Microbiology Quiz: Staphylococci and Endocarditis
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Questions and Answers

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

  • Subacute bacterial endocarditis (correct)
  • Ischemic heart disease
  • Chronic heart failure
  • Acute myocardial infarction

Which type of patients should receive prophylactic penicillin before dental procedures?

  • Patients with rheumatic or congenital valvular disease (correct)
  • Patients with healthy heart valves
  • Patients with hypertension
  • Patients with acute cholecystitis

What are the main cells found in the vegetations associated with Streptococcal endocarditis?

  • Red blood cells and plasma
  • Fibrin, bacteria, and aggregated blood platelets (correct)
  • Myocytes and leukocytes
  • Chondrocytes and fibroblasts

Which of the following staphylococcal species is known to cause food poisoning?

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

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

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

What characteristic is shared by coagulase-negative staphylococci?

<p>They are important in hospital-acquired infections. (C)</p> Signup and view all the answers

Which of the following best describes Staphylococcus epidermidis?

<p>An important agent of prosthetic implant infections. (D)</p> Signup and view all the answers

What is the primary medical concern related to coagulase-negative staphylococci?

<p>They can cause infections in patients with prosthetic devices. (C)</p> Signup and view all the answers

What characteristic defines γ-Hemolytic streptococci?

<p>They exhibit no color change or lysis of red blood cells. (C)</p> Signup and view all the answers

Which of the following groups of β-hemolytic streptococci is clinically most important?

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

What disease can be caused by S.pyogenes?

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

How is S.agalactiae primarily transmitted?

<p>From infected mother to infant at birth (A)</p> Signup and view all the answers

What shape are S.pneumoniae bacteria, and how do they exist in relation to each other?

<p>Coccal and occur in pairs (D)</p> Signup and view all the answers

Which species are regarded as the most clinically important enterococci?

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

What role do viridans streptococci play in human health?

<p>They are part of the oral flora and can cause dental caries. (D)</p> Signup and view all the answers

What characteristic is common among γ, β, or nonhemolytic enterococci?

<p>They can reside in various body compartments. (C)</p> Signup and view all the answers

What is the primary disease caused by Corynebacterium diphtheriae?

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

Which species of Listeria is associated with foodborne illness?

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

What is a common complication of untreated cutaneous anthrax?

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

What defines pulmonary anthrax?

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

What is a major cause of pseudomembranous colitis?

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

What type of bacteria are Clostridia?

<p>Anaerobic gram-positive rods (D)</p> Signup and view all the answers

What is the mortality rate for untreated pulmonary anthrax?

<p>Approaching 100 percent (B)</p> Signup and view all the answers

What main disease does Clostridium perfringens cause?

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

Which characteristic differentiates β-Hemolytic streptococci from α-Hemolytic streptococci?

<p>They cause lysis of red blood cells. (D)</p> Signup and view all the answers

How should scientific nomenclature for bacterial families and genera be written?

<p>Italics with the first letter capitalized for both. (C)</p> Signup and view all the answers

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

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

Of the following, which type of Gram-positive bacteria is known to form spores?

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

What morphological characteristic distinguishes cocci from rods in bacteria?

<p>Cocci appear spherical while rods appear cylindrical. (B)</p> Signup and view all the answers

In terms of classification, which level begins with a capital letter?

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

The term 'medically important bacteria' includes organisms that are primarily classified based on which type of characteristics?

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

Which of the following bacteria is not classified as a Gram-positive rod?

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

What is the shape and gram classification of Clostridium perfringens?

<p>Large, rod-shaped, gram-positive (B)</p> Signup and view all the answers

What are the clinical forms of botulism caused by Clostridium botulinum?

<p>Food poisoning, wound infection, and infant botulism (C)</p> Signup and view all the answers

How is the disease tetanus primarily caused?

<p>By introduction of spores into the body through wounds (B)</p> Signup and view all the answers

How does Clostridium botulinum affect the human body?

<p>It induces flaccid paralysis (C)</p> Signup and view all the answers

What is the significance of the lethal dose of botulinum toxin for humans?

<p>It indicates the strength and potential for use as a biological weapon (D)</p> Signup and view all the answers

What condition can result from antimicrobial drug treatment?

<p>Diarrhea or pseudomembranous colitis (PMC) (A)</p> Signup and view all the answers

What is the response of Clostridium tetani to oxygen?

<p>It is extremely sensitive to oxygen. (D)</p> Signup and view all the answers

Which of these statements about Clostridium perfringens is true?

