FAMILY X. LACTOBACILLACEAE 



507 



B. Heterofermentative, producing considerable amounts of carbon dioxide, ethanol 

 and acetic acid as well as lactic acid from carbohydrates. 



Genus IV. Leuconostoc, p. 531. 

 II. Strictly anaerobic (one species becomes aerotolerant with repeated transfers). 



Genus V. Peptostreptococcus , p. 533. 



Genus I. Diplococcus Weichselbaum, 1886.* 

 (Wiener med. Jahrb., 82, 1886, 483.) 



Dip.Io.coc'cus. Gr. adj. diplous double; Gr. noun coccus a grain, berry; M.L. mas.n. 

 Diplococcus paired coccus. 



Cells usually in pairs, sometimes in chains. Young cells Gram-positive. Parasites, some- 

 times growing poorl}^ or not at all on artificial media. Fermentative powers usually high, 

 most strains producing acid from glucose, lactose, sucrose and inulin. The organisms in 

 this genus are soluble in a 10 per cent bile solution. 



The type species is Diplococcus pneumoniae Weichselbaum. 



1. Diplococcus pneumoniae Weichsel- 

 baum, 1886. (Microbe septicemique du 

 salive, Pasteur, Chamberland and Roux, 

 Compt. rend. Acad. Sci., Paris, 92, 1881, 

 159; Micrococcus of rabbit septicemia, 

 Sternberg, National Board of Health Bull., 

 Washington, 2, 1881, 781; Coccus lanceole, 

 Talamon, Communication k la Society ana- 

 tom. de Paris, 58, 1883, 475; Weichselbaum, 

 Wiener med. Jahrb., 82, 1886, 485; Pneu- 

 moniemikrococcus or Pneumococcus, Fran- 

 kel, Ztschr. f. klin. Medizin, 10, 1886, 402.) 



pneu.mo'ni.ae. Gr. noun pneumon the 

 lungs; M.L. fem.n. pneumonia pneumonia; 

 M.L. gen. noun pneumoniae of pneumonia. 



Common name: Pneumococcus. 



The organisms occur as oval or spherical 

 forms typically in pairs, occasionally singly 

 or in short chains, 0.5 to 1.25 microns. The 

 distal ends of each pair of organisms tend 

 to be pointed or lancet-shaped. Encapsu- 

 lated. Non-motile. Young cells are Gram- 

 positive. 



Gelatin stab: Filiform or beaded growth. 

 No liquefaction. 



Infusion agar colonies: Small, trans- 

 parent, grayish, entire. Elevation high, 

 convex, glistening, mucoid to watery. 



On blood agar the colonies are elevated at 

 the center with concentric elevations and 

 depressions. Hemolysis usually slight but 

 often marked in anaerobic culture; met- 



hemaglobin formation with green zone 

 around colony. 



Beef heart infusion broth: Uniform tur- 

 bidity with variable amount of sediment. 



Addition of glucose, serum, whole blood 

 or ascitic fluid enhances growth. 



Meat extract media: Growth irregular, 

 usually poor if any. 



Inulin serum water: Usually acid with 

 coagulation. 



Litmus milk: Usually acid with coagula- 

 tion. 



Potato: No growth. 



Whole bile or 10 per cent solutions of 

 sodium taurocholate or sodium glycocholate 

 added to actively growing broth cultures 

 will dissolve the organisms. It is customary 

 to use from 0.1 to 0.5 ml of bile for each 0.5 

 ml of culture. 



Aerobic, facultative. 



Optimum temperature, 37° C. Usually no 

 growth between 18° and 22° C. 



Optimum initial pH, 7.8. 



Source: Sputum, blood and exudates in 

 pneumonia; cerebrospinal fluid in menin- 

 gitis; mastoiditis; otitis media; peritonitis; 

 empyema; pericarditis; endocarditis; ar- 

 thritis; saliva and secretions of respiratory 

 tract in normal persons. Commonest cause 

 of lobar pneumonia. 



Habitat : The respiratory tract of man and 

 animals. 



* Revised by Prof. E. G. D. Murray, McGill University, Montreal, P.Q., Canada, Sep- 

 tember, 1938; further revision by Lt. Col. Elliott S. Robinson, M.C., Washington, D. C, 

 January, 1944. 



