Low occurrence of antibiotic resistance in Escherichia coli and staphylococci isolated from blood cultures in two Norwegian hospitals in 1991-92 and 1995-96.

The aim of this study was to investigate the antibiotic resistance rates of major bacterial pathogens causing bloodstream infections in two very different types of hospital in Norway. We examined all Escherichia coli and staphylococci (330 isolates) causing bloodstream infections from one general county hospital and one specialist national cancer hospital during the periods 1991-92 and 1995-96. Minimal inhibitory concentrations (MICs) were determined using the E-test. E. coli and staphylococci constituted 46.7% of all isolates from bloodstream infections in the two hospitals. Overall, E. coli isolates were resistant to amoxicillin (21%), trimethoprim (21%), doxycycline (20%) and trimethoprim-sulphamethoxazole (17%), while Staphylococcus aureus strains were resistant to benzylpenicillin (66%). No methicillin-resistant S. aureus was detected. Coagulase-negative staphylococci were often multiresistant, but remained fully sensitive to vancomycin. For a few antibiotics, significantly more resistance was found in the specialist hospital. In our material we found no significant increase in resistance between 1991-92 and 1995-96. In conclusion, antimicrobial resistance still remains low in important bacterial pathogens causing bloodstream infections in Norway.