Atypical pneumonias. Clinical diagnosis and empirical treatment

Atypical pathogens play an important role in the pathogenesis of community-acquired pneumonias. Early definitive diagnosis is often difficult. Careful attention must be given to the patient's history and other diagnostic clues. When a specific pathogen seems very likely to be the cause, appropriate and cost-effective empirical therapy is best accomplished with a single-drug regimen. However, when typical and atypical pathogens are suspected, combination drug therapy is preferred until the diagnosis is firm and one of the two antibiotics can be dropped.

Erythromycin for treatment of ornithosis

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.

Psittacosis--a review of 135 cases

We reviewed retrospectively 135 cases of serologically-confirmed psittacosis that were admitted to Fairfield Hospital between January 1, 1972 and March 31, 1986. The average age of the patients was 46 years. The majority (85%) of patients described a history of recent exposure to birds. The clinical features, investigations, treatment and subsequent response were analysed in 129 patients. Psittacosis was a well-defined illness that was characterized by an abrupt onset of fever, rigors, sweats, and prominent headache, and a mild dry cough which appeared late frequently. However, respiratory symptoms were absent in 18% of patients. Diarrhoea and sore throat were occasional complaints. Over 90% of cases had an abnormal chest x-ray film, or abnormal chest signs, or a combination of both. Most patients had a normal leukocyte count. Tetracycline drugs were used for treatment in 87% of the patients. Defervescence occurred in 92% of patients after 48 h of tetracycline treatment. There were no recrudescences of psittacosis and no fatalities. The clinical diagnosis of psittacosis can be made early usually, particularly in the presence of pneumonitis on a chest x-ray film and a positive history of bird contact. Treatment with doxycycline (100 mg twice a day for 14 days) is recommended.