Systematic Bacteriology: Staphylococcus to Lactobacillus
40 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What do Streptococcus milleri produce from dietary sucrose, contributing to the development of dental caries?

  • Streptococcal pyrogenic exotoxins
  • M protein
  • Hyaluronidase
  • Fructan and/or glucan (correct)

    • What is the most serious infection occurring in patients with abnormal heart valves?

  • Tonsillitis
  • Dental caries
  • Subacute bacterial endocarditis (correct)
  • Pharyngitis

    • What is the characteristic arrangement of Streptococcus pyogenes cells?

  • Gram-positive rods
  • Gram-positive cocci in chains (correct)
  • Gram-negative rods
  • Gram-negative cocci

    • What is the most important virulence factor of Streptococcus pyogenes?

    <p>M protein</p> Signup and view all the answers

    What is the commonest infection caused by Streptococcus pyogenes?

    <p>Pharyngitis and/or tonsillitis</p> Signup and view all the answers

    What is the alternative antibiotic given to penicillin-allergic patients?

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

    What is the term for the complete hemolysis caused by Streptococcus pyogenes on blood agar?

    <p>Beta-haemolysis</p> Signup and view all the answers

    What is the purpose of giving a single large dose of ampicillin or amoxicillin before dental procedures?

    <p>To prevent subacute bacterial endocarditis</p> Signup and view all the answers

    What is the arrangement of Staphylococcus bacteria?

    <p>In grape-like clusters</p> Signup and view all the answers

    What is the primary difference between coagulase-positive and coagulase-negative Staphylococcus?

    <p>The ability to produce staphylocoagulase</p> Signup and view all the answers

    Which of the following is NOT a characteristic of Staphylococcus aureus?

    <p>Catalase-negative</p> Signup and view all the answers

    What is the primary habitat of Staphylococcus aureus?

    <p>Anterior nares</p> Signup and view all the answers

    What is the function of staphylocoagulase in Staphylococcus aureus?

    <p>Converts plasma fibrinogen to fibrin</p> Signup and view all the answers

    What type of haemolysis is produced by Staphylococcus aureus on blood agar?

    <p>Complete haemolysis</p> Signup and view all the answers

    Which of the following is a virulence factor of Staphylococcus aureus?

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

    What is the primary difference between Staphylococcus aureus and Staphylococcus epidermidis?

    <p>Pathogenic potential</p> Signup and view all the answers

    What is the primary mode of transmission of pharyngitis?

    <p>Respiratory droplets</p> Signup and view all the answers

    What is the characteristic tonsillar exudate in cases of tonsillitis?

    <p>Grayish white exudate</p> Signup and view all the answers

    What is the possible complication of streptococcal pharyngitis after 2-4 weeks?

    <p>Rheumatic heart disease</p> Signup and view all the answers

    What is the characteristic feature of scarlet fever?

    <p>All of the above</p> Signup and view all the answers

    What is the effective treatment for S.pyogenes diseases?

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

    What is the characteristic arrangement of Enterococcus species?

    <p>In short chains</p> Signup and view all the answers

    What is the ability of Enterococci to grow in broth containing?

    <p>6.5% NaCl</p> Signup and view all the answers

    Why can Enterococci survive in the root canal?

    <p>All of the above</p> Signup and view all the answers

    What is the function of a biofilm in microorganisms?

    <p>To make them more resistant to destruction and antimicrobials</p> Signup and view all the answers

    Which species is most commonly isolated from infections involving biofilm-producing microorganisms?

    <p>Enterococcus faecalis</p> Signup and view all the answers

    What is the characteristic shape of Neisseria genus members?

    <p>Kidney-shaped</p> Signup and view all the answers

    Which Neisseria species is a commensal inhabitant of the oro- and nasopharynx of healthy individuals?

    <p>Neisseria lactamica</p> Signup and view all the answers

    What is the primary function of pili in Neisseria gonorrhoeae?

    <p>To mediate attachment to epithelial cells</p> Signup and view all the answers

    What is the selective medium used to isolate Neisseria gonorrhoeae from specimens contaminated by other microbes?

    <p>Modified Thayer-Martin medium</p> Signup and view all the answers

    What is the primary symptom of gonorrhoea in males?

    <p>Acute urethritis with dysuria and purulent discharge</p> Signup and view all the answers

    What is the primary mode of transmission of Neisseria gonorrhoeae causing oral gonorrhoea?

    <p>Orogenital exposure</p> Signup and view all the answers

    What is the primary mode of transmission of diphtheriae?

    <p>By droplets or direct contact</p> Signup and view all the answers

    What is the composition of the local pseudomembrane in diphtheria?

    <p>Mucosal cell debris, infection products and fibrinous exudates</p> Signup and view all the answers

    What is the primary mechanism of toxin production in diphtheria?

