Identification of staphylococcus aureus lineage ST59 by the combined detection of delta hemolysin allelic variant G10S and beta hemolysin

Objective To investigate the identification of staphylococcus aureus lineage ST59 using the combined detection of delta hemolysin allelic variant G10S(HldG10S) and beta hemolysin(β-toxin). Methods Perspective study.A total of 82 non-duplicate clinical staphylococcus aureus were collected from November 2017 to April 2018 in the department of Clinical laboratory, the Third Xiangya Hospital of Central South University, China.The strains were routinely identified by MALDI-TOF MS and the mass spectra were obtained. According to the m/z expression intensity of delta hemolysin(Hld), all strains were divided into three groups:HldG10S (3 036±2.0)m/z, Hld (3 006±2.0)m/z and ND [no (3 036±2.0)m/z and no (3 006±2.0)m/z]. The distribution of ST59 in the three groups was detected by MLST. Reverse synergic hemolysis test was used to determine the β-toxin phenotype.And the sensitivity, specificity and accuracy of HldG10S, β-toxin and the combined detection of HldG10S and Hld to identify ST59 were compared. Results Among the 82 strains, 21 strains expressed HldG10S toxin, accounting for 25.6%. 39 strains expressed Hld toxin, accounting for 47.6%.22 strains did not express HldG10S and Hld toxin, accounting for 26.8%. In HldG10S group,16 strains were ST59, accounting for 76.19% (16/21).ST59 was not found in both Hld and ND groups. All 16 strains of ST59 in HldG10S group produced β-toxin, while none of the 5 strains of non-ST59 produced β-toxin. The specificity(100%) and accuracy(100%) of the combined detection was significantly higher than that of HldG10S and β-toxin single detection of specificity(92.4%,77.3%) and accuracy(80.5%,81.7%)(χ2=19.472,P<0.001; χ2=17.792,P<0.001). Conclusion The combined detection of HldG10S and β-toxin can preliminarily and rapidly identify ST59, which can assist the routine monitoring of the change trend of staphylococcus aureus epidemic. Key words: Staphylococcus aureus; Bacterial proteins; Hemolysin proteins; Mutation; Spectrometry, mass, matrix-assisted laser desorption-ionization