XVIII. Gram Positive Cocci

Staphylococcus saccharolyticus

All staphylococci are facultative anaerobes except _______

Catalase test

A biochemical test used to separate Staphylococci (+), Micrococci (+), Streptococci (-)

Vigorous bubbling

(+) result of Catalase Test

3% H2O2

Reagent used in Catalase test

S. aureus

Creamy, white with pinhead colonies in BAP

S. aureus

Jet black colonies on Tellurite agar/ Vogel Johnson Medium

Coagulase Test

Definitive test for S. aureus; Test to differentiate from other Staphylococci

Slide coagulase

Detects cell bounded coagulase/ Clumping factor

Clumping

Positive result of slide coagulase test

Rabbit plasma

Reagent used in Coagulase test

Tube coagulase

Detects free coagulase

Clot

Positive result of Tube Coagulase

phenol red

pH indicator for Mannitol Fermentation Test

7.5% NaCl

Inhibitor for Mannitol Fermentation Test

DNAse Test

aka Thermonuclease test, detects deoxyribuncluease

Lipase

A fat splitting enzyme; associated with skin infections such as boils, carbuncles, furuncles

Hyaluronidase

aka T factor or the Duran-Raynal Factor, a spreading factor that enhances invasion to tissue; causes hydrolysis of penicillin

Staphylokinase

aka fibrinolysis, dissolves fibrin clot and may enable infection to spread once clot is dissolved

Coagulase

Causes bacteria to agglutinate in plasma, converts fibrinogen to fibrin, may coat neutrophils with fibrin formed to protect organisms from phagocytosis

Protein A

Prevents phagocytosis, has the ability to bind FC portion of IgG; found on the cell wall

Enterotoxin A and B

Most staphylococcal related food poisoning are associated with Enterotoxin _______

TSST-1/ Enterotoxin F

Virulence factor of S. aureus correlated with most cases of menstruating women, particularly using tampons

Exfoliatin A and B

Hydrolyze tissue through cleavage of stratum granulosum, associated with staphylococcal scalded skin syndrome aka ritter disease

S. lugdunensis

May be mistaken for S. aureus.

Slide coagulase (+) but Tube Coagulase (-)

S. intermedius

May be mistaken for S. aureus.

PYR (+) and VP (-) (opposite of S. aureus’)

A dog pathogen

S.epidermidis

BB contaminant at RT together with B. cereus

S. epidermidis

Causes prosthetic valve infection due to the slime production or biofilm formation

S. saprophyticus

Most common cause of UTI among sexually active young woman

Modified Oxidase Test

Is the presumptive test for Micrococci

Blue color within 2 minutes

(+) Result of Modified Oxidase Test

Smith and Brown

This classification is based on hemolytic pattern

Alpha hemolytic pattern

Causes partial/ incomplete hemolysis on BAP

Greening/

Gamma Hemolytic Pattern

Unable to cause hemolysis; red/ no color change

Lancefield Classification

Classification that is based on the extraction of Carbohydrate from Streptococcal cell wall

Penicillin

Drug of choice for streptococci

M protein

Major Virulence Factor of Group A Strep

Scarlet fever

Form of pharyngitis with rashes and strawberry tongue

Rheumatic fever

Characterized by fever, inflammation of the heart, joints and blood vessels; it is also a complication of pharingitis

Erysipelas

Inflammation of the dermal layer of the skin with painful reddish patches

Cellulitis

Is a diffuse, spreading infection of subcutaneous skin tissue characterized by a defined area of redness (erythema) and accumulation of fluid

Necrotizing fascitis

aka Galloping gangrene or flesh-eating bacteria syndrome

Dick’s Test

A susceptibility test for scarlet fever

S. agalactiae

Grayish white, mucoid colonies with small zone of beta hemolysis

Sialic Acid

Virulence factor of S. agalactiae

S. agalactiae

Arrowhead zone of beta hemolysis or bowtie appearance

S. aureus

Known organism in CAMP test

purple

Positive result for hippurate test

ninhydrin

Reagent used in Hippurate Test

Group C Strep

They are the main source of streptokinase

Bile Esculin Test

Screening/ Presumptive test for Group D Non-enterococci

Blackening of the medium

Positive result for Bile Esculin Test

Group D Streptococci (Group D Nin-enterococci)/ S. bovis group

Isolation of this in the blood may be indicative of “ colon cancer”

S. pnemoniae

Lancet-shaped or bullet shaped diplococci

S. pneumoniae

Alpha hemolytic colonies, mucoid flat colonies with depressed center

S. pneumoniae

Young colonies: dome-shaped (24 hrs)

Aged colonies: nail-head/ crater-like appearance (48 hrs)

Bile Solubility Test

Confirmatory test; used to differentiate Pneumococcus from Viridans strep

Optochin Disk Test

Presumptive test for S. pneumoniae identification

Francis Test

Skin test for pneumonia

S. pneumoniae

#1 Cause of Adult Bacteria Meningitis

S. pneumoniae

Most common agent of Otitis Media

Lobar pneumonia

Associated with rusty or anchovy sauce

Viridans strep

Most common cause of SBE

Abiotrophia and Granulicatella

These are viridans strep needing Vitamin B6 for growth

Abiotrophia and Granulicatella

They are called satelliting strep since they satellite around colonies of S. aureus because they provide the pyridoxal needed

Bacitracin

This test is used to differentiate S. pyogenes from other beta-hemolytic strep

PYR

For identification of S. pyogenes and Enterococcus, more specific than bacitracin