Transcript Staphylococcus

Staphylococcus
Eva L. Dizon, M.D.,FPPS,FPIDSP
Staphylococcus
Staphyle- Bunch of
grapes
0.5 to 1 um
Non motile
Aerobic or Facultative
Anaerobic
Catalase positive
Grow in media
containing 10% NaCl
at temp 18 to 40 C
Present on the skin
and mucuos
membrane
Species
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S. aureus
S. epidermidis
S. saphrophyticus
S. capitis
S. haemolyticus
Micrococcus sp
Stomatococcus mucilaginosus
Alloiococcus otitidis
Physiology and Structure
Structure
Structure
CAPSULE- loose fitting polysaccharide layer
(slime layer)
- protects bacteria by inhibiting
and phagocytosis
chemotaxis
- 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
S. aureus
- mediates the attachment ofRibitolstaphylococcus
teichoic acid with
N-acetylglucosamine
to mucosal surfaces
( Polysaccharide A)
S. epidermidis
glycerol teichoic acid
with glucosyl residues
(polysaccharide B)-
PROTEIN A- covalentlylinked to
peptidoglycan
Ig
- has affinity to Fc receptor of
- blocks opsonization and
phagocytosis
Structure
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
CYTOPLASMIC MEMBRANE- osmotic barrier for the
cell and provides an anchorage for the
biosynthetic and respiratory enzyme
Toxins
A.
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
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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
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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
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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
Coagulase
Bound
convert fibrinogen
insoluble fibrin
Free
react with globulin
plasma factor
to form
staphylothrombin
Clumping
Cause formation of fibrin layer around abscess protecting
staphylococcus from phagocytosis
Staphylococcal enzymes
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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
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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
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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
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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
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Ham , salted pork, custard, potato sald,
ice cream
Hands, Nasal carriage
I.P. – 4 hrs
Vomiting, diarrhea, abd. pain
Toxic shock syndrome
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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
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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
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Bacteremia
Endocarditis
Pneumonia
Empyema
Osteomyelitis
Septic arthritis
Pneumonia
S.Epidermidis and CNS
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Endocarditis- native or artificial valves
Catheter and shunt infection
Prosthetic joint infection
UTI
Laboratory diagnosis
Microscopy
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
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Biochemical testing
Coagulase
Heat stable nuclease
Alkaline phospatase
Mannitol fermentation test
Treatment and Prevention
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Semisynthetic penicillinase resistant
penicillin
Resistance ( mecgene A –codes for PBP
2’)
References:
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