CHAPTER 37 



MISCELLANEOUS BACTERIA 



We include in this chapter a number of organisms which, for one reason or another, 

 cannot justifiably be allotted to any of the named groups. ^ 



The Morax-Axenfeld Bacillus. 



This organism, which is responsible for subacute or angular conjunctivitis in human 

 beings, was described independently by Morax (1896) and Axenfeld (1897). The name 

 B. lacunatus was suggested for it by Eyre (1900). 



Morphology. — In films of the conjunctival secretion it occurs in the form of rods^ 

 2-3 fi long and 1 fi broad, with parallel or shghtly convex sides and rounded ends. The 

 baciUi occur in pairs, placed end-to-end, and sometimes in short chains. They are found 

 free in the secretion, or within the polymorphonuclear and desquamated epithelial ceUs. 

 They are non-motile, non-sporing. Gram-negative, and except for the absence of a capsule, 

 they closely resemble Friedlander's pneumobacillus. In old cultures pleomorphic forms 

 are numerous, ranging in size and shape from short stunted diplococcal forms to long, 

 jointed or filamentous, sometimes fusiform threads (Eyre 1900). 

 Cultivation.- — Growth occurs only in the presence of some 

 natural animal protein, such as serum, blood, or ascitic fluid ; 

 there is no development on ordinary nutrient agar or potato 

 nor in broth, milk, or gelatin. Development is best on 

 Fildes' agar and on serum or egg medium ; it is poor on 

 blood agar and very poor on chocolate agar. The organism 

 is said to grow only between 30° and 40° C, and to be strictly 

 aerobic. Our own limited experience suggests that some 

 growth may occur below 30° C, and that under anaerobic 

 conditions on favourable media shght but definite growth may 

 be evident. On serum agar plates after 24 hours at 37° C. the 

 colonies are round, up to 1 mm. in diameter, raised, greyish, 

 and translucent ; during the next few days they increase in 

 size, reaching 2-5 mm. in diameter, and become differentiated 

 into a shghtly raised opaque whitish centre, and a thin, 

 translucent periphery with a lobate edge ; the medium be- 

 comes pitted owing to liquefaction of the serum. On Loeflfler's 

 serum no actual colonies are visible, but the whole surface is covered with pits of 

 liquefaction^ — hence the term lacunatus. On Fildes' agar after 24 hours at 37° C. the 

 colonies are water-clear, amorphous, low convex, 0-4 mm. or so in diameter, with a 

 smooth glistening surface and entire edge ; after 4 days they are larger, and are differ- 

 entiated into a smooth, raised, central papilla and a wide, effuse, granular, dull, trans- 

 parent, peripheral extension with an irregularly undulate margin. The central papilla 

 may be so small and the peripheral portion so transparent that the colonies are difficult 

 to see. By transmitted hght they have a frosted-glass appearance. On horse blood 



^ The terms Bad. pneumosintes and Bact. granulosis are used for convenience, but it must 

 be pointed out that neither of these organisms belongs to the Bacterium group as defined on 

 p. 664. 



898 



Fig. 211.— Mukax-Axen- 

 feld bacillus. 



Surface colonies on Fildes' 

 agar plate, 24 hours, 

 37°C. (X 8). 



