SHBC1186
P.Y.HON1, C. YANG2, C.M.Z. KANG1, N.M. THEVASAGAYAM1, D.P. PRATIM3, M.Y. ABDAD1, K. MARIMUTHU1, O.T. NG1, S.VASOO1
National Centre for Infectious Diseases1, Nanyang Technological University2, Tan Tock Seng Hospital3
The recently discovered plasmid-encoded genes causing polymyxin resistance (mcr), and less common carbapenemases and are not routinely screened for. This study aims to study the prevalence of mcr and uncommon carbapenemase-producing(CP) genes in a collection of gram negative bacilli(GNB) bacteria.
150 GNB (50 CPGNB, 60 ESBL-producers and 40 non-ESBL and non-CPGNB) were subject to a mutilplex conventional PCR for mcr detection. In addition 15 GNB isolates, positive for modified carbapenemase-inactivation method (mCIM or eCIM), but negative for blaKPC, blaNDM, blaOXA-48-type, blaVIM, blaIMP and blaIMI by PCR were subject to a panel of miscellaneous PCRs. Whole genome sequencing (WGS) was performed on mcr positive and a subset of isolates positive with a positive CIM test but negative to our PCR targets.
Of the 150 isolates screened, 1 Escherichia coli carrying the mcr-1 gene was found, also confirmed by WGS which identified it as ST131, and carrying a variety of other antibiotic resistance genes. Of the 15 GNB isolates with a positive CIM test, miscellaneous PCR revealed OXA-23 (n=2), OXA-24 (n=1) in 3 Acinetobacter baumanii isolates, and OXA-23 in one Proteus mirabilis isolate. WGS was performed on a Klebsiella pneumoniae and Enterobacter cloacae isolate and found them to belong to ST1922 and ST702, and harboring plasmid AmpCs.
Plasmid-mediated colistin resistance (mcr) was uncommon in our collection of GNB; blaOXA-23, usually confined to Acinetobacter, was unexpectedly found in a Proteus mirabilis isolate. Suspected CPGNB with no-defineable carbapenemases by extensive carbapenemase-gene PCR screening may be due to AmpC production, alongside other beta-lactamases.