The activity of phenoxymethylpenicillin (PcV), ampicillin, cefaclor, cefuroxime, chloramphenicol, co trimoxazole, doxycycline and erythromycin against clinical isolates of Branhamella catarrhalis, Haemophilus influenzae, pneumococci, group A streptococci and Staphylococcus aureus in 1983 was investigated with the MIC-method (plate-dilution technique). Forty-six percent of B. catarrhalis, 2% of H. influenzae and 78% of S. aureus were beta-lactamase producing and had high MIC-values for penicillin and ampicillin. Thus MIC for 90% of all strains of B. catarrhalis was 32 mg/l and 8 mg/l for penicillin and ampicillin while MIC for 90% of non beta-lactamase producing Branhamella strains was 2 mg/l and 0.25 mg/l respectively. This indicates a high susceptibility of penicillins to the action of Branhamella beta-lactamase. Almost all strains of B. catarrhalis, pneumococci, group A streptococci and S. aureus were inhibited at low concentrations of erythromycin. However, 4 mg/l was required to inhibit 90% of H. influenzae. Co-trimoxazole and doxycycline had good activity against all B. catarrhalis and H. influenzae strains while a few pneumococci, streptococci and staphylococci had intermediate sensitivity or were resistant. Essentially all strains were sensitive to cefuroxime and chloramphenicol.
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Forsgren et al. (1984) studied this question.