Dissemination and spread of CTX-M extended-spectrum beta-lactamases among clinical isolates of Klebsiella pneumoniae in central China.

Of 50 extended-spectrum beta-lactamase-producing (ESBL) isolates of Klebsiella pneumoniae collected from six hospitals in Hubei Province, 20 were found to produce CTX-M ESBLs (40%). Sequence analysis of the six isolates carrying bla(CTX-M) genes revealed that they all harboured bla(CTX-M-3). In the majority of isolates, bla(CTX-M) genes were within large conjugative plasmids. A high degree of diversity of the RAPD types revealed that all the isolates carrying CTX-M were genetically unrelated and horizontal transfer of plasmids was probably the main mechanism of bla(CTX-M) spread. This is the first report of the occurrence of CTX-M-3 ESBLs in central China; previously this enzyme was identified only in Europe. A more comprehensive survey of ESBL types from China is urgently needed.