staphylococcus (2)
TRANSCRIPT
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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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