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A survey was made of the frequency of resistance to amikacin, gentamicin and tobramycin among aerobic gram-negative bacilli isolated over a 4-week period in 1979 at six large, geographically separated Canadian hospitals. In the entire series of 4407 isolates the frequency of resistance was 2.5% to amikacin, 8.1% to gentamicin, 5.9% to tobramycin and 1.7% to all three. Most (81%) of the resistant bacteria were acquired by the patients after admission to hospital. The frequency of resistance to the three aminoglycoside antibiotics in each hospital largely reflected the local rate of cross-infection by endemic strains of resistant bacteria.

In a protocol study of cases of atypical pneumonia over a 1-year period an etiologic agent was established in 16 cases: Legionella pneumophila in 8, Coxiella burnetii in 3, Chlamydia trachomatis in 2, Mycoplasma pneumoniae in 1, para-influenza 3 virus in 1 and cytomegalovirus in 1. In the remaining 11 cases no agent was identified; the illnesses in these cases tended to be less severe. The pneumonia took much longer to resolve in the patients with Legionnaires' disease than in all the other patients (mean interval from onset of symptoms to clearing of the chest roentgenogram: 69 days v. an average of 16 days). However, the length of stay in hospital was similar for the three groups: those with Legionnaires' disease, those with atypical pneumonia of unknown cause and those with atypical pneumonia of various other established causes. L. pneumophila infection may explain a proportion of atypical pneumonias that previously could not be diagnosed, although in this series the cause of 41% of the pneumonias remained unexplained.

Only nine cases of Q fever were recorded in Canada in the 20 years prior to 1978. In the 18 months from August 1979 to January 1981 the disease was diagnosed serologically in six patients from the Maritime provinces. All were epidemiologically unrelated and none had been exposed to animals. Five had pneumonia and one had chronic Q fever with probable prosthetic valve endocarditis. Three of the five pneumonia patients presented with signs and symptoms of an acute lower respiratory tract infection and were indistinguishable clinically from other patients with atypical pneumonias. The other two with pneumonia presented with nonresolving pulmonary infiltrates and complained of decreased energy. Four of the five pneumonia patients responded well to treatment with erythromycin; the fifth required two courses of tetracycline. The patient with chronic Q fever had a large amount of cryoglobulins in his serum and evidence of immune complex disease. These cases indicate that Q fever should be considered as a possible cause of atypical pneumonia in Canada.