Outbreak and sporadic egg-associated cases of Salmonella enteritidis: New York's experience

Recent trends in the epidemiology of non-typhoidal Salmonella in Israel, 1999-2009

The aim of the present study was to assess the recent trends in the epidemiology of non-typhoid Salmonella in Israel using a sentinel laboratory-based surveillance network. Between 1999 and 2009, 8758 Salmonella stool isolates were reported by five sentinel laboratories. There was a significant decrease in the incidence rate of Salmonella isolates from 70·5/100,000 in 1999 to 21·6/100,000 in 2005 followed by a slight increase to 30·3/100,000 in 2009. Of all Salmonella, 64·3% were isolated from children in the 0-4 years age group. Up to 2008, S. Enteritidis was the most prevalent serotype and in 2009 S. Infantis emerged as the most common Salmonella serotype. The decrease in the incidence of S. Enteritidis and S. Typhimurium and increase in S. Infantis among humans were associated with a similar trend among breeding flocks, which followed significant preventive interventions conducted against S. Enteritidis and S. Typhimurium infections in poultry. Tight surveillance and education of food handlers and consumers should be enhanced to reduce the foodborne transmission of Salmonella in Israel.

Efficacy of several vaccination programmes in commercial layer and broiler breeder hens against experimental challenge with Salmonella enterica serovar Enteritidis

Two experiments were performed to evaluate the protective effect of various vaccination combinations given at 5 and 9 weeks of age against experimental challenge with Salmonella enterica serovar Enteritidis (SE) phage type 4 at 12 weeks of age. In Experiment 1, groups of commercial layers were vaccinated by one of the following programmes: Group 1, two doses of a SE bacterin (Layermune SE); Group 2, one dose of a live Salmonella enterica serovar Gallinarum vaccine (Cevac SG9R) followed by one dose of the SE bacterin; Group 3, one dose of each of two different multivalent inactivated vaccines containing SE cells (Corymune 4K and Corymune 7K; and Group 4, unvaccinated, challenged controls. In Experiment 2, groups of broiler breeders were vaccinated by the same programmes as Groups 1 and 2 above while Group 3 was an unvaccinated, challenged control group. All vaccination programmes and the challenge induced significant (P < 0.05) seroconversion as measured by enzyme-linked immunosorbent assay. Overall, in both experiments, all vaccination schemes were significantly effective in reducing organ (spleen, liver and caeca) colonization by the challenge strain as well as reducing faecal excretion for at least 3 weeks. Vaccinated layers in Groups 1 and 2 and broiler breeders in Group 2 showed the greatest reduction in organ colonization and the least faecal excretion. In Experiment 1, layers vaccinated with multivalent inactivated vaccines containing a SE component (Group 3) were only moderately protected, indicating that such a vaccination programme may be useful in farms with good husbandry and housing conditions and low environmental infectious pressure by Salmonella.

[Risk factors for the occurrence of sporadic Campylobacter, Salmonella and rotavirus diarrhea in preschool children]

BACKGROUND

Sporadic cases of diarrhea in preschool children are highly frequent, especially those caused by rotavirus, Campylobacter and Salmonella. The aim of this study was to identify some of the factors associated with these processes.

MATERIAL AND METHODS

A case-control study of hospitalized incident cases aged less than 3 years old was performed. Questionnaires were administered at admission, before the results of stool tests were known. Susceptibility, food exposure, and environmental factors were investigated. Infants aged less than 1 year were analyzed separately.

RESULTS

A total of 117 patients (rotavirus in 31, Campylobacter in 228 and Salmonella in 21, negative results in 37) and 84 controls were studied. Several protective factors, such as breast feeding and prior antibiotic use, were identified. Risk factors for diarrhea were exposure to meat products (eating or environmental exposure in the kitchen), some kinds of pets, and attendance at day care. Differences were found by etiology and age. In the culture-negative group, no risk factors were identified.

CONCLUSION

The problems posed by epidemiological study of this issue are discussed. The main findings in each group of cases are interpreted and proposals are made for their application in the control and prevention of these diseases.

