmune disease. CIA was induced by s.c. injection of type II collagen emulsified with CFA into the base of the tail (day 0) followed by a booster injection on day 21. To examine the ability of LPS to exacerbate CIA, varying doses of LPS were orally administered on day 50. The results showed that administration of LPS was followed by reactivation of CIA in a dose-related fashion. Histologically, on day 55 there were marked edema of synovium proliferated by day 50, new formation of fibrin, and intense infiltration of neutrophils accompanied with a large number of mononuclear cells. Severe destruction of cartilage and subchondral bone was also observed on day 70. The reactivation of CIA by oral administration of LPS was associated with increase in anti-type II collagen IgG and IgG2a Abs as well as varying kinds of cytokines including IL-12, IFN-gamma, IL-1beta, and TNF-alpha. Polymyxin B sulfate given either orally or i.v. suppressed the recurrence of CIA. Increased amounts of LPS were found in sera of mice given the endotoxin orally. LPS from Salmonella enteritidis, Salmonella typhimurium, and Klebsiella pneumoniae and its component, lipid A from Escherichia coli, also reactivated the disease. These findings suggest that LPS from intestinal bacteria may play a role in the exacerbation of autoimmune joint inflammation. (+info)
An increase in sporadic and outbreak-associated Salmonella enteritidis infections in Wisconsin: the role of eggs.
(20/802)
In Wisconsin, reported Salmonella enterica serotype enteritidis (SE) infections during 1997 more than doubled compared with the previous 9 years. A case-control study was conducted to determine risk factors for sporadic infections, and results of outbreak investigations were reviewed. Eating raw eggs (matched odds ratio [MOR]=14.5; 95% confidence interval [CI], 1.7-591.6), eating raw or undercooked eggs (MOR=5.8; 95% CI, 1.3-28.0), eating any eggs (MOR=4.2; 95% CI, 1.2-16.2), and dining at a restaurant (MOR=4.7; 95% CI, 1.4-18.4) were associated with infection in the case-control study. For 3 of the 8 outbreaks, a probable source was identified, in each instance, foods containing eggs. Human infections decreased after eggs were diverted from implicated flocks. This epidemic demonstrates the continuing need for quality assurance on egg farms and enhanced education of consumers and commercial food preparers regarding safe handling of eggs. (+info)
Growth of Salmonella typhimurium and Salmonella enteritidis in egg yolks from highly immunized hens.
(21/802)
This experiment was conducted to ascertain whether the growth of Salmonella Enteritidis (SE) or Salmonella Typhimurium (ST) would be suppressed in the presence of antibodies contained in egg yolks. Specific pathogen-free chickens (102 days of age) were subcutaneously immunized with oil-adjuvanted bacterin of SE or ST, twice within a four-week interval. During 160 to 170 days of age, eggs were collected, the yolks were removed and mixed with an equal volume of physiological buffered saline, inoculated with ten colony forming units (CFU) of SE or ST, and incubated at 37 degrees C or 20 degrees C for 23 hr. The growth of organisms in each yolk solution was examined. The egg yolk derived from non-immunized hens was examined in the same manner as the controls. There was no difference in the growth titer between the antibody-positive yolk and the negative yolk. The result suggests that the antibodies in the yolk do not influence the growth of each organism, even if the hens are highly immunized. (+info)
An international outbreak of Salmonella enteritidis associated with lasagne; lessons on the need for cross-national co-operation in investigating food-borne outbreaks.
(22/802)
We investigated an outbreak of Salmonella enteritidis involving at least 19 British tourists returning from one hotel in another European country. A retrospective cohort study of 47 hotel guests identified lasagne as the most likely vehicle of transmission (RR 11.5; 95% CI 3.0-44.1; P < 0.0001). However, difficulties in information exchange and lack of formal mechanisms to agree on the aims of the cross-national investigation hampered efficient management of the outbreak. The factors leading to contamination of the food vehicle were not identified and therefore specific action to prevent reoccurrence could not be taken. There is need to develop protocols for cross-national investigations of outbreaks in Europe which should include specifying objectives, roles and responsibilities of investigators and control agencies, with formal reporting of the outcome of the investigation. (+info)
Muscle infections caused by Salmonella species: case report and review.
(23/802)
We describe a patient with salmonella pyomyositis and review 30 other cases reported during the past 4 decades. Men outnumbered women by 2.9 to 1, and the median age of the patients was 51 years. Approximately one-half the cases were caused by Salmonella enteritidis. Infected vascular aneurysms were observed in seven patients. Prior salmonella infections and local trauma or lesions were common. Diverse underlying conditions, mainly diabetes and human immunodeficiency virus infection, were present in 81% of the patients, and the psoas muscle was involved in 55% of the cases. One-third of the patients died, and relapses were common after a median time of 5 weeks (range, 4.5-27 weeks) in those who survived. Most patients had anemia, and pathogens were recovered from blood samples from two-thirds of the patients. Salmonella should be considered as a causative agent of muscle infections in the appropriate clinical setting, particularly in patients with underlying diseases or preexisting vascular aneurysms. (+info)
Analysis of virulence of clinical isolates of Salmonella enteritidis in vivo and in vitro.
(24/802)
Salmonella enterica serotype Enteritidis (S. enteritidis) is a major food-borne pathogen, and its incidence among all Salmonella serotypes has increased dramatically in the last two decades. To study the virulence characteristics of clinical isolates of S. enteritidis, we determined the 50% lethal doses (LD(50)) in mice of isolates of two major phage types (4 and 8). Isolates of both phage types showed a wide range of LD(50) after oral inoculation, varying from under 10(2) organisms to over 10(8) organisms. No significant difference in LD(50) was observed between the phage types. These observations indicated that clinical isolates of S. enteritidis are highly heterogeneous in their ability to cause death in mice. We compared the LD(50)s of these isolates to the results observed from in vitro pathogenicity assays. We also analyzed these isolates for recognized Salmonella virulence loci (spv, sodCI, sopE, and sef). The in vitro phenotypes of the isolates showed no obvious correlation with their LD(50) in any given assay, and the virulence genes tested were present in all isolates. However, the isolate with the lowest LD(50) (isolate 97A 2472) was resistant to acidified sodium nitrite (ASN). Moreover, the most acid-susceptible, macrophage-susceptible, and ASN-susceptible isolates were attenuated for virulence in mice. These results, based on extensive analysis of clinical isolates of S. enteritidis, demonstrate the complex nature of Salmonella pathogenesis in mice. Our results also indicate the limitation of in vitro assays in predicting in vivo virulence. (+info)