Contamination, Antimicrobial Susceptibility Profiles And Molecular Characteristics Of Staphylococcus In Several Public Places Of Guangzhou

ObjectiveTo investigate the contamination state, antimicrobial susceptibility profiles and molecular characteristics of Staphylococci on objects’ surfaces in several public places of Guanghzhou, thus providing scientific clues for prevention and control of Staphylococci transmission in public places. MethodsCross-sectional studies were used to survey the Staphylococci contamination in the environments of subways, railway stations, bus stations and hospital waiting halls. A series of microbiologic assays were employed to isolate and confirm the strains. Disk-diffusion methods were introduced to conduct the antimicrobial susceptibility testing of all Staphylococci isolates. PCR assays were applied for the screening of PVL gene, qac gene and multilocus sequencing typing among Staphylococcus aureus strains and SCC mec typing in methicillin-resistant Staphylococcus aureus(MRSA) strains. ResultsThe contamination of Staphylococci:A total of 1100 samples were collected from the objects’ surfaces from public places. The isolation rate of Staphylococci is 59.64%(656/1100): the contamination rate of Staphylococcus aureus is 7.55 %(83/1100), with MRSA contamination rate of 1.73%(19/1100); the contamination rate of coagulase-negative Staphylococci(Co NS) is 52.09%(573/1100), with methicillin-resistant coagulase-negative Staphylococci is 6.09%(67/1100). The places ranked from the highest Staphylococci contamination rate to the lowest were: subway(75.63%,242/320)>hospitals(66.25%,265/400)>railway stations(43.89%,79/180)>bus stations(35.00%,70/200). The places ranked from the highest Staphylococcus aureus contamination rate to the lowest were: subway(11.25%,36/320)>bus stations(8.50%,17/200)>railway stations(6.67%,12/180)>hospitals(4.50%,18/400).Antimicrobial susceptibility testing:The resistant Staphylococci strains were found towards all the 11 antibiotics tested. The antibiotics were listed in sequence from the highest resistant rate to the lowest resistant rate: penicillin(94.05%)> erythromycin(84.15%)> clindamycin(57.62%)> rifampicin(48.78%)> trimethoprim(42.23%)> gentamycin(31.25%)> moxifloxacin(21.29%)> tobramycin(14.33%)> cefoxitin(12.65%)> teicoplanin(3.66%)> linezolid(2.44%). Staphylococcus aureus strains have higher resistant rates toward cefoxitin and tobramycin and lower resistant rates toward clindamycin and erythoromycin when compared with Co NS, and the differences are statistical significant(P<0.05); there is no statistical difference toward erythromycin resistant rate between methicillin resistant and methicillin susceptible strains, and methicillin resistant strains have statistical higher resistant rate toward other drugs when compared with methicillin susceptible strains(P<0.05); the distinctions of resistant rates between strain isolated from different palces have also been observed.PVL gene and qac gene screening:The carriage of PVL gene was screened in t wo MRSA strains(10.53%, 2/19) and nine methicillin-susceptible Staphylococcus aureus(MSSA) strains(14.06%, 9/64),and there was no statistical significance between the two groups regarding to PVL carriage rates(Fisher’s exact test,P=1.000). The carriage of qac gene was found in nine MRSA strains(47.37%, 9/19) and none was found in MSSA strains(0.00%, 0/64), there were statistical differences between the two groups regarding to qac carriage rates(Fisher’s exact test,P<0.001).SCCmec typing:Among 19 MRSA strains, one was SCCmecⅠtype(5.26%), three were Ⅱ type(15.79%), two were Ⅲ type(10.53%), five were Ⅳa type(26.32%), 8 were not typable(42.11%), and none was Ⅳb、Ⅳc、Ⅳd or Ⅴ type.MLST:A total of 27 ST types were found, the frequencies from the highest to the lowest were:ST188(26.55%)> ST5(17.19%)> ST72(15.63%)> ST398(12.50%)> ST6、ST15 and ST1462(6.25%)> ST125(4.69%)> ST59、ST97 and ST2140(3.13%)> ST8、ST25、ST30、ST88、ST221、ST338、ST537、ST789、ST808、ST1141、ST1311、ST1507、ST1860、ST2114、ST2605 and ST2668(1.56%). According to the clustering analysis between ST types, 3 clonal complexes(CC5,CC59 and CC72),4 doublets(D6,D30,D188 and D398)and singletons(ST8,ST15,ST25,ST88,ST97,ST789,ST1141 and ST2668)were formed. Based on the dendrogram analysis of 19 MRSA strains, five clone types were formed. The potential risks toward transmissions of MRSA strains between defferent public areas do exist.ConclusionsThe Staphylococci contamination in public places of Guagnzhou is rather serious. The resistant rates toward common clinical antimicrobials are high. There were several PVL-positive strains in Staphylococcus aureus, and the rate of qac-positive strains in MRSA is alarimg. The community-acquired and hospital-acquired MRSA strains were coexisted according to SCCmec typing. Based on MLST results, the ST types were in accordance with recent reports in China and were related to international epidemic clones, and there exists the potential of intertransmission between MRSA strains in different public areas.