staph and stre[[ Flashcards
culturing on blood agar plates, growing as round, smooth, white (sometimes yellowish) and beta-hemolytic (completely lyses RBCs)
staphylococcus
To differentiate Staphylococa, Micrococaus, and Streptococaus
CATALASE TEST
Transfer a small amount of colony into a clean glass slide then drop 3% H2o2
CATALASE TEST
result in catalse test
RESULT
(+) Continuous Bubbling
(-) No or few bubbles are formed
positive and negative example in catalase
QUALITY CONTROL
(*) Control = Staphylococcus aureus
(-) Control = Streptococcus pyogenes
To differentiate Staphylococcus aureus from other StaphylococcoI spp.
COAGULASE TEST
an enzyme that reacts with fibrinogen to for a clot
coagulase
SLIDE coagulase method
: Place a drop of rabbit’s plasma (EDTA) onto a slide then emulsify a loopful of bacteria to create a suspension. Rock the slide for 5-10 seconds and observe for agglutination
TUBE method
: emulsify a loopful of bacteria in 0.5ml of rabbit’s plasma and incubate in 37°C for 4 hours. Observe for clot formation every 30 mins
- detects clumping factors in the surface of bacterial cells.
COAGULASE- SLIDE METHOD
- Fibrinogen → clumping factor → Fibrin
COAGULASE- SLIDE METHOD
Detects thrombin-like molecule called coagulase reacting factor (CRF).
COAGULASE- TUBE METHOD
extracellular molecule that will react with CRF
Staphylocoagulase
- Fibrinogen→ coagulase-CRF complex → Fibrin
COAGULASE- TUBE METHOD
PURPOSE To differentiate Staphylococc from Micrococci
MODIFIED OXIDASE TEST
Bacteria that possess cytochrome C produce a dark-blue end product when reacted with Modified Oxidase rgt
MODIFIED OXIDASE TEST
result of microdase
RESULT
(+) Development of purple-blue color
(-) No Color change
positive and negative control for microdase test
(+) Control = Micrococous luteus
(-) Control = Staphylococeus aureus
Lysostaphin
Lysostaphin (200 ug/mL)
> Staphylococcus (S) ; Micrococcus (R)
Lysosome R AND S
Lysosome (50 mg disk)
Micrococcus - S
Staphylococcus - R
BACITRACIN S AND R
Bacitracin (0.04U)
Micrococcus - S
Staphylococcus - R
NovobiocinS AND R
S
S. aureus ; S. epidermidis
R
S. saprophyticus
Furazolidone S AND R
Furazolidone (100 ug)
Staphylococcus
Micrococcus
WHICH IS THE GLUCOSE FERMENTER AND OXIDIZER BETWEEN STAPH AND MICROCOCCUS
STAPH -FERMENTER
MICRO- OXIDIZER
STREP FOUND IN GENITAL TRACT AND OCCASIONAL COLONIZER OF URT
S. AGALACTIAE
strep in oral caity, GI tract, female genital tract
s. bovis
normal flora of gi tract, and female genital tract
enteroccocus faecalis
not a normal flora, skin urt
s pyogenes
causes rheumatic fever, carlet fever, pharyngitis, glomerulonephritis, pyogenic infection
s pyogenes
neonatal sepsis, meningitis and [uereral fever
s. agalactiae
pneumonia, meningitis, ottitis media
s pneumoniae
endocarditis and uti
s bovis
nosocomial infection and uti
enterococcus faecalis
- Small, transparent, smooth, sometimes beta-hemolytic
streptococus
o2 requirement of strep
The Species of Streptococci are facultative anaerobe. Some are capnophilic
how m
any hours do you incubatestrep
18-48 hours
- Grayish white, transparent to translucent, matte or glossy with large zone of hemolysis
Group A Streptococci
- Larger than GAS, translucent to opaque. Flat colonies, glossy with narrow zone of beta-hemolysis.
