Erythromycin and phenoxymethylpenicillin (penicillin V) in the treatment of respiratory tract infections as related to microbiological findings and serum C-reactive protein.

Respiratory tract pathogens (beta-haemolytic streptococci groups A, C and G, Haemophilus influenzae, Branhamella catarrhalis or pneumococci), were isolated from nasopharyngeal and/or throat swabs in 73/138 (53%) patients greater than 10 years of age with a clinical diagnosis of acute sinusitis, acute tonsillitis, purulent nasopharyngitis or acute bronchitis. Serological evidence of a viral infection (influenza A and B, parainfluenza 1, 2 and 3, respiratory syncytial virus, adenovirus) or Mycoplasma pneumoniae infection was found in 10% of the patients. The serum content of C-reactive protein (S-CRP) was increased (greater than 12 mg/l) in 26/33 (79%) patients with streptococci and in 22/59 (37%) patients without respiratory tract bacteria. In patients with a serological evidence of a virus tonsillitis, the S-CRP was also high (32-64 mg/l). At follow-up 10-12 days after the first visit, the clinical effect of erythromycin and penicillin V was judged to be similar (90% clinical effect). Relapse or re-infection with group A streptococci were seen in 7 patients (4 on erythromycin, 3 on penicillin). In another 6 patients (3 on erythromycin, 3 on penicillin), antibiotic treatment was switched owing to persisting symptoms, probably due to H. Influenzae infection in 3 cases. The patients' own estimates of their symptoms suggested treatment with erythromycin to have a more rapid effect than treatment with penicillin.