[2S] UNIT 3.1 Gram (+) Cocci - Staphylococci Flashcards by JULIA CASSANDRA RECCION

BACTERIA ACCORDING TO SHAPE

Rod-shaped

bacillus/bacilli

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Gr(+) or Gr(-) & Shape?

Neisseria and Moraxella

Gr(-) cocci

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BACTERIA ACCORDING TO SHAPE

Round/Spherical

coccus/cocci

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Gr(+) or Gr(-) & Shape?

Staphylococcus and streptococcus

Gr(+) cocci

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Gr(+) or Gr(-) & Shape?

Bacillus & Erysipelothrix

Gr(+) bacilli

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Gr(+) or Gr(-) & Shape?

most bacilli

Gr(-) bacilli

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Gr(+) or Gr(-) & Shape?

Listeria & Mycobacterium

Gr(+) bacilli

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Gr(+) or Gr(-) & Shape?

Enterobacteriaceae & Haemophilus

Gr(-) bacilli

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Gr(+) or Gr(-) & Shape?

Spirochetes: Treponema, Borrelia, Leptospira

Gr(-) spiral

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GENERALITIES

grape-like clusters; due to their morphological arrangement when seen under the light microscope

Staphylococcus

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GENERALITIES

Belong to Family Staphylococcaceae

Staphylococcus

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GENERALITIES

○ Generally seen as cocci in clusters (most cases)
○ No tetrads

Gr (+) Cocci in clusters, in pairs, singly

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GENERALITIES

All are Catalase (+) except?

S.aureus subsp. anaerobius
and S. saccharolyticus

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If tetrads are seen, it might be?

micrococcus

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GENERALITIES

would detect the enzyme catalase

Catalase test

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GENERALITIES

Positive result for Catalase Test

bubbling of solution or effervescence after addition of 3% hydrogen peroxide

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T/F: All staphyloccocus are modified oxidase negative except t S. sciuri, S. lentus, S. vitulus (are modified oxidase positive)

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Modified Oxidase Test is also known as?

Microdase Test

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Positive result for Modified Oxidase Test

blue-purple coloration

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All are non-motile and non-spore formers

Staphylococcus

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T/F: Majority of motile bacteria are bacilli and has no flagella

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T/F: All are halophilic. Growing in high amount of NaCl or salt, at around 7.5%

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T/F: Motility test is commonly done on gram (+)

F; gram -

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Gaseous Requirement: _________ except Staphylococcus aureus subspecies anaerobius &
Staphylococcus saccharolyticus

Aerobic or Facultative Anaerobe

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T/F: Staphylococcus are nitrate reducers

○ 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

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

S. AUREUS - VIRULENCE FACTORS Group? Also known as Toxic shock syndrome toxin 1 (TSST-1) / Pyrogenic Exotoxin C

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 (-)

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 -

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/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)

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

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

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

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

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

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

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

LABORATORY DIAGNOSIS T/F: After slide coagulase test, S. lugdunensis should be confirmed through tube coagulase test

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

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

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

[2S] UNIT 3.1 Gram (+) Cocci - Staphylococci Flashcards

(231 cards)