Molecular Characteristics of Causing Bloodstream Infections During 2010-2015 in a Tertiary Hospital, Shanghai, China.

BACKGROUND

The bloodstream infections (BSI) caused by pose a serious threat to human health. To explore molecular characteristics of causing BSI, we collected isolates causing BSI in Huashan Hospital, Shanghai, China during 2010-2015.

METHODS

In all isolates causing BSI collected from this study, polymerase chain reaction (PCR) was used to detect ESBLs and carbapenemase genes, and minimum inhibitory concentrations (MICs) were determined with agar dilution method. Outer membrane proteins were examined by SDS-PAGE in carbapenem-resistant strains. The genetic background of gene was investigated by combining next-generation sequencing with a PCR mapping approach. Conjugation and transformation experiments were performed to verify the mobilization of . The transcription levels of the gene were measured by RT-PCR.

RESULTS

During 2010-2015, a total of 207 BSI strains were isolated. The positive rates of β-lactamase resistant genes were 0.48% ( ), 57% ( ), 23.67% ( ), 18.84% ( ), and 1.93% ( ). High rates of , and were consistent with the poor activity of third-generation cephalosporins and aztreonam in vitro, except for carbapenem and β-lactamase inhibitor combinations. Low susceptibility rates were observed for piperacillin (25.1%) in contrast to the increased susceptibility when combined with β-lactamase inhibitors, namely piperacillin-tazobactam (90.8%). Only one KPC-producing strain was detected. Despite the combination of OmpC loss, the low expression level of KPC may be responsible for its lower resistance to carbapenems compared to DH5α (pKP12-100).

CONCLUSION

strains isolated from BSI were still highly susceptible to carbapenems and β-lactamase inhibitor combinations, and was the dominant genotype of ESBLs. The low expression of may be the reason for the low resistance to carbapenems.