Climate patterns governing the presence and permanence of salmonellae in coastal areas of Bahia de Todos Santos, Mexico

Despite the importance of salmonellae as one of the major causes of food-borne infections worldwide, data regarding the presence of these organisms in the environment are limited. We investigated the presence of Salmonella spp. in Bahia de Todos Santos (Baja California, Mexico) and evaluated the environmental factors that affect the occurrence of Salmonella spp. in this arid region. A total of 1,331 samples collected from 21 sites along the coast during a period of 3 years were analyzed for Salmonella spp. Geographical and seasonal distribution of Salmonella spp. was evaluated in association with environmental parameters and with human infections in the area. The incidence of Salmonella bacteria throughout the study was 4.8%, with the highest incidence detected in wastewater (16.2%), followed by stream water (10.6%), mollusks (7.4%), and seawater (2.3%). Twenty different serotypes were identified among the 64 Salmonella isolates. The dominant serotype was Typhimurium (23.4%), followed by Vejle (6.2%). The presence of Salmonella spp. in coastal areas was mostly confined to rainy periods and areas of stream discharges, and runoff was identified as the predominant factor influencing the transport of Salmonella bacteria from source points to the sea via streams. Isolation of Salmonella spp. was negatively and significantly associated with temperature, probably because of the effect of solar radiation in the decline of permanence of Salmonella bacteria. Conversely, human infections prevailed during the warmest months and were negatively correlated with the presence of Salmonella spp. in the marine environment.