儿童呼吸道流感嗜血杆菌分离株耐药性与ftsI基因分型研究

Antimicrobial resistance and ftsI genotyping of Haemophilus influenzae isolates from respiratory tract in children

目的调查呼吸道感染患儿流感嗜血杆菌分离株的耐药性与ftsI基因的关系。方法 2011年6月—2012年9月,收集呼吸道感染患儿呼吸道标本中分离到的流感嗜血杆菌,用微量肉汤稀释法测定常用抗菌药物最低抑菌浓度(MIC);用Nitrocefin纸片法检测细菌的β内酰胺酶;用聚合酶链反应(PCR)技术对分离株进行ftsI基因分型;比较不同ftsI基因型菌株对常用抗菌药物的耐药性。结果473株流感嗜血杆菌中产β内酰胺酶菌株占51.8%(245/473),ftsI基因突变率为33.4%(158/473);β内酰胺酶基因阴性氨苄西林耐药型菌株(gBLNAR)以GroupⅠ/Ⅱ型为主(113/154),68.1%(77/113)的该型菌株对氨苄西林敏感,85.4%(35/41)的gBLNAR GroupⅢ菌株对氨苄西林不敏感;gBLNAR菌株对头孢克洛、头孢呋辛、头孢曲松和阿莫西林-克拉维酸等β内酰胺类抗生素MIC90和耐药率明显高于gBLNAS(敏感)菌株(P<0.01),对左氧氟沙星、阿奇霉素和甲氧苄啶-磺胺甲口恶唑等非β内酰胺类抗菌药物的MIC90和耐药率与gBLNAS菌株相比差异无统计学意义(P>0.05);gBLNAR GroupⅢ菌株对β内酰胺类抗生素的MIC90和耐药率高于gBLNAR GroupⅠ/Ⅱ菌株(P<0.01),两者对非β内酰胺类抗菌药物的MIC90和耐药率差异无统计学意义(P>0.05)。结论呼吸道感染患儿呼吸道流感嗜血杆菌分离株发生ftsI基因突变的情况较为常见,突变以GroupⅠ/Ⅱ型为主,明显影响氨基青霉素类和某些第二代头孢菌素的抗菌活性。

Objective To investigate the relation between antimicrobial resistance and ftsI gene encoding PBP3 of Haemophilus influenzae isolated from respiratory tract in children. Methods From June 2011 to September 2012, H. influenzae isolates were collected from respiratory tract in children. Minimum inhibitory concentrations were determined by mircrobroth dilution with commonly-used antibiotics. Beta-lactamase production was detected by Nitrocefin disk test. PCR technique was employed for ftsI genotyping. Antimicrobial resistance was compared between beta-lactamase-nonproducing, ampicillin-resistant （gBLNAR） and beta-lactamase-nonproducing, ampicillin-susceptible （gBLNAS） isolates as well as between gBLNAR Group Ⅰ/Ⅱ and gBLNAR Group Ⅲ isolates. Results Beta-lactamase was produced in 51.8% （245/473） of the isolates while ftsI gene mutation was positive in 33.4% （158/473） of the isolates. The dominant genotype of gBLNAR isolates was Group Ⅰ/Ⅱ type （l 13/154）, and 68. 1% of gBLNAR Group Ⅰ/Ⅱ isolates were susceptible to ampicillin （77/113） whereas 85.4% of gBLNAR Group Ⅲ isolates were non-susceptible to ampicillin （35/41）. MIC90 and resistance rate of gBLNAR isolates were higher than those of gBLNAS isolates for cefaclor, cefuroxime, ceftriaxone and amoxicillin-clavulanate （ P〈 0. 01 ）, and similar to those of gBLNAS isolates for levofloxacin, azithromycin and trimethoprim-sulfamethoxazole （P〉0. 05）. MIG）t, and resistance rate of gBLNAR Group Ⅲ isolates were higher than those of gBLNAR Group Ⅰ/Ⅱ isolates for those beta-lactams mentioned previously （P〈0. 01）, but no difference was observed among gBLNAR isolates for non-beta-lactam antibiotics. Conclusions High prevalence of ftsI gene mutation is identified in the H. influenzae isolates from respiratory tract in Chengdu children, predominantly the gBLNAR Group Ⅰ/Ⅱ type isolates, which is associated with altered susceptibility to aminopenicillins and some second generation cephalosporins.