The use of social network analysis to examine the transmission of Salmonella spp. within a vertically integrated broiler enterprise

Modeling Salmonella Spread in Broiler Production: Identifying Determinants and Control Strategies

The presence of Salmonella spp. in broiler production is a food safety concern as the bacterium can be transmitted to humans via contaminated meat and derived products. Salmonella detection in litter at the pre-slaughter period has been linked to increased odds of contaminated broiler carcasses and meat derived products. To determine risk factors related to farm and broiler house characteristics and management practices, this study uses a unique longitudinal data set from a Brazilian integrated broiler enterprise, which contains official results of Salmonella spp. isolation from drag swabs collected at the end of the grow-out period. A Bayesian hierarchical spatio-temporal model found significant spatial and time influence on the odds of isolating Salmonella spp. from litter as well as significant effects from the size of a broiler house, total housing area per farm, type of broiler house, and number of litter recycles. Results indicate that recycling litter beyond 6 rearing cycles significantly increased the odds of isolating Salmonella before slaughter, and the bacterium was more likely to persist in conventional broiler houses, compared to broiler houses with controlled environment. Evidence of a potential principal-agent problem was also found in setting strategies to control the bacterium from litter, which suggests strong incentives to adopt the strategies aiming to reduce prevalence of the bacterium in the integrated enterprise. Our findings could be used to develop alternative measures to reduce the risk of persistence of the bacterium in the broiler production chain.

Traditional Salmonella Typhimurium typing tools (phage typing and MLVA) are sufficient to resolve well-defined outbreak events only

Between 1991 and 2014 the per capita notification rate of salmonellosis in Australia increased from 31.9 to 69.7 cases per 100,000 people. Salmonella Typhimurium accounted for nearly half the human cases until the end of 2014. In this study, we used cluster analysis tools to compare S. Typhimurium isolates from a chicken-meat study with those reported to the National Enteric Pathogen Surveillance System (NEPSS) from the coincident human and non-human populations. There was limited phage type diversity within all populations and a lack of specificity of MLVA profiling within phage types. The chicken-meat study isolates were not significantly clustered with the human cases and at least 7 non-human sources, based on typing profiles (PT/MLVA combination), could be implicated as a source of human cases during the same period. In the absence of a strong surveillance system representative of all putative sources, MLVA and phage typing alone or in combination are insufficient to identify the source of human cases.

Evaluation of Antimicrobial Activity of Four Organic Acids Used in Chicks Feed to Control Salmonella typhimurium: Suggestion of Amendment in the Search Standard

Today, the general public has become increasingly aware of salmonellosis problems. Organic acids are known by their antimicrobial potential and commonly used for improving the quality of poultry feed. In this context, the present work evaluated the inhibitory effect of four organic acids, namely, acetic acid, citric acid, lactic acid, and tartaric acid, at different levels of contamination by Salmonella typhimurium. The neutralization of these organic acids in vitro and in the presence of one-day-old chick's organs was also investigated during the search for Salmonella serovars in birds as described in the Moroccan standard "NM 08.0.550." The effect of four organic acids on Salmonella typhimurium was tested in vitro and in the presence of chick's organs at different concentrations set of strain and organic acids tested. The MIC results demonstrated that tartaric acid, citric acid, and acetic acid inhibited Salmonella typhimurium at concentrations of 0.312%, 0.625%, and 0.512% for the three levels of strain: 10, 100, and 103 CFU/ml, respectively, while lactic acid and depending on the amount of the strain introduced acts differently: 0.078% for 10 CFU/ml and 0.156% for 100 and 103 CFU/ml. The concentration of 0.04M of Na2HPO4 solution has proved, in vitro, in caecums and organs of chicks (in presence of organic acids) that strain introduced, even at low concentrations, can be recovered. The use of additives has beneficial effects in Salmonella control program. However, the present results recommend the amendment of Salmonella research standard, taking into account the probable presence of organic acids in digestive content of one-day-old chicks.

Salmonella spp. transmission in a vertically integrated poultry operation: Clustering and diversity analysis using phenotyping (serotyping, phage typing) and genotyping (MLVA)

The transmission of Salmonella enterica within a vertically integrated poultry operation was investigated longitudinally over an 18-month period (2013–2014). Thirty six percent of all samples collected (1503 of 4219) were positive for salmonellae with seven Salmonella enterica subsp. enterica serovars, and one Salmonella enterica subsp. salamae serovar detected. Both Salmonella enterica subsp. enterica serovars Infantis and Typhimurium were detected in all locations sampled. Salmonella Typhimurium was the most frequently detected serovar (63% of serotyped samples) with 8 phage types (PT) and 41 multiple-locus variable-number tandem-repeats analysis (MLVA) profiles identified. The most frequently identified phage types were PT135a and DT135. A total of 62 PT/MLVA combinations were observed. MLVA profiles 03-14-10-09-525 and 03-15-11-11-525 were the most frequently identified and 83% of the isolates shared at least one MLVA profile with an isolate from another phage type. The use of phage typing and MLVA profiling, on their own or in combination, were insufficient to understand the complexity of the epidemiological relationships between locations within this production system. Despite the high level of apparent diversity, cluster analysis was unable to differentiate the transmission pathways of all S. Typhimurium variants detected within the integrated enterprise. Using additional epidemiological information, the parent breeder rearing site was identified as the most likely point of introduction of two S. Typhimurium isolates into the production system with subsequent dissemination to the broiler flocks via the hatchery. This complexity is unable to be resolved in the absence of intensive sampling programs at all generations of the production system.