Gram Positive Bacteria Classification
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Questions and Answers

What condition can occur due to bacteremia in patients with abnormal heart valves?

  • Acute bacterial endocarditis
  • Viral endocarditis
  • Fungal endocarditis
  • Subacute bacterial endocarditis (correct)

Which patients should receive prophylactic penicillin before dental procedures?

  • Patients undergoing orthopedic surgery
  • At-risk patients with valvular disease (correct)
  • Patients with hypertension
  • Patients with asthma

What is the composition of the vegetation seen in streptococcal endocarditis?

  • Bacteria, fibrin, and platelets (correct)
  • Fibrin, viruses, and platelets
  • Fibrin, bacteria, and white blood cells
  • Bacteria, viruses, and red blood cells

Which species of Staphylococcus is known for causing food poisoning?

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

Which Staphylococcus species is primarily associated with urinary tract infections in women?

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

What role do coagulase-negative staphylococci primarily play in a hospital setting?

<p>Associated with prosthetic infections (C)</p> Signup and view all the answers

Which species is the most virulent among the genus Staphylococcus?

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

What is a potential complication of damaged heart valves during bacteremia?

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

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

<p>Morphologic and biochemical characteristics (A)</p> Signup and view all the answers

What is the correct way to write the name of a bacterial species in scientific nomenclature?

<p>Salmonella enterica (C)</p> Signup and view all the answers

Which of the following bacteria are classified as Gram-positive cocci?

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

What distinguishes β-Hemolytic streptococci in blood agar?

<p>They result in a clear ring around the colony. (D)</p> Signup and view all the answers

What is the mortality rate of untreated cutaneous anthrax?

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

Which of the following bacteria is an example of a spore-forming Gram-positive rod?

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

Which organism is primarily responsible for causing listeriosis?

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

Which term is used to describe the color reaction of α-Hemolytic streptococci on blood agar?

<p>Green pigment formation (A)</p> Signup and view all the answers

What typically characterizes pulmonary anthrax?

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

Which type of infection is associated with Clostridium perfringens?

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

How should the family and genus in scientific nomenclature be formatted?

<p>Family in uppercase, genus in lowercase (C)</p> Signup and view all the answers

What is a serious consequence of untreated pulmonary anthrax?

<p>Mortality rate approaching 100% (D)</p> Signup and view all the answers

Which of the following is NOT a category of Gram-positive bacteria?

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

Which organism is known to grow at a temperature as low as 4 °C?

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

Which of the following diseases is NOT caused by Clostridium species?

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

What is the primary cause of listeriosis?

<p>Consumption of contaminated food (A)</p> Signup and view all the answers

What type of paralysis is caused by the neurotoxin produced by Clostridium botulinum?

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

Which of the following diseases is associated with Clostridium perfringens?

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

What is a common source of spores for Clostridium tetani?

<p>Contaminated soil (A)</p> Signup and view all the answers

What is the estimated lethal dose of botulinum toxin for a human?

<p>2μg or less (B)</p> Signup and view all the answers

In which scenario can botulism occur?

<p>Through ingestion of contaminated food (C)</p> Signup and view all the answers

What is the main reason for the rarity of tetanus in developed countries?

<p>Extensive immunization against the exotoxin (C)</p> Signup and view all the answers

Which type of bacteria are Clostridia primarily characterized as?

<p>Gram-positive and encapsulated (D)</p> Signup and view all the answers

What complication can result from antimicrobial drug treatment?

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

What term describes streptococci that do not cause color change or lysis of red blood cells?

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

Which group of β-Hemolytic streptococci is clinically the most important?

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

What is the most frequently encountered bacterial pathogen of humans in Group A β-Hemolytic Streptococci?

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

What can happen to individuals infected with certain strains of S.pyogenes?

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

Where is Group B streptococci, represented by S.agalactiae, found?

<p>In the vaginocervical tract and the GI tract (C)</p> Signup and view all the answers

What type of infections is S.pneumoniae most commonly associated with?

<p>Respiratory infections (C)</p> Signup and view all the answers

Which group includes many species that are main facultative oral flora?

