Microbiology Quiz: Streptococcus and Proteus Species
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Questions and Answers

What defines the Lancefield groups of streptococci?

  • The type of enzymes they produce
  • The size of the bacterial colonies
  • The methods of antimicrobial resistance
  • The specific carbohydrates in their cell wall (correct)

Which specimen is typically used for diagnosing pharyngitis caused by S.pyogenes?

  • Blood for serology
  • Wound culture
  • Throat swab (correct)
  • Skin secretion

For which type of infection is a throat swab NOT typically collected?

  • Skin infections
  • Pharyngitis
  • Post-streptococcal diseases
  • Erysipelas (correct)

What type of specimen is required for post-streptococcal diseases?

<p>Blood for serology (D)</p> Signup and view all the answers

Which of the following infections is not typically associated with S.pyogenes?

<p>Bacterial pneumonia (B)</p> Signup and view all the answers

What type of colonies are observed in Proteus species on culture media containing selective agents?

<p>S colonies (C)</p> Signup and view all the answers

Which of the following biochemical patterns is characteristic of Proteus mirabilis?

<p>Urease positive (A)</p> Signup and view all the answers

On which type of agar does Proteus mirabilis grow and produce swarming colonies?

<p>Blood agar plate (C)</p> Signup and view all the answers

Which of the following statements about Proteus species is incorrect?

<p>They can ferment lactose. (C)</p> Signup and view all the answers

What is a common characteristic of colonies formed by Proteus species on lactose-containing media?

<p>Lactose-negative colonies (A)</p> Signup and view all the answers

What specimens can be used to culture Klebsiella species?

<p>Urine (A), Cerebrospinal fluid (D)</p> Signup and view all the answers

What is the result of a Gram stain for Klebsiella genus?

<p>Gram-negative cocobacilli in pairs (B)</p> Signup and view all the answers

Which of the following is NOT a method for identifying Klebsiella colonies?

<p>Blood culture (B)</p> Signup and view all the answers

Which feature describes the lactose fermentation capability of Klebsiella on MacConkey agar?

<p>Red colonies indicating lactose positive (D)</p> Signup and view all the answers

What is the biochemically significant result of Klebsiella on TSI agar?

<p>H2S negative, glucose positive, lactose and sucrose positive (B)</p> Signup and view all the answers

What identification technique uses the Quellung reaction?

<p>Antigenic structure identification (A)</p> Signup and view all the answers

Which antibiotic resistance phenotype is NOT typically associated with Klebsiella pneumoniae?

<p>Pseudomonas resistance (D)</p> Signup and view all the answers

Which of the following media is suitable for cultivating Klebsiella species?

<p>Lactose agar (B)</p> Signup and view all the answers

What characteristic identifies Pseudomonas aeruginosa as an obligate aerobic organism?

<p>It requires oxygen for growth. (C)</p> Signup and view all the answers

Which specimen type is NOT associated with Pseudomonas aeruginosa infections?

<p>Feces (D)</p> Signup and view all the answers

What property of Pseudomonas aeruginosa makes it resistant to cetrimide?

<p>It is non-fastidious. (A)</p> Signup and view all the answers

Which biochemical pattern is characteristic of Pseudomonas aeruginosa?

<p>Oxidase positive and glucose non-fermenter (A)</p> Signup and view all the answers

Which type of colony morphology is observed when Pseudomonas aeruginosa is cultivated in liquid media?

<p>Pellicle with a pigmented ring beneath (D)</p> Signup and view all the answers

In microscopy, what type of bacteria morphology is observed for Pseudomonas aeruginosa?

<p>Gram-negative bacilli with flagella (A)</p> Signup and view all the answers

What is the significance of pyocyanin production by Pseudomonas aeruginosa?

<p>It is a virulence factor specific to this bacterium. (C)</p> Signup and view all the answers

What type of hemolysis is typically associated with Pseudomonas aeruginosa on a blood agar plate?

