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.
2nd Affiliated Hospital of Zhejiang University, Zhejiang University, Hangzhou, China. chengong218@163.com
Gong-Xiang
GX
Chen
Rong
R
Zhang
Hong Wei
HW
Zhou
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