Microbiology Quiz on Corynebacterium & Gardnerella
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Which of the following is a non-spore former among aerobic Gram positive bacilli?

  • Corynebacterium (correct)
  • Clostridium
  • Bacillus
  • Staphylococcus

    • What is the primary virulence factor of Corynebacterium diphtheriae?

  • Diphtheria toxin (correct)
  • Exotoxin
  • Capsule formation
  • Endotoxin

    • Which statement accurately describes the species classification of Corynebacterium?

  • Only one species is clinically significant.
  • All species can be identified without advanced sequencing techniques.
  • All species are motile.
  • There are over 60 species, with around 40 being clinically significant. (correct)

    • Which characteristic is true for lipophilic Corynebacterium species?

    <p>They require at least 48 hours to grow on standard media.</p> Signup and view all the answers

    Which of the following is NOT a characteristic feature of Corynebacterium species?

    <p>They are motile.</p> Signup and view all the answers

    What type of bacteria is Gardnerella vaginalis classified as?

    <p>Small, non-spore forming coccobacilli</p> Signup and view all the answers

    Which of the following is a recommended method for diagnosing bacterial vaginosis?

    <p>Gram stain</p> Signup and view all the answers

    Which symptoms are typically associated with bacterial vaginosis?

    <p>Fishy vaginal odor and thin discharge</p> Signup and view all the answers

    Where is Gardnerella vaginalis typically isolated from?

    <p>Genital cultures</p> Signup and view all the answers

    Which type of agar supports the growth of Gardnerella vaginalis?

    <p>Chocolate Agar</p> Signup and view all the answers

    What is an indirect evidence of infection in tuberculosis diagnosis?

    <p>Mantoux test results</p> Signup and view all the answers

    Which drug is NOT part of the standard anti-tuberculous treatment?

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

    Which method is primarily used for direct evidence of infection in tuberculosis?

    <p>PCR testing</p> Signup and view all the answers

    What is the primary purpose of contact tracing in tuberculosis management?

    <p>To detect and treat infected individuals</p> Signup and view all the answers

    What is the primary clinical presentation of non-tuberculous mycobacteria such as M. scrofulaceum?

    <p>Cervical lymphadenopathy</p> Signup and view all the answers

    What role does BCG play in tuberculosis prevention?

    <p>It serves as a vaccine for prevention</p> Signup and view all the answers

    Which of the following statements about Mycobacterium leprae is true?

    <p>It is an acid-fast bacillus</p> Signup and view all the answers

    What characterizes the treatment of infections caused by non-tuberculous mycobacteria like M. kansasii?

    <p>Resistance to standard anti-tuberculosis drugs</p> Signup and view all the answers

    Which is NOT one of the criteria indicating a likely diagnosis of bacterial vaginosis?

    <p>Presence of yeast infections</p> Signup and view all the answers

    Which pH level of vaginal discharge suggests bacterial vaginosis?

    <p>Greater than 4.5</p> Signup and view all the answers

    What treatment is recommended for pregnant women showing symptoms of bacterial vaginosis?

    <p>Oral metronidazole</p> Signup and view all the answers

    What is the primary benefit of using the Affirm VP III Microbial Identification System?

    <p>It detects multiple bacterial infections simultaneously.</p> Signup and view all the answers

    Which of the following treatments is shown to be slightly less effective than oral metronidazole?

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

    What complication is associated with bacterial vaginosis?

    <p>Development of pelvic inflammatory disease</p> Signup and view all the answers

    What type of vaginal fluid characteristic can indicate bacterial vaginosis?

    <p>A fishy odor when mixed with potassium hydroxide</p> Signup and view all the answers

    Which of the following is a limitation of DNA probe tests for Gardnerella?

    <p>They are too sensitive for normal flora.</p> Signup and view all the answers

    What characteristic appearance do colonies of certain mycobacteria exhibit when cultured?

    <p>Chalky, matte, or velvety</p> Signup and view all the answers

    Which method is NOT commonly used for the identification of mycobacteria?

    <p>Gram staining</p> Signup and view all the answers

    What type of metabolism is characteristic of the pathogens discussed?

    <p>Oxidative type metabolism</p> Signup and view all the answers

    Which Mycobacterium species is considered a strict pathogen?

    <p>Mycobacterium leprae</p> Signup and view all the answers

    What is the typical growth time for certain mycobacteria when cultured?

    <p>3-6 days</p> Signup and view all the answers

    Which antimicrobial is Mycobacterium species generally resistant to?

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

    In the pathogenesis of tuberculosis, what happens to the macrophages after engulfing the bacilli?

    <p>They die and release the bacilli</p> Signup and view all the answers

    Which of the following features is NOT associated with ‘Runyon Group 4’ Mycobacteria?

    <p>Usually pathogenic</p> Signup and view all the answers

    M tuberculosis is associated with which key clinical presentation?

    <p>Pulmonary disease</p> Signup and view all the answers

    What is the primary pathogenic species among Erysipelothrix?

    <p>E. rhusiopathiae</p> Signup and view all the answers

    Which of the following infections can be caused by Erysipelothrix rhusiopathiae?

