[2S] UNIT 3.1 Gram (+) Cocci - Staphylococci Flashcards
BACTERIA ACCORDING TO SHAPE
Rod-shaped
bacillus/bacilli
Gr(+) or Gr(-) & Shape?
Neisseria and Moraxella
Gr(-) cocci
BACTERIA ACCORDING TO SHAPE
Round/Spherical
coccus/cocci
Gr(+) or Gr(-) & Shape?
Staphylococcus and streptococcus
Gr(+) cocci
Gr(+) or Gr(-) & Shape?
Bacillus & Erysipelothrix
Gr(+) bacilli
Gr(+) or Gr(-) & Shape?
most bacilli
Gr(-) bacilli
Gr(+) or Gr(-) & Shape?
Listeria & Mycobacterium
Gr(+) bacilli
Gr(+) or Gr(-) & Shape?
Enterobacteriaceae & Haemophilus
Gr(-) bacilli
Gr(+) or Gr(-) & Shape?
Spirochetes: Treponema, Borrelia, Leptospira
Gr(-) spiral
GENERALITIES
grape-like clusters; due to their morphological arrangement when seen under the light microscope
Staphylococcus
GENERALITIES
Belong to Family Staphylococcaceae
Staphylococcus
GENERALITIES
○ Generally seen as cocci in clusters (most cases)
○ No tetrads
Gr (+) Cocci in clusters, in pairs, singly
GENERALITIES
All are Catalase (+) except?
S.aureus subsp. anaerobius
and S. saccharolyticus
If tetrads are seen, it might be?
micrococcus
GENERALITIES
would detect the enzyme catalase
Catalase test
GENERALITIES
Positive result for Catalase Test
bubbling of solution or effervescence after addition of 3% hydrogen peroxide
T/F: All staphyloccocus are modified oxidase negative except t S. sciuri, S. lentus, S. vitulus (are modified oxidase positive)
T
Modified Oxidase Test is also known as?
Microdase Test
Positive result for Modified Oxidase Test
blue-purple coloration
All are non-motile and non-spore formers
Staphylococcus
T/F: Majority of motile bacteria are bacilli and has no flagella
T
T/F: All are halophilic. Growing in high amount of NaCl or salt, at around 7.5%
T
T/F: Motility test is commonly done on gram (+)
F; gram -
Gaseous Requirement: _________ except Staphylococcus aureus subspecies anaerobius &
Staphylococcus saccharolyticus
Aerobic or Facultative Anaerobe
T/F: Staphylococcus are nitrate reducers
T
○ Medium sized
■ Pinhead (larger than pinpoint)
○ Raised
○ Creamy with smooth margin
○ Lemon yellow or golden colonies
○ Buttery-looking
Staphylococcus
STAPH W/ DISTINCT COLORS
white
S. albus
Colonies produced after 18 to 24 hours of incubation are medium sized (4 to 8 mm)
Staphylococcus
STAPH W/ DISTINCT COLORS
golden yellow (due to the pigment staphyloxanthin)
S. aureus
STAPH W/ DISTINCT COLORS
lemon yellow (more pronounced in Loeffler’s serum slant)
S. citreus
Rare strains of _______ are fastidious, requiring carbon dioxide, hemin, or menadione for growth.
staphylococci
These so-called small colony variants (SCVs) grow on media containing ______, forming colonies about 1/10 the size of wild-type strains even after 48 hours or more of incubation.
blood
an initial test is performed to differentiate Staphylococcus spp.
Coagulase Test
T/F: Catalase test is more useful in differentiating
Staphylococcus from Streptococcus
T
Usually done after the catalase test (have identified that the organism is Staphylococcus spp.)
Coagulase Test
CONS OR COPS
Staphylococcus aureus
CONS OR COPS
S. intermedius (associated with animal infections)
COP
CONS OR COPS
S. aureus subspecies anaerobius
COPS
CONS OR COPS
S. delphini
COPS
CONS OR COPS
S. epidermidis, S. haemolyticus
CONS - Novobiocin Susceptible
CONS OR COPS
S. lutrae
COPS
CONS
After testing the isolate for the antibiotic novobiocin, if they would have a _____
zone of inhibition, they would be novobiocin susceptible.
clear
CONS OR COPS
S. saprophyticus, S. xylosus
CONS - Novobiocin Resistant
No or little zone of inhibition after testing
it with the antibiotic novobiocin.
