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Questions and Answers
What type of medium is specifically used to culture Corynebacterium diphtheria?
What type of medium is specifically used to culture Corynebacterium diphtheria?
At what temperature should Corynebacterium diphtheria be cultured for optimal growth?
At what temperature should Corynebacterium diphtheria be cultured for optimal growth?
Which disease is primarily associated with Corynebacterium diphtheria infection?
Which disease is primarily associated with Corynebacterium diphtheria infection?
What kind of toxin does Corynebacterium diphtheria produce?
What kind of toxin does Corynebacterium diphtheria produce?
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Which of the following characteristics is NOT true about Corynebacterium diphtheria?
Which of the following characteristics is NOT true about Corynebacterium diphtheria?
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What is primarily associated with Clostridium difficile?
What is primarily associated with Clostridium difficile?
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What condition may occur as a result of long-term antibiotic therapy related to Clostridium difficile?
What condition may occur as a result of long-term antibiotic therapy related to Clostridium difficile?
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Which of the following is a consequence of Clostridium difficile infection?
Which of the following is a consequence of Clostridium difficile infection?
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Which of the following symptoms is NOT typical for Clostridium difficile infections?
Which of the following symptoms is NOT typical for Clostridium difficile infections?
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What therapeutic approach could mitigate Clostridium difficile infection risk?
What therapeutic approach could mitigate Clostridium difficile infection risk?
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Which species is characterized by a polypeptide capsule?
Which species is characterized by a polypeptide capsule?
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What type of toxin do Bacillus anthracis and Bacillus cereus produce?
What type of toxin do Bacillus anthracis and Bacillus cereus produce?
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Which disease is NOT associated with the Bacillus species mentioned?
Which disease is NOT associated with the Bacillus species mentioned?
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What is a common characteristic of both Bacillus anthracis and Bacillus cereus?
What is a common characteristic of both Bacillus anthracis and Bacillus cereus?
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Which of the following is a notable feature associated with Bacillus anthracis?
Which of the following is a notable feature associated with Bacillus anthracis?
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What type of bacteria is Clostridium classified as?
What type of bacteria is Clostridium classified as?
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Which of the following Clostridium species is non-motile?
Which of the following Clostridium species is non-motile?
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Under which conditions should Clostridium be cultured?
Under which conditions should Clostridium be cultured?
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What is a significant characteristic of all Clostridium species?
What is a significant characteristic of all Clostridium species?
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Which of the following is NOT an important species of Clostridium?
Which of the following is NOT an important species of Clostridium?
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Study Notes
Lecture 7: Medical Bacteriology (II)
- Lecture covers bacilli bacteria, spirochetes, mycobacterium, and normal flora.
- Dr. Rasha Mokhtar Elnagar is the lecturer.
- Her credentials include M.B.B.C, MSc, PhD, MD, Associate Professor of Medical Microbiology & Immunology and Consultant Microbiology & Immunology.
Gram Positive Bacilli
- Divided into spore formers and non-spore formers.
- Spore forming are further divided into Aerobes and Anaerobes.
- Aerobes include Bacillus anthracis and Bacillus cereus.
- Anaerobes include C. perfringens, C. Tetani, C. botulinum, and C. difficile.
- Non-spore formers include Corynebacterium and Lactobacillus.
1-Genus Bacillus
- Morphology: Gram-positive, spore-forming, aerobic or facultative anaerobic bacilli.
- Important species: Bacillus anthracis (polypeptide capsule) and Bacillus cereus.
- Both species produce exotoxins.
Diseases of Bacillus Anthracis
- Zoonotic disease.
- Cutaneous anthrax: spore germination in skin forms malignant pustule.
- Pulmonary anthrax (Wool sorter disease).
- Intestinal anthrax.
2-Genus Clostridium
- Morphology: Gram-positive, spore-forming, obligate anaerobic bacilli.
- Important species: Clostridium tetani (motile), Clostridium botulinum (motile), Clostridium perfringens (non-motile), and Clostridium difficile.
- All species produce exotoxins.
Culture Conditions for Obligate Anaerobes
- Require anaerobic jars or incubators and blood agar.
- Cooked meat media is also used in anaerobic condition.
Diseases of Clostridium
- Clostridium tetani: Tetanus, spastic muscle paralysis.
- Clostridium perfringens: Gas gangrene (myonecrosis), post-trauma.
- Clostridium botulinum: Botulism (shellfish, salted fish, canned food), flaccid muscle paralysis.
- Clostridium difficile: Antibiotic-associated diarrhea, pseudomembranous colitis (due to long-term antibiotic therapy).
2-Non-Spore Formers Gram Positive Bacilli: Genus Corynebacterium
- Morphology: Gram-positive bacilli with club-shaped ends arranged in a Chinese-letter arrangement.
- Important Species: Corynebacterium diphtheria.
- Produces exotoxin.
