Risk of resistance related to antibiotic use before admission in patients with community-acquired bacteraemia

We analysed the association of antibiotic therapy before admission and anti biotic resistance of blood isolates in a total of 1717 community-acquired b acteraemias in the County of Northern Jutland during 1992-96. Antibiotics h ad been prescribed to 14% of the patients during the 30 days before admissi on and to 37% during the 6 months. The most frequently prescribed antibioti cs within 30 days were ampicillin (28%), penicillin G (27%), sulphonamides and/or trimethoprim (16%) and macrolides (14%). The most frequent blood iso lates were Escherichia coli (33%), other Enterobacteriaceae (8%), Streptoco ccus pneumoniae (23%) and Staphylococcus aureus (10%). Of the 575 isolates of E. coli, 425 (74%), 432 (75%) and 518 (90%) were susceptible to ampicill in, sulphonamides and trimethoprim, respectively. Previous antibiotic presc riptions were strongly associated with resistance to ampicillin, sulphonami des and trimethoprim in E. coli. The association was less pronounced for S. aureus and enteric rods other than E. coil. Antibiotic prescriptions withi n the last 3 months predicted antibiotic resistance, and this should be tak en into account when selecting empirical antibiotic therapy of severe commu nity-acquired infections.