STAPHYLOCOCCUS

catalase-positive, gram-positive cocci

● Exhibit spherical cells (0.5 to 1.5 um) on stained smears.

● Appears in single, in pairs or clusters.

● Nonmotile, non-spore-forming

● Aerobic, facultatively anaerobic, but few strains are obligate

anaerobic

Member of family Staphylococcaceae

Derived from the Greek term:

○ staphle-

“bunches of grapes”

Colonies produced after 18 to 24 hours of incubation

Pinpoint, medium size (4 to 8 mm)

○ cream-colored, white, or rarely light gold,

○ "buttery-looking."

Two main categories of infections caused by S. aureus:

Suppurative

○ toxin-mediated diseases

VIRULENCE FACTORS

enterotoxins, cytolytic toxins, and protein A.

Staphylococcal food poisoning:

Most commonly caused by enterotoxins A, B, & D

Associated with toxic shock syndrome (TSS):

Enterotoxins B, C, G, and I

A bacterial toxin produced by S. aureus

linked with Staphylococcal pseudomembranous enterocolitis:

Enterotoxin B:

Substances that can stimulate a

massive immune response by activating large

numbers of T cells.

Superantigens:

TOXIC SHOCK SYNDROME TOXIN-1 aka

as enterotoxin F

Causes the majority of menstruating-associated TSS and

approximately 50% of non-menstruating cases.

TOXIC SHOCK SYNDROME TOXIN-1

A superantigen, which stimulates T-cell proliferation.

TOXIC SHOCK SYNDROME TOXIN-1

low concentrations it causes

leakage by endothelial

cells.

● At higher concentrations,

cytotoxic to endothelial

cells.

EXFOLIATIVE TOXIN

● Also known as

epidermolytic toxin.

epidermolytic toxin.

● There are two types:

exfoliative toxin A and exfoliative toxin B.

Cause the epidermal layer of the skin to slough off.

EXFOLIATIVE TOXIN

known to cause staphylococcal SSS

(Staphylococcal Scalded Skin Syndrome), also referred to as

Ritter disease.

most common in newborns and infants, especially children younger than 5 years of age.

Ritter disease.

toxin is also implicated in bullous impetigo.

EXFOLIATIVE TOXIN

proteins that affect red

blood cells and leukocytes.

hemolysins and leukocidins

S. aureus produces four hemolysins:

alpha (α), beta (β), gamma (γ), and delta (δ).

lyses erythrocytes, damages platelets and

macrophages, and causes severe tissue damage.

α-Hemolysin

acts on sphingomyelin in the plasma membrane of

erythrocytes and is called the "hot-cold" lysin due to

its enhanced activity on incubation at 37° C and

subsequent exposure to cold (4° C).

β-Hemolysin (sphingomyelinase C)

○ used in the CAMP laboratory test to identify group

B streptococci.

β-Hemolysin (sphingomyelinase C)

found in a higher percentage of S. aureus strains

and some CoNS but is considered less toxic than α

and β-hemolysin.

delta (δ).

only found in association with Panton-Valentine

leukocidin (PVL).

gamma (γ)

exotoxin lethal to polymorphonuclear leukocytes.

Panton-Valentine leukocidin (PVL).

suppresses phagocytosis, contributes to the

invasiveness of S. aureus, and is linked to severe

cutaneous infections and necrotizing pneumonia.

Panton-Valentine leukocidin (PVL).

Though produced by few S. aureus strains, PVL is

often associated with community-acquired

staphylococcal infections.

Panton-Valentine leukocidin (PVL).

Examples of enzymes PRODUCE BY S. AUREUS

coagulase, protease, hyaluronidase, & lipase.

produced by both coagulase-positive staphylococci and CoNS.

Lipases

act on lipids on the skin's surface, particularly fats and oil from sebaceous glands.

Lipases

Hydrolyzes hyaluronic acid in connective tissues, allowing the spread of bacteria

during infection.

hyaluronidase.

cellular component found in the cell wall of S. aureus.

Protein A

ability to bind the Fc portion of immunoglobulin G (IgG).

most significant role of protein A

can block phagocytosis.

protein A

Damages erythrocytes, platelets, and

macrophages

α-Hemolysin

Also known as sphingomyelinase C;

disrupts the erythrocyte plasma

membranes. Responsible for CAMP assay

effectiveness.

β-Hemolysin

Found in some CoNS strains as well as in

S. aureus. Less toxic than other

hemolysins.

delta (δ)

Associated with Panton-Valentine

leucocidin.

gamma (γ)

Polymorphonuclear leukocyte toxicity

PVL

Enzyme that cleaves the ring structure of

penicillins and derivative antibiotics,

making them ineffective

β-lactamase

Altered membrane binding protein resulting

in resistance to some ß-lactam antibiotics.

Penicillin-binding

protein 2

Permits bacteria to spread through

connective tissues.

Hyaluronidase

Common to S. aureus and CoNS.

Degrades lipids on skin surface, making it

more susceptible to bacterial entry into

epidermal layers.

