During a 3-month period, six Klebsiella pneumoniae isolates resistant to cefoxitin and penicillin-inhibitor combinations were derived from patients in the intensive care unit of a hospital in Athens, Greece. Enterobacterial repetitive intergenic consensus PCR and pulsed-field gel electrophoresis provided evidence of the clonal origin of the isolates. Conventional techniques and ribotyping were inadequate in proving that the isolates were related. Resistance was due to a plasmidic class C ␤-lactamase.

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Seven multiresistant Klebsiella pneumoniae strains isolated in an intensive care unit were studied. Susceptibility to beta-lactams was determined with the E test. Molecular-typing of the isolates was performed by a PCR-based technique (ERIC2-PCR). Sonic cell-extracts were used as beta-lactamase preparations. Beta-lactamase quantities were evaluated measuring nitrocefin hydrolysis. The similarity of the ERIC2-PCR patterns indicated that the seven isolates constituted a single clone. The levels of resistance to oximino-beta-lactams, however, were different. There were indications that the differences in susceptibilities were due, at least partly, to differences in the levels of expression of an extended-spectrum beta-lactamase (most likely SHV-5). Related K. pneumoniae isolates may exhibit different levels of resistance to beta-lactams. Therefore, comparison of resistance phenotypes is of limited usefulness in epidemiological investigations of nosocomial infections caused by resistant K. pneumoniae.

The in vitro activity of cefodizime and two comparative cephalosporins, cefuroxime and ceftriaxone were studied against respiratory pathogens. MIC90s of cefodizime were 0.06-0.512 microgram/ml for Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae. MIC50s of cefodizime for Klebsiella pneumoniae and Staphylococcus aureus isolates were 2 micrograms/ml and 8 micrograms/ml respectively. Cefuroxime and ceftriaxone at a concentration of 2 micrograms/ml and 1 microgram/ml inhibited 50% of Klebsiella pneumoniae and 50% of Staphylococcus aureus strains studied respectively. Cefodizime inhibited many of the important respiratory pathogens and can be suggested as an active antimicrobial agent for respiratory tract infections.