| BackgroundStaphylococcus aureus is a gram-positive bacteria which can cause serious infection,including nasosinusitis,pneumonia,endocarditis and osteomyelitis,etc.The mortality rate of which reaches to 20%.At present,owing to the unreasonable use and sale of antibiotics,the drug resistance trend is becoming increasingly severe,the spread of drug resistant strains is speeding,bringing great health threat to human body.While 80% of these infections are from nasal or skin carriage of staphylococcus aureus before admission to hospital.Staphylococcus aureus colonization among healthy population is a significant risk factor community and hospital infection,as well as the spread of drug resistant strains.At present,researches from all around the world on staphylococcus aureus mainly focus on hospitals but pay less attention to the staphylococcus aureus carriage in healthy people.Therefore,it is not conducive to the investigation of the source of infection and the formulation of prevention and control measures,emphasizing that we need to study the staphylococcus aureus carried by healthy peopleObjective1.To investigate the nasal carriage of staphylococcus aureus among healthy population in Taixing,Jiangsu Province.2.To discover the current status of drug resistance among healthy population,and detect the corresponding resistant genes.To provide scientific basis for preventing and controlling the colonization and infection of drug-resistant strains.3.To observe the molecular characteristics of staphylococcus aureus among healthy population.4.Based on the colonization state and molecular differences,to future discuss the underlying risk of infection and the potential impact of drug resistance acquisition and drug resistance transmission.Methods1.Between June 7,2016 and June 14,2016,we collected nasal swab specimens on day 0,day 3 and day 7 among 144 healthy adults aged 18-65 years in Taixing,Jiangsu Province.2.We refer to GB/T 4789.37-2008 as our standard for enumeration of staphylococcus aureus.Using Baird-Parker plate for s.aureus counting and Plasma coagulation test and Vitck 2 Biochemical tests for srain identification,to separate the s.aureus positive strains.According to the three-times nasal specimens results,to distinguish these strains into three carriage patterns: persistent carriers,intermittent carriers and undetermined colonization state.3.We refer to Clinical and Laboratory Standard Institute,using K-B Disk Diffusion test toinvestigate the drug resistance of these strains to 24 different antibiotics.4.PCR method was used to detect multiple drug resistance genes of staphylococcus aureus.Mec A gene typing was also used for those methicillin resistant strains.5.Using three molecular typing method,Staphylococcal protein A typing,Multilocus sequence typing and Multiple-locus variable number tandem repeat analysis to describe the molecular epidemiological characteristics of staphylococcus aureus and compare them with global epidemic strains.Results1.The nasal carriage of s.aureus among healthy population is very universal.In this study,we found the s.aureus carriage rate is 25.69%.The persistent carriers account for 8.33% and intermittent carriers account for 17.36%,while still 74.31% are classified into undetermined colonization state.Among persistent carriers,the enumeration of s.aureus in their nasal cavity are up to 106 CFU.2.The s.aureus among healthy population shows high resistance level to ?-lacttam antibiotics,erythromycin and teicoplanin while low drug resistance detection rate to aminoglycoside antibiotics,quinolone chemosynthetic,multiple drug resistance is serious.The resistance strains of linnezolamide,rifampicin,mopirocin and vancomycin were not found.When comparing the drug resistance situation between persistent carriers and intermittent carriers,no more resistant species were observed among persistent carriers.3.The molecular types of s.aureus are widely distributed among healthy population.Most persistent carriers have fixed molecular type of s.aureus,while the intermittent carriers are prone to change from time to time,also accompany the changes of resistant strains.4.In this study,we found 23 mecA positive strains,SCCmec I,SCCmec II,SCCmec III were all observed in intermittent carriers.While among those persistent carriers,all typed SCCmec were found to be SCCmec IV,no changes for the SCCmec typing were observed among this group.5.We found 10 MRSA resistance molecular patterns.Two among persistent carriers,including t015-ST508-SCCmec IV and New-ST1920-SCCmec IV.Eight among intermittent carriers,including t437-ST59-SCCmec I,t437-ST59-SCCmec III,t437-ST59-SCCmec IV,t015-ST508-SCCmec IV,t616-ST944-SCCmec II,t5554-ST630-SCCmec III,t377-ST630-SCCmec II and t4549-ST630-SCCmec III.Conclusion1.The carriage of s.aureus among healthy population is very universal.Different colonization states and molecular type has important influence on the emergence of drug resistance and the spread of drug-resistant strains.2.In this study,we have not observed more resistant species among persistent carriers,suggesting the multiple drug resistance may not be related to the colonization state.3.People who carry diffent types of SCCmec may be acquired from various sources,and also leading to relevant risks.Different colonization status may have potential mechanism on SCCmec type.4.No main resistant molecular patterns that cause HA-MRSA in our country were found among healthy population in this study. |
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