Vidas UP-enzyme-linked fluorescent immunoassay based on recombinant phage protein and fluorescence in situ hybridization as alternative methods for detection of Salmonella enterica serovars in meat

Salmonella prevalence and serovar distribution in healthy slaughter sheep and cattle determined by ISO 6579 and VIDAS UP Salmonella methods

Prevalence of Salmonella in slaughter sheep and cattle was determined by International Organization for Standardization Method 6579 (ISO) and Vitek Immunodiagnostic Assay System UP Salmonella Phage Technology (VIDAS UP Salmonella SPT-VIDAS UP). A total of 400 healthy slaughter sheep (n = 200) and cattle (n = 200) carcass (C), fecal content (FC), mesenteric lymph node (MLN), liver (L), kidney (K), spleen (S) and gall bladder (GB) were randomly sampled and analysed. ISO and VIDAS UP results indicated 13 (3.25%) and 17 (4.25%) of 400 animals carried Salmonella, respectively, regardless of sample type. There was no isolation from L, S, GB, while 2 C (0.5%), 6 FC (1.5%), 7 MLN (1.75%), 3 K (0.75%) were contaminated with Salmonella. S. Typhimurium (27.8%), S. Enteritidis (22.2%), S. Newport (22.2%) were the three dominant serovars, followed by S. Kentucky (11.1%), S. Umbilo (5.6%), S. Corvallis (5.6%), and S. Albany (5.6%). Overall prevalence in 2800 samples was 0.46% by ISO and 0.61% by VIDAS UP. High relative trueness (RT: 99.79%) of VIDAS UP with a substantial agreement to ISO (κ value: 0.80) indicated its efficiency to accompany ISO to monitor Salmonella in slaughter animals. As the first report to evaluate ISO and VIDAS UP in detecting Salmonella from slaughter sheep and cattle, this current prevalence signifies a risk for public health in red-meat and related products in Turkey.

High prevalence of Salmonella spp. in wastewater reused for irrigation assessed by molecular methods

Salmonella spp. is one of the most important causal agents of food-borne illness in developed countries and its presence in irrigation water poses a risk to public health. Its detection in environmental samples is not easy when culture methods are used, and molecular techniques such as PCR or ribosomal rRNA probe hybridization (Fluorescent in situ Hybridization, FISH) are outstanding alternatives. The aim of this work was to determine the environmental risk due to the presence of Salmonella spp. in wastewater by culture, PCR and FISH. A new specific rDNA probe for Salmonella was designed and its efficiency was compared with the rest of methods Serotype and antibiotic resistance of isolated strains were determined. Forty-five wastewater samples (collected from two secondary wastewater treatment plants) were analysed. Salmonella strains were isolated in 24 wastewater samples (53%), two of them after disinfection treatment. Twenty-three Salmonella strains exhibited resistance to one or more antimicrobial agent. Analysis of wastewater samples yielded PCR positive results for Salmonella in 28 out of the 45 wastewater samples (62%). FISH analysis allowed for the detection of Salmonella in 27 (60%) samples. By using molecular methods, Salmonella was detected in four samples after disinfection treatment. These results show the prevalence of Salmonella in reclaimed wastewater even after U.V. disinfection, what is a matter of public health concern, the high rates of resistance to antibiotics and the adequacy of molecular methods for its rapid detection. FISH method, with SA23 probe developed and assayed in this work provides a tool for detecting Salmonella in water within few hours, with a high rate of effectiveness.