Q.1 MCQ: (Compulsory) (6×1=6)

1 Who is father of medical micro biology

A. Lister

B. Louis Pasteur

C. Robert koch 👍

D. Ruska

2 On gram staining, Gram positive cell wall appears

A. Purple in color💜

B. Pink in color

C. Yellow in color

D. Colorless

3 Schick test is done for the diagnosis of. A. Rubella B. Measles C. Diphtheria D. Mumps

4 Which is the most commonly used solidifying agent A. Peptone B.Agar C.Sodium Chloride D. Yeast extract

5 Plasmodium passes its life in… A. Only one host(man) B. Man and Mosquito C. Man/Dog and Sandfly D. Man and Cattle

6 Which of the following Immunoglobulin is most efficient to produce agglutination reaction A. Ig A B. Ig G C. Ig M D. Ig D

Q.2 Write Essay type question (1×10=10)

1.Describe different types of Hypersensitivity with example.

Types of Hypersensitivity Reactions (Gell and Coombs Classification)

Hypersensitivity reactions are exaggerated or inappropriate immune responses to antigens, which may lead to tissue injury, inflammation, or dysfunction. These responses are typically classified into four types based on the immune mechanisms involved, as proposed by Gell and Coombs.

Type I: Immediate (Anaphylactic) Hypersensitivity

This type of hypersensitivity is mediated by IgE antibodies and is characterized by an immediate reaction (within seconds to minutes) following exposure to a specific allergen. It is commonly seen in atopic individuals.

• Mechanism: On the first exposure, allergens stimulate B cells to produce IgE antibodies, which bind to Fc receptors on mast cells and basophils (a process called sensitization). Upon re-exposure, the allergen cross-links the bound IgE, causing rapid degranulation of mast cells, releasing histamine, leukotrienes, prostaglandins, and cytokines.
• Pathophysiology: These mediators cause vasodilation, increased vascular permeability, smooth muscle contraction, and mucus secretion, leading to clinical symptoms.
• Onset: Within seconds to minutes.
• Clinical Manifestations:
  • Local reactions: Allergic rhinitis (hay fever), bronchial asthma, atopic dermatitis (eczema), urticaria (hives)
  • Systemic reaction: Anaphylaxis – a potentially life-threatening condition with hypotension, bronchospasm, and laryngeal edema.
• Examples:
  • Allergies to food (e.g., peanuts, shellfish), drugs (e.g., penicillin), insect stings (e.g., bee sting), and pollen.

Type II: Antibody-Mediated (Cytotoxic) Hypersensitivity

Type II reactions are mediated by IgG or IgM antibodies directed against antigens on host cell surfaces or tissues, leading to cell destruction, inflammation, or cellular dysfunction.

• Mechanism: Antibodies bind to self or foreign antigens present on cell membranes or extracellular matrix. These bound antibodies activate the complement system or mediate antibody-dependent cellular cytotoxicity (ADCC), leading to cell lysis or tissue damage.
• Onset: Minutes to hours.
• Three main outcomes:
  1. Complement-mediated lysis (e.g., in mismatched blood transfusion)
  2. Opsonization and phagocytosis (e.g., autoimmune hemolytic anemia)
  3. Cellular dysfunction without destruction (e.g., myasthenia gravis)
• Clinical Manifestations: Hemolysis, thrombocytopenia, inflammation of basement membranes.
• Examples:
  • Hemolytic transfusion reactions
  • Erythroblastosis fetalis (hemolytic disease of the newborn)
  • Goodpasture’s syndrome (anti-GBM disease)
  • Autoimmune hemolytic anemia
  • Pemphigus vulgaris
  • Myasthenia gravis (neuromuscular junction dysfunction)

Type III: Immune Complex-Mediated Hypersensitivity

This type of hypersensitivity involves the formation of immune complexes (antigen-antibody complexes), usually composed of IgG or IgM, which circulate in the bloodstream and deposit in tissues, triggering complement activation and inflammation.

