Anaerobic Bacteria and Clostridia Quiz
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Questions and Answers

What allows some anaerobes to tolerate oxygen?

  • Ability to form spores
  • Presence of SOD or catalase (correct)
  • Lack of cell walls
  • Production of glucose

    • Why are obligate anaerobes usually susceptible to the effects of oxygen?

  • They thrive in aerobic environments
  • They are spore-formers
  • They lack SOD and catalase (correct)
  • They produce large quantities of oxygen

    • What characterizes Bacteroides fragilis as an opportunistic pathogen?

  • It is a spore-forming organism.
  • It cannot survive in oxygen-rich environments.
  • It produces high amounts of endotoxins.
  • It is bile-resistant and has adhesive surface pili. (correct)

    • What is Bacteroides fragilis most commonly implicated in?

    <p>Intra-abdominal infections</p> Signup and view all the answers

    What differentiates Bacteroides fragilis from strict obligate anaerobes?

    <p>The production of superoxide dismutase</p> Signup and view all the answers

    Which condition is associated with high mortality rates when infected by Bacteroides species?

    <p>Intra-abdominal infections</p> Signup and view all the answers

    Which of the following is NOT a member of the Bacteroides fragilis group?

    <p>Escherichia coli</p> Signup and view all the answers

    What type of infections are most commonly caused by Bacteroides fragilis after abdominal surgery?

    <p>Polymicrobial infections</p> Signup and view all the answers

    What is a significant characteristic of Bacteroides fragilis regarding its structure?

    <p>Low toxicity of its endotoxin</p> Signup and view all the answers

    What can be inferred about the transmission of Bacteroides fragilis infections?

    <p>They are primarily endogenous infections.</p> Signup and view all the answers

    What is a common characteristic of Clostridia species such as C.tetani and C.perfringens?

    <p>They produce toxins such as tetanospasmin.</p> Signup and view all the answers

    Which statement accurately describes anaerobic bacteria?

    <p>Anaerobes fail to grow in high oxygen conditions but can survive in low oxygen.</p> Signup and view all the answers

    What is one reason that most anaerobes are susceptible to oxygen?

    <p>They lack enzymes like catalase and superoxide dismutase.</p> Signup and view all the answers

    What distinguishes non-spore forming anaerobes from spore-forming ones?

    <p>Non-spore forming anaerobes do not produce spores like clostridia.</p> Signup and view all the answers

    Which of the following genera includes pathogenic anaerobes that can contribute to human disease?

    <p>Bacteroides</p> Signup and view all the answers

    Which toxin is produced by C.botulinum?

    <p>Botulinum toxin</p> Signup and view all the answers

    What is a characteristic of Bacteroides fragilis group bacteria?

    <p>They have some catalase and superoxide dismutase.</p> Signup and view all the answers

    Which of the following is NOT a non-spore forming anaerobe?

    <p>Clostridium</p> Signup and view all the answers

    Why do anaerobes often fail to grow on solid media under normal atmospheric conditions?

    <p>They need reduced oxygen tension for growth.</p> Signup and view all the answers

    Which of the following statements about anaerobes is accurate?

    <p>Some anaerobes can tolerate low levels of oxygen for short periods.</p> Signup and view all the answers

    What is the primary reason fragilis cells can withstand exposure to atmospheric levels of oxygen for up to 3 days?

    <p>Activation of an oxidative stress response</p> Signup and view all the answers

    Which Prevotella species is most commonly isolated in infections associated with the female genital tract?

    <p>Prevotella bivia</p> Signup and view all the answers

    In which type of infections are Prevotella species most likely found?

    <p>Abdominal abscesses and pelvic inflammatory disease</p> Signup and view all the answers

    What is a characteristic of Fusobacterium necrophorum?

    <p>Very pleomorphic long rod with round ends</p> Signup and view all the answers

    Lemierre’s disease is most commonly associated with which demographic?

    <p>Older children and young adults</p> Signup and view all the answers

    Which treatment is effective against infections caused by fragilis cells?

    <p>Clindamycin</p> Signup and view all the answers

    Fusobacterium necrophorum infections can progress to which serious condition?

    <p>Septic jugular vein thrombophlebitis</p> Signup and view all the answers

    Which of the following organisms is not typically a part of the healthy oral cavity microbiota?

    <p>Fusobacterium necrophorum</p> Signup and view all the answers

    Which of the following is a common manifestation of infections caused by Prevotella species?

    <p>Empyema and tubo-ovarian abscesses</p> Signup and view all the answers

    What characteristic do Porphyromonas species exhibit regarding their habitat?

