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Questions and Answers
What type of disease is diphtheria primarily caused by?
What type of disease is diphtheria primarily caused by?
Which species is primarily responsible for foodborne listeriosis?
Which species is primarily responsible for foodborne listeriosis?
What is the mortality rate of untreated cutaneous anthrax?
What is the mortality rate of untreated cutaneous anthrax?
What is a characteristic feature of pulmonary anthrax?
What is a characteristic feature of pulmonary anthrax?
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Which Clostridium species is associated with pseudomembranous colitis?
Which Clostridium species is associated with pseudomembranous colitis?
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What disease is primarily associated with the bacterium Clostridium tetani?
What disease is primarily associated with the bacterium Clostridium tetani?
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Which of the following diseases is caused by Clostridium perfringens?
Which of the following diseases is caused by Clostridium perfringens?
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Which condition is characterized by severe, swollen malignant pustules?
Which condition is characterized by severe, swollen malignant pustules?
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What type of hemolytic activity is associated with γ-Hemolytic streptococci?
What type of hemolytic activity is associated with γ-Hemolytic streptococci?
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Which group of β-Hemolytic streptococci is clinically considered the most important?
Which group of β-Hemolytic streptococci is clinically considered the most important?
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What is the primary pathogen represented by Group A β-Hemolytic Streptococci?
What is the primary pathogen represented by Group A β-Hemolytic Streptococci?
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How can S.agalactiae be transmitted to infants?
How can S.agalactiae be transmitted to infants?
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What shape do S.pneumoniae bacteria typically exhibit?
What shape do S.pneumoniae bacteria typically exhibit?
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Which of the following is known to cause dental caries?
Which of the following is known to cause dental caries?
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What capability do some strains of S.pyogenes have?
What capability do some strains of S.pyogenes have?
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The clinically important enterococci species include which of the following?
The clinically important enterococci species include which of the following?
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What condition can arise from infected heart valves in at-risk patients?
What condition can arise from infected heart valves in at-risk patients?
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Which patients should receive prophylactic penicillin before dental procedures?
Which patients should receive prophylactic penicillin before dental procedures?
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What is vegetation in the context of bacterial endocarditis?
What is vegetation in the context of bacterial endocarditis?
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Which species of Staphylococcus is noted for causing food poisoning and toxic shock syndrome?
Which species of Staphylococcus is noted for causing food poisoning and toxic shock syndrome?
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Which of the following Staphylococcus species is primarily associated with urinary tract infections, particularly cystitis in women?
Which of the following Staphylococcus species is primarily associated with urinary tract infections, particularly cystitis in women?
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What is the primary concern regarding coagulase-negative staphylococci in medical settings?
What is the primary concern regarding coagulase-negative staphylococci in medical settings?
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Which condition is primarily caused by Staphylococcus epidermidis?
Which condition is primarily caused by Staphylococcus epidermidis?
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What is the main characteristic of Staphylococcus aureus among other staphylococcal species?
What is the main characteristic of Staphylococcus aureus among other staphylococcal species?
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What type of paralysis is caused by the botulinum toxin produced by Clostridium botulinum?
What type of paralysis is caused by the botulinum toxin produced by Clostridium botulinum?
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Which of the following conditions can be caused by Clostridium perfringens?
Which of the following conditions can be caused by Clostridium perfringens?
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Why is tetanus considered rare in developed countries?
Why is tetanus considered rare in developed countries?
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Which of the following is a lethal dose of botulinum toxin for a human?
Which of the following is a lethal dose of botulinum toxin for a human?
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What is a common form of food poisoning associated with Clostridium perfringens?
What is a common form of food poisoning associated with Clostridium perfringens?
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How does Clostridium tetani generally enter the body?
How does Clostridium tetani generally enter the body?
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What severe condition can occur as a complication by antimicrobial drug treatment?
What severe condition can occur as a complication by antimicrobial drug treatment?
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Which formed toxin makes Clostridium botulinum a potential biological weapon?
Which formed toxin makes Clostridium botulinum a potential biological weapon?
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What characteristic is used primarily for the classification of medically important bacteria?
What characteristic is used primarily for the classification of medically important bacteria?
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Which of the following is NOT a type of Gram-positive bacteria?
Which of the following is NOT a type of Gram-positive bacteria?
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What is the genus of the bacteria that causes a clear ring around colonies on blood agar due to gross lysis of red blood cells?
What is the genus of the bacteria that causes a clear ring around colonies on blood agar due to gross lysis of red blood cells?
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Which of the following correctly defines the scientific naming of a bacterium?
Which of the following correctly defines the scientific naming of a bacterium?
