Transfer of resistance to oxy-imino-cephalosporins and of extended-spectrum beta-lactamase productions in Klebsiella pneumoniae strains from infected neonates.

In this communication, we describe the occurrence of strains of Klebsiella pneumoniae resistant to cephalosporins of all generations and to aztreonam due to their production of Extended Spectrum beta-Lactamases (ESBLs), in two hospitals in Slovakia. They were found to transfer the genetic determinants of resistance of cefotaxime, ceftazidime and aztreonam and of ESBL production to suitable recipient strains of Escherichia coli K-12 No. 3110 and Proteus mirabilis P-38. Six donor K. pneumoniae strains were collected from six prematurely born babies gradually infected with strains of K. pneumoniae resistant to cefotaxime, ceftazidime and aztreonam. All six strains of K. pneumoniae gave an identical pattern in ESBL testing (double-disk diffusion test). The second cycle of transfers to nalidixin-resistant E. coli K-12 No. 185 nal+ also confirmed that all transconjugants were resistant to all beta-lactams tested. We conclude that a single gene was transferred from donor strains which confers 'en bloc' the resistance to the beta-lactams tested. Four strains of K. pneumoniae produced a uniform type of ESBI. Although with different quantitative expression. All transconjugants tested produced identical types of ESBL as did the donor strains of K. pneumoniae. This transfer of an identical pattern of ESBL production was confirmed also in the second cycle of transfers. Cefotaxime, ceftazidime and aztreonam were actively hydrolysed (as shown by the relative rate of hydrolysis [Vmax]) by strains of K. pneumoniae as well as by transconjugant colonies and clavulanate inhibited the hydrolysis of these beta-lactam antibiotics.