<p>Beta hemolysis (A)</p> Signup and view all the answers

Which agar medium is selective for Aspergillus species?

<p>Czapek medium (A)</p> Signup and view all the answers

What is a characteristic feature of Penicillium spp. under microscopy?

<p>Straight or branched conidiophores (B)</p> Signup and view all the answers

What is the typical incubation temperature for deep site infections?

<p>37°C (C)</p> Signup and view all the answers

Which fungus is known to be pathogenic for humans from the Penicillium genus?

<p>P.marneffei (C)</p> Signup and view all the answers

How long do superior molds typically take to grow in culture?

<p>24 hours to 5 days (C)</p> Signup and view all the answers

Which characteristic is NOT used in identifying fungi through microscopy?

<p>Chemical composition of spores (B)</p> Signup and view all the answers

What type of conidiophores does Aspergillus spp. possess?

<p>Straight conidiophores (B)</p> Signup and view all the answers

What is a common feature of Fusarium species?

<p>Has over 100 known species (A)</p> Signup and view all the answers

What type of test is FTA-Abs?

<p>Treponemal serological test (D)</p> Signup and view all the answers

Which test is characterized by agglutination reactions?

<p>RPR (B)</p> Signup and view all the answers

What is a major disadvantage of non-treponemal serological tests?

<p>They give false-positive reactions. (A)</p> Signup and view all the answers

What is required for maintaining stock strains of Treponema pallidum?

<p>Rabbit testicles (D)</p> Signup and view all the answers

What can treponemal tests not be used to monitor?

<p>Disease evolution (D)</p> Signup and view all the answers

What does PCR stand for in the context of Treponema pallidum testing?

<p>Polymerase Chain Reaction (C)</p> Signup and view all the answers

Why are treponemal tests not suitable for monitoring disease evolution?

<p>Antibody levels do not correlate with disease course. (C)</p> Signup and view all the answers

What type of bacterium is Mycobacterium tuberculosis?

<p>Strictly aerobic (C)</p> Signup and view all the answers

What type of staining is used to identify Treponema pallidum in tissue samples?

<p>Silver stain (A)</p> Signup and view all the answers

What is the main characteristic of VDRL tests?

<p>They are rapid and inexpensive. (A)</p> Signup and view all the answers

Flashcards

Lancefield Groups

Groups that classify streptococci based on the C polysaccharide in their cell walls.

S. pyogenes (Group A)

A common streptococcus species responsible for strep throat, skin infections, and post-streptococcal diseases.

Specimen for Strep Throat

Throat swab

Specimen for Skin Infections

Secretions from the skin

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Post-Strep Infections Specimen

Blood for serology

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Klebsiella genus: Gram stain

Klebsiella are Gram-negative cocobacilli found in pairs.

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Klebsiella genus: Negative stain

Klebsiella have a capsule visible under a negative stain.

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Klebsiella genus: Cultivation

Klebsiella can be grown on blood agar, lactose agar, and MacConkey agar.

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Klebsiella genus: Lactose-positive

Klebsiella are lactose-positive, meaning they ferment lactose.

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Klebsiella genus: Biochemical pattern

Klebsiella are H2S-negative, non-motile, and variable for indole. On TSI agar, they are glucose and lactose/sucrose positive.

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Klebsiella genus: Quellung Reaction

The Quellung reaction is used to identify Klebsiella capsular antigens.

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Proteus genus: Important species

The medically important Proteus species are P. vulgaris, P. mirabilis, and P. penneri.

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Proteus genus: Specimens

Proteus can be found in urine, sputum, pus, cerebrospinal fluid, blood, and other bodily fluids.

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Proteus mirabilis

A species of Proteus bacteria known for its swarming motility and ability to produce indole. It is a common cause of urinary tract infections (UTIs).

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Proteus genus

A genus of Gram-negative, facultative anaerobic bacteria known for their swarming motility on non-selective media and ability to produce H2S.

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Swarming

The characteristic spreading growth pattern of Proteus species on non-selective culture media, appearing as a film over the agar surface.

