Objectives: To investigate the epidemiological and clinical findings of extended-spectrum beta-lactamase (ESBL)-producing Providencia stuartii infections in a large Italian university hospital.
Patients and methods: All consecutive episodes of P. stuartii infection that occurred during 1999-2002 were included in the study. For each patient, we recorded the area of hospitalization and drug susceptibility of the P. stuartii strains. Patients with ESBL-producing P. stuartii infection were considered cases and those with non-ESBL-producing P. stuartii infection were used as controls.
Results: One hundred and sixteen (52%) out of 223 P. stuartii strains collected during the study period were found to be ESBL-producing. On the basis of PCR and DNA sequencing experiments, TEM-52 was identified in 87% of isolates and TEM-72 in 13%. All ESBL-producing P. stuartii infections were nosocomially acquired. The prevalence increased from 31% of P. stuartii infections in 1999 to 62% in 2002 (P = 0.04). All 116 strains were classified as ESBL-producing multidrug-resistant P. stuartii, since 88% of the isolates were cross-resistant to ciprofloxacin and amikacin and the other 12% were cross-resistant to ciprofloxacin and gentamicin. At logistic regression analysis, advanced age (P < 0.001), previous hospitalization (P < 0.01), neoplastic disease (P < 0.001) and previous antibiotic therapy (P < 0.001) were independent risk factors for the development of ESBL-producing infections.
Conclusions: This 4 year surveillance of Providencia complaints clearly indicates that infections caused by ESBL-producing multidrug-resistant P. stuartii are an emerging problem.