Extended-spectrum TEM- and SHV-type β-lactamase-producing Klebsiella pneumoniae strains causing outbreaks in intensive care units in Italy

The aim of the present study was to investigate the production of extended-spectrum β-lactamases (ES βLs) and the epidemiological correlations in a total of 107 Klebsiella pneumoniae strains resistant to third- and fourth-generation cephalosporins. The strains were collected from patients in four intensive care units (3 neonatal and 1 general) in three hospitals in Italy between March 1996 and July 1997. All strains were found to produce ESβLs. Phenotypic (antibiotyping and ESβL patterns) and genotypic (plasmid profile and pulsed-field gel electrophoresis) analyses showed that a single strain had been responsible for each outbreak in each of the four intensive care units. Isoelectric focusing, activity on substrates and gene sequencing showed that the strains produced SHV-5, SHV-2a, SHV-12 and TEM-52 β-lactamases. This is not only the first time that ESβL-producing Klebsiella pneumoniae strains have been reported as causing epidemics in Italian hospitals, it is also, to the best of our knowledge, the first time that an outbreak caused by a TEM-52 ESβL-producing Klebsiella pneumoniae strain has been reported. The data presented here illustrate the complexity of determining the epidemiological pattern of ESβL producers in large hospitals that do not have an ESβL-monitoring program.