Practical bacteriology for chemical students / by David Ellis.

  • David Ellis
Date:
1923
Catalogue details

Licence: In copyright

Credit: Practical bacteriology for chemical students / by David Ellis. Source: Wellcome Collection.

    115/152 (page 103)
    Search for Streptococci 1. Pour contents of 4 Agar-tubes each into a Petri-dish and allow Agar to set. 2. Inoculate. First tube with *i cc from Flask No. 1 Second „ „ * 1 „ „ „ „ 2 Third „ „ *i „ „ „ „ 3 Fourth „ „ 1 „ „ „ „ 4 [See Exercise 77.] Spread liquid over the solid Agar as indicated in Exercise 80. 3. Incubate at 370 C. 4. After 48 hours examine colonies microscopically and ascertain whether any are made up of cocci arranged in a row like a string of beads. The rows will probably be very short, or considerably bent, so much so that often only a confused mass of round cells will be seen. Some, however, will show the bead arrangement. Suppose that 3 colonies of this kind are seen in the plate containing -I c.c. of No 2 dilution and none in plate containing -i c.c. No 3 dilution. In 'i c.c. containing c.c. sample are found 3 streptococci. Hence: In 1 c.c. containing c.c. sample are found 30 streptococci. Hence: 1 c.c. of pure sample contains 3000 streptococci. Exercise 85. To test a bcidlg polluted water for B. coli by means of neutral-red broth. 1. Prepare neutral-red broth. 1. 100 c.c. Broth (See Exercise 2). 2.03 „ of 1 °/0 solution of neutral-red. 2. Prepare the usual dilutions (See Exercise 77). 3. Pour 10 c.c. of broth into each of four tubes. 4. Inoculate the four tubes each with one c.c. respectively from the flasks No. 2, No. 3, No. 4, No. 5. [See Ex. 77.] 5. Incubate at 370 C. and examine after 48 hours.