Re-assessment of risk factors for sporadic Salmonella serotype Enteritidis infections: a case-control study in five FoodNet Sites, 2002-2003

Active surveillance for laboratory-confirmed Salmonella serotype Enteritidis (SE) infection revealed a decline in incidence in the 1990s, followed by an increase starting in 2000. We sought to determine if the fluctuation in SE incidence could be explained by changes in foodborne sources of infection. We conducted a population-based case-control study of sporadic SE infection in five of the Foodborne Diseases Active Surveillance Network (FoodNet) sites during a 12-month period in 2002-2003. A total of 218 cases and 742 controls were enrolled. Sixty-seven (31%) of the 218 case-patients and six (1%) of the 742 controls reported travel outside the United States during the 5 days before the case's illness onset (OR 53, 95% CI 23-125). Eighty-one percent of cases with SE phage type 4 travelled internationally. Among persons who did not travel internationally, eating chicken prepared outside the home and undercooked eggs inside the home were associated with SE infections. Contact with birds and reptiles was also associated with SE infections. This study supports the findings of previous case-control studies and identifies risk factors associated with specific phage types and molecular subtypes.

Reducing the Carriage of Foodborne Pathogens in Livestock and Poultry

Several foodborne pathogens, including Salmonella species and campylobacters, are common contaminants in poultry and livestock. Typically, these pathogens are carried in the animal's intestinal tract asymptomatically; however, they can be shed in feces in large populations and be transmitted by other vectors from feces to animals, produce, or humans. A wide array of interventions has been developed to reduce the carriage of foodborne pathogens in poultry and livestock, including genetic selection of animals resistant to colonization, treatments to prevent vertical transmission of enteric pathogens, sanitation practices to prevent contamination on the farm and during transportation, elimination of pathogens from feed and water, feed and water additives that create an adverse environment for colonization by the pathogen, and biological treatments that directly or indirectly inactivate the pathogen within the host. To successfully reduce the carriage of foodborne pathogens, it is likely that a combination of intervention strategies will be required.

Emergence of Salmonella enteritidis phage type 4 in the Caribbean: case-control study in Trinidad and Tobago, West Indies

A prospective case-control study involving 46 case patients and 92 age- and neighborhood-matched control subjects was conducted in Trinidad and Tobago (T&T) between March 1998 and May 1999 to determine the etiology, sources, and risk factors for Salmonella enteritidis (SE) infection. SE infection in T&T was found to be associated with the consumption of shell eggs, and in particular raw or undercooked eggs. SE isolates from 30 (88%) of 34 patients and from 9 implicated egg or egg-containing food samples were phage type 4. Homemade eggnog and ice cream, cake batter, and egg-containing beverages were the main raw egg-containing foods, reflecting the cultural practices of the people of T&T. Public health education on the risks of eating raw or undercooked eggs, thorough cooking of all egg dishes, and refrigeration of shell eggs and egg dishes; studies tracing infected eggs to their sources; and testing of flocks of layer chickens for SE are needed to reduce the incidence of this infection.

Origins and consequences of antimicrobial-resistant nontyphoidal Salmonella: implications for the use of fluoroquinolones in food animals

Human Salmonella infections are common; most infections are self-limiting, however severe disease may occur. Antimicrobial agents, while not essential for the treatment of Salmonella gastroenteritis, are essential for the treatment of thousands of patients each year with invasive infections. Fluoroquinolones and third-generation cephalosporins are the drugs-of-choice for invasive Salmonella infections in humans; alternative antimicrobial choices are limited by increasing antimicrobial resistance, limited efficacy, and less desirable pharmacodynamic properties. Antimicrobial-resistant Salmonella results from the use of antimicrobial agents in food animals, and these antimicrobial resistant Salmonella are subsequently transmitted to humans, usually through the food supply. The antimicrobial resistance patterns of isolates collected from persons with Salmonella infections show more resistance to antimicrobial agents used in agriculture than to antimicrobial agents used for the treatment of Salmonella infections in humans. Because of the adverse health consequences in humans and animals associated with the increasing prevalence of antimicrobial-resistant Salmonella, there is an urgent need to emphasize non-antimicrobial infection control strategies, such as improved sanitation and hygiene, to develop guidelines for the prudent usage of antimicrobial agents, and establishment of adequate public health safeguards to minimize the development and dissemination of antimicrobial resistance and dissemination of Salmonella resistant to these agents.

