| Objective To investigate the prevalence,antibiotic resistance,and molecular characteristics of Staphylococcal aureus(S.aureus)and methicillin-resistant S.aureus(MRSA)on elementary students and school environment of Guangzhou,thus providing scientific clues for prevention and control of S.aureus and MRSA transmission in schools.Methods Cross-sectional design and multistage stratified cluster sampling were used to collect samples of elementary students and school environment.A series of microbiologic assays were employed to isolate and confirm the S.aureus and MRSA strains.Disk-diffusion methods were introduced to investigate the antibiotic resistance of S.aureus isolates.Polymerase chain reaction assays were applied for the screening of the 16 S r RNA gene,nuc gene,mec A gene,resistant genes,immune evasion cluster(IEC)genes,and toxin genes.Multilocus sequencing typing(MLST)and Staphylococcal Cassette Chromosome mec(SCCmec)typing were conducted to analyze the molecular characteristics.Logistic regression modeling with cluster-correlated robust variance estimates,homologous phylogenetic,and multistage stratified cluster analyses were conducted to predict the transmitted hazards between students and school environment.The generalized linear model was used to reveal the risk factors of S.aureus and MRSA nasal colonization among students.Additionally,elucidating the associations of S.aureus and MRSA isolates between Clonal Complex(CC)45 group and non-CC45 group by influencing factors,antibiotic resistance,and molecular characteristics.All statistics were analyzed by Stata 14.2(Stata Corp LP,College Station,Tex).Results The prevalence of S.aureus and MRSA nasal colonization among students: A total of 1705 elementary students were collected from eight schools.The prevalence of S.aureus was 21.58%(368/1705)and was 23.76% [95% Confidence Interval(CI),11.11-43.71] after weighting.The prevalence of MRSA was 10.15%(173/1705)and was 11.63%(95%CI,5.53-22.81)after weighting.The prevalence of S.aureus was associated with body mass index and daily time of watching television(TV).Obesity [Odds Ratio(OR)=1.80,95%CI: 1.44-2.24] and 1.5-3 hours of watching TV(OR=1.47,95%CI: 1.19-1.80)were risk factors of S.aureus nasal colonization.There was no influencing factor for MRSA nasal colonization.The prevalence of CC45 S.aureus was 3.99%(68/1705)and was 4.13%(95%CI,1.32-12.14)after weighting.The prevalence of CC45 MRSA was 2.64%(45/1705)and was 2.67%(95%CI,1.01-6.92)after weighting.The prevalence of CC45 S.aureus was associated with daily time of watching TV and whether hospital nearby.1.5-3 hours of watching TV(OR=1.87,95%CI: 1.15-3.05)and hospital nearby(OR=4.71,95%CI: 1.90-11.64)were risk factors of CC45 S.aureus nasal colonization.The prevalence of CC45 MRSA was associated with whether hospital nearby.There was hospital nearby(OR=5.86,95%CI: 1.72-19.95)was a risk factor of CC45 MRSA nasal colonization.The prevalence of S.aureus and MRSA contamination in school environment:A total of 1240 samples were collected from the objects' surfaces from school environment.The prevalence of S.aureus was 8.47%(105/1240)and was 9.15%(95%CI,3.34-22.71)after weighting.The prevalence of MRSA was 3.87%(48/1240)and was 4.43%(95%CI,0.99-17.70)after weighting.The prevalence of CC45 S.aureus was 1.69%(21/1240)and was 1.93%(95%CI,0.14-21.79)after weighting.The prevalence of CC45 MRSA was 1.45%(18/1240)and was 1.72%(95%CI,0.11-22.49)after weighting.Association of prevalence in S.aureus and MRSA isolates between environment and students: There were positive prevalence associations of school or class environment with students on S.aureus isolates.Similarly,there were also positive prevalence associations of school or class environment with students on MRSA isolates.The ORs and 95%CIs between school or class environment and students on the prevalence of S.aureus isolates were 1.07(95%CI,1.04-1.10;P(27)0.001)and 1.03(95%CI,1.01-1.06;P=0.008),respectively.What is more,the ORs and 95%CIs between school or class environment and students on the