| Objective:To investigateantimicrobial resistance,molecular typing,resistance mechanisms of fluoroquinolone and virulence genes of Salmonella Braenderup(S.Braenderup),so as to learn the epidemic trend of S.Braenderupfor prevention and control of S.Braenderup infection and rational use of antimicrobial agents.Methods:1.The clinical data were recorded from patientswithacute diarrhea who received treatment in tow teaching hospitals of our city from April to October of 2012 to2014.Salmonella from stool sampleswas screened by culture,and identified by biochemical,PCR and serotype.2.Collected isolates of S.Braenderup were examined for the susceptibilities to 14 antibacterial agents by MIC and Kirbty-Bauer.3.Molecular typing: multi-locus sequence typing(MLST)and pulsed-field gel electrophoresis(PFGE).4.Fluoroquinolone resistance genes detection: PCR amplification was used forquinolone-resistance determining region(QRDR)of fluoroquinolone target gene(gyr A,gyr B,par Cand par E)and plasmid-mediated quinolone resistance genes(qnr A,qnr B,qnr C,qnr D,qnr S,qep A,oqx ABand acc(6’)-Ib-cr).Positive PCR products were sequenced and the sequences were analyzed by Blast.5.Detecting virulence genes: representative genes of SPIswere detected by PCRincluding SPI1~6(inv A,sit C,hil A,sse L,sif A,mgt C,sii E,sop B,pag N),SPI9~12(bap A,sef A,pag Cand ssp H2)and the regulatory gene(pho P).Results:1.Among 153 non-repetitive NTS isolates in these years,8 isolates(5.23%)of S.Breanderup were identified.2.All 8 isolatesof S.Braenderupwere resistant to nalidixic acid and intermediate resistance to ciprofloxacin and levofloxacin.They were all susceptible to otherantimicrobial agents.3.The temporal distribution among 8S.Braenderupinfection patients was1 in 2012,2 in 2013 and 5 in 2014 with 5males and 3 females.Patients’ ages were between25 and 62 years old.All cases were diagnosed with acute gastroenteritis.4.With the criterion of 100 % similarity,two PFGE patterns of 8 S.Braenderupwere found by Xbaldigestionwith 7 isolates of A pattern and 1 isolate of B pattern.The similarity between A and B was 97.3%.5.All 8 isolates of S.Braenderupwere identical ST22 by MLST analysis.The allelic profile of 7 housekeeping genes(his D,dna N,hem D,thr A,pur E,suc Aandaro C)were 14,2,15,12,11,14 and 16,respectively.6.All 8 isolates of S.Braenderup showed the same single nucleotide mutation in gyr Aof QRDR leading to Asp 87→Tyr(GAC→UAC)but only some non-sense mutations in gyr B,par Cand pareof QRDR.All 8 isolates were negative forplasmid-mediated quinolone resistance genes(qnr A,qnr B,qnr C,qnr D,qnr S,qep A,oqx ABand acc(6’)-Ib-cr).7.K-B methoddisplayed 4 susceptible isolates(50%)and 4 intermediate resistant isolates(50%)to 8 ciprofloxacin and levofloxacin,to which all 8 isolates were intermediate resistant by MIC measurement.8.All 8 isolates of S.Braenderupwere positive forsit C,hil A,sse L,sif A,mgt C,sii E,sop B,pag N,bap A,pag C,ssp H2 andpho Pbut negative for sef A.Conclusions:1.All 8 isolates of S.Braenderupin this study showed the same antibiotic resistance profile,MLST and the sense mutation ingyr Aand also displayedsame or extremely similar PFGE patterns,which probably implied an infection outbreak caused by ST22 S.Braenderup in our city.2.The possible infection outbreak probably caused that the isolation rate of S.Braenderupis apparently higher than other area of our country with persistent occurrencein 3 consecutive years.3.Some NTS of intermediate resistant to FQs were showed susceptible by K-B method of Ciprofloxacin.So the method can mislead clinical therapy.4.Clinical isolates of S.Braenderup carried genes of SPI1,2,3,4,5,6,9,11,12 and regulatory genesprobably indicatingtheir high virulence.5.Continuous surveillance and investigation for NTS is required in our city.Tianjin should join the system of Pulse Net China. |
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