34 Questions
What is a characteristic of Staphylococci?
Non-motile
Which of the following is a characteristic of Staphylococcus aureus?
Coagulase positive
What is a normal habitat of Staphylococcus aureus?
Skin and mucosal surfaces
How do Staphylococci survive on dry surfaces?
Due to thickened peptidoglycan layer
What is a common infection caused by Staphylococcus saprophyticus?
Urinary tract infections
How are Staphylococci transmitted?
Through direct contact or contaminated fomites
What is a characteristic of Staphylococcus epidermidis?
Coagulase negative
What is a common habitat of Staphylococcus epidermidis?
Skin
What is the effect of Teichoic Acid on Staphylococcus aureus?
Helps in attachment
Which virulence factor is responsible for Staphylococcal Scalded Skin Syndrome (SSSS)?
Exfoliative Toxins (ETA, ETB)
What is the effect of Peptidoglycan on Staphylococcus aureus?
Inhibits phagocytosis
Which virulence factor is responsible for Necrotizing Pneumonia?
Panton Valentine Leukocidin (PVL)
What is the effect of Protein A on Staphylococcus aureus?
Inhibits phagocytosis
What is the effect of Enterotoxins (A-E, G-I) on the body?
Increases intestinal peristalsis and fluid loss, as well as nausea and vomiting
Which Gram Positive Cocci is most likely responsible for Scalded Skin Syndrome in neonate?
Staphylococcus aureus
Which Gram Positive Cocci is most likely responsible for Neonatal meningitis?
Streptococcus agalactiae
Which Gram Positive Cocci is Optochin sensitive?
Streptococcus pneumoniae
Which Gram Positive Cocci is most likely responsible for Endocarditis in patient with artificial heart valve?
Staphylococcus epidermidis
Which Gram Positive Cocci is most likely responsible for Urinary tract infection in a 25-year-old female?
Staphylococcus saprophyticus
Which Gram Positive Cocci is most likely responsible for Pharyngitis in young adult?
Streptococcus pyogenes
Which of the following is a risk factor for Staphylococcal infections?
Presence of a foreign body
S. epidermidis is responsible for which of the following diseases?
Endocarditis and UTIs
Which of the following is a common disease caused by S. aureus?
Pneumonia
Intravenous drug abuse is a risk factor for infections with which of the following?
S. epidermidis
Use of antibiotics can lead to an increased risk of Staphylococcal infections due to the suppression of:
Normal microbiota flora
Which of the following is NOT a disease caused by S. aureus?
Cystic fibrosis
What is the main difference between folliculitis and furuncles?
Folliculitis is a superficial infection, while furuncles are deep-seated
Which of the following is a characteristic of impetigo?
It is a superficial infection that affects mostly children
What is the main difference between Staphylococcal Scalded Skin Syndrome and Staphylococcal Toxic Shock Syndrome?
SSSS is a multisystem intoxication, while STSS is a dissemination of epithelium in infants
Which of the following is NOT a pyrogenic infection?
Staphylococcal Food poisoning
What is the main cause of Staphylococcal Food poisoning?
Consumption of contaminated food with heat-stable enterotoxin
Which of the following is characterized by a honey-colored crust with a moist erythematous base?
Impetigo
What is the main difference between carbuncles and furuncles?
Carbuncles affect multiple hair follicles, while furuncles affect a single hair follicle
Which of the following is a characteristic of Staphylococcal Scalded Skin Syndrome?
Disseminated desquamation of epithelium in infants
Study Notes
Gram Positive Cocci - Staphylococci
- Staphylococci are gram-positive, non-motile, non-spore forming cocci that form grape clusters or clumps.
- They are facultative anaerobes, β-haemolytic, and catalase-positive, which distinguishes them from Streptococci.
Human Pathogens
- Staphylococcus aureus is responsible for a broad spectrum of clinical syndromes.
- Staphylococcus epidermidis is associated with medical device-related infections.
- Staphylococcus saprophyticus is responsible for urinary tract infections.
Staphylococcus Species
- Staphylococcus aureus:
- Coagulase-positive
- Golden pigmentation of colonies grown on rich media
- β-hemolytic
- Staphylococcus epidermidis:
- Coagulase-negative
- White pigmentation of colonies
- Associated with medical device-related infections
- Staphylococcus saprophyticus:
- Coagulase-negative
- Colonies can be white or golden depending on the strain
- Responsible for 20% of urinary tract infections
Staphylococci as Normal Human Flora
- Staphylococci are normal flora on human skin and mucosal surfaces.
- They can survive on dry surfaces for long periods due to their thickened peptidoglycan layer and absence of outer membrane.
- Person-to-person spread can occur through direct contact or exposure to contaminated fomites.
- S. aureus is a common inhabitant of anterior nares and can also be found in other areas of the body.
- S. epidermidis is a common inhabitant of skin.
Diseases Caused by Staphylococci
- Staphylococcus aureus:
- Skin infections
- Endocarditis
- Osteomyelitis
- Pneumonia
- Meningitis
- Food-borne diseases (toxin-mediated)
- Staphylococcus epidermidis:
- Bacteraemia
- Endocarditis
- Surgical wounds
- UTIs
- Opportunistic infections of catheters, shunts, plastic implants, and prosthetic devices
- Staphylococcus saprophyticus:
- Urinary tract infections
Staphylococcus aureus Virulence Factors
- Peptidoglycan: abscess formation, inhibits phagocytosis
- Teichoic acid: helps in attachment
- Protein A: inhibits antibody-mediated clearance, inhibits phagocytosis
- Panton Valentine Leukocidin (PVL): necrotizing pneumonia
- Exfoliative Toxins (ETA, ETB): Staphylococcal Scalded Skin Syndrome (SSSS)
- Enterotoxins (A-E, G-I): superantigens, stimulating proliferation of T cells and release of cytokines
- Toxic Shock Syndrome Toxin-1: superantigen, produces leakage or cellular destruction of endothelial cells
Specific Diseases Due to S. aureus
- Cutaneous disease:
- Folliculitis
- Furuncle or boil
- Carbuncle
- Toxin-mediated disease:
- Staphylococcal Scalded Skin Syndrome (SSSS)
- Staphylococcal Toxic Shock Syndrome (STSS)
- Staphylococcal food poisoning
- Pyrogenic infections/ Invasive Staphylococcal Diseases:
- Abscesses
- Impetigo
- Wound infections
- Pneumonia
- Mastitis
- Osteomyelitis
- Septicaemia
Identify the Gram positive cocci responsible for specific conditions, such as pharyngitis in young adults, skin infections, and others. This quiz covers Staphylococcus and Streptococcus species.
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