Dissemination in five French hospitals of Klebsiella pneumoniae serotype K25 harbouring a new transferable enzymatic resistance to third generation cephalosporins and aztreonam.

A strain of Klebsiella pneumoniae K25 resistant to newer beta-lactam drugs was isolated in clusters in five hospitals in the Paris area. The MICs of ceftazidime and aztreonam (greater than or equal to 128 mg/l) were higher than that of cefotaxime (16 mg/l) for the strain but, when measured in the presence of clavulanic acid, they were less than or equal to 1 mg/l. The donor strains and derivatives produced a beta-lactamase with a pI of 7.75-7.8 and hydrolysing activity against a wide spectrum of beta-lactams similar to that of SHV-2 and SHV-3, but with significant hydrolysis of ceftazidime. This new enzyme could be designated SHV-4.