Investigation of Salmonella spp. in backyard chickens (Gallus gallus domesticus) and eggs sold in free markets in the city of Fortaleza, Ceará

Abstract

Poultry meat and byproducts are the main protein source for man. However, such foods are related to outbreaks of food-borne infections around the world, caused mainly by Salmonella spp. Therefore, the present study aimed to investigate the presence of Salmonella spp. in material collected in properties of backyard chickens (eggs, ration, cloacal swab and drag swab) and to perform a survey of members of the Enterobacteriaceae family in eggs commercialized in the main free markets of Fortaleza. Individual cloacal swabs were collected from 405 backyard chickens from 18 houses and 10 eggs were also collected for analysis of eggshell and internal content from each sampled household, totaling 180 eggs. From the free markets, 90 eggs were collected. Once sampled, the ration, cloacal swab, drag swab, shell and internal contents of eggs were incubated in Peptone Water and aliquots were placed in Rappaport- Vassiliadis broth and Selenite-Cystine broth added Novobiocin. Following, aliquots of each broth were streaked in plates Brilliant Green agar and MacConkey agar. Suspect colonies for Salmonella spp. were submitted to biochemical identification, with the temperature and incubation time standardized in 37ºC/24h, respectively. Eggs collected from houses were broken in sterile beaker and maintained in bacteriological incubator at 37ºc/24h. After such period, aliquots collected were incubated in Rappaport- Vassiliadis broth and Selenite-Cystine broth added Novobiocin, following the same bacteriological procedure mentioned previously for swabs. Eggs from free markets were analyzed with the same methodology as the house eggs, minus the antibiotic Novobiocin in the Selenite-Cystin broth, and with further biochemical tests used to identify the different members of the Enterobacteriaceae family. No Salmonella spp. were isolated from swab or egg samples. However, Escherichia coli, Citrobacter spp., Enterobacter spp., Proteus spp., Providencia spp., Klebsiella spp., Shigella spp., Yersinia spp. were isolated from eggs of free markets. Accordingly to the methodology used, we may suggest that backyard chickens from Fortaleza present a satisfactory sanitary status. However, free market eggs did not present adequate sanitary conditions.