CONS - Novobiocin Resistant
Primary reservoir
Human nares particularly S. aureus
GENERALITIES
Belong to Family Micrococcaceae
GENERALITIES
Gram (+) cocci in clusters; in tetrads (in fours)
GENERALITIES
Usually normal flora and associated with skin lesions and more commonly isolated among immunocompromised
patients
GENERALITIES
Less medically relevant than Staphylococcus but may be easy confused as Staphylococcus
GENERALITIES
May be found in the environment (ubiquitous in nature)
MICROCOCCI
■ Negative in catalase test
■ Found in air, dust, and hospital equipments
Aerococcus
MICROCOCCI
■ Isolated in the middle ear of the infected patient
■ Commensal organisms
Alloiococcus otitis
Staph vs Micrococcus
Catalase test
Both positive
MICROCOCCI
■ emerging pathogen (UTI, endocarditis)
■ Capsulated gram (+) cocci
■ Emerging pathogen
Rothia mucilaginosa / Stomatococcus mucilaginosus
Staph vs Micrococcus
Aerobic growth
Both yes
Staph vs Micrococcus
Glucose Utilization
Staph: Fermentative
Micro: Oxidative / Nonsaccharolytic
Staph vs Micrococcus
Anaerobic growth
Staph
Staph vs Micrococcus
Benzidine
S : Negative
M : Positive
Staph vs Micrococcus
Lysostaphin (>/=200 g/L) (Resistance)
S : Susceptible
M : Resistant
Staph vs Micrococcus
Modified Oxidase/ Microdase
S : Negative except for S.
sciuri, S. lentus, S. vitulus
M : Positive
Staph vs Micrococcus
Bacitracin/Taxo A Disk
(Resistance) (0.04 unit)
S : Susceptible
M : Resistant
Staph vs Micrococcus
Production of Acid from
Glycerol in the Presence of Erythromycin
S : Positive
M : Negative
Staph vs Micrococcus
Lysosome
S : Resistant
M : Susceptible
Staph vs Micrococcus
Growth on furoxone-tween 80-oil red o agar
S : Negative
M : Allow growth of micrococcus
CLINICALLY SIGNIFICANT STAPHYLOCOCCI : Coag +/-
Staphylococcus aureus
Coag +
CLINICALLY SIGNIFICANT STAPHYLOCOCCI : Coag +/-
● Staphylococcus epidermidis
● Staphylococcus lugdunensis
● Staphylococcus saprophyticus
Coag -
Staph vs Micrococcus
○ S. warneri
○ S. capitis
○ S. hominis
○ S. schleiferi
○ S. haemolyticus
Less common but implicated as opportunistic pathogens
Most clinically significant staph
S. aureus
Can be recovered from almost any clinical specimen
○ Normally found in the human nares
○ Found in swabs
S. aureus
Can cause acne, sty, celulities & folliculitis
S. aureus
Can cause toxic shock syndrome, scalded skin syncrome, food poisoning, impetigo, and furuncles and carbuncles
S. aureus
STAPHYLOCOCCUS AUREUS
■ Systemic illness that can lead to hypotension
■ Certain groups of people would have a higher
risk, particularly females who use tampons.
Toxic Shock Syndrome
STAPHYLOCOCCUS AUREUS
Skin infections affecting the hair follicles
Furuncles and carbuncles
STAPHYLOCOCCUS AUREUS
Affect infants or neonates
Scalded Skin Syndrome
STAPHYLOCOCCUS AUREUS
more deep seated affecting the hair follicles
Furuncles
Also an important cause of nosocomial and opportunistic infections
S. aureus
STAPHYLOCOCCUS AUREUS
shallow, affectes nearby or adjacent hair follicles
Carbuncles
PROTEIN DETERMINANTS
○ Present on the cell surface
○ Cell wall component
○ Prevent opsonization
○ Binds to antibodies (IgG)
Protein A
PROTEIN DETERMINANTS
Antiphagocytic
Protein A
PROTEIN DETERMINANTS
Endotoxin like activity
Peptidoglycan and Teichoic Acids
PROTEIN DETERMINANTS
Protein A will bind to what antibody?
