Unidentified Gram Positive Bacillus Associated with Meningo-Encephalitis

Abstract

An unidentified gram positive bacillus has been procured from the blood stream of 3 newborn infants that died, having lesions determined at necropsy to be meningo-encephalitis during the past year and a half at the New Haven Hospital. The organisms were obtained during the clinical course of the disease of 2 of the infants and in all 3 instances they were isolated from the heart blood at postmortem. In 2 of the infants a routine bacteriological study of the organs at necropsy showed them to be diffusely distributed throughout the body. The organisms are pathogenic for rabbits, guinea pigs, mice and to a lesser degree young monkeys. They have an especial affinity for the tissues of the central nervous system.

The organisms are morphologically a small non-spore forming gram positive bacillus measuring 1 to 4 micron in length and 0.5 micron in breadth with an occasional tendency to form longer rods or filaments. They are usually arranged singly or in small clumps with some tendency to palisade formation. All strains are non-acid fast. The colony on a blood agar plate is round, moist, convex and semi-translucent. It is not quite as opaque or dense as colonies of Streptococcus hemolyticus, although it is necessary to make a very careful morphological study of the organism for they may very easily be mistaken for strains of hemolytic streptococci because of the colony appearance and their marked hemolytic properties on blood agar plates. Hemolysis occurs both on surface and deep pour blood agar plates, as well as a rapid hemolysis takes place in broth of both rabbit and human red blood corpuscles. The strains grow readily and rapidly in meat infusion broth without aid of further nutritive material. They ferment dextrose, maltose, salicin, dextrin, galactose, starch and rhamnose in 24 hours, while lactose and glycerin fermentation is delayed usually for 48 to 72 hours. Litmus milk is slowly acidified and decolorized, but is not coagulated. Gelatin is not liquefied. They are very sluggishly motile, but it is extremely difficult to differentiate true motility in all the cultures studied. It fails to form indol or reduce nitrates. All 3 strains are very hardy and survive in ordinary media for long periods of time without transfer.