<p>It can cause anaerobic cellulitis and myonecrosis. (D)</p> Signup and view all the answers

Flashcards

Gram-positive bacteria

A large group of bacteria characterized by a thick peptidoglycan layer in their cell walls, which retains the crystal violet dye in a Gram stain.

Gram stain

A differential staining technique used to categorize bacteria based on their cell wall structure. It helps in identifying the Gram-positive and Gram-negative bacteria.

Gram-positive cocci

Gram-positive bacteria that have a spherical shape (cocci).

Streptococcus

A genus of Gram-positive, spherical bacteria.

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α-hemolytic streptococci

A type of Streptococcus that causes a partial breakdown of red blood cells on blood agar, resulting in a greenish ring around the colony.

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β-hemolytic streptococci

A type of Streptococcus characterized by complete lysis of red blood cells on blood agar, resulting in a clear zone around the colony.

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Spore-forming rods

Gram positive bacteria appearing as rod-shaped (bacillus), that can create dormant, resistant spores.

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Cocci shape

A spherical shape in bacterial morphology.

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Lancefield Grouping

A system used to classify beta-hemolytic streptococci into groups (A-U).

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Group A β-hemolytic Streptococcus (S. pyogenes)

A gram-positive bacteria frequently infecting humans; causes rapidly progressing infections, potentially with long-term health impacts.

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Group B Streptococcus (S. agalactiae)

Gram-positive bacteria found in the vaginal tract; capable of transmitting infection from mother to baby.

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Streptococcus pneumoniae

Gram-positive, encapsulated cocci significant for pneumonia and otitis media.

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Enterococci

Gram-positive bacteria, including E. faecalis and E. faecium; can exhibit gamma, beta, or non-hemolytic properties.

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Viridans Streptococci

Main component of the facultative oral flora and linked to dental cavities.

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S. pyogenes

The most significant Group A beta-hemolytic streptococci.

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Subacute Bacterial Endocarditis

An infection of the heart valves, typically occurring in patients with pre-existing valve damage, often caused by bacteria entering the bloodstream during procedures like dental work.

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Prophylactic Penicillin

Antibiotics given to prevent infection in at-risk individuals, especially those with heart valve problems, before undergoing procedures like dental work, to prevent bacterial endocarditis.

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Vegetation

An abnormal tissue growth on a heart valve, composed of fibrin, bacteria, and blood platelets, often seen in bacterial endocarditis.

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Staphylococcus aureus

A highly virulent bacterium, commonly causing infections, food poisoning, and toxic shock syndrome.

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Staphylococcus epidermidis

A less virulent type of staphylococcus, frequently causing infections in implanted devices like prosthetics.

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Staphylococcus saprophyticus

A type of staphylococcus primarily causing urinary tract infections, especially in women.

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Coagulase-Negative Staphylococci (CNS)

A group of staphylococcal species that are not able to produce coagulase, often causing hospital-acquired infections, especially in patients with implanted devices.

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CNS and Implanted Devices

Coagulase-negative staphylococci (CNS) are a common cause of infections associated with implanted devices like prosthetic joints and catheters.

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Corynebacterium Diphtheriae

A gram-positive rod that causes diphtheria, an acute respiratory or cutaneous disease.

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Diphtheria

An acute respiratory or cutaneous disease caused by Corynebacterium diphtheriae, often life-threatening but preventable with vaccines.

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Listeria Species

Slender, short, gram-positive rods that do not form spores. L. monocytogenes causes listeriosis, a foodborne illness.

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Listeriosis

A foodborne illness caused by Listeria monocytogenes, often linked to contaminated dairy products.

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Anthrax

A serious disease caused by Bacillus anthracis, often impacting livestock and humans.

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Cutaneous Anthrax

The most common form of anthrax, leading to a painful, black, swollen pustule, potentially fatal.

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Pulmonary Anthrax

Anthrax infection contracted through inhaling spores, leading to hemorrhagic lymphadenitis, with a high mortality rate.

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Clostridia

Anaerobic, gram-positive rods, important clinically, some causing common infections like tetanus, botulism and gas gangrene.

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What causes gas gangrene?

Clostridium perfringens, a ubiquitous bacterium, can cause anaerobic cellulitis and myonecrosis (gas gangrene) when introduced into tissue.

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How does C. perfringens cause food poisoning?

Certain strains of Clostridium perfringens produce toxins that lead to food poisoning, a common ailment.

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What is botulism?

Botulism is a serious illness caused by the neurotoxin produced by Clostridium botulinum.

