2. Staphylococcus

Name 4 major staphylococcus spp responsible for disease

aureus

epidermidis

lugdunensis,

saprophyticus

Name the coagulase neg staph spp's

Epidermidis

Saprophyticus

(haemolyticus)

What parts of the body is S. aureus commonly found in

Uusally anterior nares and mucous membranes (nose/throat)

Skin

breasts

surgery wounds

heart valves (endocarditis)

blood

Mode of transmission for S. aureus

Traumatic introduction

direct contact

contact w/ fomites

What is a fomite

inanimate objects that can carry and spread disease and infectious agents (doorknob, light switches, phones, elevator buttons, etc)

MRSA stands for

methicillin resistant staphylococcus aureus

S. aureus is AKA "golden staph," why?

it forms yellow spots/colonies in agar)

What is S. epidermidis' virulence factor

Makes slime layer → very hard to remove

Easier to remove infected prosthesis

Which staph is the most common cause of hosp-acquired UTI?

Epidermidis (due to catherization)

Staphyloccocus gram stain and morphology

Gram pos cocci

Lugdunensis --> grape-like clusters

Name the coagulase-pos staph spp

aureus

Name a few infectious diseases associated w/ coag-neg staph

Endocarditis

Bacteremia

Intravenous cath infection

CSF shunt infection

Osteomyelitis

UTI

Graft/prosthesis infection

Staph latex test is only positive for which staph species?

aureus

Which 2 staph spp can show false positives on the latex test?

Saprophyticus

Lugdunensis

PYR test is only positive for which staph species?

lugdunensis

Ornithine decarboxylase test is only positive for which staph species?

Lugdunensis

DNAse test is only positive for which staph species?

aureus

What is the purpose of the catalase test?

To differentiate between staph and strep

Pos= staph

Label saprophyticus, aureus, epidermidis, and lugdunensis as susceptible, intermediate, or resistant to novobiocin

Sapro --> resistant

All others --> susceptible

What is coagulase?

Its an extracellular enzyme, sometimes called "free coagulase"

Basically, cell bound "clumping factor"

Toxic shock syndrome

Multisystem disorder characterized by high fever, hypotension, and shock

Scalded skin syndrome (aka ritters disease)

Ritters is an exfoliative dermatitis that is most commonly found in infants and previously healthy young children

Staph aureus symptoms of infection in the skin/wound

Impetigo

Furuncles

Carbuncles

Boils

Surgical wound infections

How can you get food poisoning from staph aureus

Result of ingesting enterotoxin, producing strains of staphylococci

Symptoms of staph aureus

Pus filled infection

Joint/bone infection

scalded skin syndrome

toxic shock syndrome

Are staph aureus infections superficial or systemic?

BOTH

Name a few infections that staph aureus can cause

Toxic epidermal necrolysis

pneumonia

bacteremia

osteomyelitis

endocarditis

Septic arthritis

Symptoms of staph epidermidis

Pain, redness, swelling, tissue erosion (which loosens prosthesis)

Meningitis if it gets into brain through shunts

What does epidermidis like to infect?

skin, prosthetics, pins, plates, screws, any metal implants

Which staph is the most common cause of UTI in sexually active young women?

saprophyticus

If staph saprophyticus is found in urine cultures in LOW numbers, is it still clinically significant?

YES

Lugdunensis infection symptoms

Abscesses

Meningitis

skin and soft-tissue cellulitis

shunt infections

Spondylodiscitis

prosthetic joint infection

catheter related bacteremia

septic arthritis

Osteomyelitis

Endocarditis

peritonitis (peritoneal dialysis)

toxic shock syndrome

Staphylococcus and Micrococcus genera belong to the Micrococcaceae family. TRUE OR FALSE

TRUE

Parts of body saprophyticus and epidermidis like to habitate

Skin and mucous membranes

Saprophyticus does the same for the genitourinary tract

Micrococci arent common to the enviroment and skin. T or F

False, they are

Micrococci colony appearance

yellow

Which staph spp is an increasing cause of invasive diseases

lugdunensis

Why is lugdunensis sometimes misIDd as aureus?

