Chapter 16 and 17 part 1

S. aureus, pyogenes, agalactiae, pneumoniae, Viridans Streptococcus

gram positive cocci

Neisseria gonorrhoeae, meningitidis, Moraxella catarrhalis

gram - staphylococci

gram +, catalase + cocci, spherical cells, non-motile, non-spore forming

general characteristics of staphylococcus

staphylococcus

aerobic or facultatively anaerobic, although few strains can be obligate anaerobes colonies produced after 18-24 hours, able to grow in the presence of high salt concentration and at temperatures ranging from 18 to 40

anterior nares, nasopharynx, perineal area, skin, colonizer of mucosa

habitat or reservoir for S. aureus (5)

skin, mucous membrane

habitat for S. epidermidis (2)

Skin, mucous membranes

habitat for S. haemolyticus and lugdunesis (2)

skin, genitourinary tract, mucosa

habitat for S. saprophyticus (3)

skin, mucosa, oropharynx

habitat for micrococcus spp, kocuria spp, kytococcus spp.

S. aureus

mode of transmission:

Endogenous strain: sterile site by traumatic introduction (surgical wound or microabrasions)

Direct contact: person - to - person, fomites

Indirect contact: aerosolized

S. epidermidis, S. haemolyticus, and S. lugdunesis

Mode of transmission: Endogenous strain: sterile site by implantation of medical devices ( e.g shunts, prosthetic devices)

Direct contact: person to person

S. saprophyticus

Mode of transmission: Endogenous stain: sterile urinary tract, notably in young, sexually active females

Micrococcus spp, Kocuria spp, Kytococcus spp.

Mode of transmission: Endogenous strain: uncertain, rarely implicated in infections, immunocompromised hosts: brain abscess, meningitis, pneumonia, endocarditis.

Staphylococcus

Epidemiology:

Shedding of bacteria is common; responsible for many hospital acquired (nosocomial) infections

Susceptible to high temperatures, and disinfectants and antiseptics solutions; can survive on dry surfaces for long periods

Can be transferred to a susceptible person through direct contact or contact with fomites (contaminated clothing, bed linens)

coagulase

an enzyme that clots plasma

Staphylokinase

an enzyme that breaks down clots to help the bacteria spread

TSST - 1

A toxin: toxic shock syndrome toxin

Enterotoxins

toxin that causes food poisoning

a-hemolysin

toxin that destroys red blood cells

Panton-Valentine Leukocidin

invasin that kills white blood cells

adhesins

It helps the bacteria stick to host tissues

collagen, fibronectin, elastin

3 types of adhesins

capsule

structure that is:

polysaccharide, covers the outermost layer of the cell wall, inhibits phagocytosis, and chemotaxis by leukocytes

slime layer (biofilm)

structure that is:

loose-bound, water-soluble film, produced at varying amounts, allows the organism to adhere to inorganic surfaces, inhibits the penetration of antibiotics

peptidoglycan

structure that is: half of the cell wall by weight, consist of many cross-linked layers of glycan chains, provide osmotic stability, stimulates production of endogenous pyrogen ( endotoxin-like activitiy), leukocyte chemoattractant

enzymes

these catalyze construction of the peptidoglycan layer, called penicillin-binding proteins because these are targets of panicillin and other beta lactam antibiotics

teichoic acids and lipoteichoic acids

specie- specific, phosphate-containing polymers, bound either covalently to N- acetylmuramic acid residues of the peptidoglycan layer or to the lipids n the cytoplasmic membrane; binds to fibronectin

surface adhesion proteins

most are covalently bound to the cell wall peptidoglycan; they have been designated microbial surface components recognizing adhesive matrix molecules (MSCRAMM)

staphylococcal protein A, Fibronectin-binding proteins A and B, clumping factor protein A and B