IgG
PROTEIN DETERMINANTS
Activates complement, Interleukin 1
■ Activation of complement can lead to inflammation
■ Interleukin 1 can trigger fever
Peptidoglycan and Teichoic Acids
3 Protein Determinants of S. aureus
Protein A
Capsular Polysaccharide
Peptidoglycan & Teichoic Acids
PROTEIN DETERMINANTS
Chemotactic factor for PMN
Peptidoglycan and Teichoic Acids
S. AUREUS - VIRULENCE FACTORS
affects the smooth muscle of the blood vessels
Alpha hemolysin
S. AUREUS - VIRULENCE FACTORS
■ Heat-labile (destroyed by heat)
■ Type of sphingomyelinase
■ Hot-cold lysin
Beta hemolysin
S. AUREUS - VIRULENCE FACTORS
Lyses red blood cells
Hemolysins (alpha, beta, gamma and delta)
S. AUREUS - VIRULENCE FACTORS
■ Less toxic
■ Associated to Panton Valentine Factor
Gamma
S. AUREUS - VIRULENCE FACTORS
Toxic to red blood cells and other mammalian cells
Delta
S. AUREUS - VIRULENCE FACTORS
○ Penicillin binding protein
○ Binds to penicillin making the organism resistant
○ Often studied among Methicillin-resistant
Staphylococcus aureus (MRSA)
PBP2
S. AUREUS - VIRULENCE FACTORS
Leukocidin (destroys WBC)
Panton Valentine Factor
S. AUREUS - VIRULENCE FACTORS
○ The one we detect in coagulase test
○ Significant in the identification process of the
organism
○ Clots fibrinogen
Staphylocoagulase
S. AUREUS - VIRULENCE FACTORS
○ Superantigen
■ Can cause T cells to proliferate
■ Induce cytokine release
● Cytokine - an important cell secretion in inflammation
TSST-1
S. AUREUS - VIRULENCE FACTORS
○ Causes almost all cases of menstruating TSS
○ Formerly called Enterotoxin F
TSST-1
S. AUREUS - VIRULENCE FACTORS
○ Cause staphylococcal food poisoning, diarrhea,
vomiting but the disease is self limiting
○ Heat-stable toxins
Enterotoxins
S. AUREUS - VIRULENCE FACTORS
○ Epidermolytic toxin that can cause sloughing off of the skin
○ Implicated in Scalded Skin Syndrome (SSS), Ritter-Lyell Disease or Dermatitis Exfoliativa
○ Also implicated in Bullous Impetigo
Exfoliative Toxin
S. AUREUS - VIRULENCE FACTORS
extracellular toxins that affect RBCs and WBCS
Cytolytic Toxins
S. AUREUS - VIRULENCE FACTORS
Group?
Toxic Shock Syndrome
BCGI
S. AUREUS - VIRULENCE FACTORS
Group?
Staphylococcal Food Poisoning
ABD
S. AUREUS - VIRULENCE FACTORS
Group?
Staphylococcal pseudomembranous enterocolitis
B
S. AUREUS - VIRULENCE FACTORS
Group?
Also known as Toxic shock syndrome toxin 1 (TSST-1) / Pyrogenic Exotoxin C
F
S. AUREUS - VIRULENCE FACTORS
(cell free or bound); localization of abscess
■ Virulence marker
■ Used for diagnostic purposes
ENZYME: Staphylocoagulase
4 other factors (enzyme not related to pathogenicity)
● Penicillinase
● Catalase
● Thermonuclease
● Gelatinase
ASSOCIATED INFECTIONS
Exfoliative dermatitis that occurs among newborns
and previously healthy young children; also seen
among adults with chronic renal failure
SSS: Scalded Skin Syndrome
ASSOCIATED INFECTIONS
○ Multisystemic disease
○ 2 Categories: Menstruating Associated and Nonmenstruating associated
○ S/S: sudden onset of fever, chills, vomiting, diarrhea, muscle pain, rashes, can progress to hypotension and
shock
Toxic Shock Syndrome
ASSOCIATED INFECTIONS
has multiple causes; maybe
due to a hypersensitivity reaction; very similar initial
presentation to that of SSS
Toxic Epidermal Necrolysis
ASSOCIATED INFECTIONS
○ Lesions may be localized or generalized
○ Cutaneous erythema followed by peeling of skin
SSS: Scalded Skin Syndrome
ASSOCIATED INFECTIONS
○ Involves the ingestion of a preformed enterotoxin from food that is improperly stored
○ S/S: appear rapidly (incubation period: 2-8 hrs);
nausea, vomiting, diarrhea, abdominal pain
Staphylococcal Food Poisoning
ASSOCIATED INFECTIONS
Most common enterotoxin causing food poisoning
Enterotoxin A
Most common staph for osteomyelitis
S. aureus
OTHER INFECTIONS
Has been known to occur
secondary to influenza virus infection
Staphylococcal pneumonia
OTHER INFECTIONS
Develops as a contiguous, lower respiratory tract infection or a complication of bacteremia, is characterized by
multiple abscesses and focal lesions in the pulmonary parenchyma
Staphylococcal pneumonia
OTHER INFECTIONS
○ Observed among intravenous drug users.
