Isolation and Characterization of Halophilic Kocuria salsicia Strains from Cheese Brine

Kocuria salsicia can survive in extreme environments and cause infections;including catheter-related bacteremia;in humans. Here;we investigated and evaluated the characteristics of nine K. salsicia strains (KS1–KS9) isolated from cheese brine from a farmstead cheese-manufacturing plant in Korea from June to December;2020. Staphylococcus aureus American Type Culture Collection (ATCC) 29213 was used as a positive control in the growth curve analysis and biofilm-formation assays. All K. salsicia isolates showed growth at 15% salt concentration and temperatures of 15℃;25℃;30℃;37℃;and 42℃. KS6 and KS8 showed growth at 5℃;suggesting that they are potential psychrotrophs. In the biofilm-formation analysis via crystal violet staining;KS6 exhibited the highest biofilm-forming ability at various temperatures and media [phosphate buffered saline;nutrient broth (NB);and NB containing 15% sodium chloride]. At 25℃ and 30℃;KS3;KS6;and KS8 showed higher biofilm-forming ability than S. aureus ATCC 29213. The antimicrobial resistance of the isolates was evaluated using the VITEK？？ 2 system; most isolates were resistant to marbofloxacin and nitrofurantoin (both 9/9;100%);followed by enrofloxacin (7/9;77.8%). Five of the nine isolates (5/9;55.6%) showed multidrug resistance. Our study reports the abilities of K. salsicia to grow in the presence of high salt concentrations and at relatively low temperatures;along with its multidrug resistance and tendency to form biofilms.