Diversity of Beta-Lactam Resistance Levels Among Related Klebsiella pneumoniae Strains Isolated in an Intensive Care Unit

Abstract

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.