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Questions and Answers
What is the primary disease caused by Clostridium tetani?
What is the primary disease caused by Clostridium tetani?
Which of the following describes a feature of the tetanus neurotoxin?
Which of the following describes a feature of the tetanus neurotoxin?
What condition is primarily associated with Clostridium perfringens?
What condition is primarily associated with Clostridium perfringens?
In what conditions is Clostridium tetani most commonly found?
In what conditions is Clostridium tetani most commonly found?
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What is the main cause of myonecrosis in humans?
What is the main cause of myonecrosis in humans?
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Which species is known for producing a polypeptide capsule?
Which species is known for producing a polypeptide capsule?
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What do both Bacillus anthracis and Bacillus cereus have in common?
What do both Bacillus anthracis and Bacillus cereus have in common?
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Which of the following statements is true regarding Bacillus anthracis?
Which of the following statements is true regarding Bacillus anthracis?
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Which organism is primarily responsible for food poisoning?
Which organism is primarily responsible for food poisoning?
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What distinguishes the pathogenic potential of Bacillus anthracis from Bacillus cereus?
What distinguishes the pathogenic potential of Bacillus anthracis from Bacillus cereus?
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Study Notes
Lecture 7: Medical Bacteriology (II)
- Lecture covers bacilli bacteria, spirochetes, mycobacteria, and normal flora.
- Dr. Rasha Mokhtar Elnagar is the lecturer. Her credentials include M.B.B.C., MSc, PhD, and MD in Medical Microbiology and Immunology. She is an associate professor and consultant in microbiology and immunology.
Gram Positive Bacilli
- Gram-positive bacilli are divided into spore-forming and non-spore-forming groups.
- Spore-formers (aerobes):
- Bacillus anthracis (Polypeptide capsule)
- Bacillus cereus
- Spore-formers (anaerobes):
- C. perfringens
- C. tetani
- C. botulinum
- C. difficile
- Non-spore-formers:
- Corynebacterium
- Lactobacillus
Genus Bacillus: Spore-Formers
- Morphology: Gram-positive, spore-forming, aerobic or facultative anaerobic bacilli.
- Important species:
- Bacillus anthracis (Polypeptide capsule)
- Bacillus cereus
- Both produce exotoxins.
Diseases Related to Bacillus
- B. anthracis (Zoonotic disease):
- Cutaneous anthrax: spores germinate in skin, forming malignant pustules
- Pulmonary anthrax (wool sorter disease)
- Intestinal anthrax
- Bacillus cereus: Food poisoning due to enterotoxins.
Genus Clostridium: Spore-Formers
- Morphology: Gram-positive, spore-forming, obligate anaerobic bacilli.
- All species are exotoxin producers.
- Important species:
- Clostridium tetani (motile)
- Clostridium botulinum (motile)
- Clostridium perfringens (non-motile)
- Clostridium difficile
- Clostridium tetani: characterized by microscopic drum-stick appearance.
- Clostridium perfringens: sub-terminal spores.
Culture Conditions for Obligate Anaerobes
- Blood agar in anaerobic jars or anaerobic incubators.
- Cooked meat media (anaerobic condition).
Diseases Related to Clostridium
- Clostridium tetani (Tetanus):
- Tetanus neurotoxin causes spastic muscle paralysis.
- Clostridium perfringens: Gas gangrene (myonecrosis), typically following trauma.
- Clostridium botulinum: Botulism (associated with shellfish, salted fish, and canned food), causing flaccid muscle paralysis.
- Clostridium difficile: Antibiotic-associated diarrhea and pseudomembranous colitis.
Genus Corynebacterium
- Morphology: Gram-positive bacilli with club-shaped ends, arranged in Chinese-letter arrangement.
- Important species: Corynebacterium diphtheriae.
- Produces an exotoxin.
- Culture conditions: Growth on Löffler's medium, aerobic, at 37°C.
- Disease: Diphtheria (upper respiratory tract infection).
Gram Negative Bacilli
- Divided into categories based on shape (rod-shaped, curved, coccobacilli) and lactose fermentation. Lactose fermentation is a key characteristic for classifying some species.
