WEEK 4: STAPHYLOCOCCI Flashcards
Peptidoglycan Layer: Multilayered
Teichoic acids: Present in many
Periplasmic Space: Absent
Outer Membrane: Absent
LPS Content: Virtually none
Lipid & Lipoprotein: Low
Gram positive
Peptidoglycan Layer: Single layered
Teichoic acids: Absent
Periplasmic Space: Present
Outer Membrane: Present
LPS Content: High
Lipid & Lipoprotein: High
Gram negative
i. Gram (+) cocci arranged in tetrads
or clusters
i. Facultative anaerobes
ii. Catalase positive
iii. Oxidase Negative
iv. Non-motile, non-spore-forming glucose
fermenters
v. Grows in 7.5-10% NaCl
vi. Small-colony variants- rare strain,
fastidious, req. CO2, hemin for growth.
Staphylococci
What are the organisms that are positive in catalase test?
Staphylococcus & Micrococcus
What is the test that will differentiate micrococcus to staphylococcus?
- Test for the position of Cytochrome to
produce a dark-blue end product when
reacted with the Reagent.
Microdase test or Modified Oxidase Test
▪ Most clinically significant specie of Staphylococci
▪ Present in various skin surfaces and nares
▪ It causes infection when it enters a normally sterile site
▪ Cause of nosocomial or hospital-acquired infections
▪ It is also one of the common causes of food poisoning
▪ It can be cultivated by adding 7.5% to 10% NaCl
Staphylococcus aureus
Heat stable exotoxins
A-E and G-J
These Enterotoxins are associated to food poisoning
(diarrhea, vomiting); reheating contaminated food
will not prevent disease
A, B and D
This enterotoxin is linked to pseudomembranous enterocolitis
Enterotoxin B (superantigen)
- Formerly known as Enterotoxin F
(superantigen-activate aggressive immune
response) - Causes menstruating-associated TSS (Tampon
use) absorbed through vaginal mucosa
Toxic Shock Syndrome Toxin (TSST-1)
▪ Also known as Exfoliatin serotypes A and B
▪ Causes SSS (Scalded Skin Syndrome or Ritter
disease) and bullous impetigo (large pustules with
erythema)
Epidermolytic toxins A and B
Destruction of neutrophils and macrophages
Panton-Valentine Leukocidin (γ-Hemolysin)
Lyse erythrocytes
Hemolysins (α, β, δ)
▪ Conversion of fibrinogen to fibrin
▪ Bound Coagulase & Free Coagulase
Coagulase (Staphylocoagulase)
Dissolve fibrin clots and may enable spread
of infection.
Fibrinolysin (Staphylokinase)
Cleaves protein
Deoxyribonuclease (DNAse)
Hydrolyzes hyaluronic acid in connective
tissues
Hyaluronidase
Hydrolyzes lipids in the skin
Lipase
Binds to the Fc portion of IgG, neutralizes it and block phagocytosis
Protein A
Breakdown of beta-lactam ring in
penicillin molecule
Beta lactamase (Penicillinase)
mild inflammation of hair follicle or sebaceous gland
Folliculitis
large, raised, superficial abscess
Furuncles (boils)
invasive lesions develop from multiple furuncles, may progress into deeper tissues
Carbuncles
pustules are larger and surrounded by a small zone of erythema
Bullous Impetigo
extensive exfoliative (profuse peeling) dermatitis caused by staphylococcal exfoliative or epidermolytic toxin.
Scalded Skin Syndrome (Ritter disease)
fatal disease characterized by sudden onset of fever, chills, vomiting, diarrhea, muscle aches, and rash, w/c could lead to hypotension and shock.
Toxic Shock Syndrome
clinical manifestation w/ multiple causes; it is most commonly drug induced, but some cases may have been linked to infections and vaccines.
Toxic Epidermal Necrolysis (TEN)
Enhances organisms adhesion to implanted medical devices and provides refractoriness to host defense.
Exopolysaccharide “slime” or biofilm
What is the organism that is associated with Hospital acquired UTI and prosthetic valve endocarditis?
