coli WZ51 a E. coli DH5α (WZ51) E. coli DH5α ampicillin >256 >256 >256 >256 1.5 piperacillin/tazobatam >256 16 >256 256 0.75 piperacillin >256 16 256 >256 0.038 ceftazidime >256 >256 >256 >256 0.094 cefotaxime >256 64 >256 192 0.047 cefepime >256 16 >256 4 0.047 aztreonam 32 0. 023 >256 12 0.023 cefoxitin >256 >256 >256 >256 0.75 imipenem

TPCA-1 chemical structure 8 6 24 12 0.094 meropenem >32 6 >32 3 0.016 ertapenem >32 24 >32 4 0.008 amikacin 1.5 0.75 2 0.50 0.50 gentamicin 24 0.38 16 0.125 0.125 levofloxacin 24 0.047 ≥32 0.016 0.023 trimethoprim/sulfamethoxazole 0.75 0.008 >32 0.008 0.008 polymyxin B 1.5 0.38 1.5 0.38 0.38 tigecycline 0.19 0.5 1 0.19 0.19 Fosfomycin 0.5 0.25 2 0.94 0.94 a, transformant. Co-production of carbapenemases with other β-lactamases including ESBLs and pAmpCs results in resistance to nearly all clinically available β-lactams. As both E. coli WZ33 and WZ51 were highly resistant

to all tested β-lactams, other β-lactamases other than NDM-1 were investigated. Although a ESBL gene bla CTX-M-14 was identified in E. coli WZ33 and two ESBL genes, bla CTX-M-14 and bla SHV-12, were found in E. coli WZ51, ESBL production was not detected in these two isolates, determined by CLSI-recommended double-disk test. As carbapenemases and AmpCs are not inhibited by clavulanic acid, co-production of ESBLs, AmpCs and carbapenemases can mask determination of ESBLs using the CLSI-recommended double-disk test [17]. Both E. coli WZ33 and WZ51 were highly resistant to cefoxitin (MICs ≥ 256), which was indicative of AmpC production. As expected, two tested isolates SAHA order were found to harbor pAmpC gene bla CMY-42 in accordance with phenotypic results determined by three-dimension test. bla CMY-42 was

first identified in a E. coli isolate [34]. The present study is the second report of bla CMY-42. However, it is the first report of the coexistence of bla CMY-42 and bla NDM-1. Transferability of resistance plasmids carrying blaNDM-1 bla Casein kinase 1 NDM-1 was found to be located on the plasmids with different size and genetically diverse background and disseminated among different species of organisms by the transfer of resistance plasmids [1, 5]. The plasmids conferring carbapenem resistance for E. coli WZ33 and WZ51 were not successfully self-transferred into the recipient E. coli J53 using filter mating conjugation by repeat attempts. But the plasmids conferring carbapenem resistance for both E. coli WZ33 and WZ51 could be transferred into the recipient (E. coli DH5α) using chemical transformation. WZ33 contained 2 plasmids (approximately 65- and 3-kb). WZ51 contained 3 plasmids with sizes of approximately 65-, 7- and 3-kb). The transformants each contained a single bla NDM-1-bearing plasmid with size of approximately 65 kb. The selleck products transformant from E. coli WZ51 was positive for bla NDM-1 and bla SHV-12, while the transformant from WZ33 carrying only the NDM gene was susceptible to aztreonam, which is characteristic of MBLs.