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

    What key process stops the cycle of destruction and spread of Mycobacterium tuberculosis?

    <p>Cell mediated immune response</p> Signup and view all the answers

    What lab characteristic is true for the identification of Erysipelothrix species?

    <p>Non-motile</p> Signup and view all the answers

    What type of hemolysis is associated with Erysipelothrix rhusiopathiae when cultured on blood agar?

    <p>Alpha hemolysis</p> Signup and view all the answers

    How does Erysipelothrix rhusiopathiae typically enter the human body?

    <p>Through cuts and scratches</p> Signup and view all the answers

    What is a common microscopic feature of Erysipelothrix rhusiopathiae?

    <p>Pleomorphic, thin Gram-positive rods</p> Signup and view all the answers

    What environmental condition is required for the growth of Erysipelothrix rhusiopathiae colonies?

    <p>CO2 environment</p> Signup and view all the answers

    What is a characteristic symptom of erysipeloid infection caused by Erysipelothrix rhusiopathiae?

    <p>Localized painful swelling</p> Signup and view all the answers

    What test result is expected from Erysipelothrix rhusiopathiae on the TSI agar?

    <p>H2S production</p> Signup and view all the answers

    Which of the following is true of Gardnerella vaginalis?

    <p>It is facultatively anaerobic.</p> Signup and view all the answers

    Study Notes

    Aerobic Gram Positive Bacilli

    • Spore formers include Bacillus
    • Non-spore formers include Corynebacterium, Arcanobacterium, Rhodococcus, Listeria, Erysipelothrix, Gardnerella, Rothia
    • Branching non-spore formers include Actinomycetes, Nocardia
    • Some cause significant disease
    • Most are contaminants or commensals

    Non-Spore Forming, Non-Branching Catalase Positive Bacilli

    • Corynebacterium
      • More than 60 species, 40 clinically significant
      • Common microbiota of skin and mucous membranes
      • Cell walls contain m-DAP
      • All are catalase positive, and non-motile
      • Divided into lipophilic and non-lipophilic
      • Lipophilic types are fastidious and grow slowly (at least 48 hours) on standard media
      • Gram stain shows slightly curved, club-shaped bacilli
      • Coryneform-like isolates require 16s rRNA sequencing to identify species. Species include: C. bovis, C. ulcerans, C. xerosis, C. jeikeium, C. pseudodiphtheriticum, C. pseudotuberculosis
    • Virulence factors of Corynebacterium diphtheriae:
      • Diphtheria toxin produced by lysogenic β-phage strains carrying tox gene
      • Non-toxigenic strains can be converted to toxigenic by phage infection
      • Only toxin-producing strains cause diphtheria
      • Two fragments (A and B linked by disulfide bridge) form the toxin
        • Fragment A is cytotoxic
        • Fragment B binds to receptors on eukaryotic cells causing high potency and lethality (130ng/kg body weight)
        • Acts by blocking protein synthesis
        • Excreted by the bacterial cell, non-toxic until exposed to trypsin

    Clinical Significance: Respiratory diphtheria

    • Humans are the only natural host
    • Carried in upper respiratory tract (URT and spreads via droplet and hand to mouth contact)
    • Incubation period of 2-5 days
    • Illness starts gradually, marked by low-grade fever, malaise, mild sore throat
    • Common site of infection: tonsils or pharynx
    • Rapid multiplication occurs on epithelial cells
    • Necrotic cells and exudate form a pseudomembrane
    • Toxin causes demyelinating peripheral neuritis which may cause paralysis following the acute illness

    Clinical Significance: Cutaneous diphtheria

    • Prevalent in the tropics
    • Toxin is absorbed systematically
    • Marked by non-healing ulcers with a dirty gray membrane
    • Treatment via horse-derived anti-toxin (P or E drug of choice)

    Lab DX

    • Microscopy - highly pleomorphic gram-positive bacilli in palisades or V and L forms, club-shaped swellings and beaded forms common, metachromatic areas stain intensely (Babes-Ernst granules).
    • Culture - grows best in aerobic conditions at 37ºC, requires 8 essential amino acids, may have a small zone of β-hemolysis, use CTBA, Loeffler's serum, or Pai agars, catalase-positive, non-motile, C. diphtheriae is urease negative, ferments glucose and maltose with acid but no gas, reduces nitrates.
    • Toxigenicity tests

