铜绿假单胞菌毒力因子的携带状况及其对感染预后的探讨

Carriage of the Pseudomonas aeruginosa virulence factors and prognosis after infection

目的探讨从儿科住院患儿中分离的铜绿假单胞菌的耐药性与常见的8种毒力因子的携带状况及其临床意义。方法38株铜绿假单胞菌收集自2006至2009年分离的儿科住院患儿的各种标本，均采用VITEK-2COMPACT全自动微生物鉴定仪GNI和AST—GN13卡进行细菌鉴定和药敏试验，聚合酶链式反应（PCR）方法检测毒力因子，并结合临床资料分析其临床特征及转归情况。结果检测的38株铜绿假单胞菌对氨苄西林、氨苄西林一舒巴坦、头孢唑林、呋喃妥因、复方新诺明耐药率为100％，头孢曲松耐药率为60．53％，其他抗生素（阿米卡星、庆大霉素、妥布霉素、头孢吡肟、头孢他啶、环丙沙星、亚胺培南、哌拉西林一他唑巴坦、左氟沙星）耐药率均在16％以下。PCR检测结果显示，38株菌均携带外毒素A（toxA）和一氧化氮还原酶（norA）2种毒力因子，其他毒力因子中，胞外酶Y（exoY）检出率84．21％（32／38），胞外酶s（exoS）57．89％（22／38），脓菌素（PYP）42．11％（16／38），胞外酶u（exoU）34．21％（13／38），38株菌均未检出胞外酶T（exoT）和弹力蛋白酶（1asB）。从检测结果分析发现，3株泛耐药株均为exoU＋／pyp＋组合，其他对亚胺培南中介或耐药的菌株有4株，exoU＋／PYP＋／exoY＋2株，exoU＋／pyp＋1株，exoY＋／exoS＋1株，提示与exoS＋和exoY＋比较，exoU＋／PYP＋菌株耐药性更强。分子流行病学结果显示，3株泛耐株中2株为同一克隆，另一株与之有96．3％的同源性。结论儿科住院患儿中分离的铜绿假单胞菌有34．21％以上携带toxA、norA、exoS、exoY、PYP和exoU6种毒力因子。携带exoU／pyp菌株的耐药性高，而携带PYP的菌株毒力强、易全身感染，患儿的病死率高。

Objective To investigate drug-resistance and carriage of virulence factors of Pseudomonas aeruginosa （Pa） isolated from children. Method Thirty-eight strains of Pa were collected and isolated in pediatric clinic during 2006-2009, and tests were undertaken to identify bacteria and susceptibility test was performed using VITEK-2 COMPACT GNI and AST-GN13 cards. The virulence factors were confirmed by using polymerase chain reaction （PCR） and sequencing. Result All the 38 strains of Pa were resistant to ampicillin, ampicillin/sulbactam, cefazolin, nitrofurantoin, trimethoprim/ sulfamethoxazole, resistance rates were 100%. Except for eeftriaxone （60. 53% ）, the resistance rates to other antibiotics were all below 16%. PCR test showed that all the 38 strains of Pa carried exotoxin A（toxA） and nitric oxide reductase A （norA）, however, detective ratio of the other virulence factors, exoenzyme Y （exoY） was 84. 21% （32/38）, exoenzyme S （exoS） 57.89% （22/38）,pyocyanin （pyp） 42. 11% （16/ 38） ,exoenzyme U（ exoU ）34-. 21% （ 13/38）, and 38 strains of Pa did not carry exoenzyme T （ exoT ） and elastase B （lasB） without exception. By analyzing tests, we discovered that 3 pan-drug resistant strains of Pa were all combination of exo U ＋/pyp ＋ , there were 4 strains of Pa which were moderately-resistant to imipenem, including exoU ＋/pyp ＋/exoY ＋ （2 isolates）, exo U ＋/pyp ＋ （ 1 isolate）, and exoY ＋/exoS ＋ （ 1 isolates）. It indicated that the drug-resistance rate of exoU ＋/pyp ＋ is much higher, compared with exoS ＋ and exoY ＋. Molecular epidemiological detection revealed that 2 of 3 extensive-resistance strains of Pa were the same clone, but another one had 96. 3% of homology with them. Conclusion The abovementioned 34. 21% of Pa isolated from children carried virulence factors toxA, norA, exoS, exoY, pyp and exoU. The strains with exoU/pyp had rather high resistance. The strains with pyp had strong toxicity, they easily cause generalized infection, the patients with them had very high mortality.