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Clin Microbiol Infect. 2008 Jan;14 Suppl 1:33-41.

The spread of CTX-M-type extended-spectrum beta-lactamases.

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Dipartimento di Biologia Molecolare, Sezione di Microbiologia, Università di Siena, Siena, Italy.

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  • Clin Microbiol Infect. 2008 May;14 Suppl 5:21-4.


CTX-M-type enzymes are a group of class A extended-spectrum beta-lactamases (ESBLs) that are rapidly spreading among Enterobacteriaceae worldwide. More that 50 allotypes are known, clustered into six sub-lineages. The CTX-M-encoding genes have been captured from the chromosome of Kluyvera spp. on conjugative plasmids that mediate their dissemination among pathogenic enterobacteria. CTX-M-type ESBLs exhibit powerful activity against cefotaxime and ceftriaxone but generally not against ceftazidime, which has important implications for laboratory detection. However, several CTX-M variants with enhanced ceftazidimase activity have been detected. The rapid and massive spread of CTX-M-type ESBLs is rapidly changing the ESBL epidemiology and, in some geographical areas, these enzymes are now the most prevalent ESBLs in Enterobacteriaceae.

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