○ The organisms gain entrance to the bloodstream via contaminated needles or from a focal lesion present
on the skin or in the respiratory or genitourinary tract
Staphylococcal bacteremia
OTHER INFECTIONS
○ Occurs as a manifestation secondary to bacteremia.
○ Inflammation of the bone
Staphylococcal osteomyelitis
OTHER INFECTIONS
○ Affecting the heart
○ For those who have undergone heart surgery
Endocarditis
Usually a normal inhabitant of the skin (predominant
normal flora) but is a
common source of hospital-acquired infections and
often a contaminant in improperly collected blood
culture specimens
S. epidermidis
● Can cause opportunistic infections (associated with
endocarditis)
● Most common cause of prosthetic valve endocarditis and wound infection
S. epidermidis
Able to colonize prosthetic devices or surgical devices if
not properly disinfected
S. epidermidis
T/F: S. epidermidis is coagulase (-)
T
2nd most common cause of UTIs
S. saprophyticus
○ This species adheres more effectively to the epithelial cells lining the urogenital tract than other CoNS
○ Rarely found on other mucous membranes or skin
surfaces
S. saprophyticus
T/F: S. saprophyticus is coag -
T
Associated with pyelonephritis and cystitis in young women and in older men using catheters
S. saprophyticus
Colony counts may be <100,000 CFU/mL but is still
significant to be considered as a cause of UTI
S. saprophyticus
T/F: UTI: colony count should be 100,000 or more but if it is less than 100,000, it is not typically considered UTI but there are certain exceptions, like S. saprophyticus
T
T/F: When the organism identified is S. saprophyticus, we do not regard it as UTI even if the colony count is <100,000 CFU/mL
F; we regard it as UTI
Also associated with nosocomial pneumonia
S. saprophyticus
● A cause of nosocomial infections such as endocarditis, septicemia, meningitis, skin and soft tissue infections
● Coagulase (-)
S. lugdunensis
This organism is more virulent than other and is known to contain the gene mecA, which encodes oxacillin resistance
S. lugdunensis
Causes an aggressive type of endocarditis
S. lugdunensis
Positive for the clumping factor for the Slide Coagulase Test
S. lugdunensis
OTHER STAPHYLOCOCCI
Staph in scalp
S. capitis
OTHER STAPHYLOCOCCI
is a commonly isolated CoNS. It has been reported in wounds, bacteremia, endocarditis, and UTIs. Vancomycin resistance exists
S. haemolyticus
OTHER STAPHYLOCOCCI
In dogs
S. intermedius
OTHER STAPHYLOCOCCI
In dolphins
S. delphini
LABORATORY DIAGNOSIS
T/F: Aspirates are preferred (especially if there is inflammation); if swabs are submitted, it must be at least 2 (in duplicates)
T
LABORATORY DIAGNOSIS
● Expect to find gram (+) cocci in clusters, singly, or in pairs
● Inflammation: you will find abundant neutrophils
● After doing the gram stain, you will be applying it to the culture medium
Direct Detection (Gram Stain)
CULTURE MEDIA FOR ISOLATION AND IDENTIFICATION
To see if there is a hemolytic pattern
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
○ To allow only gram (+) cocci to grow in the medium
○ CCNA: Selective for gram (+)
SELECTIVE: CCNA, PEA
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
● Generally: round, Smooth, White or Yellow pigmented,
creamy colonies with smooth edges
● To check hemolytic pattern
BAP
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
■ Usually has mauve or pink coloration in colonies;
presumptive for S.aureus
■ Other than S.aureus will grow as blue organisms
■ Differentiates S. aureus from other organisms
SELECTIVE & DIFF: CHROMagar
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
Differentiates mannitol fermenters from the
non-mannitol fermenters
MSA
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
Non-mannitol fermenter result
Pink (S. epidermidis)
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
T/F: S. aureus is a beta hemolysis
T
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
Has phenol red as indicator
MSA
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
Mannitol fermenter result (color, pH, and example)
Yellow, acidic, S. aureus
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
