Abstract
Rapidly progressing antibiotic resistance is a great challenge in therapy. In particular, the infections caused by carbapenem-resistant Enterobacteriaceae (CRE) are exceedingly difficult to treat. Carbapenemase production is the predominant mechanism of resistance in CRE. Early and accurate identification of carbapenemase-producing carbapenem-resistant Enterobacteriaceae (CP-CRE) is extremely important for the treatment and prevention of such infections. In the present study, four phenotypic carbapenemase detection tests were compared and an algorithm was developed for rapid and cost-effective identification of CP-CRE. A total of 117 Enterobacteriaceae (54 CP-CRE, 3 non-CP-CRE, and 60 non-CRE) isolates were tested for carbapenemase production using modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), Carba NP test (CNPt), and CNPt-direct test. The overall sensitivity/specificity values were 90.7%/92.1% for MHT, 100%/100% for mCIM, 75.9%/100% for CNPt, and 83.3%/100% for CNPt-direct. OXA-48-like enzymes were detected with 93.2% sensitivity by MHT and >77.3% sensitivity by two Carba NP tests. MHT could only detect half of the NDM carbapenemase producers. CNPt-direct exhibited enhanced sensitivity compared to CNPt (100% vs 25%) for detection of NDM producers. Considering these findings we propose CNPt-direct as the first test followed by mCIM for rapid detection of CP-CRE. With this algorithm >80% of the CP-CRE could be detected within 24 hours from the time the sample is received and 100% CP-CRE could be detected in day two. In conclusion, mCIM was the most sensitive assay for the identification of CP-CRE. CNPt-direct performed better than CNPt. An algorithm consisting CNPt-direct and mCIM allows rapid and reliable detection of carbapenemase production in resource-limited settings.
Highlights
Carbapenems are the antibiotics of “last-resort” that are used to treat severe infections caused by drug-resistant Enterobacteriaceae such as Klebsiella spp., Escherichia spp., Enterobacter spp., etc., which are frequently associated with both nosocomial and community-acquired infections
Rapid and accurate detection of CP-carbapenem resistance in Enterobacteriaceae (CRE) is important as early identification can optimize antibiotic therapy and minimize unnecessary/ inappropriate prescription of medicines [24]
The conventional antimicrobial susceptibility testing is sufficient for the selection of appropriate antibiotics, commonly used disc diffusion method has a minimum of two day delay to results and is not suitable for some antibiotics like colistin
Summary
Carbapenems are the antibiotics of “last-resort” that are used to treat severe infections caused by drug-resistant Enterobacteriaceae such as Klebsiella spp., Escherichia spp., Enterobacter spp., etc., which are frequently associated with both nosocomial and community-acquired infections. The emergence of carbapenem resistance in Enterobacteriaceae (CRE) poses a serious public health threat as these infections are difficult to treat [1]. It has been found that the infections caused by carbapenemase-producing carbapenem-resistant Enterobacteriaceae (CP-CRE) are associated with greater threat to human health with high fatality rates and increased healthcare cost, compared to the infections caused by non-CP-CRE [3,4,5,6]. Distinguishing carbapenemase producers from non-carbapenemase producers is important to prioritize newer antibiotics for the infection caused by CP-CRE, which might delay the development of resistance to novel drugs. Rapid and reliable detection of CP-CRE is becoming increasingly important to streamline antibiotic treatment and to minimize the spread of these difficult-to-treat bacteria both in healthcare facilities and in the community
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