Haemophilus influenzae, Pneumococci, group A streptococci and Staphylococcus aureus: sensitivity of outpatient strains to commonly prescribed antibiotics.

The degree of resistance of Haemophilus influenzae, pneumococci, group A streptococci and Staphylococcus aureus to phenoxymethylpenicillin, ampicillin, doxycycline, erythromycin and chloramphenicol was investigated with the MIC-method (plate-dilution technique). Each bacterial group consisted of 100 outpatient strains. Seven strains of H. influenzae were beta-lactamase-producing. Of the 100 haemophilus strains, 58% were sensitive and the rest intermediate sensitive to erythromycin. 99% were sensitive to doxycycline and all strains were sensitive to chloramphenicol. Essentially all pneumococcal strains were sensitive to the antibiotics tested. However, a few strains demonstrated diminished sensitivity to penicillins. All group A streptococci were sensitive to ampicillin, penicillin and chloramphenicol, and 98% were sensitive to erythromycin. Approximately 1 strain out of 5 was resistant to doxycycline. 75% of S. aureus were beta-lactamase producers. Four of the S., aureus strains were resistant to erythromycin and 8 to doxycycline. The results presented indicate a better antibiotic situation than in some other countries, but suggest the need for a more extensive antibiotic sensitivity examination of isolated bacteria.