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Which Gram-positive cocci can be classified as α-Hemolytic?
Which Gram-positive cocci can be classified as α-Hemolytic?
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Which of the following bacteria is classified as a spore-forming rod (bacilli)?
Which of the following bacteria is classified as a spore-forming rod (bacilli)?
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What type of Gram-positive cocci are known to form clusters?
What type of Gram-positive cocci are known to form clusters?
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What unique feature do β-Hemolytic streptococci exhibit on blood agar?
What unique feature do β-Hemolytic streptococci exhibit on blood agar?
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Study Notes
Gram Positive Bacteria
- Gram-positive bacteria are classified primarily by morphology (appearance) and biochemical characteristics.
- This classification only includes medically important bacteria.
- Scientific nomenclature: Italicize family, genus, and species. Capitalize the first letter of the family and genus names. Capitalize the first letter of kingdom, phylum, class, order, and suborder. All other words are lowercase.
- Binary genus-species system is used (e.g., Salmonella enterica, Escherichia coli, Staphylococcus aureus).
- Gram-positive bacteria can be cocci (spherical) or rods (elongated).
- They can be spore-forming or non-spore-forming.
- Important examples of gram-positive cocci are Streptococcus, Staphylococcus, Enterococci and Viridans streptococci.
- Important examples of gram-positive rods are Bacillus, Clostridium, Corynebacterium, and Listeria.
Classification of Medically Important Bacteria
- Bacteria are often classified based on their characteristics like morphology, spore-forming ability, and other biochemical properties.
- Gram-positive and gram-negative types are different on the basis of their cell wall characteristics.
- Examples: Streptococcus, Staphylococcus, and Enterococci are gram-positive cocci.
- Important gram-negative bacteria include Escherichia coli, Listeria, Corynebacterium.
- The study of gram-positive and gram-negative bacteria is important for understanding bacterial infections and disease processes.
Hemolytic Properties on Blood Agar
- a-hemolytic streptococci cause a change in the hemoglobin in red blood cells on blood agar, resulting in a green pigment that forms a ring around the colony.
- ẞ-hemolytic streptococci cause gross lysis (destruction) of red blood cells, showing a clear ring around the colony.
- y-hemolytic streptococci do not cause any color change or lysis (destruction) of red blood cells on blood agar.
Serological (Lancefield) Groupings
- Many streptococci have a polysaccharide in their cell wall that is antigenic (generating an immune response).
- The Lancefield scheme classifies mainly beta-hemolytic streptococci into groups A through U.
- The medically most important groups of beta-hemolytic streptococci are types A and B.
Group A B-Hemolytic Streptococci
- Streptococcus pyogenes is one of the most frequent bacterial pathogens in humans.
- Can invade intact skin or mucous membranes.
- A small inoculum (amount) is enough for infection.
- Some strains cause post-infectious sequelae (e.g., rheumatic fever and acute glomerulonephritis).
Streptococcus pneumoniae
- Gram-positive, nonmotile, encapsulated cocci (pairs).
- They are lancet-shaped.
- Common cause of pneumonia, otitis media, meningitis, and bacteremia/sepsis.
Enterococci
- Important species are E. faecalis and E. faecium.
- These bacteria can be y, β, or nonhemolytic.
Viridans Streptococci
- A group of streptococci found in the mouth.
- S. mutans and other species cause dental caries.
- Can cause subacute bacterial endocarditis in patients with abnormal or damaged heart valves.
Gram-positive rods
- The slides provide information on various gram-positive rods such as Bacillus, Corynebacterium, and Listeria.
- The slides describe characteristics like morphology, growth conditions needed, and diseases caused by each species.
Clostridia
- Anaerobic gram-positive rods of medical importance.
- C. perfringens causes histotoxic infections (myonecrosis) and food poisoning.
- C. difficile causes pseudomembranous colitis.
- C. tetani causes tetanus.
- C. botulinum causes botulism
Staphylococcus
- Staphylococcus aureus is one of the most virulent species.
- Common cause of bacterial and food poisoning.
- Staphylococcus epidermidis causes prosthetic implant infections.
- Staphylococcus saprophyticus causes urinary tract infections.
Coagulase-Negative Staphylococci
- S. epidermidis and S. saprophyticus are important causes of common CNS infections, and frequently found in hospital settings and are linked with the infections from implanted devices and catheters.
(Other information)
- Information on diseases, diagnosis, and treatment is provided in the slides, but this has been compiled into summary form.
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Description
This quiz covers the classification of gram-positive bacteria based on their morphology and biochemical characteristics. You will learn about important examples and their scientific nomenclature. Test your knowledge of bacteria that are medically significant.