prevalence of MRSA isolates were 1.09(95%CI,1.05-1.13;P(27)0.001)and 1.03(95%CI,1.01-1.06;P=0.018),respectively.There were positive prevalence associations of school or class environment with students on CC45 S.aureus isolates.Similarly,there were also positive prevalence associations of school or class environment with students on CC45 MRSA isolates.The ORs and 95%CIs between school or class environment and students on the prevalence of CC45 S.aureus isolates were 1.14(95%CI,1.04-1.26;P=0.032)and 1.09(95%CI,1.06-1.12;P(27)0.001),respectively.What is more,the ORs and 95%CIs between school or class environment and students on the prevalence of CC45 MRSA isolates were 1.17(95%CI,1.09-1.26;P(27)0.001)and 1.10(95%CI,1.06-1.13;P(27)0.001),respectively.Antibiotic resistance : The proportions of resistant to penicillin,erythromycin, clindamycin,tetracycline,and teicoplanin of S.aureus and MRSA strains whatever from students or school environment were rather high,which might be resulted from the clinically common use of these antibiotics.Moreover,the resistant proportion of MRSA strains was higher than that of methicillin-sensitive S.aureus(MSSA)strains.Particularly,the proportions of multi-resistance of S.aureus in both students and school environment were more than 85%,and the proportion of students was 90.76%.The proportions of multiresistance of MRSA in both students and school environment were more than 95%,and the proportion of school environment was 100.00%.The proportions of multi-resistance of CC45 S.aureus in both students and school environment were more than 90%,and the proportion of school environment was 100.00%.The proportions of multi-resistance of CC45 MRSA in both students and school environment were more than 95%,and the proportion of school environment was 100.00%.Gene screening:As for IEC,toxin,and resistant genes between MRSA and MSSA strains,the carriage proportions were higher in MRSA strains than in MSSA strains.IEC,toxin,and resistant genes between CC45 MRSA and CC45 MSSA strains,the carriage proportions were higher in CC45 MRSA strains than in CC45 MSSA strains.And the proportions of a majority of these genes were indifferent between students and school environment strains.SCCmec typing:The most predominant SCCmec type of MRSA in students was IV(69.36%),followed by non-typeable(NT)(11.56%),V(8.09%),I(5.20%),III(4.05%),and II(1.73%).The most predominant SCCmec type of MRSA in school environment was IV(58.33%),followed by NT(12.50%),I(8.33%),II(8.33%),III(6.25%),and V(6.25%).The most predominant SCCmec type of CC45 MRSA in students was IV(82.22%),followed by I(11.11%),NT(6.67%),V(0.00%),III(0.00%),and II(0.00%).The most predominant SCCmec type of CC45 MRSA in school environment was IV(77.78%),followed by V(5.56%),I(8.33%),III(5.56%),NT(5.56%),and,II(0.00%).MLST:A total of 110 sequence types(STs)and 32 clonal complex(CC)types were found in S.aureus strains.,the frequencies from the highest to the lowest were:ST45(13.74%),ST6(6.98%),ST188(6.77%),ST59(6.13%),and ST30(5.92%);CC45(18.82%),CC30(11.84%),CC59(10.57%),CC188(9.94%),and CC6(9.30%),respectively.There were different degrees of affinity in 12 CC(24 STs)types from 368(65.33%)S.aureus strains.Similarly,there were different degrees of affinity in eight CC(12 STs)types from 117(52.94%)MRSA strains.Conclusions The prevalence of MRSAnasal colonization among students and MRSA contamination in school environment of Guangzhou are rather high.The multi-resistance toward common clinical antimicrobials are serious.Based on MLST results,the ST and CC types are diversified and it exists the phenomenon of strains from different sources including communities,hospitals and animal.Noticeably,there were positive prevalence associations of school or class environment with students on S.aureus and MRSA isolates.There is homology of S.aureus and MRSA strains between students and school environment.Instead,there is potential inter-transmission of strains between students and school environment. |
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