CATALASE POSITIVE COCCI

Nonmotile

Spherical

Catalase +

Gram +

Characteristics of Staphylococci

Staphylococcus aureus

Staphylococcus intermedius

Staphylococci that is positive in coagulase test

Non-capsulated (except for few strains)

Capsule of Staphylococci

Aerobic or facultatively anaerobic

Staphylococci is what kind of bacteria according to oxygen needs?

Soil

Water

Skin

Staphylococci is often present where?

Grapelike cluster

Arrangement of Staphylococci

Broth medium

S.aureus arrangement of single, paired, tetrad and chains are found in what medium?

Non-spore forming

Spore formation of Staphylococci

Catalase test

Separates gram + cocci into two groups

3% H2O2 (hydrogen peroxide)

Reagent of catalase test for aerobic bacteria

15% H2O2 (hydrogen peroxide)

Reagent of catalase test for anaerobic bacteria

Catalase test

Enzyme catalase breaks down H2O2 to O2 and H2O

Bubble formation

Positive result of catalase test

Streptococci

What cocci species is catalase negative?

Coagulase test

To differentiate S.aureus from other staphylococci

Rabbit EDTA plasma

Reagent of coagulase test

Presence of coagulase

Principle of coagulase test

Plasma fibrinogen

Coagulase binds what, causing the organism to agglutinate plasma or clot

Coagulase

Binds plasma fibrinogen, causing the organism to agglutinate plasma or clot

Citrate-utilizing organisms

False positive of coagulase test

production of staphylokinase

False negative of coagulase test

Staphylokinase

Lyses fibrin clot and causes false negatives in coagulase test

Citrate (blue top)

What anticoagulant must NOT be used during coagulase test?

Slide method

Demonstrate the presence of cell-bound coagulase

6 hours

Coagulase test must be checked at regular intervals for how many hours?

Slide method

Rapid screening test of coagulase test

Tube method

Demonstrates the presence of extracellular coagulase (free coagulase)

Tube method

Confirm all negative slide coagulase test

Tube method

Confirmatory test for coagulase test

Mannitol fermentation test

Differentiate pathogenic Staphylococci from non-pathologic Staphylococci

Mannitol salt agar

Reagents of mannitol fermentation test

1% mannitol + 7.5% NaCl

Mannitol salt agar composition

Staphylococcus aureus ferments mannitol and produce acid

Principle of mannitol fermentation test

Yellow halos (around colony)

Positive result of mannitol fermentation test

Phenol red

pH indicator of mannitol fermentation test

Voges-proskauer test

To differentiate S.aureus from S.intermedius

Staphylococcus aureus

Positive result of VP test

Staphylococcus intermedius

Negative result of VP test

DNA medium

Methyl green dye

DNAse test reagent (1)

Clearing of dye

Positive result of dnase test

0.1% toluene blue

HCl precipitation

Reagent of dnase test (2)

Pink

Positive result of dnase test (0.1% toluidine blue)

Blue

Negative result of dnase test (0.1% toluidine blue)

Pink without precipitation

Positive result of dnase test (HCl precipitation)

Latex agglutination test

Detection of clumping factor, protein A, and PBPs

PYR test

Rapid colorimetric test used to identify specific gram positive cocci

Pink/cherry red

Positive result of PYR test

Anterior nares swab

Specimen of choice for molecular test for gram positive cocci

Nucleic acid probes

PCR amplification

Golden standard method for molecular test of gram positive cocci

Staphylococcus aureus habitat

Normal flora of human anterior nares, nasopharynx, perineal area and skin

Formites, air, or unwashed hands of healthcare workers

Infected skin lesions of healthworker to patient

Mode of transmission of S. aureus

Grows well

Laboratory media growth of Staphylococcus aureus

Tellurite lysine agar

Staphylococcus aureus also grows on what agar forming jet black colonies?

