Abstract：
BACKGROUND: Colistin is the last resort treatment against resistant Gram-negative bacteria, necessitating reliable and rapid means for sensitivity testing of colistin. Automated systems like VITEK®2 are adopted to determine the minimum inhibitory concentration (MIC) due to easy usage. Broth microdilution (BMD) for colistin MIC was suggested by EUCAST and CLSI.
OBJECTIVE: To compare and evaluate colistin MIC by BMD and VITEK®2 against Gram-negative organisms from the ICU in a tertiary care hospital.
METHODS: Clinically significant organisms isolated from ICU patients were included. MIC was determined using BMD and VITEK®2. Very major error (VME), major error (ME), essential agreement (EA), categorical agreement (CA), positive predictive value (PPV), negative predictive value (NPV), sensitivity, and specificity were analysed.
RESULTS: 533 isolates were obtained from blood (435,81.60%), respiratory samples (57,10.70%), pus and exudates (20,3.80%), urine (18,3.40%), and CSF (3,0.60%). The Enterobacterales were K. pneumoniae (185,34.70%) E. coli (73,13.70%) and E. cloacae (26,4.90%) while non-fermenters were A. baumannii (209,39.20%) and P. aeruginosa (40,7.50%). The VITEK®2 sensitivity was >99%; specificity ranged from 14.28 to 52.94%. PPV was 93.81% while NPV was 93.75%. VME ranged from 47 to 100% between isolates. ME was up to 20%. The highest VME was obtained in E. coli (100%). The total EA and CA observed were 68.5% and 99.79% respectively.
CONCLUSIONS: Automated system VITEK®2 failed to detect the resistance in 32 (60%) isolates. The obtained VME and ME values were >3%, which is unacceptable as per the standard guidelines. EA of ≥90% wasn\'t obtained. Sensitivity for VITEK®2 was >99%, but had low specificity (14.28%). Hence, VITEK®2 is not reliable for colistin susceptibility testing.
OBJECTIVE: To compare and evaluate colistin MIC by BMD and VITEK®2 against Gram-negative organisms from the ICU in a tertiary care hospital.
METHODS: Clinically significant organisms isolated from ICU patients were included. MIC was determined using BMD and VITEK®2. Very major error (VME), major error (ME), essential agreement (EA), categorical agreement (CA), positive predictive value (PPV), negative predictive value (NPV), sensitivity, and specificity were analysed.
RESULTS: 533 isolates were obtained from blood (435,81.60%), respiratory samples (57,10.70%), pus and exudates (20,3.80%), urine (18,3.40%), and CSF (3,0.60%). The Enterobacterales were K. pneumoniae (185,34.70%) E. coli (73,13.70%) and E. cloacae (26,4.90%) while non-fermenters were A. baumannii (209,39.20%) and P. aeruginosa (40,7.50%). The VITEK®2 sensitivity was >99%; specificity ranged from 14.28 to 52.94%. PPV was 93.81% while NPV was 93.75%. VME ranged from 47 to 100% between isolates. ME was up to 20%. The highest VME was obtained in E. coli (100%). The total EA and CA observed were 68.5% and 99.79% respectively.
CONCLUSIONS: Automated system VITEK®2 failed to detect the resistance in 32 (60%) isolates. The obtained VME and ME values were >3%, which is unacceptable as per the standard guidelines. EA of ≥90% wasn\'t obtained. Sensitivity for VITEK®2 was >99%, but had low specificity (14.28%). Hence, VITEK®2 is not reliable for colistin susceptibility testing.
摘要：
背景：粘菌素是抵抗革兰氏阴性菌的最后手段，粘菌素敏感性测试需要可靠和快速的手段。由于易于使用，采用了像VITEK®2这样的自动化系统来确定最小抑制浓度(MIC)。EUCAST和CLSI提出了用于粘菌素MIC的肉汤微量稀释（BMD）。
目的：比较和评估BMD和VITEK®2对三级医院ICU的革兰氏阴性菌的粘菌素MIC。
方法：包括从ICU患者中分离出的具有临床意义的生物。使用BMD和VITEK®2测定MIC。非常主要的错误（VME），主要错误（ME），基本协议(EA)，绝对协议(CA)，阳性预测值(PPV)，负预测值(NPV)，灵敏度,并对特异性进行了分析。
结果：从血液中获得533株（435,81.60％），呼吸道样本(57,10.70%)，脓液及渗出物(20,3.80%),尿液（18,3.40%），和脑脊液(3,0.60%)。肠杆菌是肺炎克雷伯菌(185,34.70%)、大肠杆菌(73,13.70%)和阴沟肠杆菌(26,4.90%),而非发酵菌是鲍曼不动杆菌(209,39.20%)和铜绿假单胞菌(40,7.50%)。VITEK®2敏感性>99%;特异性范围为14.28-52.94%。PPV为93.81%,NPV为93.75%。分离株之间的VME范围为47-100%。我达到了20%。在大肠杆菌中获得最高的VME(100%)。观察到的总EA和CA分别为68.5%和99.79%。
结论：自动化系统VITEK®2未能检测到32个（60%）分离株的耐药性。获得的VME和ME值>3%，这是不可接受的标准指南。未获得≥90%的EA。VITEK®2的灵敏度>99%，但特异性较低(14.28%)。因此，VITEK®2对于粘菌素敏感性测试并不可靠。
目的：比较和评估BMD和VITEK®2对三级医院ICU的革兰氏阴性菌的粘菌素MIC。
方法：包括从ICU患者中分离出的具有临床意义的生物。使用BMD和VITEK®2测定MIC。非常主要的错误（VME），主要错误（ME），基本协议(EA)，绝对协议(CA)，阳性预测值(PPV)，负预测值(NPV)，灵敏度,并对特异性进行了分析。
结果：从血液中获得533株（435,81.60％），呼吸道样本(57,10.70%)，脓液及渗出物(20,3.80%),尿液（18,3.40%），和脑脊液(3,0.60%)。肠杆菌是肺炎克雷伯菌(185,34.70%)、大肠杆菌(73,13.70%)和阴沟肠杆菌(26,4.90%),而非发酵菌是鲍曼不动杆菌(209,39.20%)和铜绿假单胞菌(40,7.50%)。VITEK®2敏感性>99%;特异性范围为14.28-52.94%。PPV为93.81%,NPV为93.75%。分离株之间的VME范围为47-100%。我达到了20%。在大肠杆菌中获得最高的VME(100%)。观察到的总EA和CA分别为68.5%和99.79%。
结论：自动化系统VITEK®2未能检测到32个（60%）分离株的耐药性。获得的VME和ME值>3%，这是不可接受的标准指南。未获得≥90%的EA。VITEK®2的灵敏度>99%，但特异性较低(14.28%)。因此，VITEK®2对于粘菌素敏感性测试并不可靠。