Staphylococcus epidermidis
This organism adheres to the epithelial cells lining the urogenital tract. It also causes UTI in sexually active, young females and in older women with indwelling catheters
Staphylococcus saprophyticus
- Coagulase negative (can give (+) slide method, but tube method negative)
- Community associated and hospital acquired infections (endocarditis and UTI)
Staphylococcus lugdunensis
encodes for oxacillin resistance
Gene mecA
- Vancomycin resistance
- Community associated and hospital acquired infections (endocarditis and UTI)
Staphylococcus haemolyticus
Enriched isolation of Staphylococci
Blood Agar
Selective medium for Gram-positive cocci
Colistin-nalidixic acid or Phenylethyl Alcohol agar
Selective and differential for Staphylococcus
Mannitol Salt Agar
CULTURAL CHARACTERISTICS:
medium to large; round, smooth, entire, translucent, creamy; mostly pigmented yellow and is beta hemolytic
S. aureus
CULTURAL CHARACTERISTICS:
small to medium; translucent, gray-white colonies, non hemolytic
S. epidermidis
CULTURAL CHARACTERISTICS:
large; smooth, opaque, convex; usually white, yellow or orange
S. saprophyticus
This organism is positive in Microdase
Micrococcus
This organism is resistant to Bacitracin and Furazolidone, but susceptible to Lysostaphin.
Staphylococcus
This organism is susceptible to bacitracin and furazolidone but resistant to lysostaphin.
Micrococcus
- Test for the ability of bacteria to convert fibrinogen into fibrin.
- Differentiate Staphylococcus aureus from coagulase negative staphylococci
Coagulase Test
Detects bound coagulase “clumping factor”
Coagulase Slide Test
Detects free coagulase
Coagulase Tube Test
Test the ability of the organism to hydrolyze DNA
DNase test
- Selective and differential Medium
- Test for the ability to ferment mannitol.
- Contains NaCl (7.5%), D-mannitol, phenol red
Mannitol Fermentation Test
Test for the position of cytochrome to produce a dark-blue end product when reacted with the Reagent
Microdase Test (Modified oxidase)
Latex Agglutination Test
Immunodiagnosis
PCR amplification or Nucleic Acid Probes
Molecular Testing
Matrix-assisted laser desorption ionization time-of-flight mass spectrometry
MALDI-TOF MS
isolates that are resistant to nafcillin or oxacillin
MRSA/MRSE (methicillin-resistant staphylococci)
gold standard for MRSA detection (detection of mecA gene)
Nucleic acid probes/PCR amplification
BORSA
borderline oxacillin-resistant S. aureus
VISA
vancomycin-intermediate S. aureus
VRSA
vancomycin-resistant S. aureus)
- useful in discrepant macrolide test results
- Modified double-disk diffusion test
- detects inducible (detectable in vitro when the bacteria are also exposed to erythromycin) clindamycin resistance
Macrolide Resistance
These organisms are positive in PYR test.
*S. aureus is negative
S. lugdunensis & S. intermedius
What organism is susceptible to NOVOBIOCIN and what is the organism that is resistant to it?
Susceptible: S. epidermidis
Resistant: S. saprophyticus
This organism is positive in Coagulase, DNAse and MSA Fermentation test.
S. aureus
what is the test that will show the hydrolysis of the surrounding medium if positive?
DNase test
There would be a development of blue to purple-blue color in this test if positive.
Microdase Test (Modified oxidase)
this test will differentiate Staphylococcus aureus from coagulase negative staphylococci
Coagulase Test
Positive: Clot of any size
(S. aureus)
Negative: No clot
(S. epidermidis and others)
Coagulase Tube Test
Positive:
Macroscopic clumping (white fibrin
clots) (S. aureus, S. lugdunensis, S.
schleiferi)
Negative:
No clumping (smooth milky suspension)
(S. epidermidis and others)
Coagulase Slide Test
Growth with fermentation: Yellow
halos surrounding growth.
(S. aureus)
Growth without fermentation:
Plate remains pink to red
(S. epidermidis)
Mannitol Fermentation Test
Susceptible: Zone diameter
greater than 16 mm
(S. epidermidis)
Resistant: Zone diameter less
than or equal to 16 mm
(S. saprophyticus)
Novobiocin Susceptability