    Listeria monocytogenes

    • Comprises 6 species, only L. monocytogenes and L. ivanovii are pathogenic
    • Found in environment (soil, water, vegetation, animal products like raw milk, cheese, poultry, and processed meats)
    • Isolated from crustaceans, flies and ticks
    • Serious infections primarily in neonates, pregnant women, elderly, and immunocompromised hosts
    • Virulence factors: Listeriolysin O (hemolysin), Catalase superoxide dismutase, Phospholipase C, Surface protein p60
    • Clinical infections:
      • Listeriosis in pregnant women is most common during third trimester, responsible for spontaneous abortion and stillbirth
      • Flu-like illness (fever, headache, myalgia) is often self-limited due to elimination during childbirth
      • Disease in newborns can be fatal (up to 50%). 2 forms exist: early onset (intra-uterine/shortly after birth, sepsis is often the outcome) and late onset (occurs several days to weeks after birth, meningitis is often the manifestation)
      • Immunocompromised patients can develop CNS infections and endocarditis from contaminated food ingestion.
    • Lab DX:
      • Microscopy - gram-positive coccobacillus, short chains, palisades
      • Culture - grows well on SBA, chocolate agar, nutrient agar, BHIB, Thio broth; small, round, smooth, translucent colonies; surrounded by a narrow zone of β-hemolysis; growth over a wide range (0.5-45°C). Optimum: 30-35°C
      • Cold enrichment is often necessary
      • Catalase-positive, motility in wet smear (umbrella pattern at room temperature). Other tests: Hippurate hydrolysis (positive), BE (positive), CAMP (positive), block-type hemolysis on CAMP, acid from glucose (positive), VP, MR (positive).

    Non-Spore Forming, Non-Branching Catalase Negative Bacilli

    • Erysipelothrix rhusiopathiae

      • Gram-positive, non-spore-forming, pleomorphic rods (can produce filaments)
      • Distributed in nature, particularly affecting swine, turkey, sheep.
      • humans are affected by occupational cuts & scratches (fish handlers, animal products)
      • Clinical infections include acute erysipeloid (self-limiting localized infection, usually on hands/fingers, painful swelling, heals 3-4 weeks), Endocarditis (less common).
      • Diagnostics
        • Colony morphology (CO2 required, grows on blood or chocolate agars, colonies may appear gray or translucent, pinpoint, alpha hemolysis or non-hemolytic)
        • Microscopy (pleomorphic, gram-positive thin rods, may form long filaments form long filaments or short rods, arranged singly, in short chains, or in V shape decolorizes easily so it may appear gram-variable).
        • Identification (catalase, nitrate, urease negative, non-motile, produce H2S on TSI, VP negative, does not hydrolyze esculin, growth in semi-solid motility media, two colony types – pin point non-hemolytic, glistening colonies, or larger rough colonies with matte, curled, irregular edges)

    • Other important genera - Arcanobacterium, (3 medically important species,A. haemolyticum, A. pyogenes, A. bernardiae). Actinomycetes, and Nocardia.

    Gardnerella vaginalis

    • Member of the normal flora of the female genital tract
    • Associated with bacterial vaginosis
    • Marked by foul odor, vaginal pH >4.5
    • Diagnostics:
      • Wet prep – look for clue cells (large epithelials with various bacterial types on edges)
      • Gram stain – small, thin gram-variable rods.
      • Culture – growth on BAP, CA; no growth on MAC; beta-hemolytic in human blood bilayer tween "V" agar - requires a CO2 environment. Catalase negative

    Mycobacterium

    • Aerobic bacilli, non-spore forming. Nonmotile, Cell walls rich in lipids, Acid fast bacilli, Very slow growing
    • Diseases associated include Tuberculosis, Leprosy (M.leprae), Non Tuberculosis Mycobacteria.
    • Classifications: Various types of mycobacteria are associated with human diseases
      • Tuberculois, Leprosy, Non Tuberculosis Mycobacteria (Nocardia)
    • Lab Diagnosis for Mycobacterium:
      • Microscopy, Gram stain, culture, Oxidative type metabolism, no specific growth factors for media or growth conditions needed, growth after 3 to 6 days.

    Bacillus

    • Aerobic, Catalase positive, Not fastidious
    • Important Bacillus include B. anthracis, B. cereus.
    • B. anthracis
      • large bacilli (3-5 μm), single or paired in clinical isolates, polypeptide capsule and exotoxins, highly resistant central spores.
      • Symptoms - Cutaneous (malignant pustule, incubation 2-3 days erythematous papule, increasing necrotic/later ruptures to form a painless black eschar), Gastrointestinal (contaminated meat), Pulmonary
      • Diagnosis: Specimen aspiration or swab from cutaneous lesion, blood culture, sputum investigation, gram stain and culture, Identification via isolate identification
      • Treatment: Penicillin / tetracycline / chloramphenicol, Erythromycin or Clindamycin
      • Prevention: Vaccination of animal herds, proper disposal of carcasses, active immunization using attenuated bacilli.
      • B. cereus:
        • Large, motile, saprophytic bacillus - heat resistant spores, airborne and dust-borne contaminants, forms heat-stable (emetic syndrome) and heat-labile toxins (diarrhoeal disease) – multiplies readily in cooked foods (rice, potato, meat).
        • Lab diagnosis - demonstration of large number of bacilli in food.
        • Symptoms - Emetic (incubation <6 hours, severe vomiting, lasts 8-10 hours), Diarrhoeal (incubation >6 hours, diarrhoea, lasts 20-36 hours)

    Note: Additional details and specifics for each topic and species are available within the provided text.

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    Test your knowledge on the characteristics and classification of Corynebacterium and Gardnerella species. This quiz covers virulence factors, diagnosis methods, and culture conditions related to these important bacteria. Perfect for microbiology students and enthusiasts alike!

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