Urinary tract infections in Norway: bacterial etiology and susceptibility. A retrospective study of clinical isolates

The objective of the present study was to determine bacterial etiology and susceptibility in urinary tract infections. The study was designed as a retrospective study of urine samples from patients both inside and outside hospitals and nursing homes that were received at our laboratory between 1 January 1997 and 31 October 1999. The Telemark Biomedical Center receives all the medical microbiology specimens from hospitals, nursing homes and general practitioners in the County of Telemark (165 000 inhabitants), Norway. All urines fulfilling the criteria for significant bacteriuria [≥10 000 colony-forming units/mL urine] were included in the study. Bacterial susceptibility testing was performed using breakpoint methodology. During the study period, we received 52 350 urine samples, of which 28 066 (53.6%) fulfilled the criteria for significant bacteriuria (pure growth of ≥10 000 CFU/mL urine). Escherichia coli was the most predominant bacterium in the urine from both inpatients (56.7%) and outpatients (68.3%). Coagulase-negative staphylococci and enterococci occurred significantly more often (P< 0.001) in urine samples from inpatients (12.5% and 7.9%) than in urine samples from outpatients (7.5% and 4.7%). Escherichia coli from both outpatients and hospitalised patients was highly susceptible (>93%) to cefalothin, mecillinam and nitrofurantoin, and more than 75% of E. coli isolates were also sensitive to ampicillin. Overall, the susceptibility to nitrofurantoin in bacteria from outpatients was 90% and from hospitalised patients was 85%. The corresponding figures for cefalothin were 92% and 90%, and for trimethoprim were 81% and 76%, respectively. Bacteria causing urinary tract infections in Norway are less resistant to antibacterial medication than in other western countries and the reason for this may be the low consumption of antibacterials by the Norwegian population. During the period from 1990 to 1999 the mean total annual consumption of antibacterial drugs in Norway was 15.3 defined daily doses per 1000 inhabitants per year.