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Indole negative

Refers to the inability of certain species, like P. mirabilis, to produce the breakdown product indole from tryptophan.

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Shigella genus

A genus of Gram-negative bacteria that cause shigellosis, a serious bacterial infection affecting the intestines.

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Pseudomonas aeruginosa: Opportunism

P. aeruginosa is an opportunistic pathogen, meaning it causes infections mainly in individuals with weakened immune systems or hospitalized patients.

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P. aeruginosa: Growth Requirements

P. aeruginosa is a non-fastidious organism, meaning it doesn't have complex nutritional needs and can grow on simple media.

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P. aeruginosa: Specimen Types

Specimens for P. aeruginosa isolation include pus, sputum, urine, blood, cerebrospinal fluid, and even conjunctival secretions.

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P. aeruginosa: Direct Examination

Direct examination of P. aeruginosa involves visual inspection of greenish pus and microscopic observation of Gram-negative bacilli with flagella.

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P. aeruginosa: Cultivation Media

P. aeruginosa grows on various media, but the most common are blood agar plates, MacConkey agar, and Cetrimide agar.

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P. aeruginosa: Colony Morphology

P. aeruginosa forms shiny S colonies on solid media, with a pellicle and pigmented ring in liquid media. On lactose-containing media, it forms lactose-negative colonies.

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P. aeruginosa: Biochemical Pattern

P. aeruginosa is oxidase positive, glucose non-fermenter, and lactose negative. It produces two soluble pigments: pyocyanin (blue) and fluorescein.

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P. aeruginosa: Beta Hemolysis

On blood agar plates, P. aeruginosa can exhibit beta hemolysis, which means it completely breaks down red blood cells.

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Septate Fungi

Fungi with cross-walls in hyphae, commonly called 'superior molds.'

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Aspergillus spp. Microscopy

Aspergillus species have straight conidiophores, apical vesicles (uniseriate or biseriate), and phialides producing conidia.

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Penicillium spp. Microscopy

Penicillium species have straight or branched conidiophores, terminal phialides, and conidia produced by the phialides.

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Aspergillus spp. Colony Characteristics

Aspergillus colonies can vary in size, shape, and color. They can be fluffy or flat.

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Aspergillus niger

A common Aspergillus species characterized by black colonies with radial lines.

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Aspergillus flavus

Aspergillus species known for its green to yellow colonies.

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Penicillium spp. Colony Characteristics

Penicillium colonies are typically blue-green or green due to the sporulating conidia.

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Culture Media for Septate Fungi

Common media for cultivating septate fungi include PDA (Potato-Dextrose-Agar), Sabouraud agar with chloramphenicol, and Czapek medium.

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Treponema pallidum Staining

Identifying T. pallidum in tissue samples requires special staining techniques like fluorescent antibody staining or silver stain.

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T. pallidum Cultivation

T. pallidum cannot be grown on traditional culture media. It requires specific environments like cell cultures or inoculation into rabbit testicles for research purposes.

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Nontreponemal Tests

These blood tests (like VDRL or RPR) detect antibodies produced in response to syphilis infection, but they aren't specific to T. pallidum. They're used for initial screening.

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Nontreponemal Test Advantages

Nontreponemal tests are quick, inexpensive, and can be used to monitor treatment progress as antibody levels decrease with successful therapy.

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Nontreponemal Test Disadvantages

Nontreponemal tests have low specificity, meaning they may produce false-positive results due to other conditions. Positive results need confirmation with specific treponemal tests.

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Treponemal Tests

These blood tests (like FTA-Abs, TPHA, ELISA) directly detect antibodies specifically against T. pallidum. They are used for definitive diagnosis.

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Treponemal Test Advantages

Treponemal tests are highly specific, indicating a confirmed T. pallidum infection. However, they don't reflect the disease course as antibody levels remain high even after treatment.

