STAPHYLOCOCCI PROF AM KAMBAL. Staphylococci Definition: Gram +ve cocci in clusters, catalase...
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Transcript of STAPHYLOCOCCI PROF AM KAMBAL. Staphylococci Definition: Gram +ve cocci in clusters, catalase...
StaphylococciStaphylococci
Definition:Gram +ve cocci in clusters, catalase positive.
Other gram positive cocci include Streptococci and MicrococciDifferences between Staphylococci, Micrococci and Streptococci
Character Staphylococci Streptococci (& Micrococci)
Gram Stain Positive Positive
Arrangement Clusters Chains(Micrococci) in Fours)
Size Large 1 um Smaller0.5 – 1 um
Catalase Positive Negative
H2O2 Catalase H2O + O2
Staphylococci are similar to Micrococci in shape But Staphylococci can be:
a) Pathogenic
b) Commensals (Normal Flora)
c) Oxidative & fermentative
While Micrococci are:
a) Commensal (Normal flora of skin)
b) Only oxidative (Non fermentative)
Can be differentiated from Staphylococci by oxidation, fermentation reactions (O – F) test
Gram Positive Cocci In Clusters
Species :Species : S.aureusS.aureus : main pathogen : main pathogen S.epidermidisS.epidermidis ( (S.albusS.albus) : opportunistic) : opportunistic S.saprophyticusS.saprophyticus : UTI : UTI
Laboratory Characteristics
Morphology:Morphology: Culture: ordinary media,aerobic/ non aerobic, Culture: ordinary media,aerobic/ non aerobic,
positive catalase reaction.positive catalase reaction.
Colonies :Colonies : S.aureus S.aureus : golden yellow-white: golden yellow-white S.epidermidis S.epidermidis : white, no pigment: white, no pigment Both tolerate 5-10 % NaCL.Both tolerate 5-10 % NaCL.
Staphylococci are divided into two main groups:
1) Coagulase +ve 2) Coagulase negative
i.e.
Staphylococcus aureus
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus
Differentiating TestsDifferentiating Tests
Coagulase test : main testCoagulase test : main test S.aureusS.aureus : coagulase positive : coagulase positive S. epidermidisS. epidermidis and albus : coagulase negative and albus : coagulase negative Two types of coagulase tests:Two types of coagulase tests:
Tube coagulaseTube coagulase Slide coagulaseSlide coagulase
Coagulase TestCoagulase Test
A) Enzyme secreted by Staphylococcus aureus.
B) Differentiate between Staphylococcus aureus and other Staphylococci
C) Coagulates Plasma Fibrinogen to Fibrin in clot form
D) Tested By:
1. Slide test for bound coagulase or clumping factor
2. Tube test free coagulase test
Other TestsOther Tests
DNAse testDNAse test Phosphatase testPhosphatase test Mannitol fermentationMannitol fermentation
Novobiocin sensitivity to differentiate between Novobiocin sensitivity to differentiate between S.epid.S.epid. and and S. saproph.S. saproph. which is resistant which is resistant
Staphylococci are divided into two main groups:
1) Coagulase +ve 2) Coagulase negative
i.e.
