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RISK FACTORS FOR SALMONELLA ORANIENBURG OUTBREAK IN A NURSING HOME IN MICHIGAN

2006; Wiley; Volume: 54; Issue: 4 Linguagem: Inglês

10.1111/j.1532-5415.2006.00668_5.x

1532-5415

M. Mokhtar Arshad, Hoda A. Asmar, Mohammad H. Rahbar, Matthew L. Boulton, Eden V. Wells, Melinda J. Wilkins, Abdulkafi Mohammed Saeed,

Viral gastroenteritis research and epidemiology

To the Editor: Salmonella Oranienburg is a relatively uncommon serotype, ranking ninth in frequency in 2003 in the United States.1 It has been associated with outbreaks in several countries.2 Besides gastroenteritis, it can cause vertebral osteomyelitis and paravertebral abscess,3 soft tissue and cartilage infection,4 and retroperitoneal abscess.5 This letter describes a S. Oranienburg outbreak in a Michigan nursing home and describes the resident-level risk factors. From June to September 1994, 13 laboratory-confirmed cases of S. Oranienburg were detected. Twelve (92%) of the cases were in women. Patients ranged in age from 76 to 97. The symptoms included diarrhea (69%), fever (53%), vomiting (30%), and nausea (15%). Three cases (23%) were asymptomatic. In November, two more cases were detected. In 1995, five cases were detected in January, 20 in February (5 symptomatic cases and 15 from stool culturing), 34 in March (all from stool culturing), one in April, three in May (all from stool culturing), two in June, two in July, four in August, two in September, and two in October. Four culture-confirmed diagnoses occurred in the nursing home staff. Inspection of the food service facilities by a certified food service sanitarian revealed that the kitchen was well run, and no Salmonella was isolated from foods. A case-control study was conducted to determine resident-level risk factors for the infection. Cases were residents of the nursing home who had diarrhea, and S. Oranienburg was isolated from their stool samples between June 1994 and October 1995. Controls were residents who were asymptomatic and stool-culture negative for Salmonella. Information about cases and controls (demographic data, use of antimicrobial agents, gastrointestinal symptoms, results of laboratory cultures, underlying illnesses, and routine medication) was abstracted from their medical records. The Mann-Whitney U test was used to compare group means for nonparametric data. Chi-square or Fisher exact tests were used to compare differences in proportions between cases and controls. Odds ratios (ORs) with 95% confidence intervals (CIs) were determined. Variables addressing comorbidities and routine medications with ORs greater than 1 were evaluated for the effect of confounding using logistic regression analysis. Variables with ORs greater than 1 using logistic regression analysis were further evaluated in the final model. EpiInfo 2004 (version 3.3, Centers for Disease Control and Prevention, Atlanta, GA) was used for all calculations. Eighteen cases were compared with 22 controls. The cases did not differ significantly from the controls with respect to sex (78% vs 68% female; OR=1.63, 95% CI=0.39–6.81), race (89% vs 91% white; OR=1.25, 95% CI=0.16–9.88), and mean age (85 vs 80, P=.17). After adjusting for the analgesic used, arthritis, diabetes mellitus, gastrointestinal disorder, hip fracture, and other mental disorder, dementia remained significantly associated with infection (OR=41.9, 95% CI=4.0–439.6) (Table 1). This study found that residents of the nursing home with dementia were at higher risk for S. Oranienburg infections than controls without dementia. This may be because residents with dementia are less able to observe their basic self-care and hygiene. As in many Salmonella outbreaks in nursing homes,6,7 the food vehicles or sources for S. Oranienburg infection in this outbreak could not be identified. The infrequently distributed number of cases over time indicates that transmission may have been person to person. Person-to-person spread by asymptomatic residents may be possible, because three cases that were detected from June to September 1994 were asymptomatic, although the index case could not be ascertained. The nursing home staff also may have played a role in the transmission of S. Oranienburg to susceptible residents, because four asymptomatic staff members were also detected. Even though the food vehicle could not be identified, it is conceivable that contaminated raw food or vegetables may have been the source of the infection directly or through cross-contamination from raw food items (e.g., in blender or meat grinder) or contamination from asymptomatic food handlers.8,9 In conclusion, nursing home residents with dementia were at higher risk of contracting Salmonella infection in this Michigan outbreak. Therefore, this group needs an elevated level of attention to prevent exposure to Salmonella. The importance of the presence of uncommon Salmonella serotypes in nursing homes should not be underestimated, because it can cause severe infection in residents with compromised immune function, diminished physiological functions, decreased gastric acidity, and treatments involving antimicrobial agents.10 Therefore, foods that are known to be vehicles for Salmonella, such as foods of animal origin and fresh produce, should be offered with caution to residents of nursing homes. Financial Disclosure: No authors received financial support, consultantships, speakers forum, or any company holdings or patents in relation to this letter. Author Contributions: A. Mahdi Saeed: study concept and design and study supervision. Hoda A. Asmar: acquisition of data. M. Mokhtar Arshad: analysis and interpretation of data and preparation of manuscript. M. Hossein Rahbar, Matthew L. Boulton, Eden V. Wells, and Melinda J. Wilkins: critical revision of the manuscript for important intellectual content. Sponsor's Role: There were no sponsors for this article.