a ISSN 0101-2061 (Print) Food Science and Technology ISSN 1678-457X (Online) DOI: https://doi.org/10.1590/fst.38719 Evaluation of a rapid detection method of Salmonella in comparison with the culture method and microbiological quality in fish from the Brazilian Amazon Paula Hellayne Costa dos SANTOS1#, Hamilton M. FIGUEIREDO1#, Luiza Helena Meller da SILVA1#* , Rafaela Santos Oliveira da SILVA1#, Gabrielle Virginia Ferreira CARDOSO2#, Carina Martins MORAES2#, Antonio Manoel da Cruz RODRIGUES1# Abstract Microbiological safety of fish is a concern of consumers, industries and regulatory agencies worldwide. Among the pathogenic microorganisms, Salmonella spp. is one of the main agents of foodborne diseases and should be absent in animal products. Rapid and accurate identification of pathogens in the supply chain is important for both quality assurance and tracking infectious agents within the chain. In this context, this study aimed to evaluate the equivalence of two rapid detection tests, as alternative methods to the conventional Salmonella detection method, as well as to verify the microbiological quality parameters of two commercially important fish species in the Amazon biome. The plate count of aerobic bacteria ranged from 7.76 x 410 to 8.71 x 107 CFU.g-1 for mesophiles and 1.70 x 106 to 4.27 x 108 CFU.g-1 for psychrotrophic whereas the maximum for this group of microorganisms in fresh fish is 106 CFU.g-1. Regarding the Staphylococcus count, the two species presented variations between 1.35 x 104 to 1.51 x 105 CFU.g-1. This represents unsatisfactory conditions of handling, storage and conservation of fish species. The immunoenzymatic and molecular methods have been shown to be reliable, fast and effective in the detection of Salmonella and for its high index of agreement with the conventional detection method. We also emphasize the convenience of multiplex PCR application due to the high sensitivity, specificity, speed and accuracy of Salmonella detection. Keywords: Brachyplatystoma filamentosum; Ilisha amazonica; mPCR; Tecra Salmonella. Practical Application: Identify the presence of salmonella through fast methods and molecular identification techniques. 1 Introduction Microbiological safety of fish is a concern of consumers, Although Salmonella is not a biologically natural pathogen of fish, industries and regulatory agencies around the world nowadays. it can be introduced to the fish chain through improper handling The rapid and accurate identification of pathogens in the and hygiene in processing or contact with contaminated water supply chain is important both for quality assurance and for by discharging sewage effluent into fishing basins.Salmonella tracking infectious agents within the chain (Välimaa et al., 2015; are facultative intracellular parasites that invade the mucous Sebastião, et al., 2015; Buncic, et al., 2019). According to data membrane with the human and animal intestinal tract being the from regulatory agencies and health inspection agencies main reservoir of this pathogen (Álvarez-Ordóñez et al., 2012; worldwide Salmonella stands out among the pathogens, as the Ertas Onmaz et al., 2015; Nhung et al., 2018). The conventional main bacterial agent, responsible for transmit diseases associated method used for the detection of Salmonella in food is based on with food consumption nowadays (Centers for Disease Control pre-enrichment in buffered peptone water (BPW) and enrichment and Prevention, 2016; European Food Safety Authority, 2018). in selective medium, followed by differential isolation and In Europe, authorities point to Salmonella as the second most serological confirmation (Suo & Wang, 2014; Lee, et al., 2015; important agent in foodborne disease transmission, with over Li, et al., 2017). The main limitation of this method is that these 91,857 cases of salmonellosis (European Food Safety Authority, tests usually require a minimum of 5 to 6 days. However, infection 2018; Trimoulinard et al., 2017). In the United States, the control increasingly depends on faster and more accurate tests incidence of Salmonella represents 15.89% of the cases associated for the diagnosis of this pathogen, especially for monitoring with diseases transmitted by food consumption (Centers for the production of animal products, food manufacturing and Disease Control and Prevention, 2016). In Brazil, Salmonella end products (Andrade et al., 2010; Frickmann, et al., 2013; is responsible for more than 30% of foodborne diseases, Gokduman et al., 2016; Lobato & O’Sullivan, 2018). In addition, according to the Brazilian Ministry of Health (Brasil, 2017). there is a strong industrial demand to comply with legislation and Received 06 Jan., 2020 Accepted 27 Jan., 2020 1 Laboratório de Análise de Alimentos - LAANALI, Programa de Pós-graduação em Ciência e Tecnologia de Alimentos - PPGCTA, Universidade Federal do Pará - UFPA, Campus Guamá, Belém, PA, Brasil 2 Laboratório de Higiene e Qualidade de Alimentos, Programa de Pós-graduação em Saúde Animal na Amazônia, Universidade Federal do Pará - UFPA, Campus Castanhal, Belém, PA, Brasil # These authors contributed equally to this manuscript. *Corresponding author: [email protected] Food Sci. Technol, Campinas, 41(1): 151-157, Jan.