Microbiology Crash Course - Lecture Notes

Introduction

• Instructor: Dr. Preeti Soharma (Pathology and Microbiology Educator)
• Course: Microbiology Crash Course for NEET, NEXT, and FMG exam students
• Previous topics covered:
  • General microbiology
  • Mycology (fungi)
  • Bacteriology

Bacteriology Focus

• Today's topic: Spore-forming bacteria

Types of Spore-forming Bacteria

1. Bacillus (Aerobic)
   • Needs oxygen
2. Clostridium (Anaerobic)
   • Prefers less oxygen

Bacillus Anthracis

Virulence Factors

• Labile toxin: Not a virulence factor
• Capsule: Made of polypeptide (exception in microbiology)
• Toxins:
  • EPL:
    • E: Edema factor
    • P: Protective factor
    • L: Lethal factor

Types of Anthrax

1. Cutaneous Anthrax
   • Also known as Hide-Poters Disease
   • Caused by contact with animal skins
2. Pulmonary Anthrax
   • Inhalation of spores (e.g., from wool)
3. Intestinal Anthrax
   • Associated with consuming undercooked meat

Diagnosis of Bacillus Anthracis

• Characteristics on microscopy:
  • Boxcar appearance or bamboo stick appearance
• Cultural characteristics:
  • Medusa head appearance on agar
  • String of pearls appearance on penicillin agar
  • Inverted fir tree appearance on gelatin

Bacillus Cereus

Food Poisoning Types

• Emetic Type: Caused by fried rice
• Diarrheal Type: Longer incubation (8-16 hours), associated with poultry and vegetables

Clostridium Species

• Anaerobic: Cannot survive in oxygen

Characteristics

• Spore Locations:
  • Terminal: Clostridium tetani (drumstick appearance)
  • Subterminal: Common for most Clostridium species
  • Central: Clostridium bifermentans
• Capsulated: Clostridium perfringens and butyricum
• Non-motile Organisms: Clostridium perfringens and tetani

Gas Gangrene

• Caused by Clostridium perfringens primarily.

Other Causes

• Clostridium septicum and novyi

Laboratory Diagnosis

• Culture Media: RCMB - Robertson's cooked meat broth
• Hemolysis: Target hemolysis
• Nagler's Reaction: Positive due to alpha toxin (lecithinase)
• Reverse CAMP Test: Positive
• Stormy Fermentation with Litmus Milk:

Enterobacteraceae Family

Key Points

• Generally aerobic and gram-negative
• Motility: All are motile except
  • Shigella and Klebsiella
• Lactose Fermenters:
  • E. coli and Klebsiella
• Indicators for Media:
  • Mekonki Agar: Neutral red
  • CLED: Bromothymol blue

Pathogenic E. Coli Types

1. EPEC: Pediatric, infantile diarrhea
2. ETEC: Traveler's diarrhea
3. EIEC: Invasive, causes dysentery
4. EHEC: O157:H7 strain, causes HUS
5. EAEC: Persistent diarrhea, stacked brick appearance on HEP2

Conclusions

• Summary of important points regarding Bacillus and Clostridium species
• Discussion on the Enterobacteriaceae family and E. coli types
• Recap on diagnostic tests and major characteristics

Resources

• PDFs will be available on Telegram and social media
• Encourage students to study effectively and review previous materials

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Key Mnemonics

• BACILLUS - Always Aerobic
• CLOSTRIDIUM - All are Anaerobic
• Enterohemorrhagic E. coli specifically causes HUS (O157:H7 strain)

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Upcoming Topics

• Continuing with more bacteria under the Enterobacteraceae family in the next session.