Identificação de genes toxigênicos em estirpes de Sthaphylococcus aureus isoladas de leite cru refrigerado, leite pasteurizado e queijos provenientes de laticínios do Estado do Maranhão, Brasil

Abstract

Staphylococcus aureus is one of the pathogens of great influence on the quality of milk and dairy products, being one of the bacterial species most involved in cases of food poisoning and infections by producing toxins responsible for several diseases in animals and humans. The objective of this study was to investigate the presence of toxigenic genes, sea, seb, sec, sed, see by multiplex PCR and tst by Uniplex PCR in strains of S. aureus with phenotypic and genotypic characterization isolated from samples of refrigerated raw milk, pasteurized milk and cheeses (rennet and mozzarella) from four dairies in the state of Maranhão. We collected 120 samples, 10 of refrigerated raw milk, 10 of pasteurized milk and 10 of cheese of each of dairies obtained from five different lots. The contamination by Staphylococcus coagulase positive was present in all samples of raw milk refrigerated with high counts to >106 UFC/mL. Regardless of the type of inspection, 100% of the samples of cheese (rennet and mozzarella) were outside the current standards. Were isolated 60 strains of S. aureus with phenotypic identification, of which 46 amplified the gene femA, specific to this species. Of these 46 strain, 31 isolated of samples from refrigerated raw milk and three of mozzarella cheese amplified a gene of toxins. Were observed 13 distinct genotypic groups for the presence of toxigenic genes, where the most frequent genotype was tst in 10 (29.4%) strains of S. aureus, followed by sed and seb+sec+sed each in four (11.8 %), sec in three (8.8%), seb, see, seb+sec and sea+seb+sec+tst each in two (5.8%), seb+sed, sea+seb+sec, sea+sec+tst, seb+sec+tst e sea+seb+sec+sed+see each present in one (3%) strain. The presence of only one gene was observed in 21 (61.8%) strains of S. aureus, three (8.8%) amplified for two genes, seven (20.6%) amplified for three, two (5.8%) amplified for four and one (3%) for five genes. The gene sec was more frequent in 15 (44.1%) strains, followed by seb and tst present in 14 (41.1%) each, sed in 10 (29.4%), sea in five (14, 7%), and see present in three (8.8%) strains of S. aureus. Molecular analysis to identify the species S. aureus showed better specificity in relation to phenotypic testing. The isolates showed genetic potential to produce one or more toxins to the simultaneous presence of two to five toxigenic genes, and multiplex PCR was effective and feasible for investigation of five different genes of toxins.