自动化微生物仪检测超广谱β-内酰胺酶漏检原因分析

Analysis on cause of some omission happened in detecting extended spectrum β-lactamases positive strains by VITEK-AMS

目的:探讨自动微生物鉴定仪检测超广谱β-内酰胺酶(ESBLs)漏检原因。方法:用VITEK-AMS专用药敏卡GNS-143进行ESBLs检测,对ESBLs阴性的菌株用纸片扩散法进行确证,并用头孢他啶、头孢噻肟、头孢曲松、氨曲南进行MIC的检测。结果:VITEK-AMS检测的168株ESBLs阴性的菌株用纸片扩散法确证为ESBLs阳性23株,占13.69%(23/168),其中CAZ抑菌圈直径增大值在5 mm的占43.48%(10/23)。ESBLs阳性株对头孢噻肟(CTX)、头孢曲松(CRX)、氨曲南(ATM)、头孢他啶(CAZ)的耐药率分别为69.56%(16/23),95.65%(22/23),86.95%(20/23)和13.04%(3/23)。结论:产酶量恰好落在3～4个稀释倍数之间,抑菌圈直径差在5 mm时,为仪器的"灰色区间"。以CAT和CTX为底物的自动微生物鉴定仪检测产ESBLs阴性时,需做纸片法补充试验,以免漏检。并根据国内细菌产酶特点,增加底物种类,以求取得更好的检测效果。

Objective：To investigate the cause of some omission happened in detecting extended spectrum β- lactamases （ ES- BLs） positive strains by using VITEK -AMS. Methods：VITEK- AMS GNS -143 was used to detect ESBLs, and testify the ESBLs negative strains with disc diffusion method, and agar dilution method for determining the minimum inhibitory concentrations （MIC） of Ceftazidime （ CAZ）, Cefotaxime （CTX） , Ceftriaxone （ CRX）, Aztreonam （ATM）. Results： Among 168 strains were found to be ESBLs negative detected by using VITEK - AMS, 23 were found to be ESBLs positive detected by using disc diffusion method, positive rate was 13.69% （23/168）. Which CAZ of antibacterial diameter increased value on 5mm were 43.48% （ 10/ 23）. When strains producing ESBLs, their CAZ, CTX, CRX, ATM resistant rate were 69. 56%, 95.65%, 86.95% and 13.04% respectively. Conclusion：The ＂grey interval＂ of VITEK AMS is enzymes content of ESBLs producing lie just between 3 -4 dilution ratio, or the difference of antibacerical circle diameter for 5mm, disc diffusion method must be used as additional experiment for ESBLs negative strains, and must be using CAT and CTX as their substrates.