staphylococcus (2)
Post on 09-Jun-2015
1.785 Views
Preview:
TRANSCRIPT
Staphylococcus
Eva L. Dizon, M.D.,FPPS,FPIDSP
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
Species S. aureus S. epidermidis S. saphrophyticus S. capitis S. haemolyticus Micrococcus sp Stomatococcus mucilaginosus Alloiococcus otitidis
Physiology and Structure
Structure
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
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)-
PROTEIN A- covalentlylinked to peptidoglycan
- has affinity to Fc receptor of Ig
- blocks opsonization and phagocytosis
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
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)
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
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
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
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
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
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
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
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
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
Epidemiology
Transient colonizer of skin Nasal carriage – anterior
nasopharynx Persistent carrier – hospital
personnel Killed by high temperature and
disinfectant Direct contact, fomites Handwashing
Sites of infection
Ritters disease or SSSS
Perioral erythema spread body bullous desquamation
Nikolsky sign Bullous impetigo – localized form
of SSSS- localized blister - culture positive
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.
Staphylococcal food poisoning
Ham , salted pork, custard, potato sald, ice cream
Hands, Nasal carriage I.P. – 4 hrs Vomiting, diarrhea, abd. pain
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
TSS
Cutaneous infection
Impetigo Folliculitis Furuncle Carbuncle Wound infection
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.
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.
Others
Bacteremia Endocarditis Pneumonia Empyema Osteomyelitis Septic arthritis
Pneumonia
S.Epidermidis and CNS
Endocarditis- native or artificial valves
Catheter and shunt infection Prosthetic joint infection UTI
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
Culture – S. aureus
S. epidermidis S. saphrophyticus
Coagulase test
Showing positive (upper tube) and negative (lower tube) coagulase tests.
Mannitol Salt Agar test
Identification
Biochemical testingCoagulase Heat stable nucleaseAlkaline phospatase
Mannitol fermentation test
Treatment and Prevention
Semisynthetic penicillinase resistant penicillin
Resistance ( mecgene A –codes for PBP 2’)
top related