Risk factors for the occurrence of sporadic Salmonella enterica serotype typhimurium infections in children in France: a national case-control study

To determine risk factors for the occurrence of sporadic Salmonella typhimurium infections among children in France, we conducted a matched case-control study. Cases were identified between 15 June and 30 September 1996. We interviewed 101 pairs of case patients and control subjects, matched for age and place of residence. The risk of illness was greater for children who ate undercooked ground beef than for those who did not (odds ratio [OR], 5.0; 95% confidence interval [CI], 1.9-13.1). Case patients were more likely than control subjects to have taken antibiotics during the month before onset of disease (OR, 2.2; 95% CI, 1.0-4.9). Case patients <5 years of age were more likely to have been in contact with a household member with diarrhea 3-10 days before onset (P=.05). Consumption of undercooked ground beef is a risk factor for the sporadic occurrence of S. typhimurium infection among children, and antibiotics may facilitate the occurrence of illness. The possibility of person-to-person transmission among young children needs to be considered.

[Factors associated with sporadic cases of salmonellosis in 1- to 7-year-old children. Study of cases and controls]

BACKGROUND

Knowledge about salmonellosis risk factors mainly comes from foodborne outbreaks, and we know little about sporadic cases epidemiology. However most of the cases are sporadic, specially children. This study aims to find out some of determinants of these cases.

METHODS

A case-control study with incident cases and controls from the same base population (laboratory diagnosed cases). Cases were children 1-7 years old, affected by diarrhea with culture stools positive to Salmonella between december 1994 and december 1995. Controls from the same source, but positive culture to Campylobacter or viruses. We study food and other environmental risk factors. Odds ratio (OR) are calculated adjusted for age, sex, and year period (cool and cold) by logistic regression.

RESULTS

Eating minced meat during three days before symptoms, OR 4.07 (1.20-13.8) and OR 5.63 (1.34-23.6); pets, OR 8.27 (1.96-34.9), and antibiotics the week before symptoms, OR 4.75 (0.84-27.0) were epidemiologically associated with salmonellosis diarrhea.

CONCLUSIONS

Epidemiology of salmonellosis sporadic cases in children seems different to the foodborne associated cases and is more complex. Minced meat tree days before symptoms, antibiotics the week before symptoms, and pets could be a risk for this kind of cases. Future studies must also take account of this factors.

Epidemic Salmonella enteritidis infection in Los Angeles County, California. The predominance of phage type 4

Between April and July 1994, 501 cases of Salmonella enteritidis infection were reported in Los Angeles County, California, nearly 5 times the number reported between April and July 1993; of these, 422 (84%) were sporadic (not related to known outbreaks). A case-control study was done to determine risk factors for sporadic illness; the distribution of S enteritidis phage types was evaluated. Case-patients (n = 58) were county residents older than 1 year with culture-confirmed S enteritidis infection in August 1994. One to two acquaintance controls (n = 98) were matched to each case by age, sex, and race. Two risk factors-eating raw or undercooked eggs (matched odds ratio [MOR] = 6.6; 95% confidence interval [CI] = 1.9, 23.0) and eating in restaurants (MOR = 4.9; 95% CI = 1.2, 19.4) in the 3 days before the onset of illness-remained significant in the conditional logistic regression model. Of 16 randomly selected S enteritidis case-isolates, 15 (94%) were phage type 4. The reasons for the regional predominance of phage type 4, an S enteritidis subtype recently associated with large and destructive increases in salmonellosis among poultry and humans in Britain and much of Europe, are unclear. To minimize human S enteritidis infection, food service workers need frequent training in the proper handling of raw foods, eggs should be kept refrigerated during distribution and storage, and eggs should be cooked until the yolk is firm, particularly for persons at the greatest risk for serious illness: pregnant women, elderly persons, and those with compromised immune systems. Clinicians should obtain stool specimens for culture from patients who present with diarrhea and fever or bloody diarrhea or who are possibly part of an outbreak.

