[Epidemiological characteristics of nosocomial bloodstream infections and their causes]

Nosocomial bloodstream infections (BSI) contribute to grater morbidity and mortality rates, as well as to increasing length of hospital stay and health care costs. All patients with nosocomial BSI identified during the one-year period were studed to identify microbiological factors associated with these infections.

A one-year prospective cohort study was performed in patients in intensive care units (ICU), and non-ICU patients. The patients were identified by active surveillance and positive blood cultures during the study period. The definitions of nosocomial BSI of the Center for Diseases Control and Prevention, Atlanta were used. Hospital laboratory detected growth in blood cultures, identified organisms, and performed susceptibility testing were in according with the American National Committee for Clinical Laboratory Standards.

The incidence of nosocomial BSI was 2.2 per 1 000 admission in non-ICU and 17.4 per 1 000 admission in ICU patients. The 28-day crude mortality rate was 44.9%. There were 60.3% primary nosocomial BSI. Gram negative organisms accounted for 50%, gram-positive organisms accounted for 44.9%, and 4.1% were caused by fungi. The most common pathogens were coagulase-negative staphylococci (21.4%), Staphylococcus aureus (14.3%), Klebsiella spp. (13.3%), Pseudomonas aeruginosa (8.2%), Acinetobacter spp. (7.1%). Methicillin resistance was detected in 64.3% of S. aureus and 100% of coagulasa-negative staphylococci. Vancomycin resistance in enterococci and staphylococci was not detected. The proportion of ceftazidim resistance among K. pneumoniae isolates was 92%.

This study might help to better understanding not only the characteristics of BSI, but also the featares of their causes, primarily the resistance of coagulase-negative staphylococci and S. aureus to methicillin, and of K. pneumoniae to ceftazidime.