Prevalence of antibiotic resistance in coagulase-negative staphylococci from spontaneously fermented meat products and safety assessment for new starters.

To provide new meat starter strains lacking antibiotic (AB) resistances, we explored the AB susceptibility in 116 coagulase-negative Staphylococcus (CNS) isolates from traditionally fermented sausages (n=40) manufactured with meat from conventional animal breeding, and from meat products (n=76) made from meat of animals raised in natural habitats under low- or no-antibiotic pressure. Less than 50% of these CNS isolates showed phenotypic resistances to at least one antibiotic (AB) by using microdilution assay. Resistances to penicillins and tetracycline were most often observed and could be traced back to blaZ and tet(K) genes. Prevalence of AB resistances was species-dependent and mainly found in isolates of Staphylococcus warneri (78%), Staphylococcus capitis (75%) and Staphylococcus epidermidis (67%), but only sporadically detected in Staphylococcus carnosus (27%) and Staphylococcus equorum (18%). AB resistances were more often observed in S. xylosus isolates originating from natural habitats compared to traditionally fermented sausages made from conventional meat. A selection of 101 isolates belonging to S. xylosus (n=63), S. carnosus (n=21) and S. equorum (n=17) were subsequently grouped by pulsed-field gel electrophoresis (PFGE) into strain clusters. No S. carnosus and only five S. xylosus strains were lacking AB resistances and exhibited a PFGE genotype different from commercial starters. These strains, together with 17 S. equorum strains, were further studied for safety and technological characteristics. The ability to produce biogenic amines was not detected in any strain. PCR amplifications for enterotoxin encoding genes seg-sej were detected in one, and for δ-hemolysin encoding gene hld in four S. equorum strains, but phenotypic hemolytic activity was visible for three S. xylosus and 15 S. equorum strains. Catalase and nitrate reductase activity was observed in all isolates tested; particularly S. equorum showed high nitrate reduction. In conclusion, we were able to select four new meat starter strains (two S. xylosus and two S. equorum strains) out of 116 investigated CNS, fulfilling all safety criteria including the absence of AB resistances, production of biogenic amines and genes encoding virulence factors but exhibiting high nitrate reductase and catalase activity as suitable technological characteristics. Thus, S. equorum isolates, often the dominant species in spontaneously fermented meat products, provided a prospective meat starter species exhibiting high nitrate reduction and low prevalence of AB resistances.

Identification of staphylococci and dominant lactic acid bacteria in spontaneously fermented Swiss meat products using PCR-RFLP.

Pathogenic, spoilage, and technologically important microorganisms were monitored in 21 spontaneously fermented Swiss meat products manufactured with meat from wildlife or animals grown in natural habitat. Thereby, PCR-restriction fragment length polymorphism (RFLP) on rpoB and 16S rRNA gene sequences provided a powerful tool for fast and accurate identification of the main microbial population. Lactobacillus sakei and Lactobacillus curvatus dominated in fermented meat products followed by Staphylococcus species, which constituted 88.2% of all Gram-positive, catalase-positive cocci (GCC(+)) with cell counts varying from 2.6 to 7.0 log cfu/g during maturation. Staphylococcus equorum was prevalent in frequency and cell counts during maturation (18.0%; 5.0-7.3 log cfu/g) and in the end products (28.4%; 1.8-6.2 log cfu/g) implicating a new presumptive starter species for meat fermentation. Nine out of 14 end products indicated safety risks to consumers due to the high incidence of Staphylococcus saprophyticus or Staphylococcus epidermidis combined with cell counts of 7.4 and 4.9 log cfu/g, respectively. This fact was supported by the detection of Staphylococcus aureus and Enterobacteriaceae in ready-to-eat products strongly exceeding the tolerable limit of 2 log cfu/g. Spontaneously fermented meat products produced from wildlife or animals grown in natural habitats not only gave rise to hygienic and safety concerns but also provided new presumptive starter strains.