Staphylococcus Flashcards
Produces white colonies that tend to turn a buff-golden color with time.
S. aureus
Found in the environment and as members of the indigenous skin microbiota.
Micrococci
[5] Most important human pathogens
- Staphylococcus aureus
- Staphylococcus epidermis, capitis, hominis
- Staphylococcus saprophyticus
- Staphylococcus lugdunensis
- Staphylococcus haemolyticus
a-toxin aka
a-hemolysin
It is a protein secreted by almost all strains of S aureus, except coagulase-negative staphylococci.
a-toxin
In addition to lysing erythrocytes, can damage platelets and macrophages and cause severe tissue damage.
[toxins]
a-hemolysin
It lyses the cytoplasmic membranes by direct insertion into the lipid bilayer to form transmembrane pores.
[toxins]
pore-forming cytotoxin
Acts on sphingomyelin in the plasma membrane of erythrocytes and is also called the “hotcold” lysin.
[toxins]
β-Hemolysin
Enhanced hemolytic activity on incubation at 37° C and subsequent exposure to cold (4° C).
“hot cold” feature
CAMP means
Christie, Atkins, and Munch-Petersen
Test performed in the laboratory to identify group B streptococci.
CAMP
It binds to a specific cell membrane ganglioside found only in the stratum granulosum of the keratinized epidermis of the skin.
Exfoliatin
Exfoliative toxin is also known as?
Epidermolytic toxin
It causes the epidermal layer of the skin to slough off and is known to cause staphylococcal SSS, sometimes referred to as
Ritter disease
This toxin has also been implicated in bullous impetigo.
Exfoliatin
It is considered a virulence marker.
Enzymes
[3] Capable of destroying tissue capable of destroying tissue.
- Protease
- Lipase
- Hyaluronidase
In the cell wall of S. aureus
Protein A
Its ability to bind the Fc portion of immunoglobulin G (IgG)
Protein A
Stimulates gastrointestinal symptoms (primarily vomiting)
S. aureus enterotoxins
Most commonly caused by enterotoxins A, B, and D
[enterotoxins]
Staphylococcal food poisoning
Sometimes G and I are associated with TSS.
[enterotoxins]
Enterotoxins B
Has been linked to staphylococcal pseudomembranous enterocolitis.
[enterotoxins]
Enterotoxin B
A family of secreted proteins that are able to stimulate systemic effects as a result of absorption from the gastrointestinal tract after ingestion.
Superantigens
Menstruating-associated TSS.
Toxic Shock Syndrome Toxin 1
Previously referred to as enterotoxin F.
Toxic Shock Syndrome Toxin 1
A superantigen stimulating T-cell proliferation and the subsequent production of a large amount of cytokines that are responsible for the symptoms.
TSST - 1
Superficial skin infection that typically develops in a hair follicle, sebaceous gland, or sweat gland.
Furuncle or boil
Often a complication of acne vulgaris.
Furunculosis
Occurs most often on the back of the neck but it may involve other skin sites.
Carbuncle
Relatively mild inflammation of a hair follicle or oil gland; the infected area is raised and red.
Folliculitis
Repeated attacks of boils.
Chronic Furunculosis
Caused by the same strain of S aureus.
Chronic Furunculosis
It has been long known as a secondary invader in group A streptococcal pustular impetigo.
[staphy]
Staphylococcus aureus
Strains of S aureus that produce exfoliatin cause a characteristic form called?
Bullous impetigo
A localized form of staphylococcal scalded skin syndrome.
Bulluos impetigo
Results from the production of exfoliatin in a staphylococcal lesion.
[skin syndrome]
Staphylococcal scalded skin syndrome
A bullous exfoliative dermatitis that occurs primarily in newborns and previously healthy young children.
SSS
Characterized by a sudden onset of fever, quickly progress to hypotension and shock.
Toxic Shock Syndrome
It is most commonly drug induced, but some cases have been linked to infections and vaccines.
Toxic Epidermal Necrolysis (TEN)
Can be resolved by the administration of steroids early in the initial stages of presentation, whereas steroids aggravate SSS.
Toxic Epidermal Necrolysis (TEN)
Staphylococci that do not produce coagulase are referred to as?
CoNS
[2] They are occasional isolates and can be significant pathogens.
S. haemolyticus
S. lugdunenesis
It is associated mainly with urinary tract infections (UTIs), predominately in adolescent girls and young women.
S. saprophyticus
A CoNS occasionally recovered in wounds, septicemia, UTIs, and native valve infections.
S. haemolyticus
It has been associated with catheter related bacteremia and endocarditis.
S. lugdunensis
Infections caused by this are predominantly hospital acquired.
S. epidermis
It is a common cause of health care-acquired UTIs.
S. epidermis
UTIs in young women.
S. saprophyticus
This organism can be more virulent and can clinically mimic S. aureus infections.
S. lugdunensis
It has been known to contain the gene mecA that encodes oxacillin resistance.
S. lugdunensis
It appears as gram positive cocci, usually in clusters.
[s&m]
Staphylococci
It appears as gram positive cocci in tetrads, rather than large clusters.
[s&m]
Micrococci
Contains salt (7.5%), the sugar mannitol, and phenol red as the pH indicator.
[culture]
Mannitol Sal Agar
S. aureus that can grow in the presence of salt and ferment mannitol produce colonies surrounded by a?
[culture]
yellow halo
It is a rapid method to differentiate Staphylococcus from Micrococcus by detection of the enzyme oxidase.
[test]
Microdase test
This test is used to detect the presence of
cytochrome oxidase enzymes.
[test]
Catalase test
[2] S. aureus produces two forms of coagulase:
- Bound
- Free
[2] They are require susceptibility testing.
- S. aureus
- S. lugdunensis
Breaks down the β-lactam ring of many penicillins, most S. aureus isolates are resistant to penicillin.
β-lactamases (penicillinases)
Does not require routine antimicrobial susceptibility testing because isolates typically are sensitive to agents commonly used to treat UTI.
[staphy]
S. saprophyticus
Remains the treatment of choice for MRSA.
Vancomycin
A better inducer of mecA-mediated resistance.
Cefoxitin
Yellow colonies fermenting mannitol as evident by the yellow color of the agar.
Staphylococcus aureus
White colonies, no mannitol fermenting, as evident by the original pink color of the agar.
Staphylococcus epidermidis
Bacitracin resistant and Furazolidone sensitive.
Staphylococcus epidermis
Bacitracin sensitive and Furazolidone resistant.
Micrococcus
MRSA means
Methicillin - Resistant Staphylococci Aureus
CAMRSA means
Community Associated Methicillin - Resistant Staphylococcus Aureus
HACO - MRSA means
Health care - Associated Community - Onset Methicillin - Resistant Staphylococcus Aureus
It is often found only in association with Panton-Valentine leukocidin (PVL).
[cytolytic toxins]
δ-Hemolysin
Bacitracin resistant and Furazolidone sensitive
Staphylococcus epidermis
Bacitracin sensitive and Furazolidone resistant.
Micrococcus
How much drop of hydrogen peroxide solution is placed on a slide, and a small amount of the bacterial growth is placed in the solution.
3%
It is unstable and breaks down easily on exposure to light.
Hydrogen peroxide
A third type of MRSA is termed
HACRO - MRSA or Health care - associated community - onset methicillin resistant Staphylococcus areus
To determine the organism’s susceptibility to clindamycin, this test has been used in microbiology laboratories.
Modified Kirby Bauer Test