3 adehesive matrix molecules (MSCRAMM)

cytoplasmic membrane

complex of proteins, lipids, and a small amount of carbohydrates, serves as an osmotic barrier of the cell and provides and anchorage for the cellular biosynthetic and respiratory enzymes

staphyloccoci

the ability of _ to cause diease depends on the abiity of the bacteria to:

evade immune clearance

produce surface proteins that mediate adherance of the bacteria to host tissues during colonization, produce disease through the elaboration of specific toxins and hydrolytic enzymes leading to tissue destruction

evade immune clearance, adhere to host tissues, produce toxins and enzymes

the ability of staphylococci to cause diseases depends on: (3)

capsule, slime layer, peptidoglycan, teichoic acid, protein A

virulence factors of staphylococcus aureus (5)

capsule

virulence factor of staphylococci: inhbits chemotaxis and phagocytosis; inhibits mononuclear cell proliferation

slime layer

virulence factor of staphylococci: facilitates adherance to foreign bodies

peptidoglycan

virulence factor of staphylococci: provides osmotic stability; endotoxin-like activity

teichoic acid

virulence factor of staphylococci: binds to fibronectin

protein A

virulence factor of staphylococci: bound to the cytoplasmic membrane, binds to immunoglobulins → decrease immune mediated clearance of organisms from the sites of infection

coagulase

mainly produced by S. aureus (+), coagulase + CRF (coagulase reacting factor) from plasma form thrombin-like factor

staphylokinase

converts fibrinogen to fibrin (clot),

fibrin clot

coats staphylococci and protects them from phagocytosis, localizes the infection and protects the organisms from phagocytosis

bound coagulase

can directly convert fibrinogen to insoluble fibrin and cause staphylococci to clump

cell-free coagulase

accomplishes the same result by reacting with a globulin plasma factor to form staphylothrombin

catalase

produced by al staphylococci, catalyzes the conversion of hydrogen peroxide to H2O and O2, protects the organism from toxic H2O2 that accumulates during bacterial metabolism and is released during phagocytosis

hyaluronidase

virulence factor: hydrolzes hyaluronic acid in connective tissues, promoting spread of staphylocci in tissue

firbrinolysis

virulence factor: dissolves fibrin clots

lipases

virulence factor: hydolyzes lipids

nucleases

virulence factor: hydrolazes DNA

cytotoxins

virulence factor: toxic for many cells, including erythrocytes, fibroblasts, leukocytes, macrophages, and platelets

exfoliative toxin

serine proteases that split the intracellular bridges in the stratum granulosum epidermis

enterotoxin

stimulates release of inflammatory mediators in mast cells, increasing peristalsis and fluid loss, as well as nausea and vomitting

toxic shock syndrome toxin

produces leakage or cellular destruction of endothelial cells

alpha hemolysin, beta hemolysin, delta toxin, gamma toxin and PV leukocidin

4 types of cytotoxins

alpha hemolysin

Cytotoxin

• 33,000 Da polypeptide

• Disrupts the smooth muscle in blood vessels

• Toxic to erythrocytes, leukocytes, hepatocytes, and platelets

• Binds to the cell surface, aggregates into a heptamer forming 1-2 nm pore

and allows the rapid reflux K+ and influx Na+ and Ca+ and other small molecules

• Leads to osmotic swelling and cell lysis

Beta hemolysin

cytotoxin:

35,000 Da heat-labile protein produced by most strains of S. aureus

• Also known as Sphingomyelinase C

• Works in conjunction with the alpha toxin

• Catalyzes the hydrolysis of membrane phospholipids in susceptible cells

• Acts on Sphingomyelin in the plasma membrane of erythrocyte

• Enhanced hemolytic activity on incubation on 37°C and subsequent

exposure to cold temperatures such as 4°C

• "Hot - Cold Lysin

Delta toxin

cytotoxin:

3,000 Da polypeptide produced by almost all strains of S. aureus and other Stpahylococci

Considered less toxic to alll cell than either alpha or beta hemolysin

Acts as a surfactant (reduces surface tension)