Jet black colonies

Tellurite lysine agar growth of Staphylococcus aureus

Mannitol salt agar

Staphylococcus aureus forms yellow halo on what agar?

Yellow halo

Mannitol salt agar growth of Staphylococcus aureus

7.5% NaCl

In mannitol salt agar, what helps in preventing the growth of other bacteria?

Sheep blood agar plate

Primary isolation of of Staphylococcus aureus

Beta-haemolytic colonies

Sheep blood agar growth of Staphylococcus aureus

No pigment

Broth and anaerobic culture growth of Staphylococcus aureus

Alpha haemolytic

Partial hemolysis on BAP

beta-haemolytic

Complete hemolytic on BAP

Gamma haemolytic

Non hemolytic growth on BAP

Soft butter-like;

Pin head

Uniform turbidity (broth)

Circular, opaque color

Hemolytic pattern of Staphylococcus aureus

Uniform turbidity

Haemolytic pattern growth on broth of Staphylococcus aureus

37 degC

Staphylococcus aureus readily grows on ordinary media at what temperature?

Ribitol techoic acid

Antigenic structure in cell wall of Staphylococcus aureus

Peptidoglycan

Protects S.aureus from lysis

Protein a

Unique to S.aureus; prevents antibody mediated phagocytosis PMNs

Clumping factor

Responsible for the clumping of the whole Staphylococci in the presence of plasma

Capsular polysaccharide

Protects from phagocytosis

Fc receptor

Protein A blocks what receptor immunoglobulin?

Phagocytosis

Protein a inhibits what?

Duran-reynal factor

Hyaluronidase is also known as what?

Hyaluronidase

Spreading factor

Hyaluronidase

Breaks down hyaluronic acid;

Allows the spread of bacteria in deep tissues

Staphylokinase

Fibrinolytic activity;

Dissolves clots

Lipase

Fat-splitting enzyme;

Produced by all Staphylococcus species

Sebaceous glands

Lipase targets what?

Furuncles

Carbuncles

Boils

Lipase target sebaceous glands causing what?

DNAse and phosphatase

Lowers viscosity, giving the pathogen more mobility

Beta lactamase

Breaks down beta-lactam drugs;

Giving resistance to drugs

100 degC for 30 min

Staphylococcus aureus is heat stable at what temp?

Gastric acid and jejunal enzymes

Staphylococcus aureus toxin is resistant to what?

Vagus nerve

S.aureus stimulates what (neurotoxin)

Vomiting

S.aureus produces neurotoxins that stimulates the vagus nerve causing what?

Enterotoxins a,b,d

S.aureus toxin that is responsible for causing food poisoning and diarrhea

Pseudomembranous enterocolitis

S.aureus enterotoxin b causes what?

Enterotoxin f

S.aureus enterotoxin associated with TSS

Exfoliative toxins

S.aureus enterotoxin that causes Ritter’s disease and Bullous impetigo

Alpha toxin

S.aureus cytolytic toxin that is lethal and dermonecrotic

Beta toxin

S.aureus cytolytic toxin that is lethal and dermonecrotic and produces hot and cold lysin

Leukocidin (Panton-valentine)

S.aureus cytolytic toxin that suppresses phagocytosis;

Associated with cutaneous infections, necrotizing pneumonia, and community associated Staphylococcal infections

TSST-1

Causes TSS that is seen in menstruating women who use tampons;

Causes staphylococcal scarlatiniform syndrome

Methicillin

S.aurues is resistant to what? (MRSA)

Penincillin resistant (S.aureus)

mechA gene coding for an altered penincillin binding protein;

Cell wall is incapable of binding penincillin

Mauve colonies within 24 hrs

S.aureus chromogenic positive result

Erm gene

Methylation of 23s rna-resistance to erythromycin

Msr A gene

Efflux mechanism;

Erythromycin resistance but susceptible to clindamycin

Erythromycin

S.aureus msr a gene causes what resistance?