<p>Viridans Streptococci (A)</p> Signup and view all the answers

Which species are the clinically most important enterococci?

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

Flashcards

Gram-positive Cocci

A type of bacteria that stains purple in a Gram stain and has spherical shapes.

Gram-positive Bacteria

Bacteria that retain crystal violet stain in a Gram stain procedure.

Spore-forming Rods

Gram-positive bacteria that produce spores for survival in harsh conditions, rod shaped.

Non-spore-forming Rods

Gram-positive bacteria that do not form spores. Rod shaped.

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α-Hemolytic streptococci

A type of Streptococcus that causes a chemical change in red blood cells creating a green ring on blood agar.

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β-Hemolytic streptococci

A type of Streptococcus that completely lyses red blood cells, creating a clear zone on blood agar.

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Staphylococci

Gram-positive cocci bacteria arranged in grape-like clusters.

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Streptococci

Gram-positive cocci bacteria arranged in chains.

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Lancefield Grouping

A classification system for streptococci based on the antigenic properties of their cell wall polysaccharides.

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Group A β-Hemolytic Streptococci

Streptococci belonging to the Lancefield Group A, characterized by complete lysis of red blood cells on blood agar plates.

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S. pyogenes

The most clinically important member of Group A β-Hemolytic Streptococci, responsible for various infections like strep throat and impetigo.

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Group B β-Hemolytic Streptococci

Streptococci belonging to the Lancefield Group B, commonly found in the vaginal tract of carriers and can cause infections in newborns.

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S. agalactiae

The representative pathogen of Group B β-Hemolytic Streptococci, commonly found in the vaginal tract of carriers, and can cause neonatal infections.

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S. pneumoniae

Gram-positive, encapsulated cocci responsible for common infections like pneumonia, otitis media, and meningitis.

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Enterococci

A group of bacteria, including E. faecalis and E. faecium, that can be found in the intestines and cause infections.

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Subacute Bacterial Endocarditis

An infection of the heart valves caused by bacteria entering the bloodstream, often during procedures like dental work.

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At-Risk Patients for Endocarditis

Individuals with heart valve conditions like rheumatic, congenital, or arteriosclerotic valve disease are more susceptible to bacterial endocarditis.

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Prophylactic Penicillin

Antibiotic given to prevent infection before procedures like dental work, especially for patients with heart valve conditions.

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What are Vegetations?

Abnormal growths on heart valves composed of fibrin, bacteria, and blood platelets. They form during bacterial endocarditis.

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Staphylococcus aureus

A common bacterium that causes various infections, including food poisoning, toxic shock syndrome, and skin infections.

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Staphylococcus epidermidis

A type of staphylococcus bacteria that commonly causes infections related to medical implants.

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Staphylococcus saprophyticus

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

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Coagulase-Negative Staphylococci

A group of staphylococcal bacteria that do not produce coagulase, often associated with hospital-acquired infections.

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C. perfringens

A large, rod-shaped, nonmotile, gram-positive, encapsulated bacillus found in the vagina and gastrointestinal tract. Its spores are found in soil. It can cause anaerobic cellulitis and myonecrosis (gas gangrene). Some strains cause food poisoning.

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C. botulinum

A bacterium that produces a neurotoxin called botulinum toxin, causing botulism. This toxin is extremely potent and can cause flaccid paralysis. Botulism can occur from food poisoning, wound infection, and infant botulism.

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What is the mode of transmission for C. botulinum?

Contact with the organism is not required for infection; the disease can be a pure intoxication.

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C. tetani

A bacterium that produces a neurotoxin causing tetanus. It's found in soil and can enter the body through even small wounds.

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What makes tetanus rare in developed countries?

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

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What is the difference in paralysis between C. botulinum and C. tetani?

C. botulinum causes flaccid paralysis (muscle weakness) while C. tetani causes spastic paralysis (muscle stiffness).

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What is pseudomembranous colitis (PMC)?

A life-threatening complication of antimicrobial drug treatment, characterized by severe diarrhea and formation of a pseudo-membrane in the colon.

