760 LACTOBACILLUS 



Agar Slope.— 24 hours, 37° C. Poor filiform growth of small transparent granular colonies, 

 0-25 to 0-5 mm. in diameter. Sometimes after a few days a thick greyish-yellow 

 secondary growth occurs, having a contoured surface, and an edge from which 

 thin translucent branching tufts, looking like sea-anemones, project. 



2 per cent. Glucose Agar Shake. — 48 hours, 37° C. Good growth throughout tube of small, 

 spherical, lenticular, or lobulated colonies, 0-25 mm. in diameter, having an entire 

 edge (Y type), or of small irregular spherical colonies with a fuzzy, filamentous 

 border (X type). The agar is clouded and has an almost milky look. After a 

 week the colonies are 0-5 mm. in diameter, are porcelain-white in colour, and look 

 like colonies of moulds. 



Gelatin Stab. — 7 daps, 22° C. Very poor greyish-white filiform growth ; no surface growth ; 

 no liquefaction. 



Broth. — 48 hours, 37° C. Poor to moderate growth with a very slight, only just perceptible 

 turbidity, and a moderate flocculn-granular deposit disintegrating to some extent 

 on shaking ; sometimes the deposit sticks to the walls of the tube. 



2 per cent. Glucose Broth.— Growth is better than in plain broth. Sometimes after a week 

 an enormous loose flocculent deposit forms, filling the lowest 1 cm. of the tube ; 

 it disintegrates partly on shaking, producing a dense turbidity. 



Potato. — No growth. 



Horse Blood Agar Plates. — 48 hours, 37° C. Small discrete colonies, similar to those on 

 agar. No haemolysis. 



Glucose Blood Liver Agar Plates. — 48 hours, 37° C. Flat, dingy colonies with a serrated edge. 



MacConkey Plate. — Results discrepant. Cruickshank (1931) says that all strains grow 

 on this medium, but this has not been our own experience. 



Resistance. — Not particularly resistant. Killed by moist heat at 56° C. in 30 minutes. 

 Very resistant to acids, living for 1 to 3 days in broth containing 0-5-1 -0 per cent, 

 acetic or lactic acid. Glucose broth cultures at 37° C. remain viable for about a 

 fortnight. 



Metabolism. — Often microaerophilic on first isolation. Grows better under aerobic than 

 anaerobic conditions. Grows shghtly or not at all at 20° C. ; optimum temperature 

 for growth 37° C. Forms no pigment and no toxin. Does not lyse horse blood. 

 Growth is improved by glucose and by whey, but not by blood serum. Grows 

 best at pH 6-0, but wiU grow even at pH 5 0. 



Biochemical. — Sugar reactions variable. Produces acid in glucose and in lactose ; often 

 in maltose and sucrose ; sometimes in mannitol, salicin, and rafiinose ; less fre- 

 quently in other sugars. L.M. acid and clot in 24 to 48 hours ; the clot is really 

 an acid precipitate, and does not contract ; on shaking it breaks up into flocculent 

 masses ; the litmus is at first reduced at the bottom of the tube only, but later 

 the decolorization spreads upwards. Indole negative. M.R. positive. V.P. nega- 

 tive. Nitrates reduced slightly or not at all. Catalase very weak positive. HjS 

 negative. NH3 negative. 



Antigenic Structure. — Not studied fully. By agglutination numerous groups can be made 

 out, having little affinity with each other. Some group relationship to L. bifidus. 



Pathogenicity. — Non-pathogenic to man or to laboratory animals. 



Lactobacillus odontolyticus I 



Isolation, — Isolated by Mcintosh, James, and Lazarus-Barlow in 1922 from carious teeth 



and from sahva, and called B. acidophilus odontolyticus I. 

 Morphology. — Thin bacillus, 2-3 n long by 0*75 fi broad, occurring singly, in pairs, 



or chains, and in pahsades. Non-motile. Gram-positive. 

 Agar Plates. — 48 hours, 37° C. Small, round, grejash, opaque colonies, 0-6-1 -0 mm, in 



diameter, with a finely granular appearance and an entire edge. On serum agar 



the colonies are larger up to 2 mm. in diameter. 



