Address correspondence to Athanassios Tsakris, rg. All Rights Reserved. This article has been cited by other articles in PMC. Abstract Carbapenemase-producing Enterobacteriaceae CPE are an increasing problem worldwide, and rectal swab surveillance is recommended as a component of infection control programs. The screening methods were applied to detect CPE in rectal swab specimens taken from different hospitalized patients.
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Address correspondence to Athanassios Tsakris, rg. All Rights Reserved. This article has been cited by other articles in PMC. Abstract Carbapenemase-producing Enterobacteriaceae CPE are an increasing problem worldwide, and rectal swab surveillance is recommended as a component of infection control programs.
The screening methods were applied to detect CPE in rectal swab specimens taken from different hospitalized patients. Identification and antimicrobial susceptibility were performed by the Vitek 2 system. Carbapenem MICs were checked by Etest. Carbapenemase production was confirmed using the modified Hodge test, combined-disk tests, and PCR assays. In total, presumptive CPE strains were detected. However, during the last decade carbapenem resistance has been increasingly reported and carbapenemase-producing Enterobacteriaceae CPE are emerging as a growing challenge in health care facilities Moreover, oxacillinase OXA; Ambler class D has recently been isolated in Enterobacteriaceae from Turkey 6 , and it has since been reported from other countries in the Mediterranean Basin and Western Europe 13 , Carbapenemase-producing pathogens have been associated with high rates of morbidity and mortality, particularly among critically ill patients with prolonged hospitalization 4 , 21 , 32 , Furthermore, CPE are usually multidrug-resistant pathogens, making them even more worrisome, since the treatment options are very restricted 4.
These facts suggest the need to implement adequate preventive measures, including active surveillance, in order to contain the spread of these pathogens.
Since gastrointestinal carriers of CPE are thought to be the reservoir of cross-transmission in health care settings, surveillance has been deemed necessary 2 , 3 , 7 , Therefore, collection of rectal swab specimens seems to be the most appropriate sampling method for microbiologic surveillance, which can be accomplished using either culture or molecular techniques. Although direct detection by molecular assays exhibits high sensitivity and has the advantage of rapid identification of CPE 16 , 31 , these methods are not available for daily use in many laboratories.
Even more, molecular methods do not give the possibility for further strain typing and susceptibility testing. However, these screening methods are designed to detect carbapenem-resistant Enterobacteriaceae and not specifically CPE. The aim of the present study was to evaluate the performance of chromID CARBA and compare it to that of four other culture-based screening methods for CPE detection directly from rectal swabs.
Rectal swab specimens were collected from different patients at high risk for colonization with CPE admission from other institutions or periodic surveillance of high-risk units hospitalized from February to April in the intensive care unit and medical wards of an bed tertiary care hospital in Piraeus, Greece. As per survey protocol, rectal swab sample collection was performed using a nylon flocked swab system with 5 ml of Amies gel transport medium.
The tip of the sterile swab, premoistened with sterile saline, was inserted approximately 1 in. Samples were immediately transferred to the laboratory and processed. Culture screening methods. The swab containing the sample was transferred into 1 ml phosphate-buffered saline buffer and was agitated to release the microorganisms from the swab tip.
The last medium was used within 48 h after preparation. All chromID agar plates were also inoculated with the following control strains: carbapenemase-negative Klebsiella pneumoniae ATCC , carbapenemase-positive K. Detection and identification of CPE colonies. Phenotypic and molecular identification of carbapenemase and other ESBL genes. LOD of screening methods. Reference strains were thawed and subcultured onto MacConkey agar plates before use.
Strains were suspended in normal saline to the density of a 0. The experiments were performed in triplicate. The LOD of each screening method was the lowest concentration of the reference strain that resulted in recovery of viable colonies. Sensitivity and specificity. The sensitivity, specificity, positive predictive value PPV , negative predictive value NPV , and overall accuracy were calculated for each of the screening methods.
True-positive strains were defined as all presumptive CPE growing on the media and genotypically confirmed to be CPE positive. False-positive strains were defined to be all presumptive CPE growing on the media that were genotypically confirmed to be CPE negative.
No growth by all screening methods was characterized as a true-negative result. No recovery of a genotypically confirmed CPE-positive strain using a particular screening method was characterized as a false-negative result for this specific screening method. Differences in sensitivity and specificity among the various screening methods were analyzed using the chi-square test.