34The aim of this study was to examine the resistance genes in clinical isolates which 35 produced IMP-6 type metallo-β-lactamase lactamase (MBL) and had mildly reduced 36 susceptibilities to levofloxacin and/or amikacin. The inoculum size effect was also 37 assessed. A total of 14 Enterobacteriaceae isolates (2 Escherichia coli and 12 Klebsiella 38 pneumoniae) which produced IMP-6 MBL, and had mild increases in their MICs for 39 levofloxacin and amikacin were examined. Thirteen out of 14 isolates harbored 40 CTX-M-2, with the remaining isolate co-harboring CTX-M-2 and CTX-M-1 as ESBLs. 41All isolates carried one or more PMQRs; aac(6′)-Ib-cr was the most prevalent (92.8%), 42 followed by oqxA (64.3%), qnrS (42.9%) , oqxAB (21.4%), and qnrB (14.3%). The 43 inoculum size effects were significant in all strains for meropenem, 13 for imipenem, 7 44 for levofloxacin, and 3 for amikacin. Conjugation was successfully performed with 8 45 isolates and 11 strains were obtained. Eleven of the experimental strains (100%), and 8 46 strains (72.7%) showed inoculum size effects for meropenem and imipenem, 47