The Analysis About The Distribution Of Types, Drug Resistance And The Conservatism Of Virulence Factors Of The Streptococcus Pneumoniae Isolated From Children In Chongqing

Objective To investigate the differences of the sequence types, theserotypes and the drug resistance between the Streptococcus pneumoniaeisolated from invasive infection and the strains isolated fromnasopharyngeal carriage among children in Chongqing as well as theconservatism of the base sequences of the important virulence factors inorder to provide information for the prevention and therapy for S.pninfection and protein vaccine development.Methods A total of51strains of S.pn were isolated from thechildren with IPD under11years old in the Children’s Hospital ofChongqing Medical University between2010and2013.At the sametime,14carriage isolates were isolated from healthy children withoutrespiratory tract diseases under6years old.The7housekeeping genesincluding aroE,gdh,gki,recP,spi,xpt,ddl were amplified by PCR,thensequenced and blasted them in MLST database to get the ST patterns. Multiplex PCR typing was used for serotyping of S.pn. The11virulencefactors including ply, lytA, nanA, phtD, clpP, cps2A, bacteriocin, psaA,piaA, pcsB, stkP were also amplified by PCR and sequenced for theanalysis about the mutation of base sequences. Drug resistance of the65isolates to15antibiotics were determined by MIC.Results19STs were detected in the65isolates. ST876,ST81andST3173were detected in the both groups. ST320,ST2296,ST242,ST90,ST99,ST2754, ST902,ST271,ST4112and ST3263were only found ininvasive strains while ST983,ST2912,ST7759,ST3397, ST7752andST7392were only detected in carriage group.11serotypes were identifiedamong the65isolates. Serotypes14,6A/6B,23F,19F were detected in bothkinds of isolates. Serotypes19A,1,33/33B,11/11A，17F were only foundin invasive group and15,6C were only detected among carriageisolates.All the65strains of S.pn were sensitive to vancomycin, linezolid,levofloxacin and moxifloxacin. At the same time,the14carriage strainswere also sensitive to cefotaxime and telithromycin. The nonsensitiverates of invasive strains to erythromycin(P=0.001), penicillin(P=0.001),meropenem(P=0.018), cefotaxime(P=0.007) and clindamycin(P=0.034)were all higher than the carriage isolates.While the nonsensitive rates ofthe carriage strains to chloramphenicol (P=0.005)and tetracycline(P>0.05)were higher than the invasive isolates. And the nonsensitive rates ofinvasive strains to the other4antibiotics were all higher than carriage strains, which had no statistically significant differences(P>0.05). Theconservatism of the virulence factors including ply, lytA,nanA, phtD, clpP,cps2A, bacteriocin, psaA, piaA, pcsB,stkP were97.82%,96.31%,82.96%,87.50%,98.48%,83.68%,66.27%,99.46%,98.63%,88.72%,96.67%,respectively.Conclusion The proportion of serotype19A is the highest amongthe invasive strains of S.pn in Chongqing, so the children had betterchoose PCV13to protect against S.pn infection. The conservatism of thebase sequences of ply, stkP,piaA,lytA,clpP,psaA is better than the othervirulence factors in our study,which may have the potential to be thecandidates for pneumococcal vaccine proteins. It’s preferred to choosetelithromycin which is the new generation of macrolides antibiotics forchildren with IPD in Chongqing.While there exist some differencesbetween the invasive and carriage strains in genetic polymorphism,distribution of serotypes and drug resistance, which will provide referencefor epidemiologic study and clinical therapy.