Actinomycosis and nocardiosis: A review of basic differences in therapy

Actinomycosis and nocardiosis are closely related and often clinically indistinguishable diseases, chronic pleuropulmonary involvement, subcutaneous abscesses and multiple draining sinuses typifying both. Nevertheless they possess too many essential differences to be considered anything but two separate and distinct diseases. Especially important is the difference in therapy. Stated in the most elementary fashion, if one chooses to treat with penicillin all diseases caused by branching, fragmenting, filamentous fungi, then most patients with actinomycosis will recover, while almost all patients with nocardiosis will die. The natural habitat of A. bovis is the human mouth; that of the nocardia is soil. Either can exist saprophytically in the oropharynx or respiratory tract, however, and mere recovery of the organism from sputum does not constitute absolute proof of the disease. A. bovis is extremely sensitive to penicillin and for actinomycosis this constitutes the treatment of choice. The sulfonamides, although responsible for many earlier cures, show a far inferior inhibitory effect. In vitro sensitivity studies and clinical use have also shown that, depending upon strain sensitivity, one or another of the broad-spectrum antibiotics may be highly effective, so much so that undoubtedly some cases of very early actinomycosis are cured by random antibiotic therapy of seemingly minor infections without even suspecting the possibility of actinomycosis. N. asteroides, the cause of most cases of systemic nocardiosis, is a relatively resistant organism, much less likely to be eradicated by indiscriminate drug administration. Perhaps this accounts for the growing importance of nocardiosis as opposed to the contrasting decrease in frequency of actinomycosis. All strains of nocardia that we have isolated have shown marked penicillin resistance. Sulfadiazine exhibits greater in vitro effectiveness and provides the best animal protection. More important still, its use in clinical nocardiosis has proved life-saving and has been responsible for practically every clinical recovery. The broadspectrum antibiotics and streptomycin show a less marked and more variable inhibitory effect. Because of the extremely serious implications of most nocardial infections sulfadiazine is probably best combined with whatever drug appears most effective in vitro. Regardless of sensitivity tests, however, sulfadiazine should constitute the one essential component of any drug regimen for no