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What is the characteristic symptom of botulism?

Botulism causes flaccid paralysis, a weakness and loss of muscle control.

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What is the mode of transmission of botulism?

Botulism is caused by a neurotoxin, not by direct contact with the bacteria.

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What is tetanus?

Tetanus is a serious infection caused by Clostridium tetani, which produces a neurotoxin causing spastic paralysis.

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How is tetanus transmitted?

Tetanus is usually contracted when C. tetani spores enter a wound.

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How is tetanus prevented?

Widespread vaccination against the C. tetani exotoxin makes tetanus rare in developed countries.

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Study Notes

Gram Positive Bacteria

  • Gram-positive bacteria are classified primarily based on morphological and biochemical characteristics.
  • Only medically important bacteria are included.

Scientific Nomenclature of Bacteria

  • Italicize family, genus, species, and variety/subspecies.
  • Capitalize first letter of family and genus names.
  • Capitalize first letter of kingdom, phylum, class, order, and suborder, but these are capitalized.
  • Use binary genus-species format (e.g., Salmonella enterica, Escherichia coli, Staphylococcus aureus).

Gram-Positive Bacteria - Morphology

  • Cocci (spherical): Staphylococci, Streptococci, Enterococci.
  • Rods: Bacillus, Clostridium, Corynebacterium, Listeria.
  • Spore-forming rods: Bacillus, Clostridium.
  • Non-spore forming rods : Nonfilamentous, Filamentous
  • Gram-negative bacteria.

Gram-Positive Cocci -Streptococcus

  • Streptococcus species have a polysaccharide in their cell walls which is antigenic.
  • The Lancefield scheme classifies beta-hemolytic streptococci into Groups A-U.
  • Clinically important groups are A and B.
  • Streptococcus pyogenes, group A beta-hemolytic streptococci, is a common human pathogen, capable of invading skin and mucous membranes & causing serious infections.
  • S. pyogenes can cause rheumatic fever and acute glomerulonephritis.
  • Streptococcus pneumoniae is the most common cause of pneumonia and otitis media, & also an important cause of meningitis and bacteremia/sepsis.

Gram-Positive Cocci - Staphylococcus

  • Staphylococcus aureus is the most virulent, commonly causing food poisoning, toxic shock syndrome, and various infections.
  • Staphylococcus epidermidis is less virulent but causes prosthetic implant infections, and Staphylococcus saprophyticus is associated with urinary tract infections, especially cystitis in women.
  • Diseases caused by Staphylococcus aureus include furuncles, carbuncles, wound infections, cellulitis, etc.

Gram-Positive Rods

  • Corynebacterium diphtheriae: Causes diphtheria, an acute respiratory or cutaneous disease; and can lead to death. The widespread immunization has decreased cases in developed countries.
  • Listeria species, particularly L. monocytogenes is capable of growing in food at 4°C, leading to food poisoning (dairy products like ice cream or cheese). It can cause septicemia and meningitis (listeriosis).
  • Bacillus anthracis causes anthrax; forms spores (very resistant).
  • Forms of anthrax exist: cutaneous anthrax (95% of cases) is characterized by a papule that develops to a sore, pulmonary anthrax through inhalation, and affects the lungs.
  • Clostridium, a group of anaerobic gram-positive rods, is of greatest clinical importance. They cause various illnesses: Tetanus (lockjaw), Gas gangrene (myonecrosis), Botulism, and Diarrhea.
  • C. perfringens produces toxins leading to histotoxic infections(myonecrosis), and food poisoning
  • C. botulinum causes botulism; a lethal neurotoxin, causes flaccid paralysis

Enterococci

  • E. faecalis and E. faecium are the most clinically important species. They are usually nonhemolytic.

Viridans Streptococci

  • Includes various species that form the primary facultative oral flora;
  • Streptococcus mutans, can cause dental caries.
  • Can cause bacterial endocarditis in individuals with abnormal valves.

Filamentous

  • Actinomyces, Nocardia are filamentous gram-positive rods.

Gram-Positive Bacteria Summary

  • Streptococcus, Staphylococcus, Corynebacterium, Listeria, Bacillus anthracis, Clostridium, and Enterococci; are gram-positive bacteria, each having significant roles in both public health and medical interventions.

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Description

Test your knowledge on the key aspects of staphylococci and their relationship to conditions like bacteremia and endocarditis. This quiz covers important bacteria, patient management, and clinical implications related to heart valve abnormalities and dental procedures. Ideal for students in microbiology and medical fields.

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