Phenotypic and molecular identification of carbapenemase-producing Enterobacteriaceae - challenges in diagnosis and treatment

Abstract

Introduction: Infections due to carbapenemase-producing carbapenem-resistant Enterobacteriaceae (CPCRE) are an emerging global public health threat. The purpose of this study was to investigate phenotypic and genotypic features of CP-CRE strains isolated from hospitalized patients. Material and methods: Between 1st of January - 1st of July 2017, in the Department of Microbiology, “Dr. Constantin Opriş” County Emergency Hospital Baia Mare, Romania, 1110 strains of Enterobacteriaceae were isolated from bronchial secretions, urine, wounds and blood cultures. Bacterial identification and antimicrobial susceptibility tests were performed by conventional methods, Vitek 2 Compact and M.I.C.E. strips. We analysed all Enterobacteriaceae strains non-susceptible to carbapenems according to CLSI 2017 criteria. The modified Hodge test (MHT), the modified carbapenem inactivation method (mCIM) and the combination disks test (KPC, MBL, OXA-48 Confirm kit, Rosco Diagnostica) were used for phenotypic confirmation, whereas a multiplex PCR assay for genes blaKPC, blaNDM and blaOXA-48 was used for genetic confirmation. Results: 19 non-duplicate strains isolated from 16 patients were phenotypically identified as CP-CRE: Klebsiella pneumoniae (n=14), Escherichia coli (n=2), Providencia stuartii (n=2) and Serratia marcescens (n=1). Most strains were isolated from bronchial secretions (n=9). The carbapenem-hydrolizing enzymes were identified by the combination disks test as: KPC (n=9), OXA-48-like (n=5) and MBL (n=5). Molecular confirmation was performed in 18 phenotypically positive isolates with 100% concordant results with mCIM and combination disks test. Discrepant results were noticed with the MHT in case of 4 NDM-producers confirmed by PCR. All CP-CRE strains were resistant to all tested cephems. Three out of 9 K. pneumoniae strains tested against colistin were found resistant. Conclusions: The most common carbapenemase detected was KPC. Therapeutic options were limited in all positive cases. Rapid and reliable detection of CP-CRE is critical for preventing the spread of these pathogens

Evaluation of the Performance of Routine Phenotypic Methods for Accurate and Rapid Detection of Carbapenem-Resistant Enterobacteriaceae in Clinical Samples

“…In the present study the mCIM that is a new phenotypic method for detection of carbapenemases activity in CRE was positive in all 65 CP-CRE strains which is completely consistent to the result of Foldes et al, where the mCIM was positive in all 19 CP-CRE strains and no false-positive results were noticed [40]. This is also relatively consistent to Pawar et al, who reported that only one isolate which was positive by PCR study was negative by mCIM method [17], making this new method most sensitive (98.48%) among the phenotypic test studied.…”

Molecular epidemiology and the clinical impact of carbapenemase-producing Enterobacterales isolates among adult patients: aspects from a Romanian non-teaching hospital

“…Five out of the 7 participants with urinary CPE isolates treated with monotherapy had a favourable outcome. (12)(13)(14)(15)(16)(17)(19)(20)(21). The present study did not find any strain harbouring multiple carbapenemase-encoding genes.…”

“…In 2018 the European Centre for Disease Prevention and Control (ECDC) alerted about the emergence of resistance of CPE isolates to ceftazidime-avibactam, a newly authorized drug with activity especially against Klebsiella pneumoniae carbapenemase (KPC) producers (11). Some large Romanian medical institutions have confirmed the presence and dissemination of different types of carbapenemases (12)(13)(14)(15)(16)(17)(18)(19)(20)(21), but the involvement of risk factors, clinical impact of CPE pathogens, treatment, and patients' outcomes have not been sufficiently explored. Furthermore, a Romanian national centralized database of circulating carbapenemase types is not yet available.…”

Multiplex lateral flow immunochromatographic assay is an effective method to detect carbapenemases without risk of OXA-48-like cross reactivity

“…Identification of carbapenemase genes can be done either by molecular tests, which detect the presence of a resistant carbapenemase gene, or by phenotypic tests, which detect the in vitro activity of carbapenemase enzymes [ 24 , 25 ]. Molecular techniques, such as PCR, have several advantages, including accurate results and high sensitivity.…”