Microbiological Characteristics of Clinically Isolated Staphylococcus aureus with Different Hemolytic Phenotypes in China.

ABSTRACT

Purpose: This study aimed to investigate the microbiological characteristics of clinically isolated Staphylococcus aureus with different hemolytic phenotypes in China. Materials and Methods: Using the three-point inoculation method, the hemolytic phenotypes of 1295 clinically isolated S. aureus strains were detected and categorized. Antimicrobial susceptibility testing of all strains was performed using a VITEK 2 Compact System. After sample size matching, plasma coagulase activity, catalase activity, mRNA expression of hemolysin genes (hla, hlb, hlc, and hld), biofilm formation, growth kinetics, inflammatory response of macrophages and cytotoxicity of S. aureus with different hemolytic phenotypes using the rabbit plasma kit, the catalase test on slides, qRT-PCR, crystal violet staining, the microcultivation assay, the ELISA kits, and the CCK-8 assay, respectively. Results: Seven categories of hemolytic phenotypes were identified. Accordingly, strains were categorized into seven different groups, including S. aureus with complete hemolytic phenotype (SCHP), S. aureus with weak hemolytic phenotype (SWHP), S. aureus with incomplete hemolytic phenotype 1 (SIHP-1), SIHP-2, SIHP-3, SIHP-4 and SIHP-5, the last three of which were reported for the first time. Except for the hemolytic phenotype, all seven groups differed in clinical isolation rates, antibiotic resistance profile, plasma coagulase activity, mRNA expression of hemolysin genes, biofilm formation, growth kinetics, inflammatory response of macrophages, and cytotoxicity. Conclusion: S. aureus with different hemolytic phenotypes have distinctive microbiological characteristics. Clinical microbiologists need to be vigilant about the hemolytic phenotypes when culturing S. aureus strains, and actively enhance communication with clinicians to optimize the treatment of infection.