During the 21-month period from October 1968 to July 1970, Serratia marcescens was recovered from the sputum of 65 patients. Many of these infections resulted from contaminated sodium chloride solution used as diluting fluid for medication nebulizers.
Five patients in the sixth decade or older were suspected of having developed pneumonitis. There were no distinctive signs or symptoms, and pseudohemoptysis was not noted in spite of the presence of pigmented strains in three of the patients. Mild leukocytosis was characteristic, and roentgenograms usually revealed moderate lobular infiltration of the upper or lower lobes that was not cavitary, but often was accompanied by metapneumonic pleural effusion. The present antibiotic of choice is gentamicin. Many respiratory infections are the result of nonpigmented strains that must be distinguished from other gram-negative paracolon bacilli.