    <p>They can be cultured from the oral cavity and other sites</p> Signup and view all the answers

    Study Notes

    Anaerobic Bacteria

    • Anaerobic bacteria do not use oxygen for growth and metabolism, obtaining energy from fermentation reactions
    • They require reduced oxygen tension for growth and do not grow on solid medium with 10% CO2 in ambient air
    • Examples include Bacteroides and Clostridium species
    • They lack enzymes catalase and superoxide dismutase, making them susceptible to oxygen
    • Anaerobes lack cytochromes needed to use oxygen as a terminal electron acceptor

    Clostridia

    • Clostridia are opportunistic pathogens, responsible for deadly diseases like gas gangrene, tetanus, and botulism
    • Also cause less severe diseases like pseudomembranous colitis and food poisoning
    • Clostridia cause disease primarily by producing numerous exotoxins
    • Examples of Clostridium species: C. perfringens, C. tetani, C. botulinum, C. difficile

    Clostridium Species

    • Morphology: Highly pleomorphic, rods with slightly curved ends, Gram-positive, motile (except C. tetani Type VI & C. perfringens), and often capsulated
    • Spores: Central or subterminal, sometimes oval or terminal
    • Cultural characteristics: Anaerobic, optimal growth temperature 37°C, pH 7-7.4, use Robertson's cooked meat broth as a medium
    • Resistance: Spores survive autoclaving, but boiling destroys vegetative cells rapidly, halogens can eradicate spores

    C. perfringens

    • Morphology: Non-motile rods with square ends, large Gram-positive bacilli, occurring singly or in chains
    • Spores: Central or subterminal
    • Reactions: Produce large amounts of hydrogen and CO2
    • Toxin production: Produces several toxinotypes (A-E), based on toxins α, β, ε, ι ; Toxin A is most important for humans

    C. botulinum

    • Characteristics: Anaerobic, gram-positive, rod shaped, spore forming, neurotoxic
    • Toxin Production: Neurotoxin production in food, destroyed by boiling
    • Classification: Divided into classes based on antigenic specificity of neurotoxins
    • Mechanism: Cleaves attachment protein, blocking the release of acetylcholine at presynaptic membrane of synapse

    C. tetani

    • Characteristics: Anaerobic, gram-positive, rod shaped and spore forming
    • Toxin: Neurotoxic exotoxin, tetanospasmin, that degrades a protein required for neurotransmitter release
    • Mechanism: Tetanospasmin affects inhibitory neurotransmitters, causing uncontrolled activation of motor neurons, yielding spastic paralysis
    • Epidemiology: Found in soil, occasionally in human intestinal flora
    • Manifestations: Causes tetanus or lockjaw following wounds, contaminated soil, nails or glass splinters.

    C. difficile

    • Associated with antibiotic use, decreasing normal intestinal flora
    • Secretes enterotoxins triggering pseudomembranous colitis (PMC), a serious disease
    • Pathogenesis: Antimicrobial effect on the microbiota selects C. difficile, spore germination triggered by bile salts increases toxin injury, and hypervirulent strains create 3 toxins
    • Diagnosis: Stool toxin detection is the primary diagnostic tool
    • Manifestation: Diarrhoea ranges from mild to toxic megacolon

    Miscellaneous Diseases and Concepts

    • Anaerobes: Important in intra-abdominal infections, usually under circumstances of disruption of the intestinal wall.
    • Bacteroides: Normal inhabitants of the bowel, implicated in intra-abdominal infections
    • Prevotella: Gram-negative bacilli, found in various infections
    • Porphyromonas: Gram-negative bacilli, often part of the oral microbiota
    • Fusobacteria: Morphological and species variation, cause of severe infections (such as Lemierre’s disease)
    • Treatment: Metronidazole, surgical removal of contaminated tissue, antitoxins
    • Prevention: Proper food handling, sterilization, vaccination, and antibiotic use in needed dosages & concentrations

    Other Anaerobic Infections

    • Food poisoning
    • Gangrenous appendicitis
    • Necrotizing enteritis
    • Brain abscess & meningitis
    • Thoracic infections
    • Urogenital infections (often following UT surgery)
    • Wound botulism

    Epidemiology

    • Source is endogenous or environmental (hospital outbreaks)
    • Frequent cause of antibiotic-associated diarrhea (ADD)

    Pathogenesis (general)

    • Spores germinate in appropriate conditions
    • Toxins are produced locally

    Manifestation

    • Symptoms vary by pathogen and type of disease

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    Lecture 10 Microbiology Anaerobic Bacteria PDF

    Description

    Test your knowledge on anaerobic bacteria and the Clostridia group. This quiz covers their growth conditions, pathogenicity, and examples of various species. Understand the implications of their exotoxin production and clinical significance in human diseases.

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