Diverse efficacy of CarbaNP test among OXA-48 carbapenemase producing Enterobacterales in an endemic region

Abstract

After the first description of OXA-48 type carbapenemase, it has become endemic in Europe, Mediterranean and North African countries in a short time. OXA-48 carbapenemase is the most difficult type to determine and accurate diagnosis is crucial especially in endemic areas.

The CarbaNP test was described as a rapid phenotypic evaluation method of carbapenemases activity. Sensitivity and specifity of this test were high within all carbapenemases genes. In our study, we evaluated the efficacy of CarbaNP test in routine laboratories located in an endemic area of OXA-48 producing Enterobacterales.

A total of 53 Enterobacterales isolates were included in this study. Antimicrobial susceptibility of the isolates to imipenem, meropenem and ertapenem was determined. Polymerase Chain Reaction (PCR) was carried out for the detection of carbapenemases genes (bla(KPC), bla(NDM), bla(BIC), bla(IMP), bla(VIM), bla(SPM), bla(AIM), bla(DIM), bla(GIM), bla(SIM), and bla(OXA-48)). The Carba NP test was performed as in the protocol described previously.

Altogether 31 isolates (58.4%) were bla(OXA-48) positive (18 Klebsiella pneumoniae, 8 Escherichia coli, 2 Serratia marcescens, 1 Enterobacter aerogenes, 1 Pantoea agglomerans and 1 Morganella morganii). Among these isolates 3 (5.6%) and 2 (3.7%) isolates were also positive for bla(VIM) and bla(SPM), respectively.

The sensitivity and specifity of CarbaNP test were found 64.5, and 68.2% respectively. It was observed that determination of positive isolates is hard to distinguish and subjective.

The CarbaNP test has suboptimal results and low of sensitivity and specifity for detection of OXA-48 producing Enterobacterales, and not suitable for detection of bla(OXA-48) positive isolates in routine laboratories in endemic areas.