Lobar pneumonia caused by Mycoplasma pneumoniae.

Seven patients with Mycoplasma pneumoniae pneumonia presented with moderate to dense consolidation in one (in five patients) or more lobes. The diagnosis was suspected in five patients after failure to respond to 1 to 6 (average 2.6) antibiotics administered for 2 to 12 (average 7) days, and in one patient upon the development of hemolytic anemia. Clues to the diagnosis of nonbacterial pneumonia included a nonrespiratory viral-like prodromal period (in five), a nonproductive cough (in five), lack of rigors (in seven), recent "pneumonia" in family members (in ;three), normal total leukocyte and neutrophil counts (in six) and the absence of bacterial pathogens in smears and cultures of sputum (in all seven). The diagnosis of M. pneumoniae infection was supported by the presence of cold agglutinins (in a titre of 1.64 or greater) in ;the serum of five or six patients and was confirmed by diagnostic levels or increases in the titre of M. pneumoniae complement fixing antibodies. Awareness of the fact that M. pneumoniae can present as lobar consolidation and close attention to the clinical and laboratory data can usually suggest a nonbacterial cause and thus prevent delay in appropriate antibiotic treatment.