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What are the types of diphtheria?

Diphtheria can be either a respiratory or cutaneous disease.

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What is the primary mode of transmission for diphtheria?

Diphtheria spreads through direct contact, respiratory droplets, or contact with contaminated objects.

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Why is listeria called 'foodborne'?

Listeria bacteria are commonly found in food, particularly milk.

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What is the effect of Listeria monocytogenes on the human body?

Listeria can cause infection in the nervous system and bloodstream.

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What is Anthrax?

Anthrax is a serious disease caused by the bacteria Bacillus anthracis.

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What are the most common types of Anthrax?

The most common type of Anthrax is Cutaneous Anthrax, affecting the skin.

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What's the main reason for Clostridia's clinical significance?

Clostridia bacteria cause a range of serious infections, including myonecrosis, pseudomembranous colitis, tetanus and botulism.

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How are Clostridium diseases treated?

Clostridium diseases are treated with antibiotics and antitoxins.

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Study Notes

Gram Positive Bacteria

  • Gram-positive bacteria are classified primarily by their morphology and biochemical characteristics.
  • Only medically significant bacteria are included in the classification.
  • Scientific names of bacteria are Italicized.

Scientific Nomenclature of Bacteria

  • Family, genus, species and varieties should be Italicized.
  • Family and genus names start with a capital letter.
  • Kingdom, phylum, class, order, and suborder also begin with a capital letter

Classification

  • Gram-positive bacteria are divided into Cocci (round shapes) and Rods.
  • Cocci can be described as Staphylococci, Streptococci, and Enterococci.
  • Rods can be Spore-forming (Bacillus and Clostridium) and Non-Spore forming (Corynebacterium and Listeria).

Gram-Positive Cocci

  • Streptococcus is a gram-positive cocci

  • Hemolytic properties on blood agar

    • a-hemolytic streptococci cause a chemical change in hemoglobin, resulting in a green pigment around the colony.
    • β-hemolytic streptococci cause gross lysis of red blood cells, and a clear ring around the colony.
    • γ-hemolytic streptococci cause no color change, or lysis of red blood cells.

  • Streptococcus is also classified by Lancefield. The most important groups are A and B.

  • Group A strepococci are medically significant bacteria, easily causing infection of skin and mucous membranes. They cause significant diseases such as: -Pneumonia - Pharyngitis -Impetigo -Facial Erysipelas

  • Group B strepococci are also gram-positive cocci. They are commonly transmitted from mother to child during birth.

  • Other gram positive cocci includes: Streptococcus pneumonia and Enterococci.

Gram Positive Rods

  • Corynebacterium diphtheriae

    • Most species are facultative anaerobes.
    • Their growth is on selective medium like Tinsdale agar with tellurite,
    • Cause diphtheria, an acute respiratory or cutaneous disease.

  • Listeria species

    • Are gram-positive, short, slender rods.
    • Do not form spores.
    • Commonly found in dairy products.

  • Bacillus (anthrax)

    • Also Gram-positive, spore-making rods.
    • Cause the disease anthrax. Different forms of anthrax include cutaneous, pulmonary, and inhalation.

Clostridia

  • Clostridia are anaerobic, gram-positive rods.

    • Clostridium perfringens

      • Causes gas gangrene and food poisoning.

    • Clostridium botulinum

      • Causes botulism (neurotoxin).

    • Clostridium difficile

      • Associated with antibiotic use, causes pseudomembranous colitis.

Filamentous

  • Actinomyces
  • Nocardia

Staphylococcus

  • Staphylococcus aureus is the most important staph and very virulent.
    • Causes food poisoning, toxic shock syndrome, and various common skin issues.
  • Staphylococcus epidermidis and Staphylococcus saprophyticus
    • Coagulase-negative, and cause various infections related to implants/catheters.

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Gram Positive Bacteria PDF

Description

Explore the classification of gram-positive bacteria, including their morphological and biochemical characteristics. This quiz delves into the distinctions between cocci and rods, along with the scientific nomenclature used to describe these bacteria. Test your knowledge on medically significant strains and their properties!

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