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Questions and Answers
Which characteristic is NOT true about Kocuria spp. based on the provided content?
Which characteristic is NOT true about Kocuria spp. based on the provided content?
What is the result of the Furazolidone test for Micrococcus?
What is the result of the Furazolidone test for Micrococcus?
Which species listed is NOT a notable species of Streptococcus?
Which species listed is NOT a notable species of Streptococcus?
What type of infections can Kocuria spp. cause in immune-compromised individuals?
What type of infections can Kocuria spp. cause in immune-compromised individuals?
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What is the characteristic morphology of Streptococcus bacteria?
What is the characteristic morphology of Streptococcus bacteria?
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Which of the following antibiotics is NOT typically used to treat Micrococcus infections?
Which of the following antibiotics is NOT typically used to treat Micrococcus infections?
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Which media enhances the growth of Streptococcus species?
Which media enhances the growth of Streptococcus species?
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Which of the following statements about Kocuria spp. is TRUE?
Which of the following statements about Kocuria spp. is TRUE?
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What characterizes beta-hemolytic streptococci?
What characterizes beta-hemolytic streptococci?
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Which classification system categorizes streptococci based on carbohydrate antigens in the cell wall?
Which classification system categorizes streptococci based on carbohydrate antigens in the cell wall?
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Which of the following is an example of an alpha-hemolytic streptococcus?
Which of the following is an example of an alpha-hemolytic streptococcus?
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What type of hemolytic reaction is associated with gamma-hemolytic streptococci?
What type of hemolytic reaction is associated with gamma-hemolytic streptococci?
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Which group is identified as Group A in Lancefield classification?
Which group is identified as Group A in Lancefield classification?
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What does Brown's classification depend on?
What does Brown's classification depend on?
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Which organism is found in the untippable group of Lancefield classification?
Which organism is found in the untippable group of Lancefield classification?
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In Sherman's classification, which physiological characteristic is NOT considered?
In Sherman's classification, which physiological characteristic is NOT considered?
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What is the general shape and arrangement of Micrococcus species?
What is the general shape and arrangement of Micrococcus species?
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Which of the following is a characteristic of Micrococcus species?
Which of the following is a characteristic of Micrococcus species?
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Identify a notable species of Micrococcus.
Identify a notable species of Micrococcus.
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Which classification system is used to organize Streptococcus species?
Which classification system is used to organize Streptococcus species?
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What kind of media supports the growth of Micrococcus species?
What kind of media supports the growth of Micrococcus species?
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Which characteristic is NOT true about Micrococcus species?
Which characteristic is NOT true about Micrococcus species?
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What is the pathogenic risk of Micrococcus in certain populations?
What is the pathogenic risk of Micrococcus in certain populations?
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Which biochemical test is important for diagnosing Streptococcus species?
Which biochemical test is important for diagnosing Streptococcus species?
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What is one of the diseases caused by S.pyogenes that is classified as a post-streptococcal condition?
What is one of the diseases caused by S.pyogenes that is classified as a post-streptococcal condition?
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Which enzyme produced by S.pyogenes facilitates the spread of bacteria through tissues by breaking down connective tissue?
Which enzyme produced by S.pyogenes facilitates the spread of bacteria through tissues by breaking down connective tissue?
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Which of the following is a major virulence factor of S.pyogenes that aids in adherence to host tissues?
Which of the following is a major virulence factor of S.pyogenes that aids in adherence to host tissues?
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What type of testing is initially performed to differentiate S.pyogenes from S.agalactiae?
What type of testing is initially performed to differentiate S.pyogenes from S.agalactiae?
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What is the role of exotoxins produced by S.pyogenes?
What is the role of exotoxins produced by S.pyogenes?
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How does the hyaluronic acid capsule of S.pyogenes contribute to its pathogenicity?
How does the hyaluronic acid capsule of S.pyogenes contribute to its pathogenicity?
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Which type of specimen is NOT suitable for diagnosing S.pyogenes infections?
Which type of specimen is NOT suitable for diagnosing S.pyogenes infections?
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What is a common symptom associated with scarlet fever caused by S.pyogenes?
What is a common symptom associated with scarlet fever caused by S.pyogenes?
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What is a primary characteristic of Enterococcus faecalis?
What is a primary characteristic of Enterococcus faecalis?
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Which of the following diseases is commonly associated with Enterococcus faecalis?
Which of the following diseases is commonly associated with Enterococcus faecalis?
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Which characteristic differentiates Enterococcus faecalis from non-enterococcal streptococci?
Which characteristic differentiates Enterococcus faecalis from non-enterococcal streptococci?
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What type of hemolysis is Enterococcus faecalis typically classified under?
What type of hemolysis is Enterococcus faecalis typically classified under?
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Why is Lancefield Grouping not reliable for identifying Enterococcus faecalis?
Why is Lancefield Grouping not reliable for identifying Enterococcus faecalis?
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Which of the following is NOT a biochemical test commonly performed for Enterococcus faecalis?
Which of the following is NOT a biochemical test commonly performed for Enterococcus faecalis?
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What notable feature is characteristic of Viridans group streptococci?