• Mechanism: Soluble antigens combine with antibodies to form immune complexes, which are deposited in various tissues (e.g., blood vessels, kidneys, joints). The deposited complexes activate complement, attracting neutrophils that release enzymes and reactive oxygen species, causing tissue injury.
• Onset: Typically occurs 6–12 hours after antigen exposure.
• Tissue Damage Sites: Glomeruli, synovial membranes, blood vessels, and skin.
• Clinical Manifestations: Fever, rash, arthralgia, proteinuria, vasculitis, nephritis.
• Examples:
  • Systemic lupus erythematosus (SLE)
  • Post-streptococcal glomerulonephritis
  • Serum sickness (e.g., following anti-toxin therapy)
  • Arthus reaction (localized dermal vasculitis after injection)
  • Rheumatoid arthritis (partly)

Type IV: Delayed-Type (Cell-Mediated) Hypersensitivity

Type IV reactions are T-cell-mediated and do not involve antibodies. The reaction occurs 24–72 hours after antigen exposure, hence the name “delayed” hypersensitivity.

• Mechanism:
  • CD4+ T-helper (Th1) cells recognize antigens presented by antigen-presenting cells (APCs), leading to cytokine release, macrophage recruitment, and inflammation.
  • In some cases, CD8+ cytotoxic T-cells directly destroy target cells (e.g., graft rejection).
• Onset: 24–72 hours after exposure.
• Tissue injury is primarily due to the release of cytokines and the action of recruited macrophages.
• Clinical Manifestations: Erythema, induration, contact skin eruptions, granulomatous inflammation.
• Examples:
  • Tuberculin skin test (Mantoux test using PPD)
  • Contact dermatitis (e.g., due to nickel, latex, poison ivy)
  • Chronic transplant rejection
  • Granulomatous diseases (e.g., tuberculosis, leprosy, sarcoidosis)
  • Type 1 diabetes mellitus (autoimmune T-cell destruction of β-cells)

Each type of hypersensitivity involves distinct immune players—Type I (IgE), Type II (IgG/IgM against cells), Type III (immune complexes), and Type IV (T-cell-mediated)—and leads to different forms of tissue damage. Correctly identifying the type is crucial for appropriate diagnosis and treatment in clinical immunology.

2 Explain in detail the Morphology. Cultural Characteristic, Pathogenicity, Laboratory Diagnosis of Pneumococci

🦠 Streptococcus pneumoniae (Pneumococci)

A Gram-positive, encapsulated diplococcus, S. pneumoniae is a major human pathogen responsible for pneumonia, meningitis, otitis media, sinusitis, and bacteremia.

🔬 1. Morphology

Microscopic Features:

• Shape: Lanceolate (flame-shaped) or oval cocci, with pointed ends.
• Arrangement: Typically in pairs (diplococci); rarely seen singly or in short chains.
• Gram Staining: Gram-positive, appearing deep violet; old cultures may appear Gram-variable.
• Capsule:
  • Made of polysaccharide, antiphagocytic, and a major virulence factor.
  • Visualized by India ink, negative staining, or Quellung reaction.
• Spores & Motility: Non-spore forming and non-motile.

🧫 2. Cultural Characteristics

Growth Requirements:

• Facultative anaerobe; grows best in 5–10% CO₂ at 35–37°C.
• Requires enriched media such as:
  • Blood agar
  • Chocolate agar

Colony Morphology (on Blood Agar):

• Small, round, moist, glistening colonies initially.
• Produces alpha-hemolysis: greenish discoloration due to partial hemolysis of RBCs.
• After 24–48 hours, colonies become flattened with central depression – “draughtsman” or coin-shaped appearance due to autolysis.

Special Cultural Features:

• Growth enhanced by blood, serum, or ascitic fluid.
• Inhibited by bile salts, optochin, and sodium deoxycholate – useful for identification.

🧫 3. Pathogenicity

Source & Transmission:

• Part of the normal flora of the human nasopharynx.
• Transmitted via droplet infection or direct contact from infected secretions.