Disrupts cellular membrane by means of detergent-like action

found in higher percentage of S, aureus strains and some CoNS

Gamma toxin

Bicomponent toxin composed of 2 polypeptide chains

• S (slow-eluting proteins) component - HIgA, HIgC and LuKS-PV

• F (fast-eluting proteins) component - HIgB and Lukf- PV

HIgA, HIgC and LuKS-PV

S( slow -eluting proteins) component

HlgB and LuKf- PV

F (fast-eluting proteins) component

Panton-Valentine Leukocidin (PVL)

endotoxin lethal to polymorphonuclear leukocytes

exfoliative toxin

also known as epidermolytic toxin

exfoliative toxin A

type of exfoliative toxin:

heat-stable, gene is phage-associated

exfoliative toxin B

type of exfoliative toxin: heat-liable, located on plasmid

serine proteases

Exfoliative toxins A and B act as _, which are enzymes that cut specific proteins

Serine proteases

spit cell adhesion structures responsible for forming the intracellular bridges in the stratum granulosum epidermis; protective neutralizing antibodies develop, leading to resolution of the toxic processes

Toxic shock syndrome toxin - 1 (TSTT-1)

22,000 Da, heat- and proteolysis-resistant

• Previously referred to as Enterotoxin F

• Chromosomal-mediated toxin that causes the majority of cases of

menstruating-associated TSS and approximately 50% of non-menstruating

c a s e s

• At low concentrations, causes leakage by endothelial cells, and is cytotoxic

to these cells at higher concentrations

• absorbed through the vaginal mucosa, leading to systemic effects as seen with prolonged tampon use

cutaneous infections, staphylococcal scalded skin syndrome (SSSS) or ritter disease, toxic shock syndrome, food poisoning, bacteremia, endocarditis, pneumonia, osteomyelitis and septic arthritis

infections cause by staphylococcus aureus (9)

cutaneous infections

typically the abscess is filled with pus

and surrounded by necrotic tissues

and damaged leukocytes

• Usually occurs as a result of previous

skin infections such as cuts, burns, and surgical incisions

folliculitis

type of cutaneous infection: mild inflammation of a hair follicle or oil gland; base of the folllicle is raised and reddended with small collections of pus beneath epidermal surface

furnucles (boils)

extensions of folliculitis, large, painful, raised nodules with underlying collection of dead and necrotic tissue, can drain spontaneously or through surgical incisions

carbuncles

type of cutaneous infection:

carbuncles: occurs when furnucles coalesce and extend to deeper subcutaneous tissue, multiple sinus tracts are usually present, chills and fevers

wound infections

type of cutaneous infection: occur after organisms on skin or external source enter wound from a surgical procedure or trauma; characterized by edema, erythema, pain, accumulation of purulent material

Staphylococcal scalded skin syndrome or ritter disease

Bullous exfoliative dermatitis that occurs primarily in newborns and previous healthy young children

Characterized by:

• Abrupt onset of localized perioral erythema

• Slight pressure displaces the skin (+ Nikolsky sign)

• Large bullae or cutaneous blisters form, followed by desquamation of epithelium

Bullous impetigo

localized form of SSSS

specific strain of toxin producing S. aureus are associated with formation of superficial skin blisters, S. aureus is present in the localized blisters, erythema does not extend beyond the borders of the blister ( nikolsky sign not present), occurs primarily in infants and young children, highly communicable

toxic shock syndrome (TSS)

• rare but potentially fatal multisystem disease

• Characterized by:

• F e v e r

• Hypotension y

• Diffuse, macular, erythematous rash

• Desquamation of the entire skin

• Multiple organ system involvement

Staphylococcal scalded skin syndrome or ritter disease

Cutaneous blisters contain clear fluid but no organisms or leukocytes

• Epithelium becomes intact again within 7-10 days, when antibodies against

the toxin appear

• Scarring does not occur as only the top layer of epidermis is affected

• Primarily affects neonates and young children (<5% mortality rate, deaths

caused by secondary bacterial infection of denuded skin)

• Infections in adults - occur in immunocompromised hosts or patients with

renal disease (60% mortality rate)

toxic shock syndrome (TSS)

first desvribed in 1978 and was associated with women using highly absorbent tampons, although some cases appeared in men, children, and non-menstruating women; initial fatality rate - 5%, risk of recurrent diease - as high as 65% unless patient is treated with effective antibiotic

purpura fulminans

Characterized by:

