WEEK 4: STAPHYLOCOCCI Flashcards by ZACHARIE JAEDIEL GONZAGA

Peptidoglycan Layer: Multilayered
Teichoic acids: Present in many
Periplasmic Space: Absent
Outer Membrane: Absent
LPS Content: Virtually none
Lipid & Lipoprotein: Low

Gram positive

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Peptidoglycan Layer: Single layered
Teichoic acids: Absent
Periplasmic Space: Present
Outer Membrane: Present
LPS Content: High
Lipid & Lipoprotein: High

Gram negative

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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

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What are the organisms that are positive in catalase test?

Staphylococcus & Micrococcus

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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

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▪ 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

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Heat stable exotoxins

A-E and G-J

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These Enterotoxins are associated to food poisoning
(diarrhea, vomiting); reheating contaminated food
will not prevent disease

A, B and D

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This enterotoxin is linked to pseudomembranous enterocolitis

Enterotoxin B (superantigen)

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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)

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▪ 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

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Destruction of neutrophils and macrophages

Panton-Valentine Leukocidin (γ-Hemolysin)

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Lyse erythrocytes

Hemolysins (α, β, δ)

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▪ Conversion of fibrinogen to fibrin
▪ Bound Coagulase & Free Coagulase

Coagulase (Staphylocoagulase)

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Dissolve fibrin clots and may enable spread
of infection.

Fibrinolysin (Staphylokinase)

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Cleaves protein

Deoxyribonuclease (DNAse)

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Hydrolyzes hyaluronic acid in connective
tissues

Hyaluronidase

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Hydrolyzes lipids in the skin

Lipase

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Binds to the Fc portion of IgG, neutralizes it and block phagocytosis

Protein A

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Breakdown of beta-lactam ring in
penicillin molecule

Beta lactamase (Penicillinase)

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mild inflammation of hair follicle or sebaceous gland

Folliculitis

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large, raised, superficial abscess

Furuncles (boils)

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invasive lesions develop from multiple furuncles, may progress into deeper tissues

Carbuncles

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pustules are larger and surrounded by a small zone of erythema

Bullous Impetigo

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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