Bacteria of Skin & Nasopharynx Flashcards
Where do streptococci reside?
nasopharynx, skin, GI, GU
What are the two genus of pyogenic gram + bacteria?
What are the two genus of pyogenic gram + bacteria?
What is the main morphological difference between staphylococci and streptococci?
Staphylocci: clusters
Streptococci: pairs/chains
What is a catalase test used for?
differentiating between staphylococci and streptococci species
What does catalase do?
Converts Hydrogen peroxide into water and oxygen
Which bacteria lack catalase?
Streptococci
Which bacteria produce catalase?
Staphylococci
Will a cell culture with H2O2 and streptococci produce Water and oxygen gas?
No
Will a cell culture with H2O2 and staphylococci produce Water and oxygen gas?
Yes
What makes staphylococci a major problem in hospitals? (2)
Resistant to drying/heat and resistant to many antibiotics
How is staphylococci species usually spread in hospital settings?
nasal and skin carriage
What are the two species of staphylococci?
staphylococcus aureus
staphylococcus epidermidis
Which staphylococcus species is less pathogenic?
s. epidermidis, part of normal microbiota
endocarditis from sharing needles or surgery would be most associated with which staphylococcus species?
staphylococcus epidermidis
what diagnostic test is used to differentiate between staphylococcus aureus and staphylococcus epidermidis?
coagulase test
Which species of staphylococcus produces coagulase?
staphylococcus aureus
prothrombin in combination with coagulase will cause fibrinogen to do what?
convert to fibrin (blood will clot)
What virulence factors make up the pathogenic capacity of staphylococcus aureus? (3)
Surface molecules
Extracellular factors
Toxins
List two surface molecules of S. aureus
Fibronectin binding protein
Protein A
Fibronectin binding protein is what kind of virulence factor?
adhesin
Which virulence factor of Staph aureus
- binds to Fc of IgG1, IgG2, IgG4
- linked to peptidoglycan
- prevents phagocytosis (opsonization)
protein A
the surface molecule of S. aureus, fibronectin acts as what?
adhesin
Give an example of the extracellular factors produced by Staph aureus
Hemolysins “alpha toxin”
What does the alpha toxin produced by staph aureus do?
pokes holes in the membrane, forming transmembrane channels
Where do staphylococci reside?
nasopharynx, skin, GI
Why are the transmembrane channels formed by Staph aureus alpha toxin damaging to the cell?
lyses the mammalian cells
How is Staph aureus alpha toxin used diagnostically?
observe whether mixture of red blood cells lyses on contact with bacterial culture (if yes, bacteria contain alpha toxin)
What is the alpha toxin produced by Staph aureus primary virulence function?
lyse white blood cells
What are the three exotoxins associated with Staph aureus?
- TSST-1
- Exfoliative toxins A & B
- Enterotoxins
- TSST-1
- Exfoliative toxins A & B
- Enterotoxins
TSST-1 and enterotoxins
Which of the Staph aureus exotoxins cause toxic shock syndrome?
TSST-1
What does exfoliative toxins A & B do? (Staph aureus exotoxin)
Proteases that cleave desmosomal proteins of the skin
Exfoliative toxins A & B produced by Staph aureus were thought to be superantigens but are actually?
proteases
What is the protein that exfoliative toxins A & B of Staph aureus cleave?
desmosomal proteins of the skin
Enterotoxins produced by Staph aureus causes what kind of symptoms?
food poisoning
Why don’t the enterotoxins of Staph aureus cause toxic shock syndrome since they are superantigens like TSST-1?
location, enterotoxins occur in the gut producing food poisoning
Where can Staph infections occur? (5)
- endocarditis
- genitourinary
- muskuloskeletal
- skin & soft tissue
- Toxin based
List several skin infections caused by Staphylococcus species
- Carbuncle
- Folicullitis
- Furuncle
- Impetigo
Skin infection that Starts as a pus-filled epidermal blister that breaks to leave thick yellowish crust (common in children)
impetigo
What are symptoms of a Furuncle (boil)?
hot, tender, low fever
What is folicullitis?
infection in or around hair follicle and usually confined to that area
Why can furuncles be hard to treat?
the coagulase produced by bacteria can cause clotting wall around bacteria
What is a carbuncle?
confluence of boils which have traversed deep into the dermis entering subcutaneous fat
Suppurative infections can occur on the skin and where else?
surgical/burn wound infections and pneumonia
Scalded skin syndrome is common in?
children (esp <5)
What are symptoms of scalded skin syndrome?
Rash and peeling skin, fever
Are the rash and peeling skin of scalded skin syndrome infected with bacteria?
no, peeling caused by exfoliative toxins
scalded skin syndrome is caused by?
exfoliative toxins A & B from Staph aureus bacteria
What are symptoms associated with Toxic shock syndrome caused by TSST-1?(6)
Fever, rash, respiratory distress, irrational behavior, vomiting, multi-organ failure
What is treatment consist of for toxic shock syndrome (tsst-1)?
supportative measures & antibiotics
Staph food poisoning is different from other staph related infections because?
No infection, only intoxication by staph enterotoxins
What is the common cause of staph food poisoning?
staphylococcal enterotoxin
What is one of the ways to differentiate between intoxication and bacterial infection (of GI)?
time period of when symptoms first appear, bacterial toxins act much quicker (span of hours) while bacterial infection can take up to 48 hours
Why will heating food not make staph aureus infected food safe to eat?
the enterotoxins are heat stable
What is treatment for Staph food poisoning? (2)
- hydration
- monitor/correct electrolytes
What are symptoms of food poisoning? (2)
severe vomiting and diarrhea
Why is there only clinical presentation in diagnosing staph food poisoning?
There is no infection, (no diagnostic test to do), only toxins are causing distress to body
diagnosis of localized & systemic infections of Staph include: (3)
- culture from abscess, lesion, sputum, or blood sample
- catalase, coagulase tests
- antibiotic sensitivity (bc MRSA!)
What is normal treatment for Staph skin infection? (2)
- Drainage, topical treatment
- Chronic - systemic antibiotic
What is typical treatment for focal & systemic staph infection?
a
80-90% of Staph aureus strains are have what?
Beta lactamase
Most strains of Staph aureus even though they may have betalactamase are resistant to […] spectrum of B-lactams
Most strains of Staph aureus even though they may have betalactamase are resistant to limited spectrum of B-lactams
What is methicillin?
betalactam antibiotic that was used some time back
What protein confers resistance to methicillin?
mecA - encodes mutant penicillin binding protein (PBP2a)
HA-MRSA has a high chance of having what kind of resistance to antibiotics?
broad spectrum of antibiotics (MDR) as well as most all first line antibiotics
CA-MRSA is rarely accompanied by resistance to what?
other antibiotics
Hospital Acquired MRSA is typically found where? In whom?
hospitalized, older individuals with immunological deficiencies
HA-MRSA is MDR, list some antibiotics that it is resistant to? (5)
tetracycline, macrolides, fluoroquinolones, aminoglycosides, Tm/sulfa)
Transposable genetic elements that have gotten so big that they no longer able to transpose (large, non-mobile cassette that captures transposons & plasmids)
pathogenicity islands
HA-MRSA is found in hosptialized individuals while CA-MRSA is usually found in whom?
otherwise healthy individuals who have not been in the hospital for at least one year
CA-MRSA is usually found as what kind of infections? (area of body)
skin
What size “pathogenicity island” is found to be in CA-MRSA genomes?
small
the mecA small “pathogenicity island” has lost and gained what functions?
loss of MDR but now it’s mobile
