Microbiology Quiz on Bacteria Classification
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Questions and Answers

Which characteristic is used primarily for the classification of medically important bacteria?

  • Genetic sequencing
  • Antibiotic resistance patterns
  • Environmental adaptability
  • Morphologic and biochemical characteristics (correct)

What is the primary focus when italicizing scientific nomenclature of bacteria?

  • Only the genus name
  • Kingdom and phylum
  • Family, genus, species, and variety or subspecies (correct)
  • Only the species name

Which of the following is a Gram-positive cocci?

  • Escherichia coli
  • Bacillus
  • Staphylococcus aureus (correct)
  • Corynebacterium

Which type of hemolytic streptococci causes a clear ring around colonies on blood agar?

<p>β-Hemolytic (B)</p> Signup and view all the answers

What characterizes α-Hemolytic streptococci on blood agar?

<p>Presence of green pigment around the colony (A)</p> Signup and view all the answers

Which group of bacteria includes non-spore-forming rods?

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

Which of the following is NOT a factor in naming bacteria scientifically?

<p>Common name (C)</p> Signup and view all the answers

What determines if a bacterium is classified as Gram-positive or Gram-negative?

<p>Cell wall composition (C)</p> Signup and view all the answers

Which type of streptococci is characterized by the absence of color change or lysis of red blood cells?

<p>γ-Hemolytic streptococci (B)</p> Signup and view all the answers

What is the most clinically significant member of Group A β-Hemolytic Streptococci?

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

Which condition can be a post-infectious sequela of S. pyogenes infection?

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

Where is Group B streptococci, S. agalactiae, commonly found in carriers?

<p>Vaginocervical tract and intestinal tract (D)</p> Signup and view all the answers

Which type of bacteria is most commonly responsible for pneumonia?

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

Which of the following species are the most clinically important enterococci?

<p>E. faecium and E. faecalis (C)</p> Signup and view all the answers

What characteristic is associated with viridans streptococci?

<p>They are part of the main facultative oral flora. (B)</p> Signup and view all the answers

What is the typical shape of S. pneumoniae?

<p>Lancet-shaped cocci in pairs (B)</p> Signup and view all the answers

What condition can occur in patients with abnormal or damaged heart valves during a bacteremia?

<p>Subacute bacterial endocarditis (A)</p> Signup and view all the answers

Which patient group is recommended to receive prophylactic penicillin before dental procedures?

<p>Patients with rheumatic valvular disease (A)</p> Signup and view all the answers

What is the main component of vegetation formed on diseased heart valves?

<p>Fibrin, bacteria, and aggregated blood platelets (C)</p> Signup and view all the answers

Which species of Staphylococcus is known as the most virulent?

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

What type of infections is Staphylococcus epidermidis primarily associated with?

<p>Prosthetic implant infections (D)</p> Signup and view all the answers

Which Staphylococcus species is commonly known to cause urinary tract infections, especially in women?

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

Coagulase-negative staphylococci are primarily significant in which context?

<p>Hospital-acquired infections related to implanted devices (B)</p> Signup and view all the answers

Which Staphylococcus species is frequently a cause of food poisoning?

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

What is the predominant form of disease caused by Corynebacterium diphtheriae?

<p>Acute respiratory disease (B)</p> Signup and view all the answers

Which of the following is NOT a significant clinical strain of Clostridium?

<p>C.lactis (B)</p> Signup and view all the answers

How does Pulmonary anthrax primarily enter the body?

<p>Inhalation of spores (D)</p> Signup and view all the answers

What is a key characteristic of Listeria monocytogenes?

<p>It can grow at low temperatures. (B)</p> Signup and view all the answers

What type of infections are primarily associated with Clostridium perfringens?

<p>Histotoxic infections and food poisoning (C)</p> Signup and view all the answers

What is the mortality rate of untreated cutaneous anthrax?

<p>20 percent (A)</p> Signup and view all the answers

Which Clostridium species causes pseudomembranous colitis?

<p>C.difficile (A)</p> Signup and view all the answers

Which symptom is characteristic of pulmonary anthrax?

<p>Progressive hemorrhagic lymphadenitis (C)</p> Signup and view all the answers

What form does Clostridium perfringens take in its vegetative state?

<p>Rod-shaped (C)</p> Signup and view all the answers

Which clinical condition is NOT caused by Clostridium botulinum?

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

What is the toxic effect of botulinum toxin on the human body?

<p>Flaccid paralysis (A)</p> Signup and view all the answers

What is a common characteristic of Clostridium tetani regarding its growth?

<p>Local growth only (C)</p> Signup and view all the answers

What potential risk does Clostridium botulinum pose in terms of bioterrorism?

