Underlying mechanisms of carbapenem resistance in extended-spectrum β-lactamase-producing Klebsiella pneumoniae and Escherichia coli isolates at a tertiary care centre in Lebanon: role of OXA-48 and NDM-1 carbapenemases

• Published in: International journal of antimicrobial agents 2013-01, Vol.41 (1), p.75-79
• Main Authors: Baroud, M, Dandache, I, Araj, G.F, Wakim, R, Kanj, S, Kanafani, Z, Khairallah, M, Sabra, A, Shehab, M, Dbaibo, G, Matar, G.M
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; beta-Lactam Resistance; beta-lactamase; beta-Lactamases - genetics; beta-Lactamases - secretion; Carbapenem resistance; carbapenems; Carbapenems - pharmacology; Enterobacteriaceae; Enterobacteriaceae Infections - microbiology; ESBL; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - isolation & purification; genes; Humans; Infectious Disease; Klebsiella pneumoniae; Klebsiella pneumoniae - drug effects; Klebsiella pneumoniae - genetics; Klebsiella pneumoniae - isolation & purification; Lebanon; Microbial Sensitivity Tests; minimum inhibitory concentration; mutation; NDM-1; OXA-48; Plasmids; porins; Random Amplified Polymorphic DNA Technique; screening; sequence analysis; Sequence Analysis, DNA; Tertiary Care Centers; transporters
• ISSN: 0924-8579; 1872-7913
• DOI: 10.1016/j.ijantimicag.2012.08.010

Abstract A recent increase in carbapenem resistance among extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae and Escherichia coli isolates at a major tertiary care centre in Lebanon prompted the initiation of this study. Consecutive ESBL-producing isolates were tested for resistance to carbapenems, with initial screening by disk diffusion and Etest using ertapenem. The modified Hodge test was also performed. PCR of β-lactamase-encoding genes, including blaNDM-1 , blaKPC , blaOXA-48 , blaCTX-M , blaTEM , blaSHV , blaCMY-2 and blaOXA-1 , as well as outer membrane porin genes ( ompC and ompF ) was performed. Sequencing, efflux pump inhibitor tests and random amplified polymorphic DNA (RAPD) analysis were performed. In total, 14 (2.45%) of 572 K. pneumoniae and 24 (1.07%) of 2243 E. coli were ertapenem-non-susceptible [minimum inhibitory concentration (MIC) ≥0.25 μg/mL]. Resistance to other carbapenems was variable. PCR and sequencing analysis revealed that isolates harboured different β-lactamase genes, including blaOXA-1 , blaCTX-M-15 , blaTEM-1 , blaCMY-2 , blaOXA-48 and blaNDM-1 . In addition, K. pneumoniae lacked the outer membrane porin-encoding genes, whilst E. coli harboured them with detected mutations. CTX-M-15 was carried on a 90 kb plasmid, whilst OXA-48 was carried on a 70 kb plasmid. Efflux pump inhibition significantly decreased MICs in E. coli . RAPD analysis demonstrated genomic variability. In conclusion, carbapenem resistance in ESBL-producing K. pneumoniae and E. coli is due to the combined effect of β-lactamases with porin impermeability and/or efflux pump activity observed in these organisms, and in a number of isolates is due to the production of the carbapenemase-encoding genes blaOXA-48 and the newly emerging blaNDM-1.