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Time-3 hours. Maximum Marks: 100
Instruction-
1) All questions are compulsory.
2) Draw diagram wherever necessary.
3) Answer of questions and sub question must be written strictly according to serial order of question papers.
Q.1 Very short answer the question (Maximum 50-60 words ) 10×2 = 20
1) MacConkey agar media:
It is a selective and used to differentiate different characteristics of Bacteria.
Example - on Mac Conkey's agar the Lactose fermenters shows Pink Caloured Colonies where as Non-Lactose fermenters produces Colourless or pale colonies.
2) Indole test:
It determines the ability of an organism to Decompore amino acid tryptophan into indole. Tryptophan is decomposed by an enzyme tryptophanase pecduced by Certain Bacteria
Indole positive A Red Coloured Ring near the surface of the medium. Ring
ex- E.Coli, proteus sp.
Indole Negative - yellow Caloured Ring near the surface of the medium
ex-: Klebsiella SP, proteus mirabilis
3) IgG antibody:
IgG is the major serum globulin constituting Approximately 75% of total immuglobin. It provides long-term immunity, crosses the placenta to protect newborns, and plays a key role in secondary immune responses.
4) Incineration:
It is a waste disposal method that involves burning biological and hazardous materials at high temperatures to destroy pathogens and reduce waste volume.
5) Enumerate different types of microscopes and their uses:
Light microscope: Used for observing stained and living specimens.
Electron microscope: Provides high-resolution images of cell structures.
Fluorescence microscope: Detects fluorescently labeled molecules in cells.
6) Sodium hypochlorite:
It is a disinfectant and bleaching agent commonly used for sterilization, surface cleaning, and water purification.
7) Name 3 important protozoa and disease caused by them :
Plasmodium spp. – Malaria
Entamoeba histolytica – Amoebiasis
Trypanosoma spp. – Sleeping sickness
8) Draw a well labeled diagram of plasmodium vivax in peripheral :
A well-labeled diagram should include ring forms, trophozoites, schizonts, and gametocytes in peripheral blood.
9) Name five RNA virus and disease caused by them :
HIV – AIDS
Influenza virus – Flu
Rabies virus – Rabies
Hepatitis C virus – Hepatitis C
SARS-CoV-2 – COVID-19
10) What precaution you would take to prevent needle stick injury while drawing blood from a patient:
Use safety-engineered needles, avoid recapping needles, dispose of used needles in puncture-proof containers, wear gloves, and follow proper handling protocols.
Q.2 Short type question (Maximum 250-300 words) 5x10-50
1) VDRL Test :
2) Bacterial Growth Curve :
When a bacterium is inoculated into a suitable fluid medium and incubated, its growth follows a definite course. When bacterial count of such culture is determined at different intervals and plotted in relation to time, a growth curve is obtained ,The growth curve has four phases.
1. Lag Phase:
This is the initial phase where bacteria adapt themself in a new environment.
There is increase in the size of the cells but there is no increase in numbers.
Enzymes and other molecules required for growth are synthesized.
2. Log (Exponential) Phase:
Bacteria multiply at a constant and rapid rate through binary fission.
The population doubles at regular intervals, showing a characteristic exponential growth pattern.
This phase is ideal for antibiotic susceptibility testing as bacteria are most metabolically active.
3. Stationary Phase:
Growth slows down due to exhaustion of nutrient and accumulation of toxic byproducts.
The rate of bacterial reproduction equals the rate of bacterial death.
4. Death (Decline) Phase:
The number of dying bacterial cell increases
Nutrients are exhausted, and toxic waste accumulates, leading to a decline in the population.
3) Anaerobic culture method :
Anaerobic bacteria grow only in the absence of oxygen (anaerobic conditions). These anaerobic conditions or anaerobiosis can be established by various methods. Methods of Anaerobiosis
1.Displacement of oxygen.
2. By displacement and combustion of oxygen.
3.Absorption of oxygen by chemical or biological methods.
4. By reducing agent
5.Anaerobic chamber.
1. Displacement of Oxygen :
Displacement of oxygen by inert gases like hydrogen, nitrogen, carbon dioxide or helium is sometimes employed. Oxygen can never be removed completely by this method. A popular, but ineffective, method is the use of candle. A lighted candle is kept in a large air tight container loaded with inoculated plates. It is expected that burning candle will use up all the oxygen inside before it is extinguished but some amount of oxygen is always left behind.
2. By Displacement and Combustion of Oxygen :
Anaerobiosis obtained by "McIntosh and Fildes anaerobic jar is the most dependable and mostly used method
Method-
The culture plates are placed inside a sealed jar.
A GasPak containing chemicals that react to remove oxygen is used.
An indicator strip (e.g., methylene blue) confirms anaerobic conditions.
3.Absorption of Oxygen by Chemical or Biological Methods :
CHEMICAL METHODS -
(A) Pyrogallol
(B)Chromium and sulfuric acid
(C) Gas-pak
4. By Reducing Agents
Oxygen in culture media can be reduced by various agents similar as glucose, thioglycollate, cooked meat pieces, cysteine and ascorbic acid.
the two most extensively employed anaerobic liquid culture media are
(A) THIOGLYCOLLATE BROTH - It contains nutrient broth and 1 % thioglycollate.
(B) COOKED MEAT BROTH( CMB)- It's also known as Robertson's cooked meat( RCM) medium. It contains nutrient broth and pieces cooked meat of ox heart
5.Anaerobic Chamber :
It's an anaerobic incubation system. It provides oxygen free terrain for enduing culture media and for their incubation. It's fitted with watertight rubber gloves to fit hands for working with samples. These anaerobic chambers contain a catalyst, dessicant, hydrogen gas, carbon dioxide gas, nitrogen gas and an indicater.
4) Principle and Method of Gram Staining :
Principle of Gram Stain :
Gram staining is a differential staining technique developed by Christian Gram in 1884. It categorizes bacteria into Gram-positive and Gram-negative, based on their cell wall structure. Gram-positive bacteria have a thick peptidoglycan layer that retains the crystal violet-iodine complex, whereas Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane that allows the stain to be washed away during decolorization.
Requirement for gram Staining :
1) Crystal violet (primary stain)
2) Iodine (mordant)
3) 95% Ethanol (decolorizer)
4) Safranin
5) Glass slide
6) Inoculating loop
7) Burner
Method of Gram Staining :
1. Smear Preparation: A thin bacterial smear is prepared on a clean glass slide, air-dried, and heat-fixed.
2. Primary Staining (Crystal Violet): The smear is flooded with crystal violet for 1 minute and then gently washed with distilled water.
3. Mordant (Iodine Treatment): The slide is treated with Gram's iodine for 1 minute to form a crystal violet-iodine complex, followed by washing with distilled water.
4. Decolorization:
The smear is washed with 95% alcohol or acetone for 10–30 seconds until no more purple dye is removed.
The slide is immediately rinsed with distilled water to stop decolorization.
5. Counterstaining (Safranin): The smear is stained with safranin for 30–60 seconds and then washed with distilled water.
6. Drying and Microscopy: The slide is air-dried or blot-dried with absorbent paper and examined under a microscope using oil immersion (100x objective lens).
Interpretation :
-Gram-positive bacteria appear purple/violet due to the retention of crystal violet.
-Gram-negative bacteria appear pink/red due to the uptake of safranin.
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