<p>Lethal dose is very small (B)</p> Signup and view all the answers

What is a primary cause for the rarity of tetanus in developed countries?

<p>Widespread immunization against its exotoxin (B)</p> Signup and view all the answers

Which symptom is associated with antimicrobial drug treatment complications?

<p>Pseudomembranous colitis (A)</p> Signup and view all the answers

Where are Clostridium perfringens spores commonly found?

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

Flashcards

Gram-Positive Bacteria

Bacteria that stain purple with Gram stain. This is due to their thick peptidoglycan layer in the cell wall.

Cocci

Round shaped bacteria.

Rods

Rod-shaped bacteria. Can either be spore-forming or non-spore-forming.

Streptococcus

A type of Gram-positive cocci that form chains. Known for causing various human infections, including pneumonia.

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α-Hemolysis

A type of hemolysis where red blood cells are partially broken down, resulting in a greenish color around the bacteria colony on a blood agar plate.

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β-Hemolysis

A type of hemolysis where red blood cells are completely broken down, resulting in a clear ring around the bacteria colony on a blood agar plate.

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γ-Hemolysis

A type of hemolysis where there's no change in the red blood cells around the bacteria colony on a blood agar plate, resulting in no color change.

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δ-Hemolysis

A type of hemolysis that is specific and difficult to interpret.

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What is a γ-hemolytic streptococcus?

Streptococci that do not cause any visible change in the color of red blood cells on a blood agar plate. This indicates that the bacteria do not break down red blood cells.

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What is a polysaccharide antigen?

A specific type of molecule found in the cell walls of many streptococci. This molecule acts as a trigger for the immune system, causing a reaction.

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What is the Lancefield grouping system?

This classification scheme groups streptococci based on their unique polysaccharide antigens. It primarily focuses on β-hemolytic streptococci, using letters from A to U.

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What is S.pyogenes?

The most common and dangerous type of streptococcus for humans. It is responsible for a variety of infections and can cause rapid disease progression.

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What is S.agalactiae?

A type of streptococcus that is often found in the vaginal and rectal regions of women. It is a potential cause of infections in newborns.

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What is S.pneumoniae?

This type of bacteria causes a wide range of infections, with pneumonia being the most common. It is also responsible for ear infections and meningitis.

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What are Enterococci?

A group of bacteria with the ability to cause infections in the intestinal tract. They can be found in various locations in the body, like the intestines and urinary tract.

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What are Viridans Streptococci?

A diverse group of bacteria that naturally reside in our mouths. They can cause dental problems, like cavities.

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Subacute Bacterial Endocarditis

A bacterial infection that affects the heart valves, often occurring in individuals with pre-existing valve damage or abnormalities.

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How does Subacute Bacterial Endocarditis develop?

A bacterial infection that happens when bacteria from the bloodstream settle on damaged heart valves.

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What bacteria causes Subacute Bacterial Endocarditis?

A type of bacteria that often infects damaged heart valves, leading to Subacute Bacterial Endocarditis.

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What is a vegetation (in the context of Subacute Bacterial Endocarditis)?

A layer of fibrin, bacteria, and blood platelets that builds up on a damaged heart valve, often a sign of Subacute Bacterial Endocarditis.

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What is Staphylococcus epidermidis?

A type of bacteria that is often found in the normal flora of the skin but can cause infections, especially in patients with weakened immune systems, artificial implants, or central nervous system problems.

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What is Coagulase-Negative Staphylococcus (CNS)?

A type of bacteria that is a common cause of infections associated with implanted prosthetic devices and catheters.

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What is Staphylococcus saprophyticus?

A type of bacteria that causes urinary tract infections, especially in women.

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What is Staphylococcus aureus?

A common type of bacteria that causes a wide variety of infections, including food poisoning, toxic shock syndrome, and skin infections.

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Diphtheria

A life-threatening, acute respiratory or cutaneous disease caused by Corynebacterium diphtheriae, which is rare in developed countries due to vaccinations.

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Corynebacterium diphtheriae

A type of bacteria that causes the disease diphtheria. It is a gram-positive rod.

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Listeria species

A type of bacteria that is a slender, short, gram-positive rod. It does not form spores. It is found in food like dairy products and can cause food poisoning.

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Listeriosis

A type of food poisoning caused by Listeria monocytogenes.

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Bacillus anthracis

A type of bacteria that forms spores and is responsible for anthrax. Anthrax is an infectious disease found in animals, but can be transmitted to humans. This type of bacteria is aerobic, meaning it needs oxygen to survive.

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Cutaneous anthrax

A type of anthrax that is acquired through skin contact with infected animals. It begins with a painless papule that turns into a pustule that can lead to septicimia.