• Large, purpuric skin lesion

• F e v e r

• Hypotension

• Disseminated intravascular coagulation

• A s s o c i a t e d w i t h overwhelming

meningitidis infections

food poisoning

Enterotoxins, most commonly

• A (78%)

• D (38%)

• B (10%)

• Characterized by:

• N a u s e a

• Vomiting

- abdominal pain

• severe cramping

food poisoning

• Results from ingestion of a toxin formed outside the

body

• D i s e a s e o c c u r s w h e n f o o d b e c o m e s c o n t a m i n a t e d

with enterotoxin-producing strains of S. aureus

• F o o d s u c h as:

• Salads with mayonnaise and eggs

• Meat or Meat products

• Poultry

• Egg products

• Food kept at room temperature

bacteremia

presence of bacteria in the blood, most likely originated from skin infections, more than 50% are nosocomial, commonly observed among intravenous drug users, prolonged episodes are associated with dissemination to other body sites

endocarditis

50% mortality rate unless promply diagnosed, initally have nonspecific influenze like symptoms that can deteriorate rapidly to include disruption of cardiac output and peripheral evidence of septic embolization

pneumonia

occur secondary to influenza virus infection, can develop after aspiration of oral secretion or from hematogenous spread of the organism from a distinct site; develops as a contigious, lower respiratory tract infection or a complication of bacteremia;

characterized as:

multiple abscesses and focal lesions in pulmonary parenchyma

aspiration pneumonia

seen in the young, elderly, and patients with cystic

fibrosis, influenza, chronic obstructive pulmonary disease, and bronchiectasis

hematogenous pneumonia

common for patients with bacteremia or endocatditis

necrotizing pneumonia

caused by community acquired MRSA; massive hemoptysis, septic shock, and high mortality rate

Empyma

occurs in 10% of patients with pneumonia, pus-filled pockets that develops in pleural space S. aureus responsible for ½ of cases

Osteomyelitis

results from hematogenous dissemination to bone or

by secondary infection resulting from trauma or

extension of disease from an adjacent area

• Occurs as a manifestation secondary to bacteremia

• Children - results from cutaneous infection and

involves long bone

• Sudden onset of localized pain and high fever

• Adults - Vertebral osteomyelitis, intense back pain with fever

septic arthritis

occurs in children and adults who are receving intraarticular injections or who have mechanically abnormal joints, usually seen in large joints, characterized by: painful erythematous joint with purulent material obtained on aspiration, childre: patients with trauma to the extremities, adults: histor of rheumatoid arthritis, diabetes mellitus, joint surgery, skin infections, or intravenous drug abuse

endocarditis, Catheter and Shunt infections, prosthetic joint infections, urinary tract infections

two coagulase negative S. (4)

Catheter and Shunt infections

more than 50% causes by CoNS, leads to persistent bacteremia as CoNshave continual access to the blood

native valve endocarditis

S. lugodunesis, otherwise more commonly caused by streptococci

artificial valve endocarditis

more commonly caused by staphylococci;

CoNS are introduced at time of valve replacement

indolent course of infection, clinical signs and symptoms not developing up to 1 year after procedure

infection occurs at site where valve is sewn to heart tissue - abscess formation can lead to separation of valve at suture line and to mechanical heart failure( heart valve replacement),

infections have high mortality rate

immune complex-mediated glomerulonephritis

occurs in patients with long-standing diease

prosthetic joint infections

characterized by: localized pain, mechanical failure of joint; treatment: joint replacement and antimicrobial therapy

urinary tract infections

S. saprophticus - most common staphylococcal pathogen in young sexually active women; characterized by: dysuria; pyuria, bacteriuria

Staphylococci

Recovery of ___ requires no special procedure; specimens should be taken from the site of infection after appropriate cleaning of surrounding area to avoid contamination by skin microbiota

stain, staining reaction, shape, arrangement in clusters

Sheep's Blood Agar

staphylococci produce round, smooth, white, creamy colonies _ after 18- 24 hours of incubation at 35° to 37° C

what is the agar used

staphylococci

they can produce hemolytic zones around the colonies and may rarely exhibit pigment production