U2.2.2 Gr (+) Cocci : Laboratory Diagnosis Flashcards
Samples preferred
Aspirates are preferred
Swabs submitted
Swabs are submitted, it must be at least 2
Gram Stained Smears are used for ____
Direct Detection
Culture Media for Isolation and Identification
BAP, CAP, Broth, Selective Media, Selective & Differential Media
Broth used in Culture Media
Thioglycollate, BHI, Blood-Broth
Selective Media used in Culture Media
Columbia Colistin Nalidixic Agar, PEA
Selective and Differential Media used in Culture Media
MSA, CHROMagar Staph aureus
Colonial Characteristics
BAP
Round, Smooth, White or Yellow pigmented, creamy colonies
Hemolysis seen in S. aureus colonies
Beta-hemolvsis
Staph spp.
Colonies are small-medium sized, gray colonies; non-hemolytic
S. epidermidis
Staph spp.
medium sized colonies, yellow pigmented colonies
S. saprophyticus
Staph spp.
medium sized colonies; Beta-hemolytic
S. lugdunensis
Staph spp.
pinhead colonies (greenish discoloration) on CAP
S. aureus
detection of enzyme catalase
Catalase Test
Catalase Test
converts H2O2 to water and O2
Catalase
Catalase Test
Reagent
3% H2O2
Catalase Test
(+) Result Test
Bubbling/Effervescence
Important Test to differentiate
Staphylococcus and Micrococcus from Streptococcus
Catalase Test
Oxidase reagent reacts with cytochrome C in the cytochrome oxidase
Modified Oxidase Test
Uses Rgt: 6% tetramethyl phenylenediamine HCI
in dimethyl sulfoxide (DMSO)
Modified Oxidase Test
Modified Oxidase Test
(+) Result
Dark Blue
Differentiates Staphylococcus from
Micrococcus
Modified Oxidase Test
detection of staphylocoagulase (coagulase)
Coagulase Test
uses Rabbit Plasma
Coagulase Test
Two Types of Coagulase Test
- Slide Coagulase (Screening)
- Tube Coagulase (Confirmatory)
to differentiate organisms based on the ability to oxidize or
ferment sugars
Oxidation Fermentation Test
Oxidation Fermentation Test
(+) Color of Fermenters
Yellow
Oxidation Fermentation Test
(+) Color of Oxidizers
Red + Yellow
Oxidation Fermentation Test
(+) Color of Non-utilizer
Red
detection of DNAse activity
DNAse Test
Reagent: Use of Toluidine Blue or methyl Green
DNAse Test
DNAse Test
(+) Result
Hydrolysis of surrounding medium (clear zone)
formation of acetoin from glucose (Butylene Glycol Pathway)
Voges Proskauer Test
Differentiates Coagulase (+) Staphylococcus
Voges Proskauer Test
Voges Proskauer Test
Positive Result
Red coloration in MRVP Broth
Differentiates Coagulase (+) Staphylococcus
PYR Test (Pyrrolidonyl Arilamadase) Test
PYR Test (Pyrrolidonyl Arilamadase) Test
(+) Result
Pink or Cherry-Red coloration
Useful Test to differentiate CONS
Novobiocin (5ug)
Susceptibility
T/F Staphylococcus saprophyticus is resistant to novobiocin, indicated by the lack of a zone of inhibition around the disk.
T
Helpful for CONS
Susceptibility to Polymyxin B (300 units)
Most useful test for confirming S. lugdunensis
Ornithine Decarboxylase Test
Ornithine Decarboxylase Test
(+) Result
Violet Coloration on ODC tube
used to differentiate S. aureus from CONS
Commercially Available Rapid Agglutination Kits
useful for ID MRSA
Commercially Available Rapid Agglutination Kits
- more specific and sensitive from traditional methods
- use of plasma coated latex beads
Commercially Available Rapid Agglutination Kits
Detection of Resistance
Detection of resistance to macrolides such as clindamycin
Macrolide Resistance
Detection of Resistance
Method used in Macrolide Resistance
D-Zone Test
Detection of Resistance
Place Erythromycin and Clindamycin Disk close together
D-zone Test
Detection of Resistance
Detection of mecA gene - gold standard
MRSA
Detection of Resistance
Recommended Screening for MRSA
Cefoxitin Test
Detection of Resistance
MIC of VRSA
> 16 ug/mL
Detection of Resistance
Use of Vancomycin Agar Plate (spot inoculation)
VRSA
Detection of Resistance
T/F Healthcare Associated MRSA include sepsis, infection of surgical wound sites, pneumonia
T
Detection of Resistance
MIC of MRSA
≥ 4ug/mL
Detection of Resistance
Treatment of VRSA
Linezolid
