AUTHOR=Zhang Haifang , Zheng Yi , Gao Huasheng , Xu Ping , Wang Min , Li Aiqing , Miao Minhui , Xie Xiaofang , Deng Yimai , Zhou Huiqin , Du Hong 

TITLE=Identification and Characterization of Staphylococcus aureus Strains with an Incomplete Hemolytic Phenotype

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=6

YEAR=2016

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2016.00146

DOI=10.3389/fcimb.2016.00146

ISSN=2235-2988

ABSTRACT=<p><italic>Staphylococcus aureus</italic> is a common pathogen causing both hospital and community-acquired infections. Hemolysin is one of the important virulence factors for <italic>S. aureus</italic> and causes the typical β-hemolytic phenotype which is called complete hemolytic phenotype as well. Recently, <italic>S. aureus</italic> with an incomplete hemolytic phenotype (SIHP) was isolated from clinical samples. To study the microbiologic characteristics of SIHP, the special hemolytic phenotype of SIHP was verified on the sheep blood agar plates supplied by different manufacturers. Expression of hemolysin genes <italic>hla, hlb, hlgC</italic>, and <italic>hld</italic> of SIHP was detected by qRT-PCR and it was showed that expression of <italic>hlb</italic> in SIHP was obviously increased compared to the control <italic>S. aureus</italic> strains with complete hemolytic phenotype (SCHP), while the expression of <italic>hla, hlgC</italic>, and <italic>hld</italic> in SIHP was significantly decreased. In addition, the α-hemolysin encoded by gene <italic>hla</italic> was decreased obviously in SIHP compared to SCHP by western blot. All 60 SIHP strains were identified to be the methicillin resistant <italic>S. aureus</italic> (MRSA), and moreover these SIHP strains all contains <italic>mecA</italic> gene. The virulence gene <italic>tst</italic> were all present in SIHP, and the intracellular survival ability of SIHP was much greater than that of the gene <italic>tst</italic> negative <italic>S. aureus</italic>. We also found that IL-2, IL-6, and IL-17A secreted in the supernatant of SIHP infected macrophages increased significantly compared to <italic>tst</italic> negative control strains infected ones. MLST analysis showed that all of SIHP strains were classified into ST5 clone. To our knowledge, this study firstly showed that SIHP strains are a kind of methicillin resistant strains which express β-hemolysin highly and possess a potential high virulence, and it was suggested that SIHP should be paid more attention in hospital.</p>