BAP : Medium sized colonies; Beta-hemolytic
S. lugdunensis
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
BAP : small-medium sized, gray colonies; nonhemolytic or gamma hemolytic
S. epidermidis
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
BAP : Medium-sized colonies, yellow pigmented colonies
S. saprophyticus
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
For isolation and direct differentiation of Staphylococcus aureus in clinical and industrial sample
CHROMagar
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
T/F: On CAP, S. aureus has pinhead colonies with greenish discoloration
T
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
T/F: MSA
● Staphylococcus epidermidis (yellow)
● Staphylococcus aureus (pink)
F;
● Staphylococcus epidermidis (pink)
● Staphylococcus aureus (yellow)
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
CHROMagar:
○ Staphylococcus aureus → _________
○ Other bacteria are _________ or inhibited
pink to mauve
colorless, blue
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
Selective medium containing the antibiotic Cefoxitin, which inhibits other members of staph and allows the growth of S. aureus
CHROMagar
CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION
CHROMagar that is very selective for MRSA
CHROMAgar Versa
LABORATORY DIAGNOSIS
Detection of enzyme catalase
Catalase Test
LABORATORY DIAGNOSIS
converts H2O2 to water and O2
Catalase
LABORATORY DIAGNOSIS
Reagent for catalase tests
3% H2O2
LABORATORY DIAGNOSIS
Important test to differentiate staphylococcus (+) and micrococcus (+) from streptococcus (-)
Catalase Test
LABORATORY DIAGNOSIS
T/F: If doing catalase test, get colonies from blood agar plate
F; AVOID GETTING FROM BAP
LABORATORY DIAGNOSIS
Oxidase reagent reacts with cytochrome C in the cytochrome oxidase
Modified Oxidase Test
LABORATORY DIAGNOSIS
Uses filter paper; get a loopful of the specimen then apply on the filter paper then drop the reagent
Modified Oxidase Test
LABORATORY DIAGNOSIS
Reagent used in modified oxidase test
6% tetramethyl phenylenediamine HCl in
dimethyl sulfoxide (DMSO)
LABORATORY DIAGNOSIS
Positive result for Modified Oxidase Test
Dark Blue
LABORATORY DIAGNOSIS
Differentiates staphylococcus (most members are (-) from micrococcus (+)
Modified Oxidase Test
LABORATORY DIAGNOSIS
T/F: MOT : Staphylococcus are negative except for three species
■ S. sciuri
■ S. lentus
■ S. vitulinus
T
LABORATORY DIAGNOSIS
T/F: Use nichrome or iron loops in MOT
F; DO NOT USE. False (+) and iron is a component of the cytochrome. Use applicator stick or plastic loop instead
LABORATORY DIAGNOSIS
Detection of staphylocoagulase (coagulase)
Coagulase Test
LABORATORY DIAGNOSIS
Coagulase Test Reagent
Rabbit Plasma
LABORATORY DIAGNOSIS
● For screening
● Detect bound coagulase or clumping factor (sand-like)
Slide Coagulase
LABORATORY DIAGNOSIS
Positive & negative result for slide coagulase
P : Grainy / Clumping
N : Homogenous / No Clumping
LABORATORY DIAGNOSIS
● Detection of free coagulase enzyme
● Will not confirm if it is coagulase positive because this test would have many false positive result
Slide Coagulase
LABORATORY DIAGNOSIS
T/F: Rabbit plasma are added in Slide Coagulase then add colony from MSA, not BAP & CAP
F; colony from BAP & CAP, not MSA
LABORATORY DIAGNOSIS
T/F: In slide coagulase, high amounts of salt can interfere with the test
T
LABORATORY DIAGNOSIS
● Confirms if the test is really coagulase positive
● Detects free coagulase
● More specific
Tube Coagulase
LABORATORY DIAGNOSIS
Tube Coagulase (+) result
Clot formation
LABORATORY DIAGNOSIS: TUBE COAGULASE
T/F: If 4 hours, there is still no clot formation, that is not yet a negative result. Continue the incubation at room temperature. After 20 hrs from the time you put it at room temperature, check again if there is already a clot. If there is, it is positive, if there is no clot formed, it is negative
T
LABORATORY DIAGNOSIS: TUBE COAGULASE
Prepare a test tube, add colony on rabbit plasma, incubate the tube for ____ hrs at ___ C. Every 30 minutes, check if it is coagulase positive
4 hours at 37 degrees C
LABORATORY DIAGNOSIS
Why don’t we just put the tube in the incubator for 24
hours?