Virulence Factors:

1. Capsule: Antiphagocytic and essential for virulence.
2. Pneumolysin: Cytotoxin that damages respiratory epithelium and activates complement.
3. Autolysin: Helps in the release of pneumolysin and causes autolysis of bacteria.
4. IgA protease: Cleaves secretory IgA, helping in mucosal colonization.

Diseases Caused:

• Respiratory:
  • Lobar pneumonia (classic presentation in adults)
  • Sinusitis
  • Otitis media (especially in children)
  • Bronchitis
• Invasive diseases:
  • Meningitis
  • Bacteremia / septicemia
  • Peritonitis
• High-risk populations: Children under 5, elderly, immunocompromised individuals, splenectomized patients.

🔍 4. Laboratory Diagnosis

Specimen Collection:

• Depends on site of infection:
  • Sputum, blood, CSF, ear discharge, nasal swabs, pleural fluid

Microscopy:

• Gram stain: Shows Gram-positive, lanceolate diplococci, often in pairs.
• India ink or negative staining may show clear capsule.
• Quellung reaction: Capsule swells upon exposure to type-specific antisera (positive reaction is diagnostic).

Culture:

• Inoculate on blood agar or chocolate agar.
• Look for alpha-hemolysis, moist colonies with central umbilication after 24–48 hrs.
• Optochin sensitivity test: Pneumococcus is sensitive (zone of inhibition ≥14 mm).
• Bile solubility test: Pneumococci are bile soluble (colonies dissolve).

Biochemical Tests:

• Catalase test: Negative
• Ferments inulin: Positive (differentiates it from other streptococci)

Antigen Detection:

• Latex agglutination test or countercurrent immunoelectrophoresis can detect pneumococcal capsular antigen in CSF, pleural fluid, or urine.

Molecular Diagnosis:

• PCR for pneumococcal DNA – highly sensitive and specific (used in critical cases).

Serotyping:

• Over 90 capsular serotypes identified.
• Useful for epidemiological surveillance and vaccine development.

💉 Prevention

• Pneumococcal vaccines:
  • PCV (Pneumococcal Conjugate Vaccine) – e.g., PCV13
  • PPSV (Pneumococcal Polysaccharide Vaccine) – e.g., PPSV23

Q.3 Write Short Notes on: (Any three out of four)

1 Principles of Microbiology.

2 VDRL Test

3.Clostridium Tetani

4 Compound Microscope

Q.4 Write very short answers: (Any two out of three) (3X2=6)

1 Bacterial growth curvet

2 Lab diagnosis of vibrio cholera

3 Normal Flora

Section-2

Q5 Multiple choice questions. (7×1=7)

1. Most important aspect of hand washing is? A. Time B. Type of soap C. Friction D. Surface tension

2. Which of the following is not considered a portal of entry for bacteria? A. Eyes B. Nose C. Mouth D. Intact Skin

3.Which of the following in an international patient safety goal?A. Identify Patient Correctly B. Reduce the risk of healthcare associated function C. Reduce the harm associated with clinical alarm system D. All of the above

4.In meningitis which of the following specimen is most commonly collected A. Pus B. CSF C. Faeces D. Urine

5.Culture Media is sterilized by which of the following method? A. Hot air oven B. Autoclaving C. Boiling D. Ionizing radiation

6 What are the main objectives of risk assessment? A. To evaluate hazard and minimize the risk B. Remediation of contaminated sites C.Hazards Management D. To know sources of pollutants

7. Transmission of pathogen from a pregnant women to her fetus is known as …A. Droplet infection B. Vector borne transmission C. water borne Infection D. transplacental transmission

Q.6 Long Essay. (Any one) (1×10=10)

1.Define Sterilization, Classify Sterilization and discuss about moist heat sterilization.

2 Describe the sources, modes of transmission and prevention of Nosocomial infection RA

Q.7 Write Short Notes: (Any three) (3×5=15)

1.BMW Management

2 Post exposure prophylaxis for HIV

3 Corrective and preventive action(CAPA)

4 Disaster Management

Q.8 Short Answers: (Any two) (3×2=6)

1.Antibiotic sensitivity test

2.Nurses role in specimen collection

3.Explain Occupational safety for health care workers