Recurrent outbreaks of Salmonella Enteritidis infections in a Texas restaurant: phage type 4 arrives in the United States

In recent years infection caused by Salmonella serotype Enteritidis (SE) phage type 4 has spread through Europe but has been uncommon in the USA. The first recognized outbreak of this strain in the USA occurred in a Chinese restaurant in EI Paso, Texas, in April 1993; no source was identified. In September 1993, a second outbreak caused by SE phage type 4 was associated with the same restaurant. To determine the cause of the second outbreak, we compared food exposures of the 19 patients with that of two control groups. Egg rolls were the only item significantly associated with illness in both analyses (first control group: odds ratio [OR] 8.2, 95% confidence interval [CI] 2.3-31.6; second control group: OR 13.1, 95% CI 2.1-97.0). Retrospective analysis of the April outbreak also implicated egg rolls (OR 32.4, 95% CI 9.1-126.6). Egg roll batter was made from pooled shell eggs and was left at room temperature throughout the day. These two outbreaks of SE phage type 4 likely could have been prevented by using pasteurized eggs and safe food preparation practices.

Drug resistance, plasmids, biotypes and susceptibility to bacteriophages of Salmonella isolated from poultry in Canada

Salmonella isolates from 295 layer and 294 broiler flocks in Canada were examined to determine resistance to antimicrobial agents, plasmid profiles, biochemical properties, and susceptibility to polyvalent bacteriophages. Except for the high number of strains resistant to spectinomycin (97.8%), the frequency of drug resistance of Salmonella isolates from layer flocks was low. None of 457 isolates from layer flocks was resistant to amikacin or ciprofloxacin, and less than 2% of the strains were resistant to cephalothin, chloramphenicol, cotrimoxazole, gentamicin, kanamycin, neomycin, nitrofurantoin, and/or polymyxin B. About 3% of the strains were resistant to ampicillin, carbenicillin and/or tetracycline, whereas 8% of the strains were resistant to sulfisoxazole. Salmonella anatum var. O15+ and S. typhimurium var. copenhagen strains were resistant to multiple antimicrobial agents. None of 1159 Salmonella strains from broiler flocks was resistant to amikacin, cephalothin, ciprofloxacin or polymyxin B, less than 1% of the strains were resistant to chloramphenicol, 2% were resistant to ampicillin, carbenicillin and/or chloramphenicol; 5-7% were resistant to the aminoglycosides gentamicin, kanamycin and/or neomycin; 6% were resistant to nitrofurantoin; 10% to tetracycline; 14% to sulfisoxazole; and 99% to spectinomycin. A high percentage of S. binza, S. anatum var. O15+, S. schwarzengrund and S. heidelberg strains were resistant to antimicrobial agents. Some of the single or multiple resistances were encoded by conjugative plasmids or by plasmids that were thermosensitive for transfer. Eight percent of S. heidelberg strains did not produce hydrogen sulfide. Ninety-seven percent of the Salmonella strains were susceptible to the lytic effect of polyvalent bacteriophages.

Susceptibility of suspended and surface-attached Salmonella enteritidis to biocides and elevated temperatures

The differential resistance of substratum-attached, detached, and planktonic cells of Salmonella enteritidis phage type 4 was studied by using several inimical processes and in vivo bioluminescence as a nondestructive, real-time reporter of metabolic activity. Bioluminescence in this strain was mediated by a construction containing the entire lux operon from Photorhabdus luminescens. An excellent correlation between bioluminescence and classical plate count data was obtained when we compared attachment profiles, biocide concentration exponents, and thermal inactivation D values (D value was the time required for a 10-fold reduction in the number of survivors). Biocide challenge of surface-adherent S. enteritidis resulted in concentration exponents that were experimentally indistinguishable from those obtained with Luria-Bertani broth-grown planktonic cells. It appears that cleansing regimes developed by using planktonic cell data are effective against surface-attached cells of this bacterium. Both attached and detached cells exhibited an approximately twofold increase in D values at 52 degrees C compared with values calculated for planktonic cells, strongly indicating that the detached cells exhibited an attached phenotype during the heating process. A model of a physiological adaptive response induced in attached cells and also reflected in detached cells is presented.