It can produce bound coagulase (remember its universally neg for free coag though)

Colonial morphology of lugdunensis

Beta-hemolytic

Opaque

2-4mm in diameter

Yellow, yellow0orange, cream

glossy

smooth

Strep colonies are transluscent while staph is?

opaque

How is lugdunensis IDd

Catalase pos

Coag tube neg

PYR pos

Ornithine decarboxylase pos

How are lesion/wound/abscess specs stored

room temp

How to process lesion/wound/abscess specs

Gram stain (direct)

BA, CHOC, MAC, eosin methylene blue, anerobic BA, thioglycolate broth

Use colistin-nalidixic acid agar gram stain shows gram +/-

How are urine specs stored

room temp if urine is preserved and refrigerate if unpreserved

How to process urine specs

BA, MAC, or eosin methylene blue agar

Can S. aureus produce beta-hemolysis on BA?

It can

Is epidermidis hemolytic?

Not usually

How to differentiate staphylococci vs micrococci?

Microsafe (modified oxidase) test

Susceptibility testing

Using oxidation-fermentation rxns on O/F glucose

Oxidation-fermentation reaction of micrococci vs staphylococci

Staph= ferment glucose, produce acid

Micrococci dont

What is the novobiocin susceptibility test for?

to differentiate coag-neg staphylococci from S. saprophyticus in urine samples

Other CNS are susceptible

Breakpoint: >16mm

Catalase purpose

Diff between strep and staph

Staph=bubble

Strep=no bubble

Tube coag purpose

Differentiate S aureus from other staphylococci

Aureus = coag

Staph latex purpose

Diff staph aureus (BUT some bound-coagulase from other spp can cause false +)

Novobiocin test purpose

Differentiate S. saprophyticus (its resistant, other 3 are susceptible)

PYR purpose

ID strep. Pyogenes and enterococcus species

How does PYR detect strep pyogenes/enterococci?

detects enzymes they produce

DNAse test purpose

Differentiate S aureus (shows up strongly pos w/ big clearing, which means it produces DNAse enzyme)

What does a positive DNAse test result mean

the staph spp produces DNAse enzyme

Staphaurex test purpose

Differentiate staph aureus (it agglutinates)

Main tests and the spp they target (remember this one!)

Tube coag: aureus

PYR: lugdunensis

Ornithine decarboxylase: lugdunensis

DNAse: aureus

Staph latex: aureus (BUT sapro and lugdunensis can show false +)

Novobiocin: saprophyticus is resistant (all other susceptible)

What does a pastorex staph plus test ID?

Clumping factor

Protein A

Capsular polysaccharides

What are capsular polysaccharides

Capsule= protein/sugar layer of the virus

Polysaccharides= many sugars

MRSA has this

What is the pastorex staph plus test useful for?

Helps ID strains of MRSA

What type of test is the pastorex staph plus?

Rapid agglutination slide test

How can staphylococci and micrococci be differentiated using susceptibility testing?

Staph

-bacitracin (R)

-lysostaphin (S)

-Furazolidone (S)

Micro

-bacitracin (S)

-lysostaphin (R)

-Furazolidone (R)

Breakpoints for bacitracin and firazolidone (susceptible)

Bacitracin > 10mm

Furazolidone > 15mm

Bound coagulase is tested how?

Slide coag test

Free coagulase is tested how?

Tube coag test

Free coagulase is a virulence factor. T or F

FALSE, thats bound coag (it can cause clotting to hide w/in them)

How often do you have to check a tube coag? Whats the growth requirement

Mix colony w/ tube

4hr, 45C, check every 30min

coag tube tests help ID which staph

aureus

Bound coagulase is not part of the cell envelope structure. T or F

FALSE, it IS

If the slide coag test is negative, what do you do?

Follow up w/ tube test

Slide coag test set-up

Mix organism w/ saline and rabbit plasma, let it run

Why do we mix organisms into saline instead of regular water?

Keeps it isotonic so you don't kill your bacteria