Clot will be dissolved by Staphylokinase or Staphylococcal fibrinolysin or Muller’s Factor
LABORATORY DIAGNOSIS
Result when the clot is destroyed by Staphylokinase
False negative
LABORATORY DIAGNOSIS
Oxidation Fermentation Test color for fermenter in open and oxidizer in closed tube
O : Yellow
C: No color (oxidizer; can be microccocus)
LABORATORY DIAGNOSIS
● To differentiate organisms based on the ability to oxidize or ferment sugars
● Use of OF Medium
Oxidation Fermentation Test
LABORATORY DIAGNOSIS
DNAse Test positive result
Hydrolysis of surrounding medium (clear zone)
LABORATORY DIAGNOSIS
Would react with a thermostable thrombin like molecule (coagulase reacting factor)
Tube Coagulase
LABORATORY DIAGNOSIS
● Detection of DNAse activity
● Useful to identify S. aureus
● Use of special DNA Agar
DNAse Test
LABORATORY DIAGNOSIS
DNA agar contains (2)?
DNA & toluidine blue / methyl green
LABORATORY DIAGNOSIS
DNAse reagent
Toluidine Blue or Methyl Green
LABORATORY DIAGNOSIS
Gelitinase Liquefaction Test (-)
Not melted
LABORATORY DIAGNOSIS
● Makes use of 12% gelatin in a tube medium where the suspected organism is inoculated
● Incubate for 4-5 days
Gelitinase Liquefaction Test
LABORATORY DIAGNOSIS
Formation of acetoin from glucose (Butylene Glycol
Pathway)
Voges Proskauer Test
LABORATORY DIAGNOSIS
Gelitinase Liquefaction Test (+)
Liquified - S. aureus
LABORATORY DIAGNOSIS
is a byproduct of the metabolism of glucose
following the Butylene Glycol Pathway
Voges Proskauer Test
LABORATORY DIAGNOSIS
Useful test to differentiate Coagulase-negative
Staphylococcus (CONS)
Novobiocin (5ug) Susceptibility
LABORATORY DIAGNOSIS
● Differentiates Coagulase (+) Staphylococcus
● Can differentiate S. aureus from S. intermedius
Voges Proskauer Test
LABORATORY DIAGNOSIS
Voges Proskauer Test (+)
Red coloration in MRVP broth
LABORATORY DIAGNOSIS
● Differentiates Coagulase (+) Staphylococcus
● Used to differentiate S. aureus (-) from S. lugdunensis, S. intermedius, and S. schleiferi (+).
PYR (Pyrrolidonyl) Test
LABORATORY DIAGNOSIS
PYR (Pyrrolidonyl) Test (+)
Pink or Cherry-Red Color
LABORATORY DIAGNOSIS
Urine isolates that are coagulase-negative are tested further to identify S. saprophyticus.
