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Staphylococcus Eva L. Dizon, M.D.,FPPS,FPIDSP

Staphylococcus (2)

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Page 1: Staphylococcus (2)

Staphylococcus

Eva L. Dizon, M.D.,FPPS,FPIDSP

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Staphylococcus

Staphyle- Bunch of grapes0.5 to 1 umNon motileAerobic or Facultative AnaerobicCatalase positiveGrow in media containing 10% NaCl at temp 18 to 40 CPresent on the skin and mucuos membrane

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Species S. aureus S. epidermidis S. saphrophyticus S. capitis S. haemolyticus Micrococcus sp Stomatococcus mucilaginosus Alloiococcus otitidis

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Physiology and Structure

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Structure

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StructureCAPSULE- loose fitting polysaccharide layer (slime layer)

- protects bacteria by inhibiting chemotaxis and phagocytosis

- facilitates adherence of bacteria to catheters and synthetic materials

PEPTIDOGLYCAN- half of the cell wall

- consist of layers of glycan chains with alternating subunits of N –acetylmuramic acid and N- acetylglucosamine

- has endotoxin like activity

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Structure

TEICHOIC ACID- phosphate containing polymers bound to peptidoglycan layer or to cytplasmic membrane

- mediates the attachment of staphylococcus to mucosal surfaces

S. aureus

Ribitol teichoic acid with N-acetylglucosamine ( Polysaccharide A)

S. epidermidis

glycerol teichoic acid with glucosyl residues (polysaccharide B)-

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PROTEIN A- covalentlylinked to peptidoglycan

- has affinity to Fc receptor of Ig

- blocks opsonization and phagocytosis

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Structure

CYTOPLASMIC MEMBRANE- osmotic barrier for the cell and provides an anchorage for the

biosynthetic and respiratory enzyme

COAGULASE and other SURFACE PROTEIN-Clumping factor or Bound coagulase binds fibrinogen convert to insoluble fibrin causing staphylococcus to

clump

- collagen , elastin and fibronectin binding protein

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ToxinsA. 5 Cytolytic or membrane damage toxin

1. Alpha

2. Beta

3. Gamma

4. Delta

5. Panton Valentine

B. 2 Exfoliative toxin

C. 8 Enterotoxin

D. Toxic Shock Syndrome Toxin(TSST 1)

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Cytotoxins

Lyse neutrophils release of lysosomal enzymes damage sorrounding tissues

Alpha toxin – disrupts the smooth muscle in blood vessels

- toxic to erythrocytes, hepatocytes, platelets, cultivated cells

- integrates to host cell membrane pores efflux of K and influx

of Na,Ca osmotic swelling cell lysis

- septic shock

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Cytotoxin

Beta Toxin - Sphingomyelinase C

- specific for sphingomyelin and lysophosphatidylcholine

- toxic to RBC, WBC,Macrophage and fibroblast

- catalyze hydrolysis of membrane phospholipids in susceptible cells

- tissue destruction and abscess formation

Delta toxin- disrupts cell membrane

- toxic to variety of cells

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Cytotoxin

Gamma toxin and Panton Valentine

-both damage membrane of susceptible cells

- lyze nuetrophils and macrophages

- cell lysis is mediated by pore formation

-Cause necrotizing skin infection

--PVL -potent leukotoxicity

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Exfoliative toxin ETA - heat stable ETB – heat labile Serine protease Exposure splitting of desmosomes or

intercellular bridges in the stratum granulosum epidermis

Common in neonates – ETA and ETB binds to GM4 like glycolipids present in neonates

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Enterotoxin A-E, G-I Stable to heating , resistant to

hydrolysis Enterotoxin A – most commonly

associated with disease Enterotoxin C and D- contaminated milk

products Enterotoxin B- Pseudomembranous

colitis Superantigens

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TSST-1

Formerly pyrogenic exotoxin C and entertoxin F

Induce cytokine release from macrophage and T lymphocytes

Increase sensitivity to endotoxin Produce leakage of endothelial

cells Penetrate mucosal barrier

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Staphylococcal enzymes

convert fibrinogen react with globulin plasma factor insoluble fibrin to form

staphylothrombin

Clumping

Cause formation of fibrin layer around abscess protecting staphylococcus from phagocytosis

Coagulase

Bound Free

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Staphylococcal enzymes

Catalase- catalyze the conversion of toxic hydrogen peroxide to water and oxygen

Hyalurodinase- hydrolyzes hyaluronic acid in acellular matrix of connective tissue spread

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Staphylococcal enzymes

Fibrinolysin- staphylokinase . Dissolve fibrin clot- aid in bacterial spreading

Lipases hydrolyse lipid to ensure survival in sebaceous areas of the body

Nuclease Penicillinase- plasmid Fatty acid modifying enzyme

(FAME)- antibacterial lipid- prolonged bacterial survival

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Epidemiology

Transient colonizer of skin Nasal carriage – anterior

nasopharynx Persistent carrier – hospital

personnel Killed by high temperature and

disinfectant Direct contact, fomites Handwashing

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Sites of infection

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Ritters disease or SSSS

Perioral erythema spread body bullous desquamation

Nikolsky sign Bullous impetigo – localized form

of SSSS- localized blister - culture positive

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SSSS

most commonly in children and neonates. Starts abruptly with perioral (around the mouth) erythema with sunburn-like rash rapidly turning bright red spreading to bullae (large vesicle appearing as a circumscribed area) in 2-3 days and desquamating (peeling) within 5 days.

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Staphylococcal food poisoning

Ham , salted pork, custard, potato sald, ice cream

Hands, Nasal carriage I.P. – 4 hrs Vomiting, diarrhea, abd. pain

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Toxic shock syndrome

Growth of organism in vagina or wound release of TSST-1

Fever, macular erythematous rashes, hypotension, multiorgan involvement, desquamation of palm and sole

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TSS

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Cutaneous infection

Impetigo Folliculitis Furuncle Carbuncle Wound infection

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Folliculitis - superficial folliculitis is essentially a staphylococcal impetigo in which a small area of erythema develops around a hair follicle and subsequently becomes a dome-shaped pustule.

Carbuncle - a deep-seated pyogenic infection of the skin and subcutaneous tissues.

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Impetigo - a contagious superficial pyoderma, caused by S. aureus and Streptococcus pyogenes, that begins with a superficial flaccid vesicle which ruptures and forms a thick yellowish crust, most commonly occurring in the face.

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Others

Bacteremia Endocarditis Pneumonia Empyema Osteomyelitis Septic arthritis

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Pneumonia

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S.Epidermidis and CNS

Endocarditis- native or artificial valves

Catheter and shunt infection Prosthetic joint infection UTI

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Laboratory diagnosisMicroscopy

Culture

Grow rapidly within 24 hours

Large, golden, smooth colonies

Blood Agar- hemolysis

Selective media- add NaCl 7.5%

Mannitol – fermented by S. aureus

Serology

Insensitive

Antibody against teichoic acid

Bacteremia. Endocarditis

After 2 weeks

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Culture – S. aureus

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S. epidermidis S. saphrophyticus

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Coagulase test

Showing positive (upper tube) and negative (lower tube) coagulase tests.

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Mannitol Salt Agar test

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Identification

Biochemical testingCoagulase Heat stable nucleaseAlkaline phospatase

Mannitol fermentation test

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Treatment and Prevention

Semisynthetic penicillinase resistant penicillin

Resistance ( mecgene A –codes for PBP 2’)

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