Prevalence and antibiotic sensitivity pattern variations of bacterial isolates in different settings and different periods of time.

The problem of bacterial antibiotic resistance emerged as soon as the first antibiotics became available for clinical use. The aim of this study was to estimate differences in the prevalence and antibiotic sensitivity pattern of the most frequent isolates between two different hospitals (Sveti Duh General Hospital, Zagreb, und University Hospital of Traumatology, Zagreb), different wards of the same hospital (nephrology, urology and surgery of Sveti Duh General Hospital) and different periods of time (01. 03.--31. 12. 1993 and 01. 01.--31.07. 1995). E. coli was the most frequent urine isolate at the Sveti Duh Hospital, whereas more resistant K. pneumoniae was the most frequent urine isolate at the University Hospital of Traumatology. S. pneumoniae was the most frequent lower respiratory tract isolate in the Sveti Duh Hospital, whereas in the University Hospital of Traumatology P. aeruginosa and A. anitratus prevailed. In both hospitals, staphylococci were the most frequent blood culture isolates, but in gram-negative sepsis E. coli was the most frequent pathogen in the Sveti Duh Hospital, and S. marcescens in the University Hospital of Traumatology. Difference in the prevalence of microorganisms may have partially been due to the different patient profile in the two hospitals, but we showed that the antibiotic sensitivity pattern of the most frequent nosocomial pathogens P. aeruginosa and K. pneumoniae differed between different settings as well, and that this pattern may change with time. This clearly points to the need of continuous surveillance of the prevalence and antibiotic sensitivity pattern of microorganisms in local environment, which should be the basis for effective empiric therapy.