Identification and molecular phylogeny of coagulase-negative staphylococci isolates from Minas Frescal cheese in southeastern Brazil: Superantigenic toxin production and antibiotic resistance

Abstract

Minas Frescal is a typical Brazilian fresh cheese and one of the most popular dairy products in the country. This white soft, semiskimmed, nonripened cheese with high moisture content is obtained by enzymatic coagulation of cow milk using calf rennet or coagulants, usually in industrial dairy plants, but is also manufactured in small farms. Contamination of Minas Frescal by several staphylococci has been frequently reported. Coagulase-negative staphylococci (CNS) strains are maybe the most harmful, as they are able to produce heat-stable enterotoxins with super antigenic activities in food matrices, especially in dairy products such as soft cheeses. The aim of the present study was to investigate the presence of CNS strains in Minas Frescal marketed in southeastern Brazil concerning the risk of staphylococci food poisoning by the consumption of improperly manufactured cheese and the possibility of these food matrices being a reservoir of staphylococcal resistance to antimicrobials. Ten distinct CNS strains were found in 6 cheeses from distinct brands. The most frequent species were Staphylococcus saprophyticus (40%), Staphylococcus xylosus (30%), Staphylococcus sciuri (20%), and Staphylococcus piscifermentans (10%). Three strains were identified to the Staphylococcus genera. Three major species groups composed of 3 refined clusters were grouped by phylogenetic analyses with similarities over to 90%. All CNS strains carried multiple enterotoxin genes, with high incidence of sea and seb (90 and 70%, respectively), followed by sec/see, seh/sei, and sed with intermediate incidence (60, 50, and 40%, respectively), and, finally, seg/selk/selq/selr and selu with the lowest incidence (20 and 10%, respectively). Real-time reverse transcription PCR and ELISA assays confirmed the enteroxigenic character of the CNS strains, which expressed and produced the enterotoxins in vitro. The CNS strains showed multiresistance to antimicrobial agents such as β-lactams, vancomycin, and linezolid, which have therapeutic importance in both human and veterinarian medicines. The risk of staphylococci food poisoning by the consumption of improperly manufactured Minas Frescal was emphasized, in addition to the possibility of these food matrices being a reservoir for antibiotic resistance. More effective control measures concerning the presence and typing of staphylococci in raw milk and dairy derivatives should be included to prevent the spread of pathogenic strains.

Nonconventional starter cultures of coagulase-negative staphylococci to produce animal-derived fermented foods, a SWOT analysis

“…; Casaes Nunes et al . ). Moreover, strains of S. epidermidis , S. equorum and S. saprophyticus that are free of common enterotoxins can nevertheless harbour other variants, or the gene coding for toxic shock syndrome toxin‐1 (Soares et al .…”

“…; Casaes Nunes et al . ). For example, some enterotoxigenic CNS species have been isolated from Minas cheese that were involved in food poisoning outbreaks, but as they were not the only enterotoxigenic bacteria isolated from those samples a robust evidence for involvement of CNS species in food poisoning is lacking (Veras et al .…”

“…In Minas cheese, the presence of genes can either parallel the production of SE (Casaes Nunes et al . ) or not (Rall et al . ).…”

Antibiotic Resistance Genetic Markers and Integrons in White Soft Cheese: Aspects of Clinical Resistome and Potentiality of Horizontal Gene Transfer

“…In addition, their manufacture involves technological steps that require the use of equipment without efficient treatments to reduce the microbial load [ 14 , 15 , 16 ]. Although sanitary legislations consider only classical foodborne pathogens such as coagulase-positive Staphylococcus , Listeria monocytogenes , and coliforms as quality indicators, other drug-resistant putative bacteria (DRB) may occur, posing a health issue [ 17 , 18 , 19 ].…”

Species level identification of coagulase negative Staphylococcus spp. from buffalo using matrix-assisted laser desorption ionization–time of flight mass spectrometry and cydB real-time quantitative PCR

“…can be transmitted by food products including milk and affect healthy people. Like Staphylococcus aureus, some CoNS species secrete enterotoxins that are responsible for food poisoning (Nunes et al, 2016).…”