-Mar. 2021 151/157 151 Rapid Detection Method of Salmonella in Fish the rapid release of food products to the market. Recent advances Public Health Association, 2001) was followed. Briefly, 25 g of in technologies for the detection and identification of contaminated the samples were homogenized with 225 mL buffered peptone foodborne pathogens have provided faster, more sensitive and water (Oxoid CM509) using a stomacher mixer (Logen Scientifc, specific alternatives to conventional methods (Paula, et al. LS1901n, ALPAX) at 2000 rpm for 2 min. From the initial 2002; Kawasaki, et al., 2009; Koo, et al., 2016; Suo, et al., 2017) suspension, decimal dilutions were prepared by transferring These assays are generally referred as “fast” or alternative 1 mL from the previous dilution to 9 mL of buffered peptone methods, terms commonly used to describe a variety of assays water and so on until reaching the desired dilution. From the including miniaturized biochemical kits, immunoassays, DNA/ decimal dilutions obtained, analyzes of total and thermotolerant RNA-based assays, and combinations with cultural methods coliforms, Staphylococcus aureus and total and psychrotrophic (Lofstrom et al., 2010; Almeida et al., 2013; Kim, et al., 2017). aerobic bacteria count were performed as follows. Molecular testing uses a specific sequence of bacterial nucleic acids as a target for pathogen detection and this is the category 2.3 Microbiological analysis of alternative methods that most improved in recent years (Valderrama et al., 2016; Hu, et al., 2018; Bundidamorn, et al., 2018). The presumptive coliforms test was performed using the CC The PCR assay, Polymerase Chain Reaction, is the molecular test PetrifilmTM commercial kit (3M Company, St. Paul, MN, USA), that has also been widely used to detect Salmonella in food. It is where 1 mL of the dilution, obtained according to item 2.2, a highly sensitive technique based on enzymatic amplification was inoculated into the kit plates, according to manufacturer’s of specific segments of DNA in vitro, which enables to obtain instructions. The plates were incubated at 35 °C for 48 h, and thousands of copies from a single nucleic acid sequence, within the result was expressed in MPN of total coliforms per gram two or three hours (Shabarinath et al., 2007; Singh et al., 2019). of sample. For Thermotolerant Coliforms, 1 mL aliquots of three dilutions of the sample obtained according to item 2.2 Another rapid assay that has been extensively studied in the were inoculated into a series of 3 tubes containing 10 mL of analysis for pathogen detection is multiplex PCR. This technique Tryptose Lauryl Sulfate Broth - LST (ACUMEDIA 7142) and involves more than one pair of oligonucleotides and allows, among incubated at 35 °C. After 48 h, 1 mL aliquots of each positive other applications, to perform a single reaction to detect various tube of LST were transferred to tubes containing 10 mL of types of microorganism, their serotypes or different genes of the Escherichia coli broth - EC (Acumedia 7206) and incubated same microorganism (Malorny et al., 2009; Wang, et al., 2015; at 45 °C for 24 h in a water bath, and the result was expressed Chin et al., 2017). in MPN of thermotolerant coliforms per gram of sample. In this context, the objective of this study was to evaluate the For quantification ofStaphylococcus aureus, the commercial equivalence of two rapid detection tests as alternative methods PetrifilmTM Staph express Cout Plate kit (3M Company, St. Paul, to the conventional method of bacteriological detection of MN, USA) was used, where 1 mL of the sample dilution Salmonella in two fish species with commercial importance obtained according to item 2.2 was inoculated into kit plates, and large occurrence in the Amazon biome and associated and the plates were incubated at 36 °C for 24 h according to the with this verify the parameters of microbiological qualities of manufacturer’s instructions. After the plates incubation period, the two species of fish. typical Staphylococcus colonies were counted and the result expressed in CFU.g-1. In the mesophilic and psychrotrophic aerobic 2 Materials and methods bacterial count assays, the “pour plate” technique with standard agar (PCA) was performed. The plates were incubated at 35 °C 2.1 Samples and procedure for isolation and identification for 48 h (mesophilic) and 7 °C for 10 days (psychrotrophic). The result of the count was expressed in CFU.g-1. The fish samples included in this study wereBrachyplatystoma filamentosum and Ilisha amazonica species. These two species 2.4 Salmonella spp. detection are of large occurrence in the Amazon biome and commercially important for their high consumption. The total of 10 collections In Salmonella detection were applied three protocols, which of fish samples were performed in the period from January are described briefly as follows: to June 2018, at the main North fish landing port in Brazil (Ver-o-Peso market, 01°27’21”S and 48°30’14”W).