Highlights of the molecular bases of antimicrobial resistance in EnterobacteriaceaeSunday, April 01, 2012, 12:30 - 13:30
Occurrence of carbapenemase-producing Enterobacteriaceae in Sultanate of OmanL. Dortet*, L. Poirel, F. Alyaquobi, P. Nordmann (Le Kremlin Bicetre, FR; Muscat, OM)
Background. Carbapenemase-producing Enterobacteriaceae are increasingly identified worldwide and represent a major public health concern. The most clinically significant carbapenemases are KPC, IMP, VIM and more recently NDM and OXA-48.
Methods. Our study focused on a retrospective collection of enterobacterial isolates recovered at the Royal Hospital, Muscat, Sultanate of Oman. Twenty-two multidrug resistance Enterobacteriaceae (15 Klebsiella pneumoniae, 5 Escherichia coli, 1 Citrobacter freundii, 1 Serratia marcescens) isolated over a 5-month period (November 2010 to March 2011) were selected, all showing decreased susceptibility to carbapenems. The MICs were determined by Etest and PCR assays followed by sequencing were carried out for detection and identification of carbapenemase genes. Multi locus sequence typing (MLST) and pulsed-field electrophoresis (PGFE) were performed to evaluate the clonal relationship. Plasmids were isolated by mating-out assays and typed by PCR-based replicon typing (PBRT).
Results. Twelve non-clonally related carbapenemase-producing isolates were identified. Seven produced NDM-1 and four produced OXA-48. One K. pneumoniae isolate co-produced NDM-1 and OXA-181, which is a point-mutant derivative of OXA-48. With the exception of a single K. pneumoniae isolate that only expressed OXA-48, all other isolates co-produced an extended-spectrum beta-lactamase.
In all NDM-1 producers, the blaNDM-1 gene was plasmid-located and bracketed upstream by insertion sequence ISAba125 (entire or partial) and downstream by the bleMBL gene encoding resistance to bleomycin.
In OXA-48 producers, the blaOXA-48 gene was always associated to insertion sequence IS1999. A single IncL/M plasmid of ca. 62 -kb was responsible for the acquisition of the blaOXA-48 gene among all OXA-48 producers, whereas the blaNDM-1 gene was identified on different plasmid backbones.
Conclusions. This study emphasizes the dissemination of carbapenemase-producing enterobacterial isolates in the Middle East and especially in Gulf countries where populations from the Indian subcontinent and North African countries (respectively important reservoirs of NDM-1 and OXA-48 producers) are important.