Further preliminary reports on flies as carriers of infection.

Date:
1909
Catalogue details

Licence: In copyright

Credit: Further preliminary reports on flies as carriers of infection. Source: Wellcome Collection.

    12/46 (page 10)
    specimens of the genus Spilogaster, Small flies mainly, Homalomyia canicularis, Blue-bottles, including Calliphora erythrocephala and vomitoria, and Stomoxys catcitrans. In 60 instances a fly was seized with sterile forceps, placed in a tube of lactose-bile-salt broth, and the tube well shaken. The surface organisms were thus cultivated. In 88 cases the intestinal contents were alone examined. The intestine was removed by seizing the thorax of the fly with one pair of forceps and the terminal segments of the abdomen with another. By gentle traction the intestine can easily be pulled out intact, and without coming into contact with the surface of the insect. A portion of the intestine was then cut off and emulsified in lactose-bile-salt broth. The broth was incubated at 37° C. for 24 hours or longer. Plate cultures were then made on Conradi-Drigalski medium, bile- salt neutral-red lactose agar, and ordinary agar. Colonies were picked off from these plates and pure cultures made. The staining reactions, morphology and motility of the organisms obtained were examined, and cultures made in broth, gelatine, milk, peptone water, and peptone water containing 1 per cent, of glucose, lactose, saccharose, dulcite, mannite, and dextrin. In this series of experiments the intention was to ascertain what proportion of flies were infected with organisms of the colon-group, and no attempt was made to work out completely all the organisms belonging to this group which occurred in each infected fly. Characters of the Oryanisms. Altogether 35 lactose fermenting organisms of the colon group were isolated, 22 from surface cultures, and 13 from the intestines. All these organisms had the following characters in common :— short—Gram negative, non-spore producing bacilli with rounded ends—gi’eyish white colonies on agar—gelatin never liquefied—moist white or cream-coloured growth on potato—permanent acidity and clotting in milk. Most of them produced indol, and the majority showed some motility, especially in peptone water cultures. Following MacConkey’s classification of the lactose fermenting bacteria, these organisms may be divided according to their reactions, which are given in the following table, into four groups. Group. No. of cul- tures. Glucose. Lactose. Saccharose. Dulcite. Mannite. Dextrin. Milk. Indol. I 10 A-PG A-pG 0 0 A+G A A+C + II 6 A-PG A-pG 0 A+G A+G A A+C + Ill 15 A-pG A-pG A+G A+G A+G A A+C + IV 4 A+G A-pG A+G 0 A+G A A+C + O = No change. A = Production of acid without gas. A-pG = Acid and gas produced. A-pC = Acid and clotting. -P = Positive reaction.