Laboratory and Clinical Evaluation of Screening Agar Plates for Detection of Carbapenem-Resistant Enterobacteriaceae from Surveillance Rectal Swabs

Abstract

The increased worldwide spread of carbapenem-resistant Enterobacteriaceae (CRE) emphasizes the need for a sensitive screening procedure to identify these microorganisms. Gastrointestinal carriers may serve as the reservoir for cross-transmission in the health care setting, and thus active surveillance is a key part in preventing the spread of such strains. Three agar-based methods for direct CRE detection from rectal swabs were compared: CHROMagar-KPC (Chrom); MacConkey agar with imipenem at 1 g/ml (MacI); and MacConkey plates with imipenem, meropenem, and ertapenem disks (MacD). First, we compared the levels of detection (LODs) of 10 molecularly characterized carbapenemase-producing Enterobacteriaceae strains by the three methods. Second, we compared their performance in a surveillance study using rectal swabs (n ‫؍‬ 139). The LODs of carbapenemase-producing Enterobacteriaceae strains were influenced by their MICs to carbapenems and were best for MacI, followed by Chrom. The MacD method was able to detect only the strains exhibiting MICs of >32 g/ml to at least ertapenem. In the surveillance study, both Chrom and MacI had greater sensitivity (85%) than MacD (76%). However, MacI was the most specific method. In conclusion, MacI appears to be most appropriate medium for the detection of CRE in settings in which multiclonal CRE strains with various MICs to carbapenems are circulating.Carbapenem-resistant Enterobacteriaceae (CRE) have emerged globally and have become a major threat to public health (1, 17). Carbapenem resistance may be caused by a variety of mechanisms and has been identified in a variety of Enterobacteriaceae species (1, 20). In 2006, an epidemic strain of KPC-3-producing Klebsiella pneumoniae, exhibiting resistance to nearly all antimicrobial agents, spread in all major Israeli hospitals (11,16). This strain, identified as sequence type (ST) 258, is identical to the epidemic strain that had spread across the United States (9, 12) and is characterized by high MIC values of carbapenem antibiotics (16).As gastrointestinal carriage may serve as a reservoir for CRE cross-transmission in health care settings, active surveillance among high-risk patients has been deemed important for controlling this epidemic in acute-care facilities (2, 23). The implementation of a reliable and sensitive method for detection of this strain as well as other CRE is therefore critical to the success of infection control measures. Although PCRbased methods have been proven to be highly sensitive and reliable for rapid diagnosis (8,22), these methods require expertise that is not readily available in many centers. Moreover, as the emergence and spread of other types of CRE are increasingly reported (7, 19), culture-based methods are still essential for the initial detection of these strains.In our center, we have been using MacConkey agar supplemented with imipenem at 1 g/ml (HyLabs, Rehovot, Israel) as the main screening agar plate for the detection of CRE from rectal swabs. In the present study, we compared this method to...

Comparative Evaluation of a Prototype Chromogenic Medium (ChromID CARBA) for Detecting Carbapenemase-Producing Enterobacteriaceae in Surveillance Rectal Swabs

“…Even more, molecular methods do not give the possibility for further strain typing and susceptibility testing. Thus, several culture techniques for screening carbapenem-resistant Enterobacteriaceae have been tested, including methods that use in-house-prepared selective media, such as MacConkey agar or tryptic soy broth containing a 10-g carbapenem disk (3,8,19,20), or commercial chromogenic agar media, like CHROMagar KPC (HyLabs, Rehovot, Israel) (1,23,29) and chromID ESBL medium (bio-Mérieux, Marcy l'Etoile, France) (5). However, these screening methods are designed to detect carbapenem-resistant Enterobacteriaceae and not specifically CPE.…”

Comparative evaluation of a novel chromogenic medium (chromID OXA-48) for detection of OXA-48 producing Enterobacteriaceae

“…Adequate preventive measures and efficient screening are needed for an active surveillance to prevent outbreaks of nosocomial infections by these organisms Adler et al, 2011. The main carbapenemases identified in Enterobacteriaceae belong either to the Ambler class A (KPC-type) hydrolysing all β-lactams except cephamycins, the Ambler class B (NDM, VIM and IMP) which are zinc-dependent metallo-β-lactamases (MBL) hydrolysing all β-lactams except aztreonam, and the Ambler class D enzymes (OXA-48-like) hydrolysing carbapenems but weakly and not at all broadspectrum cephalosporins (Nordmann et al, 2011(Nordmann et al, , 2012a(Nordmann et al, , 2012b(Nordmann et al, , 2012c.…”

An optimized work-flow to reduce time-to-detection of carbapenemase-producing Enterobacteriaceae (CPE) using direct testing from rectal swabs

“…16,17 Within our laboratory, our current CPE screening process, utilizing selective chromogenic agar (CHROMagar TM KPC, Paris, France) and GeneXpert Ò Carba-R for in-house molecular confirmation of CPE positive specimens (Cepheid, Buckinghamshire, United Kingdom), had an average turnaround time of 48/72 h from specimen arrival in the laboratory to final CPE result for the clinician. The 48/72 h delay in diagnosis was in keeping with other centers worldwide using selective cultures, [18][19][20] but was resulting in use of empiric broad-spectrum antimicrobials and an inefficient use of limited isolation facilities.…”