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Pulmonary anthrax

Anthrax that is acquired by inhaling spores. This type of anthrax is very deadly and has a 100% mortality rate if left untreated.

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Clostridium

Anaerobic bacteria that can cause serious infections, like: Tetanus (Lockjaw), Botulism, and Gas Gangrene.

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What is Clostridium perfringens?

A large, rod-shaped, nonmotile, gram-positive, encapsulated bacterium commonly found in the vagina and gastrointestinal tract. Its spores are present in soil.

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What is Botulism?

A rare, life-threatening neuroparalytic disease caused by the botulinum toxin, produced by C. botulinum. It can manifest as food poisoning, wound infection, and infant botulism.

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What is Botulinum toxin?

An extremely potent neurotoxin produced by Clostridium botulinum, one of the most lethal poisons known. It causes a flaccid paralysis, leading to botulism.

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What is infant botulism?

A type of botulism where infants ingest the spores of Clostridium botulinum, which then germinate in the gut, producing the toxin.

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What is Tetanus?

A bacterial infection caused by Clostridium tetani, characterized by a powerful neurotoxin that causes spastic paralysis.

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What is Clostridium difficile (C. difficile) infection?

A common complication of antimicrobial drug treatment characterized by diarrhea, ranging from loose stools to life-threatening pseudomembranous colitis.

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How is Tetanus spread?

The introduction of C. tetani spores into even small wounds, often via contaminated soil, can lead to tetanus.

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Why is tetanus rare in developed countries?

The extreme O2 sensitivity of vegetative C. tetani and widespread immunization against its exotoxin make tetanus rare in developed countries.

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Study Notes

Gram-Positive Bacteria

  • Gram-positive bacteria have a thick cell wall
  • Classification is primarily based on morphology and biochemical characteristics
  • Only medically important bacteria are included in the current classification scheme
  • Scientific nomenclature follows specific rules (italicize family, genus, species)

Scientific Nomenclature of Bacteria

  • Italicize family, genus, species, and variety/subspecies
  • Capitalize first letter of family and genus
  • Capitalize first letter of kingdom, phylum, class, order, and suborder

Morphology and Appearance

  • Bacteria can be classified as cocci (spherical) or rods (cylindrical)
  • Gram-positive cocci include Staphylococci, Streptococci, and Enterococci
  • Gram-positive rods include Bacillus, Clostridium, and Corynebacterium
  • Additional characteristics like spore formation (forming structures called spores to survive adverse conditions) are used for classification

Gram-Positive Cocci: Streptococcus

  • a-hemolytic - causes a green pigment in blood agar, partial hemolysis
  • β-hemolytic - creates a clear ring on blood agar, complete hemolysis
  • γ-hemolytic - no color change or lysis on blood agar, no hemolysis
  • Classified by Lancefield groupings (A-U), crucial for clinical identification

Gram-Positive Cocci: Staphylococcus

  • The most virulent species is Staphylococcus aureus, causing various infections
  • Other species, like Staphylococcus epidermidis, are associated with implanted devices
  • Food poisoning and toxic shock syndrome are related to Staphylococcus aureus
  • Staphylococci infections include boils, impetigo, and scalded skin syndrome

Gram-Positive Rods: Bacillus and Clostridium

  • Spore-forming rods (aerobic Bacillus species): Anthrax, characterized by spore formation and resistance
  • Anaerobic Gram-positive rods (Clostridium species): Tetanus, Gas gangrene, Botulism, and Diarrhea diseases, typically associated with contaminated soil/food
  • Clostridium perfringens: causes gas gangrene, food poisoning
  • Clostridium botulinum: causes botulism, a potentially fatal intoxication
  • Clostridium difficile: causes severe diarrhea often associated with antibiotic use

Gram-Positive Rods: Corynebacterium

  • Corynebacterium diphtheriae: causes diphtheria, an acute respiratory disease
  • Often characterized by a characteristic "picket fence" or "Chinese character" appearance in cultures

Other Gram-Positive Bacteria

  • Listeria species are capable of growing in refrigerators, can cause food poisoning, septicemia and meningitis
  • Actinomyces and Nocardia: filamentous (thread-like) bacteria; related to specific types of infections.

Classifications of Medically Important Bacteria

  • Summarized table of significant bacteria, characteristics, and representative diseases.

Additional Notes

  • There are other Gram-positive and Gram-negative bacteria; this is a subset of the types
  • Proper identification of bacterial species is key to prescribing the correct treatment for infection

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Gram Positive Bacteria PDF

Description

Test your knowledge on the classification of medically important bacteria with this quiz. Questions cover various characteristics, nomenclature, and types of streptococci. Perfect for students studying microbiology or anyone interested in bacterial classification.

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