Novobiocin (5ug) Susceptibility
LABORATORY DIAGNOSIS
is resistant to novobiocin
S. saprophyticus
LABORATORY DIAGNOSIS
T/F: Most CoNS are susceptible (usually S. epidermidis) to Novobiocin
T
LABORATORY DIAGNOSIS
Most useful test for confirming S. lugdunensis
Ornithine Decarboxylase Test
LABORATORY DIAGNOSIS
Helpful for Coagulase Negative Staphylococcus
Susceptibility to Polymyxin B (300 Units)
LABORATORY DIAGNOSIS
Ornithine Decarboxylase Test (+)
Violet Coloration on OCD Tube
LABORATORY DIAGNOSIS
T/F: S. lugdunensis is also usually slide coagulase-positive, however, we don’t consider it coagulase-positive
T
LABORATORY DIAGNOSIS
T/F: After slide coagulase test, S. lugdunensis should be confirmed through tube coagulase test
T
LABORATORY DIAGNOSIS
Identify certain species of Staphylococcus
Urease Production
RAPID METHODS FOR DIAGNOSIS
To differentiate S. aureus from CONS (Coagulase
Negative Staphylococci). A variation or an improvement of the slide coagulase test
Commercially Available Rapid Agglutination Kits
RAPID METHODS FOR DIAGNOSIS
● Use of plasma coated latex beads
● More specific and sensitive from traditional methods
● Useful for identification of MRSA
Commercially Available Rapid Agglutination Kits
RAPID METHODS FOR DIAGNOSIS
Negative results should be confirmed with the tube
coagulase test, nucleic acid amplification test, or
MALDI-TOF
Commercially Available Rapid Agglutination Kits
RAPID METHODS FOR DIAGNOSIS
T/F: Third-generation agglutination kits contain antibodies that bind capsular antigens 5 and 8, or other surface
molecules. Thus, these assays are more sensitive but less specific – false positive results
T
RAPID METHODS FOR DIAGNOSIS
To identify the presence of certain genes, such as the
mecA gene, to confirm MRSA & MSSA
Molecular Methods
RAPID METHODS FOR DIAGNOSIS
Able to directly identify staphylococci from a positive blood culture sample as an aid in the diagnosis of sepsis and for targeted antimicrobial therapy treatment.
Molecular Methods
RAPID METHODS FOR DIAGNOSIS
Gold standard for MRSA
Detection of mecA gene - RT-PCR
RAPID METHODS FOR DIAGNOSIS
Cannot distinguish genetic differences, such as MRSA versus MSSA strains.
MALDI-TOF
RAPID METHODS FOR DIAGNOSIS
● A rapid diagnostic method that can identify antibiotic
susceptibility
● Automated machine to identify organisms
MALDI-TOF
DETECTION OF RESISTANCE: MRSA
Recommended for screening MRSA
Cefoxitin Test
DETECTION OF RESISTANCE: MRSA
Found in patients who lack traditional healthcare-associated risk factors, such as recent hospitalization, long-term care, hemodialysis, or indwelling devices
Community-acquired MRSA (CA-MRSA)
DETECTION OF RESISTANCE: MRSA
○ Infection and outbreaks have been reported in
athletes, military recruits in close contact
environments, correctional facility inmates, pediatric
patients, and tattoo recipients.
○ Can cause nosocomial infections
Community-acquired MRSA (CA-MRSA)
DETECTION OF RESISTANCE: MRSA
Drug of choice
Vancomycin
DETECTION OF RESISTANCE: MRSA
Using oxacillin and with 2-4% NaCl; growth indicates methicillin resistance
MRSA Screen Agar
DETECTION OF RESISTANCE: MRSA
T/F: MRSA isolates should be considered susceptible to all βlactam antibiotics, including the carbapenems, except for fifth-generation cephalosporins with MRSA activity
F; resistant
DETECTION OF RESISTANCE
Detection with the use of oxacillin disks and cefoxitin
MRSE
DETECTION OF RESISTANCE
● Screen plates with 2-4% NaCl
● Use of ChromAGAR
MRSE
DETECTION OF RESISTANCE
Gold standard for MRSE
Detection of mecA gene
DETECTION OF RESISTANCE
Use of vancomycin agar plate (spot inoculation) for
screening
VRSA
DETECTION OF RESISTANCE
MIC for VRSA
: ≥16 μg/mL
DETECTION OF RESISTANCE
MIC for Cefoxitin & Oxacillin
C : ≥8 μg/L
O : ≥4 μg/L
DETECTION OF RESISTANCE
Detection of resistance to macrolides such as clindamycin
Macrolide Resistance
DETECTION OF RESISTANCE
T/F: Staphylococcal resistance to clindamycin is occasionally inducible, meaning it is only detectable in vitro when the
bacteria is exposed to erythromycin
T
DETECTION OF RESISTANCE
Macrolide Resistance Method
D-Zone Test
DETECTION OF RESISTANCE: MACROLIDE RESISTANCE
Place erythromycin and clindamycin disk close together (____ distance between the two disks)
15 mm
