20 High Yield Microbiology Flashcards NEET PG 2025

Flashcard 1 

Differential Stains

1. Gram stain (+/-)

• Mnemonic: Come In And Stain
  • Crystal Violet (primary stain)
  • Iodine (mordant)
  • Alcohol/ Acetone (decolorizer) - Important step
  • Safranin (secondary stain)
• Results
  • Gram +ve: Purple
  • Gram -ve: Pinkish reddish color (decolorized)
• Poorly gram staining
• Mnemonic- MRCS
  • Mycoplasma
  • Rickettsia
  • Chlamydia
  • Spirochetes

2. Acid-Fast Stain (Ziehl Neelsen Stain)

• Mnemonic: Class Has Asked Mnemonic
  • Carbol Fuschin (red) - Organism colors
  • Heating (mordant)
  • Acid/ Acid-alcohol - Sulphuric acid (decolorized)
  • Methylene Blue - Background color

Flashcard 2

Capsulated organisms

(Mnemonic: Pretty NIce Capsule)

• Streptococcus Pneumonia
• Klebsiella Pneumoniae
• Bordetella Pertussis
• Vibrio Parahaemolyticus
• Clostridium Perfringens
• Yersinia Pestis
• Neisseria meningococcus
• Hemophilus Influenza
• Cryptococcus (fungus)
• Staphylococcus Aureus
• Bacillus Anthracis

To Remember

• All capsules are made of polysaccharides.
• Except
  • Yersinia pestis - F1 peptide
  • Bacillus anthracis - polypeptide
• S. aureus has microcapsule

Flashcard 3

CRISPR-Cas9

• Genome editing
• Trick
  • Cas9 - Scissors
  • C - Clustered
  • R - Regularly
  • I - Interspaced : viral memories
  • S - Short
  • P - Palindromic
  • R - Repeats
• CRISPR-Cas9 is a bacterial defense system against viruses
• FELUDA test, based on CRISPR-Cas9 for COVID

Flashcard 4

Enterotoxins

• Enterotoxins A-I (no F) cause food poisoning.
• Incubation period: <6 hours
• Organisms that have enterotoxins and cause food poisoning with an incubation period shorter than 6 hours
  • Staphylococcus aureus.
  • Bacillus cereus.
• B. cereus food poisoning caused by consumption of Chinese fried rice.
• S. aureus food poisoning caused by consumption of meat and milk.
• Vomiting occurs due to the vagomimetic action of enterotoxins.

Flashcard 5

ꞵ Hemolytic Streptococci 

Lancefield classification

• Based on C antigen.
• Classes A-V, no I and J.
• Group A β hemolytic streptococci - S. pyogenes.
• Group B β hemolytic streptococci - S. agalactiae.
• Group A can be subdivided further based on their typing.
  • Griffith typing - M protein.
  • EMM typing - Gene for M protein.

Flashcard 6

Toxins that decrease protein synthesis (Mnemonic: DPSS)

• Diphtheria toxin.
• Exotoxin A of pseudomonas.
• Shiga toxin - Shigella.
• Shiga-like toxin/Verocytotoxin - E. coli.

Mechanisms

• Diphtheria toxin and exotoxin A of pseudomonas cause ADP ribosylation of Elongation Factor-2 (Ef2).
• Shiga and Shiga-like toxins inhibit 60S ribosomes.

Flashcard 7

Clostridium tetani 

• Muscle spasms due to tetanospasmin.
• Tetanospasmin is oxygen stable while tetanolysin is oxygen labile.
• Both tetanospasmin and tetanolysin molecules are heat labile.
• The 1st muscle to be affected is the masseter muscle, Lockjaw/Trismus

Complications

• Risus sardonicus
• Opisthotonus position

Mechanism of action

• C. tetani acts presynaptically at the inhibitory neuron terminal.
• Prevents GABA and glycine release.
• The same effect can be seen in strychnine poisoning. Acts post-synaptically.

Flashcard 8

Foci

• Ghon foci : Lung involvement only.
• Ghon complex : Lung and hilar lymph node involvement.
• Ranke complex:  Lung and hilar lymph node involvement with calcification.
• Simon focus: Apex involvement.
• Puhl's focus:  Supraclavicular region involvement.
• Assman focus:  Infraclavicular region involvement.
• Simmond focus:  Liver involvement.
• Weighert's focus : Blood vessel involvement.
• Rich's focus : Brain involvement.

