The Study Of Molecular Epidemiology And Biocides Resistance Of Staphylococcus Aureus Colonized In Nasal Cavity Of School Students In Guangzhou

Background:The infection caused by Staphylococcus aureus seriously endangers public health,and its drug resistance is also very serious.Community-associated methicillin-resistant Staphylococcus aureus(CA-MRSA),which usually colonize in the nasal cavity of normal individuals,offering conditions for its rapid spread and causing serious public health problems.Objective:Herein,we explored the molecular epidemiological characteristics and antibiotic/biocides susceptibility features of S.aureus in the nasal colonization of school-age students in Guangzhou.Moreover,we analyzed the distribution of biocide-resistant genes,biofilm formation ability,and resistance to biocides such as chlorhexidine and mupirocin in S.aureus isolates,providing strategies for the prevention and control of community-associated S.aureus infections and guidance for the use of antibiotics and daily protective biocides in clinic.Method:722 isolates of Staphylococcus aureus were isolated from nasal swabs of 2375 students from 5 schools(elementary,junior,and senior high)in Guangzhou from October to November 2018.The antibiotic resistance of these strains against 16 antibiotics was tested,and the fem B and mec A genes of S.aureus were detected by PCR and MLST typing was performed to analyze the epidemiological and drug-resistant characteristics.The carriage of 9 biocide resistance genes in S.aureus strains was detected,and qac A/B and mupA gene positive strains were selected for testing their resistance to chlorhexidine and mupirocin as well as their biofilm formation ability.Chi-square analysis were used to analyze the correlation of prevalence and biocide resistant genes.Results:1.Among the 722 Staphylococcus aureus isolates,72 were MRSA and 4 were OS-MRSA;the proportions of S.aureus and MRSA were both higher in younger students.The antibiotics with the highest resistance rates among S.aureus were penicillin(85.5%),erythromycin(43.3%),and clindamycin(41.0%).2.The most prevalent MSSA sequence types(STs)were ST30,ST45,and ST188,while the most prevalent MRSA strains were ST45,ST59,and ST188.The most widespread CC types were CC30,CC45,CC5,CC1,CC15,CC944,CC398,and CC59,which accounted for 86.7% of all S.aureus strains.3.All CC30 strains were resistant to erythromycin and clindamycin(D test positive).CC30 and CC45 strains were highly resistant to penicillin(99.2% and95.2%,respectively).CC45 and CC59 strains were closely related to MRSA,82.5%of the MRSA strains were derived from these two types.4.The most common disinfectant resistance genes were mepA(95.57%),nor A(78.81%),lmr S(77.01%),and sepA(58.17%),and the qac G gene was not detected.The sepA gene was more frequently found in CC30 and CC45 S.aureus strains,and its presence was associated with resistance to clindamycin,erythromycin,and other antibiotics.5.64(94.1%,n=68)qac A/B-positive S.aureus strains were resistant to chlorhexidine,while 12(100%,n=12)mupA-positive strains were resistant to mupirocin.6.Among the 85 qac A/B or mupA-positive S.aureus strains,84(98.8%)had varying degrees of biofilm-forming ability,and biofilm formation was positively correlated with resistance to chlorhexidine and mupirocin.Conclusion:1.This study found that MRSA was more prevalent and resistant in nasal colonization of primary and secondary school students in Guangzhou,and younger students had a higher proportion of colonization of both S.aureus and MRSA and CC45 may replace CC59 as the most prevalent S.aureus in South China.2.The main source of MRSA in school-age students in Guangzhou was S.aureus CC30 and CC45.3.The S.aureus strains isolated from the nasal cavity of school-age students in Guangzhou carried a certain degree of biocide resistance genes,and the distribution of disinfectant genes such as sepA may be related to specific CC types of S.aureus.4.This study confirmed a significant correlation between qac A/B and mupA genes and the resistance of S.aureus to chlorhexidine and mupirocin.Biofilm formation may be one of the important factors for the resistance of S.aureus to chlorhexidine and mupirocin.