    <p>The diphtheria bacilli produce toxins that are absorbed and disseminated through blood</p> Signup and view all the answers

    What is the typical duration of the incubation period of diphtheria?

    <p>2-5 days</p> Signup and view all the answers

    What is the most common complication of diphtheria?

    <p>Myocarditis and neuritis</p> Signup and view all the answers

    What is the primary purpose of laboratory diagnosis in diphtheria?

    <p>To confirm the clinical diagnosis</p> Signup and view all the answers

    What is the primary method of identification of C. diphtheriae?

    <p>Colony morphology and microscopic examination</p> Signup and view all the answers

    What is the primary specimen used for microbiological diagnosis of diphtheria?

    <p>Throat swabs</p> Signup and view all the answers

    Study Notes

    Staphylococcus

    • Staphylococcus species are Gram-positive, spherical bacteria arranged in grape-like clusters, and are facultative anaerobes and catalase-positive.
    • The catalase test is important in distinguishing streptococci (catalase-negative) from staphylococci.
    • The ability to produce staphylocoagulase divides the genus into two groups: "coagulase-positive" and "coagulase-negative".
    • Staphylococcus aureus is coagulase-positive, has the greatest pathogenic potential, and is the most medically important member of the genus.
    • Anterior nares and the skin are the main habitats for S. aureus and S. epidermidis, respectively.
    • S. aureus grows on:
      • Nutrient agar, forming golden yellow pigmented colonies
      • Blood agar, producing colonies surrounded with a zone of ß-haemolysis (complete haemolysis)
    • Important virulence factors of S. aureus include:
      • Staphylocoagulase: converts plasma fibrinogen to fibrin, leading to the formation of a fibrin barrier, protecting bacteria from phagocytes and immune defences, and localizing infection.

    Streptococcus pyogenes

    • Streptococcus pyogenes are Gram-positive cocci arranged in chains, and produce beta-haemolysis (complete haemolysis) on blood agar.
    • Important virulence factors of S. pyogenes include:
      • M protein: enables the bacteria to colonize the skin and inhibits phagocytosis.
      • Streptococcal pyrogenic exotoxins (SPE-A, B, and C): pyrogenic exotoxin A is referred to as erythrogenic toxin or scarlet fever toxin.
      • Enzymes (e.g., streptokinase and hyaluronidase): contribute to the spreading nature of streptococcal infections.
    • Important diseases caused by S. pyogenes include:
      • Pharyngitis (sore throat) and/or tonsillitis
      • Scarlet fever: characterized by the development of scarlet red rash, strawberry tongue, and a whitish coating on the back of the throat.
      • Skin and soft tissue infections (e.g., cellulitis)

    Enterococcus

    • Enterococcus species are Gram-positive cocci arranged in short chains, are catalase-negative, and are found normally in the oral cavity, human intestine, and female genital tract.
    • The commonest two species are Enterococcus faecalis and Enterococcus faecium.
    • Enterococci are:
      • Facultative anaerobes
      • Able to grow at 45°C
      • Able to grow in broth containing 6.5% NaCl
      • Able to grow on mitis salivarius agar, producing dark, blue-black colonies
      • Able to grow on bile esculin agar, giving black colonies
    • Enterococci are responsible for oral conditions, including:
      • Periodontitis (chronic infection of the gingival and periodontal ligaments)
      • Failed root canal treatment
    • Enterococcus faecalis is the species most commonly isolated from these infections.

    Neisseria

    • Neisseria species are Gram-negative cocci arranged in pairs with adjacent sides flattened to give a characteristic kidney-shape, and are aerobic and oxidase-positive.
    • The genus includes:
      • Neisseria gonorrhoeae (gonococci): causes the sexually transmitted disease gonorrhoea.
      • Neisseria meningitidis (meningococci): causes meningitis.
      • Commensal Neisseria species: inhabitants of oro- and nasopharynx of healthy individuals (e.g., N. lactamica and N. sicca).
    • Neisseria gonorrhoeae:
      • Is a fastidious species which grows on:
        • Chocolate agar (enriched medium)
        • Modified Thayer-Martin medium (MTM): a selective medium containing antibiotics, allowing easier isolation of the organism from specimens contaminated by other microbes.
      • Important virulence factors include:
        • Pili that mediate attachment to epithelial cells
        • Outer membrane proteins that contribute to invasion
        • IgA1 protease that may have a role in colonization
      • Important diseases caused by N. gonorrhoeae include:
        • Gonorrhoea: a sexually transmitted infection affecting males and females, causing acute urethritis with dysuria and purulent discharge in males, and cervicitis with a purulent cervical discharge in females.
        • Oral infection (oral gonorrhoea): usually occurs after orogenital exposure.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz covers the morphology, culture characteristics, virulence factors, diseases, and laboratory diagnosis of bacteria including Staphylococcus, Streptococcus, Enterococcus, Neisseria, Corynebacterium, and Lactobacillus.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser