Evaluating risk factors for endemic human Salmonella Enteritidis infections with different phage types in Ontario, Canada using multinomial logistic regression and a case-case study approach

Abstract

BackgroundIdentifying risk factors for Salmonella Enteritidis (SE) infections in Ontario will assist public health authorities to design effective control and prevention programs to reduce the burden of SE infections. Our research objective was to identify risk factors for acquiring SE infections with various phage types (PT) in Ontario, Canada. We hypothesized that certain PTs (e.g., PT8 and PT13a) have specific risk factors for infection.MethodsOur study included endemic SE cases with various PTs whose isolates were submitted to the Public Health Laboratory-Toronto from January 20th to August 12th, 2011. Cases were interviewed using a standardized questionnaire that included questions pertaining to demographics, travel history, clinical symptoms, contact with animals, and food exposures. A multinomial logistic regression method using the Generalized Linear Latent and Mixed Model procedure and a case-case study design were used to identify risk factors for acquiring SE infections with various PTs in Ontario, Canada. In the multinomial logistic regression model, the outcome variable had three categories representing human infections caused by SE PT8, PT13a, and all other SE PTs (i.e., non-PT8/non-PT13a) as a referent category to which the other two categories were compared.ResultsIn the multivariable model, SE PT8 was positively associated with contact with dogs (OR=2.17, 95% CI 1.01-4.68) and negatively associated with pepper consumption (OR=0.35, 95% CI 0.13-0.94), after adjusting for age categories and gender, and using exposure periods and health regions as random effects to account for clustering.ConclusionsOur study findings offer interesting hypotheses about the role of phage type-specific risk factors. Multinomial logistic regression analysis and the case-case study approach are novel methodologies to evaluate associations among SE infections with different PTs and various risk factors.

Antimicrobial resistance in fecal Escherichia coli and Salmonella enterica isolates: a two-year prospective study of small poultry flocks in Ontario, Canada

“…In the fecal E. coli isolates in our study, there was a very low frequency of resistance to cephalosporins, carbapenems, macrolides, and quinolones, which are antimicrobials classified in Canada as being of very high or high importance in human medicine [20]. This is an encouraging finding from a human health viewpoint because flock owners can be exposed to antimicrobial resistant zoonotic pathogens [6,13,15] through direct contact with their birds [10] or their environment [11], or consumption of contaminated meat or eggs [8,9]. However, there was a moderate to high frequency of resistance to tetracycline, streptomycin, sulfonamides, and ampicillin; antimicrobials frequently used to treat bacterial infections in poultry [35].…”

“…Non-commercial poultry flocks (denoted as "small flocks") are increasingly popular in urban, suburban, and rural areas in North America [1][2][3]. Small flocks can pose a health risk to their owners by exposing them to zoonotic pathogens [4][5][6][7] through consumption of contaminated meat or eggs [8,9], or direct contact with infected birds [10] or their environment [11]. Antimicrobial resistance (AMR) in zoonotic pathogens adds to this risk [12][13][14][15] because infections with antimicrobial resistant bacteria are more difficult to treat, and result in higher morbidity and mortality [16,17].…”

Spatial-temporal epidemiology of human Salmonella Enteritidis infections with major phage types (PTs 1, 4, 5b, 8, 13, and 13a) in Ontario, Canada, 2008–2009

“…Subtyping is useful for differentiating between endemic and outbreak cases, especially for common Salmonella serotypes, such as Enteritidis, that occur sporadically throughout the year [ 34 ]. Differences in reservoirs and exposure settings might exist for different S. Enteritidis phage types, and molecular differentiation can help to understand potential sources of the different phage types [ 8 , 34 ]. We defined a cluster as a health region, time period, or a health region during a particular time period with a statistically significant higher than expected phage type-specific S. Enteritidis infection rate.…”

“…Several research studies conducted in North America have evaluated phage type-specific risk factors for S. Enteritidis infections in humans. In Ontario, Canada, researchers demonstrated that cases with PT 8 were more likely to have had contact with dogs compared to cases with other phage types [ 8 ]. In British Columbia, Canada, a concurrent increase in the incidence of S. Enteritidis infections with PT 8 in humans and the prevalence of PT 8 in poultry was observed between 2007 and 2010 [ 9 ].…”

Case–Case Analysis Using 7 Years of Travelers' Diarrhea Surveillance Data: Preventive and Travel Medicine Applications in Cusco, Peru

“…A case–case approach allows a comparison of symptom severity between pathogens identified in the stool, although it lacks mechanisms to question if a particular pathogen present in the stool is causally related to diarrheal disease. A case–case approach allows restricted and refined analysis of some unique exposures associated with different pathogens detected through a surveillance system 11–13…”