Heterogeneity of metallo-beta-lactamases in clinical isolates of Chryseobacterium meningosepticum from Hangzhou, China.
OBJECTIVE
To determine the distribution and heterogeneity of metallo-beta-lactamases (MBLs) responsible for imipenem resistance in Chryseobacterium meningosepticum.


METHODS
Clinical C. meningosepticum isolates (n = 170) were collected from hospitals in Hangzhou, China. Production of MBLs was investigated by determination of imipenem MICs, and by using both a three-dimensional test and a 2-mercaptopropionic acid inhibitory test. Genes encoding BlaB and GOB MBLs were amplified by PCR, sequenced and compared with genes in GenBank.


RESULTS
More than 95% of the 170 isolates showed high (MIC > 16 mg/L) or intermediate resistance to imipenem, but only 94 isolates (55%) were shown phenotypically to produce MBLs (imipenem MIC range, 8-256 mg/L), with MBL genes detected in 93 of these. Among them, 83 isolates had blaB alleles and 65 isolates had bla(GOB) alleles; 38 isolates possessed one MBL gene and 55 isolates contained two genes. The major blaB alleles encoded BlaB-2, -3 and -11, while the major bla(GOB) alleles encoded GOB-2, -4, -8 and -10. MBLs or their genes were not detected in 76 (45%) isolates, including many that were highly resistant to imipenem.


CONCLUSIONS
High levels and rates of imipenem resistance in C. meningosepticum from Hangzhou often result from the presence of heterogeneous BlaB and/or GOB MBLs, although undefined carbapenem resistance mechanisms also exist. Susceptibility testing and screening for MBLs should be conducted in order to inform effective treatment for C. meningosepticum infections.
Chen
Gong-Xiang
GX
2nd Affiliated Hospital of Zhejiang University, Zhejiang University, Hangzhou, China. chengong218@163.com
Zhang
Rong
R
Zhou
Hong Wei
HW
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002681:China; D045247:Chryseobacterium / Q000187:drug effects* / Q000201:enzymology / Q000302:isolation & purification; D005838:Genotype; D006801:Humans; D015378:Imipenem / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D015378:Imipenem; D001618:beta-Lactamases