Group B Streptococci
Small, gray, glistening umbilicated colonies (might resemble a doughnut). May appear mucous if
polysaccharide producing strain. Alpha hemolytic
Pneumococci
Minute to small, translucent, gray, Dome-shaped or umbonate center. Alpha hemolytic or non hemolytic
Viridans
- Small, Cream or white colored colonies. Smooth, entire margin. Alpha, Beta, or non-hemolytic
Enterococcus
partial lysis of rbc around colony
alpha hemolytic
greenish discoloration of area around colony
beta hemolysis
no lysis around colony
nonhemolytic
small area of intact rbc around colony or no change in agar
nonhemolytic
small area of intact rbc around colony
alpha prime (a’) or wide zone
alpha hemolytic in respiratory tract
viridians
respiratory tract, pathogenic
s pneumoniae
alpha hemolytiv in gi tract
enterococcus
beta hemolytic strep in gi tract
pyogenes
genitourinary tract, b hemolytic
s agalactiae
drug very useful for treating superficial skin infections but it is too toxic for systemic use;
Bacitracin
bacitracin is a polypeptide antibiotic produced by
Bacillus subtilis
Interferes with the peptidoglycan synthesis of bacteria
bacitracin
To differentiate GAS from other Beta-hemolytic streptococci.
BACITRACIN SUSCEPTIBILITY
taxo a test result
RESULT
Susceptible -Zone of inhibition > 10mm
Resistant- No zone of inhibition
positive and negative control in taxo a
QUALITY CONTROL
Susceptible Control = Streptococcus pyogenes
Resistant Control = Streptococcus agalactiae
Interferes ATPase and ATP production.
aka optochin
ethyl hydrocupreine hydrochloride (Optochin)
To determine the effect of ethyl hydrocupreine hydrochloride
taxo p or optochin susceptibility
sensitive to optochin
Pneumococci is sensitive while other alpha hemolytic streptococci are not
optochin test result
RESULT
Susceptible - Zone of Inhibition 214mm
Resistant - No zone of inhibition
result remark in optochin
Results that are <1.4mm, must be confirmed by doing bile solubility
CAMP (
Christie, Atkins, and Munch- Petersen)
To differentiate GBS from other streptococcal specie.
CAMP
that acts synergistically to beta hemolysins produced by s. aureus.
CAMP factor
RESULT OF CAMP
RESULT
(+) Presence of enhanced hemolysis (arrow head hemolysis near the Juncture point of the organism
- Streptococcus agalactiae
(-) no enhanced hemolysis
- Streptococcus pyogenes
test cAn also be used for Listeria monocytogenes
CAMP
hydrolyzed by the enzyme hippuricase into glycine and Benzoic acid
hippurate
Glycine will be deominated by ninhydrin reagent to from a purple colored product.
Hippurate hydrolysis
Hippurate hydrolysis procedure
PROCEDURE
Make a bacterial suspension in Iml of sterile water then place a hippurate disk.
Incubate for 2 hrs then add 0.2 ml ninhydrin reagent. Reincubate for 15-30 min and observe for color development
hippurate hydrolysis result
RESULT
(+) Deep purple color
(-) Colorless or yellow-pink color
positive and negative control in hippurate hydrolysis
QUALITY CONTROL
(+) Control = Streptococcus agalactiae (ATCC| 2386)
(-) Control = Streptococcus pyogenes (ATCC19615)
False positive result may occur if incubated more than 30 min
hipppurate hydrolysis
For presumptive identification of GAS and enterococci,
L- pyrrolidonyl Arylamidase (PYR) TEST
result in pyr
(+) Bright Red Color
(-) No color change / orange color
To determine the ability of an organism to grown in high salt environment
SALT TOLERANCE TEST
SALT TOLERANCE TEST result
RESULT
(+) Visible turbidity w/ or w/o color change (Purple to yellow)
(-) No turbidity and no color change.
Presumptive Identification of Enterococci and Streptococcus bovis group.
BILE ESCULIN TEST PURPOSE:
are Inhibited by bile salts.
Gram positive bacteria, besides Streptococcus bovis and Enterococcus,
result of be test
RESULT
(+) Growth and Blackening of the agar slant
(-) No growth and no blackening of the agar
positive and negative control in slat tolerance test
v+) Control = Enterococcus faecalis
(-) Control = Escherichia coli
Steps in laboratory identification
- Perform Direct examination first
- Gm(+) cocci → Perform Catalase
- If Catalase (+) → Proceed to Staphylococcal ID
- If Catalase (-) → Proceed to Streptococcal ID
- For Streptococcal ID, observe for Hemolysis