In the case of pulmonary TB the sample taken is Sputum. Concentration of sample:

• Modified Petroff method using 4% NaOH.
• Further modification using N-acetyl-L-cysteine with 2% NaOH.

Flashcard 9

Lowenstein-Jensen medium

• Rough, buff, and tough colonies.
• 6-8 weeks to grow.
• Sensitivity: 10-100 AFB/ml.
• Composition
  • Coagulate hen's egg.
  • Mineral salt solution.
  • Asparagine
  • Malachite green

Flashcard 10

Mantoux test/Tuberculin test

• Type IV hypersensitivity or cell-mediated hypersensitivity.
• 0.1 ml of purified protein derivative is given intradermally.
• Induration is checked after 48-72 hours.
  • > 10 mm – Positive.
  • < 5 mm – Negative.
  • 5-9 mm – Equivocal.
• Interpretation
  • Positive: Present or past infection.
  • False positive: BCG vaccination and non-TB mycobacterium.
  • False negative: HIV or immunodeficient states.

Flashcard 11

Mycobacterium avium complex (MAC)

• M. avium and M. intracellulare.
• Lady Windermere syndrome.

Vaccine

• M. indicus pranii.
  • Immunomodulator
• MW vaccine for leprosy.

Flashcard 12

Mycobacterium leprae

• Hansen's bacillus.
• Obligate intracellular.
  • Cannot be grown on any culture medium.
  • Grown on a 9-banded armadillo or footpad of mice.

Flashcard 13

Gram negative bacilli: Enterobacteraceae

Flashcard 14

Shigella 

• S.dynsentriae - only catalase negative and non-mannitol fermenter
• S.flexneri - Most common in India
• S.boydii
• S.sonnei - Most common in the world, Late lactose fermenter.

Salmonella 

• Enteric fever (salmonella)
• Step ladder pattern fever
• Longitudinal ulcers in GIT
• Pea soup diarrhea
• Fever with bradycardia - Faget's sign
• Soft palpable spleen, liver
• Rose spots (2nd 3rd week) [fade on pressure]
• Wilson blair media - jet black colonies
• Transport – (SBGS) Sach's Buffered glycerol Saline
• Treatment- Ciprofloxacin

Flashcard 15

Slide widal test

• Dot means Agglutination test occurred
• Widal is a non specific test so serial testing needed

Flashcard 16

Pseudomonas

• Pyocyanin - Blue green (diffusible)
• Pyoverdin - Green yellow
• Pyorubin – Red
• Pyomelanin - Black

Flashcard 17

Spirochetes

Diseases

• T.pallidium
• Venereal syphilis: STD
• Incubation period: 9 - 90 days

Flashcard 18

Leptospira

(Mnemonic: LEPTOSPIRRRRA)

• It has hooked ends
• Causes Weil's disease [Ictero-Hemorrhagic fever / Hepatorenal syndrome]
• Features
  • Jaundice
• Rat urine Contaminates rainy water
  • Rice field workers affected

Flashcard 19

Coxiella

• Coxiella burnetii (Inhalation)
• Intracellular Parasite
• Causes Q fever - Doughnut granuloma, which is a fibrin ring granuloma.
• Has
  • No vector
  • No Weil Felix reaction
  • No rash
• Treatments: Tetracycline [DOC]

Flashcard 20

• Most common cause of sporadic acute Hepatitis in India - Hepatitis E.
• Most common cause of fulminant viral Hepatitis - Hepatitis D.
• Most common cause of fulminant viral Hepatitis in pregnancy - Hepatitis E.
• Most common cause of transfusion-related Hepatitis - Hepatitis B
• The most common cause of chronic Hepatitis - Hepatitis B.
• Maximum risk and potential of chronicity - Hepatitis C.
• The most common cause of carrier state - Hepatitis B.
• The most common cause of viral Hepatitis causing cancer - Hepatitis B.
• Most strong association with viral Hepatitis causing cancer - Hepatitis C.

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