Tsering Dechen C, Das Shyamasree, Adhiakari Luna, Pal Ranabir, Singh Takhellambam Sk
Department of Microbiology, Sikkim-Manipal Institute of Medical Sciences(SMIMS) and Central Referral Hospital (CRH), Gangtok, Sikkim, India.
J Glob Infect Dis. 2009 Jul;1(2):87-92. doi: 10.4103/0974-777X.56247.
Resistance to third generation cephalosporins by acquisition and expression of extended spectrum beta lactamase (ESBL) enzymes among gram-negative bacilli is on a rise. The presence of ESBL producing organisms significantly affects the course and outcome of an infection and poses a challenge to infection management worldwide.
In the period from June 2007 to 2008, we collected 1489 samples from patients suspected of nosocomial infection. The isolates were identified based on colony morphology and biochemical reaction. Gram negative bacilli resistant to third generation cephalosporins were tested for ESBL by double disc synergy test (DDST- a screening test)and then phenotypic confirmatory test. Antimicrobial susceptibility testing was done by modified Kirby Bauer disc diffusion method.
From the sample of 238 gram-negative bacilli, we isolated Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Citrobacter freundii, Proteus mirabilis, Morganella morganii and Enterobacter cloacae. Following both methods, 34% isolates were ESBL-positive. The ESBL producing isolates were significantly resistant (p < 0.01) to ampicillin, piperacillin, piperacillin/tazobactam, trimethoprim/sulfamethoxazole, tetracycline, ciprofloxacin and gentamicin as compared to non-ESBL producers. Multidrug resistance was significantly (p < 0.01) higher (69.14%) in ESBL positive isolates than non-ESBL isolates (21.66%).
High prevalence of ESBL in our hospital cannot be ignored. ESBL producers can be detected by DDST and phenotypic confirmatory test with equal efficacy. The sensitivity of screening test improved with the use of more than one antibiotic and addition of one or two antibiotics would not increase cost and labor. We recommend DDST using multiple antibiotics in all microbiology units as a routine screening test.
革兰氏阴性杆菌通过获得并表达超广谱β-内酰胺酶（ESBL）而对第三代头孢菌素产生耐药性的情况正在增加。产ESBL生物的存在显著影响感染的病程和结果，并给全球感染管理带来挑战。
在2007年6月至2008年期间，我们从疑似医院感染的患者中收集了1489份样本。根据菌落形态和生化反应对分离株进行鉴定。对耐第三代头孢菌素的革兰氏阴性杆菌通过双纸片协同试验（DDST，一种筛查试验）检测ESBL，然后进行表型确证试验。采用改良的 Kirby Bauer 纸片扩散法进行药敏试验。
从238株革兰氏阴性杆菌样本中，我们分离出大肠杆菌、铜绿假单胞菌、肺炎克雷伯菌、弗氏柠檬酸杆菌、奇异变形杆菌、摩根氏摩根菌和阴沟肠杆菌。通过两种方法，34%的分离株为ESBL阳性。与非产ESBL菌株相比，产ESBL菌株对氨苄西林、哌拉西林、哌拉西林/他唑巴坦、甲氧苄啶/磺胺甲恶唑、四环素、环丙沙星和庆大霉素有显著耐药性（p < 0.01）。ESBL阳性分离株的多重耐药性（69.14%）显著高于非ESBL分离株（21.66%）（p < 0.01）。
我院ESBL的高流行率不容忽视。DDST和表型确证试验检测产ESBL菌株的效果相同。使用多种抗生素可提高筛查试验的敏感性，增加一种或两种抗生素不会增加成本和工作量。我们建议在所有微生物学单位将使用多种抗生素的DDST作为常规筛查试验。