What notable feature is characteristic of Viridans group streptococci?
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Which species within the Viridans group is known for causing dental caries?
Which species within the Viridans group is known for causing dental caries?
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Study Notes
Micrococcus
- Gram-positive cocci arranged in tetrads (groups of four)
- Non-motile, non-capsulated, and non-sporulated
- Found in the upper respiratory tract and skin, often as commensals or opportunistic pathogens in immunocompromised individuals
- Notable species include Micrococcus varians, Micrococcus luteus (Milk Micrococci), and Micrococcus roseus (Dust of the air)
- Strictly aerobic, growing at 37°C
- Grows on ordinary media (Nutrient agar) and Blood agar (Gamma hemolysis)
- Produces rose or pink colonies on mannitol salt agar, except for M. luteus which produces yellow colonies
- Previously classified into the genus Micrococcus, but now reclassified into Kocuria species based on phylogenetic and chemotaxonomic analysis
Streptococcus
- Gram-positive cocci arranged in chains
- Non-motile and non-sporulated
- May or may not be capsulated
- Facultative anaerobic, growing poorly on ordinary media but better in the presence of blood, serum, and glucose
- Notable species include Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae, and Enterococcus faecalis
Classification of Streptococcus
-
Brown's classification: based on hemolytic reactions on blood agar
- Beta-hemolytic (β): complete lysis of red blood cells, clear zone around colonies; most pathogenic
- Alpha-hemolytic (α): partial hemolysis, greenish discoloration around colonies; mild pathogenic
- Gamma-hemolytic (γ): non-hemolytic; saprophytic
-
Lancefield classification: based on carbohydrate antigens in the cell wall; groups A-H, K-V, and untippable groups
- Group A: S. pyogenes - pharyngitis, skin infections
- Group B: S. agalactiae - neonatal infections
- Group D: Enterococcus faecalis (previously Streptococcus faecalis) - nosocomial infections, endocarditis
- Untippable group: S. pneumoniae - pneumonia in humans
- Sherman's classification: based on hemolytic reaction, Lancefield group, and specific physiological characteristics including fermentation and tolerance tests
Streptococcus pyogenes
- Causes pharyngitis (strep throat), scarlet fever (complication of strep throat), skin infections (impetigo, necrotizing fasciitis, cellulitis)
- Associated with post-streptococcal diseases like rheumatic fever and rheumatic kidney, which are autoimmune reactions triggered by similarities between heart muscle antigens and Streptococcus antigens
- Virulence factors include:
- M protein: evades phagocytosis by immune cells, helps adherence to host tissues
- Hyaluronic acid capsule: resists phagocytosis by immune cells
- Protein F: adherence to host cells
- Lipoteichoic acid: found in gram-positive cell walls
- Hyaluronidase: breaks down connective tissue, facilitates bacterial spread
- Streptokinase: dissolves blood clots, facilitating bacterial spread
- DNase: breaks down DNA
- C5a peptidase: inactivates complement system for immune evasion
- Hemolysins (Streptolysin O and S): lyse red and white blood cells, causing tissue damage and infection spread
- Exotoxins (e.g., SpeA, SpeB): cause toxic shock syndrome and scarlet fever
Diagnostic Tests for Streptococcus pyogenes
- Samples: blood, throat swabs, or other infected sites
- Gram stain: Gram-positive cocci in chains
- Blood culture: Streptococcus pyogenes is Beta-hemolytic
- Antibiotic sensitivity: Bacitracin-sensitive
- PYR test: positive
- Rapid antigen detection: latex agglutination tests from throat swabs
- Serological tests: detect antibodies against Streptococcus pyogenes including Lancefield grouping
Enterococcus faecalis (Group D Streptococcus)
- Often arranged in pairs or short chains
- Commensal bacterium found in the human large intestine
- Can tolerate high salt concentrations (6.5% NaCl) and bile presence
- Usually non-hemolytic or alpha-hemolytic
- Naturally resistant to many antibiotics
- Major cause of nosocomial infections, particularly in patients with indwelling medical devices
- Causes urinary tract infections (UTIs)
- Diagnostic tests:
- Samples: blood, urine, CSF, wound swabs, catheter tips
- Biochemical tests: PYR test positive, growth in 6.5% NaCl
- Lancefield grouping is not reliable for identifying E. faecalis because it lacks typical group-specific carbohydrates.
Viridans Group Streptococci (VGS)
- Heterogeneous group of organisms; can be commensals or pathogens
- Alpha-hemolytic or non-hemolytic
- Optochin-resistant
- Not soluble in bile salts
- Notable species: Streptococcus mutans (dental caries), Streptococcus salivarius
- Causes endocarditis and bacteremia
Streptococcus pneumoniae (Diplococcus pneumoniae)
- Untippable group in Lancefield classification - lacks Lancefield antigens
- Differentiated from VGS through specific tests and characteristics.
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Description
Explore the fascinating characteristics of Micrococcus and Streptococcus, including their morphology, growth conditions, and clinical significance. This quiz covers the classification, notable species, and the environments where these bacteria thrive. Perfect for microbiology students looking to test their knowledge on these important genera.