Patients with
pneumonia not responding to treatment with betalactam drugs and patients where an "atypical" etiology is suspected from the beginning, are often given
erythromycin to cover mycoplasma and legionella.
Erythromycin has also been effective for Chlamydia pneumoniae. If, however,
ornithosis is suspected the recommended
drug has been
tetracycline. Since we noted that several patients had a favourable course on
erythromycin despite a final serological diagnosis of
ornithosis, we retrospectively studied patients admitted with acute lower
respiratory tract infection and a 4-fold titer rise to C. psittaci. We found 35 patients treated with a betalactam
drug (n = 12),
tetracycline (n = 2), or
erythromycin (n = 5) alone, or with a betalactam, which because of non-responsiveness was followed by either
tetracycline (n = 4) or
erythromycin (n = 12). The data were analysed with survival analysis by a Cox' regression model. There was a significant (p less than 0.001) effect of treatment on the time to defervescence, mainly due to a difference between the
erythromycin treated group and the betalactam treated group. We found
erythromycin to be at least as effective as
tetracycline for treating C. psittaci
pneumonia. Since
erythromycin has to be used to cover legionella in patients with severe
pneumonia when an atypical etiology cannot be excluded, it is an important conclusion that this
drug seems to cover C. psittaci as well.