Question

Microbiology

ONLY answer

1

Salmonella is associated with the handling of contaminated beef True False

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Answer 1

1.True. Salmonella is associated with the handling of contaminated beef. It is also present in raw egg, chicken, pork, contaminated water. It is contracted by coming into contact with infected animals and causes disease and sickness in the body. Raw and not properly cooked meat can easily be contaminated with salmonella. Leftover foods may contaminated by salmonella within 2hrs.

2.True. E.coli is red pigmented organism as it is gram negative it is pinkish red in colour. Some of them are colourless. Over production of the bacterial coloni shows it raddish in colour.

3. False. Napthol and KOH are added and shaked vigorously and kept for 1hr to read the results of the MR-PV test.

4. Lactose and Glucose Broths contains a pH indicator to show change caused by fermentation. Phenol red is mainly used for carbohydrate fermentation.

5.E.coli is a gram negative bacteria as it do not catch the purple colour of crystal violet. It can be stained with safranin that is the counter stain in gram staining process.

6. There is a bubble that collects in the Durham tube , for gas production during glucose fermentation.

7. Black is the colour of the SIM medium if it is positive for sulfur. Iron in the media combined with H2S( H2S is basically colourless) and form Ferrous sulfied (FeS) which is precipitate and there is blackening of the media. Absence of blackening indicates that the medium is negative for sulfur.

8.None . is used to find out more about gram positive organisms.

9. Fermentation of sugars usually results in acidic end products and mainly produces lactate, formate, acetate and ethanol.

10. The organism is fermenting glucose and the organism will ferment lactose as well because all are carbohydrates and the gas bubbles in the Durham tube is the test for gas production during carbohydrates fermentation.

11. Hydrogen sulphide production and motility can be detected using SIM medium. Ferrous ammonium sulfate and sodium thiosulfate present in the medium produced hydrogen sulphide and the organism may swim ( be motile) though the media.

12. Pseudomonads pathogen can cause urinary tract infections. Mainly Pseudomonads aeruginosa.

13. Gram stain results can help classify bacteria. It decides bacteria into two groups that are gram -positive bacteria and gram-negative bacteria.

14. Crystal violet is the primary stain in gram stain procedure, which stained the bacteria in purple colour (gram-positive) and gram-negative bacteria become colourless after decolourization with ethanol and then stain with counter stain or secondary stain safranin and become pink/ pinkish-red in colour.

15. Safranin is the counter stain and gram negative bacteria stained pink/red by safranin. So , if safranin is left in gram stain procedure gram positive cells would be purple and gram negative cells would be colourless.