Lampropeltis californiae as reservoir of Salmonella spp. in Gran Canaria island. Validation of the concentration of magnesium chloride in the diagnosis

Abstract

The California kingsnake (Lampropeltis californiae) was introduced in Gran Canaria island 20 years ago, which represents a serious problem for endemic fauna. Since 2007, an eradication program with search and capture is carried out to control the expansion of this snake. Since then, approximately 7900 specimens have been caught. The role of free-living snakes in the transmission of bacteria that may be potentially zoonotic has not been studied in depth. Due to the excessive population of wild snakes (Lampropeltis californiae) in various areas of the island of Gran Canaria, we have established as objective of this study to determine if these snakes can act as carriers of Salmonella spp. in the stool, which may represent a public health problem. Furthermore, the influence of different concentrations of magnesium chloride on the primary isolation of Salmonella spp. was evaluated. For the development of this study, a total of 37 fecal samples from apparently healthy snakes identified as Lampropeltis californiae, were tested during the period between September and October of 2019. The processing of the samples and the isolation of Salmonella was carried out following the ISO 6579:2002/Amd:2007 standard, using Rappaport Vassiliadis as an enrichment medium with different concentrations of magnesium chloride (13.58 g/L and 36 g/L). Of a total of 37 analyzed snakes, 15 (40.54%) were positive to the isolation of colonies compatible with Salmonella spp., identified by using API 20E. The results of our study confirm that Lampropeltis californiae may represent an important reservoir of Salmonella spp. in rural areas of the island of Gran Canaria, which may pose a risk to wildlife and public health. Furthermore, our work provides that the use of the HK medium in the diagnosis of Salmonella spp. primary isolation, as well as the use of double concentrations of MgCl2, reduces the number of false negative diagnoses.