Correlation Among Antimicrobial Drug Resistance With Panton-Valentine Leukocidin(PVL) Gene And Hemolytic Phenotype Of Staphylococcus Aureus

Backgroud:Staphylococcus aureus(S.aureus)is one of the most common pathogens isolated from both healthy individuals and patients worldwide,which can produce a variety of secreted toxins and cause various infections to the human.S.aureus is one of the most common opportunistic pathogens in the clinic,which can produce a variety of toxins such as hemolytic toxin,Panton-Valentine Leukocidin,enterotoxin,toxic shock syndrom toxin-1(tsst-1).S.aureus causes various infections in humans and animals through the combined action of various toxins and invasive enzymes.Its virulence factor,PVL,is one of the important virulence factors of S.aureus,which can induce various infections,such as skin soft tissue infection and necrotizing pneumonia.In laboratory,S.aureus are cultured in Columbia sheep blood agar plates for 24 hours.Usually,S.aureus produces completely ?-hemolytic phenotype,termed as SCHP(S.aureus strains with complete hemolytic phenotype).However,it was observed that a small number of S.aureus strains produces incompletely ?-hemolytic phenotype,and the antibiotic susceptibility between this small number of S.aureus strains with SCHP was different.Objective:This experiment aimed to evaluate the correlation among the incomplete hemolytic phenotype of Staphylococcus aureus(SIHP)and Panton-Valentine Leukocidin gene(pvl)in characteristics of antimicrobial resistance.Methods:After excluded the duplicate samples,two hundreds and eleven strains were randomly isolated from patients in the First Hospital of Anhui Medical University(AMU)from 2016 to 2017.All the strains were identified as S.aureus by matrix-assisted laser desorption ionization time-of-flight mass spectrometry(BioMérieux,MALDI-TOF MS VITEK V3.0,France).All strains were cultured in Columbia sheep blood agar plates for 24 hours and then underwent 10 passages for investigation of their hemolytic phenotypes.S.aureus produces ?-hemolytic phenotype,termed as SIHP(S.aureus strains with incomplete hemolytic phenotype).In contrast,S.aureus produces incomplete hemolytic phenotype termed as SCHP.The antibiotic susceptibility of 211 hospital-acquired S.aureus to 20 antibiotics were determined by MicroScan WalkAway 96(Beckman Coulter,Brea,CA).The PVL gene are characterized by PCR amplification followed by sequencing.Statistical analyses of the data were performed using SPSS version 16.0 software(SPSS Inc,Chicago,IL).Results:Fifty-two(24.64%)strains were confirmed to keep the incomplete hemolytic phenotype of S.aureus(SIHP).Meanwhile,15(7.11%)of 211 strains were identified to carry pvl,and 8 of 15 strains were SIHP.Compared with the SCHP strains,among the 20 antibiotics,the antimicrobial susceptibility testing of SIHP to 7 antibiotics(oxacillin,ciprofloxacin,gentamicin,ceftriaxone,cefoxitin,levofloxacin and moxifloxacin)presented statistically significant differences(P < 0.05).The resistance rates of pvl-positive bacteria to 4 antibiotics(rifampin,ciprofloxacin,levofloxacin and moxifloxacin)were statistically different compared with those of pvl-negative strains(P < 0.05).Conclusions:Compared with the SCHP strains,PVL gene had a higher frequency than those identified in SIHP.The pvl-positive isolates showed less resistance to rifampin,ciprofloxacin,levofloxacin and moxifloxacin.Additionally,SIHP strains had significantly higher antibiotic susceptibility to oxacillin and cefoxitin when compared with SCHP,while SCHP strains had significantly higher antibiotic resistance rates to ciprofloxacin,gentamicin,ceftriaxone,levofloxacin and moxifloxacin.The results may provide medical advice for the clinical treatments of S.aureus.