- Culture Conditions: Grow on Löffler's medium, aerobic, at 37°C..
- Disease: Diphtheria (upper respiratory tract infection).
2. Gram Negative Bacilli
- Divided into Rod-shaped (Enterobacteriaceae), Curved, and Coccobacilli.
- Rod-shaped (Enterobacteriaceae) are further divided by lactose fermentation (positive or negative) and motility (motile or non-motile). Key genera include E. coli, Klebsiella, Salmonella, Shigella, and Proteus
- Curved: Vibrio cholera (comma-shaped), H. pylori, Campylobacter.
- Coccobacilli: Brucella, Haemophilus influenzae
Enterobacteriaceae
- Gram-negative bacilli.
- Facultative anaerobes.
- Important genera include E. coli, Klebsiella, Salmonella, Shigella, Proteus.
Diseases caused by Enterobacteriaceae
- E. coli: Urinary tract infection, Neonatal meningitis.
- Klebsiella: Urinary tract infection, Pneumonia.
- Proteus: Urinary tract infection, Bacteremia.
- Salmonella: Enteric fever (Typhoid and paratyphoid), Food poisoning, Septicemia.
- Shigella: Bacillary dysentery (bloody diarrhea).
1. Vibrio cholerae
- Gram-negative, comma-shaped, motile bacilli.
- Alkaliphilic: grows on alkaline media like alkaline peptone water.
- Disease: Cholera (rice water diarrhea).
2. Helicobacter pylori
- Gram-negative, curved, motile bacilli.
- Microphilic, Acidophilic.
- Disease: Peptic ulcer.
3-Coccobacilli
- Brucella: Gram-negative coccobacilli, Capnophilic (5-10% CO2), Zoonotic disease (Malta fever).
- Important species: Brucella melitensis (in goats and sheep), Brucella abortus (in cows and cattle).
- Haemophilus influenzae: causes meningitis, pneumonia in infants. Requires X (hemin) and V (NAD) growth factors on Chocolate agar.
Pseudomonas aeruginosa
- Gram-negative rod (pleomorphic), motile, obligate aerobes.
- Diseases: Urinary tract infections, Bacteremia, Bone and joint infections, particularly in patients with severe burns and immunocompromised patients.
Spirochetes: Treponema pallidum
- Spiral shape, motile (endoflagella).
- Difficult to see by Gram stain, can be stained by Giemsa and Silver stain.
- Motility observed using dark field microscopy.
- Cannot be cultured.
- Disease: Syphilis (sexually transmitted disease).
Genus Mycobacterium
- Acid-fast, non-motile, non-spore-forming bacilli.
- Cannot be stained by Gram stain due to waxy 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 may also include fungi (e.g., Candida).
- Do not cause disease in immunocompetent individuals.
- Beneficial role: compete for nutrients, produce antimicrobial substances, stimulate immune system development in newborns, provide nutrients to the body, maintain vaginal pH (lactobacilli).
Harmful Effects of Normal Flora
- Cause infections in immunocompromised individuals (opportunistic infections).
- Change of site in the body: (e.g., S. epidermidis into the bloodstream).
- Change in normal flora (e.g., overuse of antibiotics).
- Colon: Clostridium difficile overgrowth causing pseudomembranous colitis.
- Vagina: Lactobacilli depletion leads to overgrowth of other pathogens (e.g., Candida).
Distribution of Normal Flora in the Body
- Skin: Staphylococcus epidermidis (90%) and Staphylococcus aureus, Propionibacterium acnes.
- Nose: Same as skin flora.
- Eye: Staphylococcus epidermidis, Staphylococcus aureus and Moraxella catarrhalis.
- Mouth: Streptococcus mutans, Lactobacillus, and Candida species.
- Intestinal tract: E. coli, Klebsiella, Enterococcus faecalis, and Candida.
- Female Vagina: Lactobacillus, Candida albicans, and Streptococcus agalactiae.
Pathogenicity of Microorganisms: Source of Infection
- Environment (soil, air, water).
- Animals (zoonotic diseases).
- Humans (patient or carrier).
Mode of Transmission
- Direct contact (hand-to-hand, body secretions, sexual)
- Indirect contact (contaminated surfaces/objects)
- Airborne, droplet, ingestion (fecal-oral), bloodborne, arthropod-borne, vertical (mother to fetus), tranplacental,
Case Study
- 25-year-old woman with dysuria, afebrile, mild pubic tenderness.
- Urine analysis shows many pus cells and Gram-negative bacilli.
- Likely cause: Escherichia coli urinary tract infection.
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Description
Explore the nuances of Medical Bacteriology in Lecture 7, focusing on Bacilli bacteria, including spore formers and non-spore formers. Learn about significant species such as Bacillus anthracis and their associated diseases with insights from Dr. Rasha Mokhtar Elnagar, an expert in Medical Microbiology & Immunology.
