Glupczynski Youri, Berhin Catherine, Bauraing Caroline, Bogaerts Pierre
Laboratoire de Bactériologie, Cliniques Universitaires UCL de Mont-Godinne, 1, Av. Dr Gaston Thérasse, B-5530 Yvoir, Belgium.
J Clin Microbiol. 2007 Feb;45(2):501-5. doi: 10.1128/JCM.02221-06. Epub 2006 Dec 20.
A novel chromogenic agar medium (ESBL-Bx; bioMérieux, Marcy l'Etoile, France) was compared to MacConkey agar supplemented with 2 mg ceftazidime/liter (MCKC) for the selective isolation and presumptive identification of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae directly from clinical samples. Of a total of 644 clinical specimens (including 551 fecal samples), 496 yielded no growth and 148 yielded growth on one or both media. Overall, 44 ESBL-producing Enterobacteriaceae strains (Escherichia coli [n=17], Enterobacter aerogenes [n=17], Klebsiella spp. [n=5], and Citrobacter freundii [n=5]) were isolated from 37 specimens by a combination of both methods after 18 to 24 h of incubation. The sensitivities were 97.7 and 84.1% for ESBL-Bx and MCKC, respectively, with 43 ESBL-positive strains isolated as colored colonies from 36 specimens on ESBL-Bx versus 37 ESBL-positive organisms isolated from 32 specimens on MCKC. The specificities by specimens were 89 and 91% for ESBL-Bx and MCKC, respectively. On either one of the two media, natural AmpC-hyperproducing Enterobacter spp. (n=25) and Citrobacter spp. (n=14) were the most common false positives as well as non-ESBL-producing Klebsiella oxytoca (n=18) on ESBL-Bx and Morganella morganii (n=10) on MCKC. We conclude that ESBL-Bx is a sensitive and specific medium for the isolation of ESBL-producing Enterobacteriaceae from clinical samples. The main advantages of ESBL-Bx over MCKC reside in its chromogenic character and its sensitivity and selectivity, which enabled the recovery and presumptive identification of most ESBL-producing Enterobacteriaceae within 24 h and reduced by 27% the need for unnecessary identification and confirmation of ESBL testing when disregarding all colorless colonies growing on this medium.
将一种新型显色琼脂培养基（ESBL - Bx；法国生物梅里埃公司，马西伊图瓦勒）与添加了2毫克/升头孢他啶的麦康凯琼脂（MCKC）进行比较，用于直接从临床样本中选择性分离和初步鉴定产超广谱β-内酰胺酶（ESBL）的肠杆菌科细菌。在总共644份临床标本（包括551份粪便样本）中，496份未生长，148份在一种或两种培养基上生长。总体而言，经过18至24小时培养后，通过两种方法结合从37份标本中分离出44株产ESBL的肠杆菌科菌株（大肠杆菌[n = 17]、产气肠杆菌[n = 17]、克雷伯菌属[n = 5]和弗氏柠檬酸杆菌[n = 5]）。ESBL - Bx和MCKC的敏感性分别为97.7%和84.1%，在ESBL - Bx上从36份标本中分离出43株呈有色菌落的ESBL阳性菌株，而在MCKC上从32份标本中分离出37株ESBL阳性菌。按标本计算，ESBL - Bx和MCKC的特异性分别为89%和91%。在这两种培养基中的任何一种上，天然AmpC高产的肠杆菌属（n = 25）和柠檬酸杆菌属（n = 14）是最常见的假阳性，以及在ESBL - Bx上的非产ESBL的产酸克雷伯菌（n = 18）和在MCKC上的摩根摩根菌（n = 10）。我们得出结论，ESBL - Bx是一种从临床样本中分离产ESBL肠杆菌科细菌的敏感且特异的培养基。ESBL - Bx相对于MCKC的主要优势在于其显色特性以及敏感性和选择性，这使得大多数产ESBL的肠杆菌科细菌能够在24小时内被回收并初步鉴定，并且在忽略该培养基上生长的所有无色菌落时，将不必要的ESBL检测鉴定和确认需求减少了27%。
