[Study of susceptibility and genotype characterization of plasmid-mediated class I cephalosporinase in gram-negative bacteria].
OBJECTIVE
To investigate the susceptibility and genotype characteristics of gram-negative bacteria producing plasmid-mediated class I cephalosporinase (AmpC beta lactamase) epidemic in Southern China.


METHODS
A total of 1,187 clinical isolates of nonrepetive gram-negative bacteria were collected from different cities in Southern China. AmpC beta lactamase producing isolates were identified by cefoxitin three-dimensional test, and antimicrobial susceptibility test was identified by Kirby-Bauer agar diffusion test; plasmid conjugation, plasmid extraction, universal PCR for gene amplication of corresponding group was done, and the PCR products were sequenced subsequently.


RESULTS
The positive rate of cefoxitin three-dimensional test in gram-negative bacteria was 5.9% (70/1,187), and the prevalence of plasmid-mediated AmpC beta lactamase was: E. coli: 4.2% (19/451), Klebsiella: 4.7% (16/339), Enterobacter: 2.1% (4/190), Alcaligenes: 5.3% (1/19), Acinetobacter: 2.2% (1/45) and the total positive rate was: 3.5% (41/1,187). The susceptibility test showed that compared with the clinical isolates, the transconjugations remained resistance to cephamycins and ampicillin, and susceptible to cefepime and imipenem. PCR amplication and sequencing confirmed them to be bla(DHA-1) gene and bla(ACT-1) gene, and they were mainly distributed in Klebsiella and Escherichia.


CONCLUSIONS
DHA-1 and ACT-1 were the most common genotypes in plasmid-mediated AmpC beta-lactamase produced by clinical isolates in Southern China. Fourth-generation cephalosporins and carbapenems could be better choices for the treatment of infection caused by AmpC betalactamase producers.
Song
Wei
W
Department of Respiratory Medicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou 510630, China.
Tang
Ying-chun
YC
Lu
Jian
J
Zhu
Jia-xin
JX
Zhang
Yong-biao
YB
Tan
Shu-qing
SQ
D001426:Bacterial Proteins / Q000235:genetics*; D005838:Genotype; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000235:genetics*
D001426:Bacterial Proteins; C048795:AmpC beta-lactamases; D001618:beta-Lactamases