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Characterization of coagulase-negative staphylococci from brining baths in Germany
P Hammer1, J Jordan1, C Jacobs1
1Department of Safety and Quality of Milk and Fish Products, Max Rubner-Institut, Federal Research Institute of Nutrition and Food, 24103 Kiel, Germany.
Journal of Dairy Science
|August 19, 2019
Summary
Coagulase-negative staphylococci (CNS) in German cheese brines showed antibiotic resistance but lacked enterotoxin genes. The study found no unacceptable risks from these CNS strains, despite some antibiotic resistance observed.
Area of Science:
- Food microbiology
- Dairy science
- Bacteriology
Background:
- Brining is crucial in German cheese production, influencing flavor and ripening.
- Coagulase-negative staphylococci (CNS) are part of the cheese brine microbiota.
- Some CNS strains can produce staphylococcal enterotoxins and exhibit antibiotic resistance.
Purpose of the Study:
- To isolate and identify CNS from German cheese brines.
- To assess the antibiotic resistance profiles and presence of enterotoxin genes in these CNS isolates.
- To investigate the influence of environmental stressors on antibiotic resistance expression.
Main Methods:
- Isolation of presumptive CNS from 52 cheese brine samples across 13 German factories.
- Species identification using sodA gene sequencing and subspecies-level subtyping.
- Antibiotic resistance profiling, PCR for resistance genes (blaZ, blaTEM), and challenge tests with lactic acid and NaCl.
- Testing for genetic determinants of staphylococcal enterotoxins (entA-E).
Main Results:
- 50 of 52 isolates were identified as CNS, predominantly Staphylococcus saprophyticus.
- 19 CNS isolates showed resistance to oxacillin, penicillin, or cefoxitin; blaZ and blaTEM genes were detected in 7 isolates.
- Environmental stressors (lactic acid, NaCl) had minimal impact on antibiotic resistance, with one isolate showing increased trimethoprim/sulfamethoxazole resistance.
- No staphylococcal enterotoxin genes (entA-E) were detected in any of the isolates.
Conclusions:
- The study identified common CNS species in German cheese brines, with Staphylococcus saprophyticus being dominant.
- While antibiotic resistance was present in some CNS strains, the absence of enterotoxin genes suggests a low risk.
- The findings indicate no unacceptable risks associated with the isolated CNS from German cheese brines regarding enterotoxin production.
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