Evaluation of a New Selective Chromogenic Agar Medium for Detection of Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae

Abstract

Microbial resistance through extended-spectrum ␤-lactamase (ESBL) was first reported in the early 1980s in Europe and subsequently in the United States soon after the introduction of third-generation cephalosporins in clinical practice (12). Today, this resistance mechanism has emerged globally, and ESBL-producing Enterobacteriaceae are recognized worldwide as nosocomial pathogens of major importance (19,28). Many clinical microbiology laboratories have problems with the detection of ESBL-mediated resistance, and the recent emergence and spread of novel types of community-acquired ESBLs, such as the CTX-M enzymes (2, 4), have created additional challenges that further complicate the detection of this resistance mechanism (1, 13). Several phenotypic tests have been recommended for screening and confirmation of ESBLs, but these are usually performed on isolated organisms following culture and antibiotic susceptibility testing (7, 24).The failure to detect ESBL-mediated resistance has led to treatment failure (17, 26) and contributed to uncontrolled spread of ESBL-producing organisms (18). On the other hand, laboratory-based detection of patients infected or colonized by ESBL-producing organisms by surveillance cultures has proven useful to control and terminate nosocomial outbreaks (16,19,21).Various selective media have been proposed to assess the carriage of ESBL producers in stools. Examples of such media include Drigalski agar supplemented with cefotaxime (27), MacConkey agar supplemented with ceftazidime (20), and nutrient agar supplemented with ceftazidime, vancomycin, and amphotericin B (21). In recent years, chromogenic media were initially developed for the detection and presumptive identification of urinary tract pathogens (6, 11) as well as for the improved isolation of Staphylococcus aureus from clinical specimens (5, 10). Recently, selective antibiotic-containing chromogenic media have been made available for the rapid detection of methicillin-resistant S. aureus (9, 23). One of the great advantages of such chromogenic selective media is that they allow the rapid and reliable screening of methicillin-resistant S. aureus colonization directly from contaminated clinical specimens (14).The purpose of this study was to evaluate the sensitivity and specificity of a novel prototype of selective chromogenic agar medium (ESBL-Bx; bioMérieux, Marcy l'Etoile, France) that enables the detection and presumptive identification of ESBLproducing Enterobacteriaceae directly from clinical specimens. MATERIALS AND METHODS Specimens.A total of 644 clinical samples, including 561 stool, 63 lower respiratory tract (sputum, bronchial, or endotracheal aspirates), and 20 miscellaneous samples (wound swabs or ear-nose-throat specimens), were referred to our department for the screening of ESBL-producing organisms. The specimens originated from 460 patients who had been hospitalized in various wards (geriatric unit, general medicine, oncohematology, and general surgery departments) for more than 48 h.Inoculation of media and i...

Extended-Spectrum Beta-Lactamase Detection with Different Panels for Automated Susceptibility Testing and with a Chromogenic Medium

“…So Glupczynski et al (7) decided to record only the definitive results after 18 to 24 h. In our study, the agar delivered false-positive results for the Enterobacter spp. and E. coli isolates carrying chromosomal or plasmid-located ampC, which confirms the results of Glupczynski et al (7). Interestingly, all ampC-positive Enterobacter spp.…”

“…In the case of bacterial strains which showed conspicuous resistance patterns in the results from the automated systems together with a negative Etest, we included screening for chromosomal and plasmid-mediated ampC beta-lactamase genes. (7). We completely excluded copy strains.…”

Current Trends in Culture-Based and Molecular Detection of Extended-Spectrum-β-Lactamase-Harboring and Carbapenem-Resistant Enterobacteriaceae

“…Cefpodoxime was already known as a reliable, selective substrate for most TEM-and SHV-derived ESBLs more than a decade ago, and it is also preferred because it can be utilized as a single substrate, in contrast to ceftazidime, which is combined with cefotaxime, in order to reliably detect both CTX-M producers and those with ceftazidimase-type TEM variants. The superior recovery of CTX-M-type ESBLs on chromogenic media containing cefpodoxime (chromID ESBL and Brilliance ESBL) compared to that on MacConkey agar supplemented with ceftazidime (2 g/ml) alone or with a ceftazidime disk (30 g) has been demonstrated in several studies (9,10). Nonetheless, a reported lack of specificity due to growth of AmpC and K1 hyperproducers while using cefpodoxime disks (5 or 10 g) indicates that cefpodoxime concentrations incorporated in media need to be chosen carefully, as MICs to cefpodoxime in the range of 2 to 4 g/ml for Escherichia coli might be due to changes in porin or AmpC overexpression rather than ESBL production (15).…”

Validitas Metode Konvensional Modifikasi Terhadap Metode Konvensional Dan ChromidTM Esbl Untuk Deteksi Bakteri-bakteri Penghasil Extended-spectrum Beta-lactamases

“…Media ini mengandung pepton, glukosa dan antibiotik yaitu sefpodoksim yang digunakan sebagai marker mekanisme resistensi ESBL serta memiliki sensitivitas yang tinggi untuk mendeteksi ESBL. 6,7 Sensitifitas dan spesifisitas ChromID TM ESBL dalam mendeteksi E. coli dan K. pneumoniae cukup tinggi sekitar 97,7% dan 89%. 8 Media ChromID TM ESBL ini memiliki kekurangan, antara lain harga yang relatif mahal, masa kadaluarsa yang pendek, waktu pemesanan media yang lama dan hanya dapat mendeteksi 3 kelompok bakteri penghasil ESBL, yaitu E. coli, KESC (Klebsiella, Enterobacter, Serratia, Citrobacter) dan Proteeae (Proteus, Providencia, Morganella).…”