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Treponemal Test Disadvantages

Treponemal tests are more expensive, time-consuming, and don't show disease progression. They are mainly used for confirming late-stage syphilis when nontreponemal tests are negative.

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Syphilis Diagnosis Algorithm: First Step

The diagnosis begins with a non-treponemal test (VDRL or RPR) to screen for possible syphilis infection.

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Syphilis Diagnosis Algorithm: Confirmatory Step

If the non-treponemal test is positive, a treponemal test is performed to confirm the presence of T. pallidum-specific antibodies.

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Study Notes

Bacterial Infections

  • Diagnosis of infections caused by cocci (Staphylococcus spp., Streptococcus spp., Enterococcus spp., Neisseria spp., Haemophilus spp.)

Gram positive bacteria

  • Staphylococcus

    • non-fastidious
    • catalase positive
    • oxidase negative
    • aerobic, facultative anaerobic Gram-positive cocci
    • classification based on free coagulase production
    • coagulase-positive: S. aureus
    • coagulase-negative staphylococci (CNS): S. lugdunensis, S. schleiferi, S. hyicus, S. epidermidis, S. haemolyticus, S. saprophyticus, etc.

  • Streptococcus

    • aerobic, facultative anaerobic Gram-positive cocci
    • some species are obligate anaerobic
    • medically important streptococci prefer a CO2 enriched atmosphere
    • some of the species are fastidious
    • catalase negative
    • oxidase negative

  • Enterococcus

    • non-fastidious
    • catalase negative
    • oxidase negative
    • aerobic, facultative anaerobic Gram-positive cocci

Gram negative bacteria

  • Neisseria spp.

    • saprophytic, non-fastidious
    • pathogenic; Neisseria meningitidis
    • pathogenic; Neisseria gonorrhoeae

  • Haemophilus spp.

    • Haemophilus influenzae
    • Haemophilus parainfluenzae
    • Haemophilus aegyptius
    • Haemophilus ducreyi
    • other Haemophilus species

Other Bacteria

  • Vibrio cholerae
    • aerobic, oxidase positive, glucose fermenter Gram-negative curved rod
    • found in aquatic environments.
    • Serogroups 01 and 0139 cause cholera
  • Klebsiella genus
  • Proteus genus
  • Shigella genus
  • Salmonella genus
  • Yersinia enterocolitica
    • Acinetobacter genus

Treponema pallidum

  • The causative agent of syphilis

  • a sexually transmitted disease

  • specific tests (Confirmatory tests):

  • FTA-Abs (Fluorescent Treponemal Antibody Absorption Test)

  • TPPA (Treponema pallidum hemagglutination assay)

  • ELISA

  • Non-specific tests (Screening tests):

    • VDRL (Venereal Disease Research Laboratory) – flocculation tests (precipitation in liquid medium)
    • RPR (Rapid Plasma Reagin Test) - agglutination

Mycobacterium tuberculosis

  • strictly aerobic rod-shaped bacterium
  • cannot be stained by Gram due to high lipids in cell wall
  • causative agent of tuberculosis
  • pulmonary tuberculosis (sputum/secretions/gastric secretion in infants)
  • renal tuberculosis (urine)
  • genital tuberculosis (vaginal/sperm/prostatic secretions)
  • joint, bone tuberculosis (joint fluid/pus)
  • lymph node tuberculosis (lymph node aspirate/pus)
  • meningitis (CSF)
  • Microscopy: Ziehl-Neelsen stain (acid-fast staining) and Kinyoun stain.
  • Acid-fast stain: positive for Mycobacterium spp., Nocardia spp., Legionella micdadei, Rhodococcus spp
  • PCR and mass spectrometry used for testing
  • Cultivation: Lowenstein-Jensen agar, a specific selective medium

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Description

This quiz tests your knowledge on the Lancefield classification of streptococci and the characteristics of Proteus species. Questions cover specimen collection, biochemical patterns, and growth characteristics relevant to clinical microbiology. Challenge yourself and deepen your understanding of these important bacteria in infectious diseases.

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