Staphylococcus aureus
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus
Staph. aureus Staph. epidermidis
Habitat Certain areas All skin of skin surface
(see diagram)
Colour Mainly golden White yellow (on Blood (on Blood agar) agar medium)
Catalase +ve +ve
Staph aureus Staph
epidermidis
Coagulase +ve -ve
Dnase +ve -ve
Phosphalase +ve -ve
Growth on Yellow RedMannitol salt agardue to fermentationof mannitol
Phage typing available Not available Groups I, II, III
(Continued)
Staphylococcus aureusStaphylococcus aureus
Carried by 20 – 50 % of healthy people on the skin mainly in
a. Nose
b. Axilla
c. Perineum
d. Throat
e. Gut
Species Frequency Coagulase Common Human of Infection Production Habitat
S. aureus Common Positive Anterior nares, perineum
S. epidermidis Common Negative Anterior nares, head,
axilla, arms and legs
S.saprophyticus Common Negative Urinary tract
Human Staphylococcal Species most important are:
Species Frequency Coagulase Common Human of infection production habitat
Other species are:
S. hemolyticus Uncommon Negative Axilla, pubes (apocrine glands)
S. hominis Uncommon Negative Axilla, pubes (apocrine glands)
S. simulans Uncommon Negative -
S. auricularis Rare Negative Ear canal
S. capitis Rare Negative Scalp, forehead (sebaceous gland)
S. cobnii Rare Negative - S. saccharoly- Rare Negative -
ticus
S. warneri Rare Negative -
S. xylosis Rare Negative -
Virulence Factors:A. Toxins and toxic components produced by
Staphylococcus aureus
Toxins Activity
Haemolysins a, B, y and - Cytolytic, lyse erythrocytes of various animal species
Coagulase Clots PlasmaFibronolysin Digests fibrinLeucoccidin Kills leucocytesHyaluronidase Breaks down hyaluronic
acidDNAase Hydrolysis DNA
Toxins ActivityLipase Lipolytic (produces opacity in egg-
yolk medium)
Protein A Antiphagocytic
Epidermolytic toxins Epidermal splitting and exfoliation
A and B
Enterotoxin(s) Causes vomiting and diarrhoeaToxic shock syndrome Shock, rash, desquamationtoxin - 1
Virulence Factors: (Continued)
B. Other virulence factors include:
1. Peptidoglycan of the cell wall
2. Teichoic acid
Pathogenecity Or Infections Caused By: Staph. aureus
1) Superficial Infection
1. Pustules
2. Boils
3. Carbuncles
4. Impetigo
5. Collection of pus
6. Abscesses
7. Wound infection (Hospital Acquired)
8. Paronychia – Infection of nail bud
Toxic epidermal necrocysis S.S.S.S. = Staphylococcus Scalded Skin Syndrome
3) Deep Infections Septicaemia, Endocarditis Pyaemia Osteomyelitis – Infection of bone Pneumonia
2) Skin Exfoliation
Due to an enterotoxin produced in the food before ingestion. An intoxication not infection
5) Toxic Shock Syndrome
4) Food Poisoning
Treatment: Drain Pus if any + Antibiotics
Antibiotic Sensitivity (Staphylococcus aureus)
1. Penicillin 95% ®: if sensitive, it is the best drug
2. Flu/Cloxacillin (Methicillin) Drug of choice
3. Fucidic Acid penetrate well in bones
4. Vancomycin if the organism is resist to methicillin (MRSA)
5. Erythromycin
6. Clindamycin
7. Rifampicin
MRSA = Methicillin Resistant Staphylococcus aureus
MRSA: Also Resistant to Cloxacillin & Flucloxacillin
Treatment For MRSA = Vancomycin
Treatment of Staphylococcus aureus
95% Resistant to Penicillin so treated by Cloxacillin if Resistant to Cloxacillin or Methicillin = MRSA = so treat with Vancomycin.
MRSA = Methicillin Resistant Staphylococcus aureus
MRSA: Also Resistant to Cloxacillin & Flucloxacillin
Treatment For MRSA = Vancomycin
Treatment of Staphylococcus aureus
95% Resistant to Penicillin so treated by Cloxacillin if Resistant to Cloxacillin or Methicillin = MRSA = so treat with Vancomycin.
M.R.S.AM.R.S.A
Methicillin and cloxacillin resistant Methicillin and cloxacillin resistant S.aureus.S.aureus. Due toDue to mec A gene mec A gene which codes for PBP which codes for PBP 2a2a with with
low affinity to beta lactam antibiotics nosocomial low affinity to beta lactam antibiotics nosocomial infections.infections.
TreatmentTreatment: vancomycin for systemic infections : vancomycin for systemic infections only.only.
B) Staphylococcus saprophiticus
It causes urinary tract infection in young female.
Coagulase Negative Staphylococci (it is novobiocin resistant)The commonest coagulase negative is:
Staph. epidermidis
Pathogenesis: They produce very small amounts of toxins. Pathogenesis is mainly due to production of (slime) which consists of:
a. Polysaccharideb. Techoic acid enhanced by presence of fibrinogen.
This makes them sticky on biomaterial like catheters. Sticky material called is Biofilm.
They Cause:
1. Endocarditis in artificial valves “shunts”.2. Infections of spitz holter valves connecting brain ventricle
with jugular vein3. Infection of cannulae4. Infection of Intravenous catheters5. Infections of prosthesis
e.g. Artificial valves (heart) Orthopaedic fixing nails
6. Infection in premature babies (Bacteriaemia)7. Infection in Oncology patients8. Staphylococcus saprophyticus causes urinary infection in
young females