- Rod-shaped examples: E. coli, Klebsiella, Salmonella, Shigella, and Proteus
- Curved examples: Vibrio cholerae, Campylobacter, and Helicobacter pylori
- Coccobacilli examples: Brucella, and Haemophilus influenzae
Enterobacteriaceae
- Gram-negative bacilli
- Facultative anaerobes
- Examples of diseases:
- E. coli: Urinary tract infection, neonatal meningitis
- Klebsiella: Urinary tract infections, pneumonia
- Proteus: Urinary tract infections, bacteremia
- Salmonella: Enteric fever (typhoid and paratyphoid), food poisoning, septicemia
- Shigella: Bacillary dysentery (bloody diarrhea)
Vibrio Cholerae
- Morphology: Gram-negative, comma-shaped, motile bacilli.
- Culture conditions: Alkaliphilic (grows in alkaline media like alkaline peptone water).
- Disease: Cholera (rice water diarrhea).
Helicobacter pylori
- Morphology: Gram-negative, curved, motile bacilli.
- Culture conditions: Microphillic, acidophilic.
- Disease: Peptic ulcer.
Genus Brucella
- Morphology: Gram-negative coccobacilli.
- Characteristics: Capnophilic (needs 5-10% CO2), zoonotic disease (Malta fever, undulating fever).
- Important species:
- (Brucella melitensis: affects goats and sheep.)
- (Brucella abortus: affects cows and cattle.)
Genus Haemophilus influenzae
- Causes meningitis and pneumonia in infants.
- Culture conditions: Chocolate agar, needs X (hemin) and V (NAD) growth factors.
Pseudomonas aeruginosa
- Morphology: Gram-negative rod (pleomorphic), motile, obligate aerobes.
- Causes of diseases: urinary tract infections, bacteremia, bone and joint infections, particularly in patients with severe burns or immunosuppression
Spirochetes: Treponema pallidum
- Morphology: Spiral shape, motile (endoflagella), difficult to see with gram stain, stainable with Giemsa and silver stain
- Dark field microscopy is needed to observe motility
- Cannot be cultured
- Disease: Syphilis (sexually transmitted disease).
Genus Mycobacterium
- Morphology: Acid-fast, non-motile, non-spore-forming bacilli.
- Cannot be stained using gram stain—wax-like lipid (mycolic acid) in cell wall.
- Important species:
- Mycobacterium tuberculosis: Pulmonary tuberculosis (chronic cough, night fever, sweating)
- Mycobacterium leprae: Leprosy
Commensal Bacteria (Normal Flora)
- Normally inhabit the human body.
- Mostly bacteria, but can include fungi like Candida.
- Do not cause disease in immunocompetent individuals.
- Beneficial roles:
- Competing for nutrients and attachment sites
- Producing antimicrobial substances
- Stimulating the immune system in newborns
- Providing essential nutrients (e.g., gut bacteria)
- Maintaining the vaginal pH (e.g., Lactobacilli)
- Harmful effects (in altered conditions):
- Immunocompromised individuals
- Changes in normal site within the body
- Changes in numbers due to antibiotic use (e.g., Clostridium difficile overgrowth in the colon, Candida overgrowth in the vagina)
Distribution of Normal Flora in the Body
- Skin: Staphylococcus epidermidis, Staphylococcus aureus, Propionibacterium acnes
- Nose: Similar to skin flora
- Eyes: Staphylococcus epidermidis, Staphylococcus aureus, Moraxella catarrhalis
- Mouth: Streptococcus mutans, Lactobacillus, Candida
- Intestinal tract: E. coli, Klebsiella, Enterococcus faecalis, Candida
- Female vagina: Lactobacillus, Candida albicans, Streptococcus agalactiae
Pathogenicity of Microorganisms: Source of Infection.
- Sources: environment (soil, air, water), animals (zoonotic diseases), and humans (cases and carriers).
- Patient = person exhibiting active disease.
- Carrier = person carrying a pathogen but exhibiting no symptoms.
Pathogenicity of Microorganisms: Modes of Transmission
- Modes: Contact (direct/indirect), airborne, droplet, ingestion, bloodborne, arthropod-borne, vertical (mother-to-fetus, trans-placental),
Case Study
- 25-year-old woman with dysuria, normal vitals, midline tenderness above pubis, many pus cells in urine.
- Microscopic examination reveals gram-negative bacilli.
- Likely cause: Escherichia coli (urinary tract infection).
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Description
This quiz focuses on Medical Bacteriology's Lecture 7, exploring various bacteria including Gram-positive bacilli, spirochetes, and mycobacteria. It covers key species such as Bacillus anthracis and Bacillus cereus, along with their diseases and characteristics. Test your knowledge on these essential microbiological concepts.
