Background: Carbapenemase producing Enterobacteriaceae are becoming a major public health concern globally,\r\nhowever, relatively little is known about the molecular and clinical epidemiology of these organisms in many parts\r\nof the world.\r\nMethods: As part of a laboratory surveillance programme, 96 carbapenem non-susceptible Enterobacteriaceae\r\nisolates from clinical samples from patients in seven hospitals were referred for investigation for carbapenemases.\r\nUsing polymerase chain reaction (PCR) to screen for a collection of genes encoding carbapenemases, 33 of 96\r\n(34.5%) isolates were confirmed as carbapenemase producers. NDM-1 producers were the most prevalent at 64%\r\n(21/33) whilst OXA-181 was the second most common carbapenemase constituting 24.5% (8/33) of the\r\ncarbapenemase producing isolates. Seven of these eight OXA-181 positive isolates underwent further\r\ncharacterisation with screening for other transmissible antimicrobial resistance determinants using PCR. Clonal\r\nrelatedness was explored using Multilocus sequence typing (MLST) and Pulsed Field Gel Electrophoresis (PFGE).\r\nPlasmid characterisation was performed including restriction analysis and transfer by conjugation or transformation.\r\nResults: In addition to the OXA-181 gene, all contained other transmissible resistance determinants including\r\nextended spectrum �Ÿ-lactamases, oxacillinases or 16S rRNA methylase genes, but none contained\r\nmetallo-�Ÿ-lactamases or serine carbapenemases. All isolates had a multidrug resistant phenotype with two isolates\r\nbeing resistant to every antibiotic tested including colistin. Multilocus sequence typing confirmed five isolates\r\nbelonged to ST17 and two to ST14, with those belonging to the same sequence type having identical PFGE\r\nprofiles. The OXA-181 gene was typically carried on large plasmids which were mostly non-conjugative.\r\nConclusions: OXA-181 carbapenemase appears to be an important and probably under-recognised cause of\r\ncarbapenem resistance in Enterobacteriaceae in Singapore. Further coordinated research into clinical and molecular\r\nepidemiology of carbapenemases is urgently required in Singapore and throughout Asia.
Loading....