Lipase

Responsible for a positive tube coagulase

test result. Also present inS. intermedius,

S. pseudintermedius, S. hycius, S. delphini,

S. lutrae, S agnetis, and some S. schleiferi.

Staphylocoagulase

A superantigen causing an over-reactive

immune response. Formerly known as

enterotoxin F.

TSST-1

Binds IgG and prevents phagocytosis.

Protein A

Enterotoxins A, B, and D are the cause of

the majority of staphylococcal food

poisoning cases; heat stable.

Enterotoxins

A-E, G-J

Enterotoxins B and C, and rarely G and I,

can cause enterocolitis.

Enterotoxins

A-E, G-J

Also known as epidermolytic toxin. Types A

and B. Solely responsible for SSS and

present in a minority of S. aureus species.

Exfoliative toxins

May also cause bullous impetigo.

Exfoliative toxins

folliculitis, furuncles, and

bullous impetigo

S. aureus

bullous exfoliative dermatitis occurring primarily in

newborns and previously healthy young children

SCALDED SKIN SYNDROME

Associated with women using highly absorbent tampons

S. saprophyticus, TOXIC SHOCK SYNDROME

Septic arthritis

S. aureus

osteomyelitis, septic arthritis, and prosthetic joint infections

S. aureus

Considered as normal skin biota but is a common source

of hospital-acquired infections and often a contaminant

in improperly collected blood culture specimens

S. epidermidis

intravascular catheters, CSF shunts, and other prosthetic

devices

S. epidermidis

Also a common cause of healthcare-acquired UTIs

S. epidermidis

bacterial factor involved in

adherence of S. epidermidis that provides a protective

advantage against host defenses

Poly(y-DL-glutamic acid)

Associated with UTIs in young women

S. saprophyticus

● Second most common cause, after E. coli, of

uncomplicated cystitis in the population

S. saprophyticus

Adheres more effectively to the epithelial cells lining the

urogenital tract

S. saprophyticus

Rarely present on other mucous membranes or skin

surfaces

S. lugdunensis

cause both community-associated and

hospital-acquired infections

S. lugdunensis

More virulent than other known to contain the mecA gene

that encodes resistance to oxacillin

S. lugdunensis

Important pathogen in infective endocarditis, septicemia,

meningitis, skin and soft tissue infections, UTIs, and

septic shock

S. lugdunensis

Endocarditis caused by this species is particularly

aggressive, frequently requiring valve replacement , and

infections have a high mortality rate

S. lugdunensis

Pathogenicity more closely resembles S. aureus

S. lugdunensis

selective medium s. aureus

mannitol salth agar (MSA),

Columbia colistin-nalidixic agar (CNA), or

phenylethyl alcohol (PEA) agar

small to medium-sized, non-hemolytic,

gray-to-white colonies

S. epidermidis

Forms slightly larger colonies

○ About 50% of the strains produces a yellow pigment

S. saprophyticus

medium-sized colonies with moderate or weak

hemolysis and variable pigment production

S. haemolyticus

Colonies are often hemolytic and medium-sized, although

small colony variants can occur

S. lugdunensis

Bacitracin (0.04 Units Disk) Micrococcus

+

Bacitracin (0.04 Units Disk) S. aureus

-

Novobiocin (5ug) S. saphro

-

Novobiocin (5ug) S. Epidermidis

+

Slide coag V

Tube coag +

VP -

PYR +

S. intermedius

VP +

PYR -

S. aureus VAPe YaRn

VP -

PYR +

S. intermedius

ODC +

VP +

PYR +

Gamma Hemolytic

Small - medium

gray - white colonies

S, lugdunensis

Polymixin B -/R

S. epideRmidis

Polymixin B +/S

Other CoNS

Infective Endocarditis

s. aureus

Subacute endocarditis

HACEK group

Habitat of S. aureus

Skin and nares

CATALASE TEST substrate

• Hydrogen peroxide (H2O2).

OXIDASE TEST Substrate

• 1% Tetramethyl-p-phenylenediamine

dihydrochloride (oxidase reagent).

Modified Oxidase Test: Substrate

Kovac’s Oxidase Test

Bacitracin is also called

Taxo A

edta plasma will cause what in Coagulase test

False positive

Tube coagulation test process

Must incubate @37 for 4 hours

if none, @RT for 24 hours

Fibrinolysis activate if left @ 37 for more than 4 hours

COAGULASE TEST substrate

Fibrinogen in the plasma.

METHYL RED Substrate

• Glucose

METHYL RED process

Bacteria are incubated in Clark-Lubs (MR-VP)

broth for 3-5 days at 37°C.

METHYL RED Indicator

• Methyl Red (4.4 – 6.4 pH)

Red at pH ≤ 4.5 (indicating strong acid

production).

Yellow at pH ≥ 6.2 (indicating less acidic

conditions).

VOGES-PROSKAUER TEST process

Bacteria are incubated in Clark-Lubs broth,

glucose broth, or MR-VP broth for 48 hours.