The plasmid-mediated extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases in spp. have increasingly been reported. In this study, we investigated the prevalence of the plasmid-mediated β-lactamases in from bloodstream isolates at a medical center in southern Taiwan. ESBL and genes were detected by PCRs and DNA sequencing. Conjugation experiments were conducted to confirm the transferability of the genetic resistance trait. Among 41 non-repetitive blood isolates of cefuroxime-resistant , eight isolates exhibited ESBL phenotype confirmed by double-disk synergistic tests. Nearly all the strains were susceptible to carbapenems. The prevalence rate of the plasmid-mediated genes was 73% (30/41), including one , one , two novel genes and other genes. Coexistence of plasmid-mediated and ESBL genes (10 with and one with ) was observed. Successful transmissions of the and were demonstrated in some transconjugants. The inducible or derepressed CMH-1 had expanded activity of isolates versus ceftazidime. Enterobacterial repetitive intergenic consensus (ERIC)-PCR analysis and pulsotype showed distinct patterns suggesting non-clonal relationship. In conclusion, plasmid-mediated genes in isolates have been highly prevalent in southern Taiwan and may continue genetic evolution, contributing to the complexities in antibiotic-resistant mechanisms.