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?

Staphylococcus aureus Signup and view all the answers

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

Staphylococcus saprophyticus Signup and view all the answers

What characteristic is shared by coagulase-negative staphylococci?

They are important in hospital-acquired infections. Signup and view all the answers

Which of the following best describes Staphylococcus epidermidis?

An important agent of prosthetic implant infections. Signup and view all the answers

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

They can cause infections in patients with prosthetic devices. Signup and view all the answers

What characteristic defines γ-Hemolytic streptococci?

They exhibit no color change or lysis of red blood cells. Signup and view all the answers

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

Groups A and B Signup and view all the answers

What disease can be caused by S.pyogenes?

Rheumatic fever Signup and view all the answers

How is S.agalactiae primarily transmitted?

From infected mother to infant at birth Signup and view all the answers

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

Coccal and occur in pairs Signup and view all the answers

Which species are regarded as the most clinically important enterococci?

E.faecalis and E.faecium Signup and view all the answers

What role do viridans streptococci play in human health?

They are part of the oral flora and can cause dental caries. Signup and view all the answers

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

They can reside in various body compartments. Signup and view all the answers

What is the primary disease caused by Corynebacterium diphtheriae?

Diphtheria Signup and view all the answers

Which species of Listeria is associated with foodborne illness?

L. monocytogenes Signup and view all the answers

What is a common complication of untreated cutaneous anthrax?

Septicemia Signup and view all the answers

What defines pulmonary anthrax?

Inhalation of spores Signup and view all the answers

What is a major cause of pseudomembranous colitis?

Clostridium difficile Signup and view all the answers

What type of bacteria are Clostridia?

Anaerobic gram-positive rods Signup and view all the answers

What is the mortality rate for untreated pulmonary anthrax?

Approaching 100 percent Signup and view all the answers

What main disease does Clostridium perfringens cause?

Food poisoning Signup and view all the answers

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

They cause lysis of red blood cells. Signup and view all the answers

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

Italics with the first letter capitalized for both. Signup and view all the answers

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

Streptococcus Signup and view all the answers

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

Clostridium Signup and view all the answers

What morphological characteristic distinguishes cocci from rods in bacteria?

Cocci appear spherical while rods appear cylindrical. Signup and view all the answers

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

Order Signup and view all the answers

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

Morphologic and biochemical characteristics. Signup and view all the answers

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

Staphylococcus Signup and view all the answers

What is the shape and gram classification of Clostridium perfringens?

Large, rod-shaped, gram-positive Signup and view all the answers

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

Food poisoning, wound infection, and infant botulism Signup and view all the answers

How is the disease tetanus primarily caused?

By introduction of spores into the body through wounds Signup and view all the answers

How does Clostridium botulinum affect the human body?

It induces flaccid paralysis Signup and view all the answers

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

It indicates the strength and potential for use as a biological weapon Signup and view all the answers

What condition can result from antimicrobial drug treatment?

Diarrhea or pseudomembranous colitis (PMC) Signup and view all the answers

What is the response of Clostridium tetani to oxygen?

It is extremely sensitive to oxygen. Signup and view all the answers

Which of these statements about Clostridium perfringens is true?

It can cause anaerobic cellulitis and myonecrosis. Signup and view all the answers

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.