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STAPHYLOCOCCI

STAPHYLOCOCCI. PROF AM KAMBAL. Staphylococci. Definition: Gram +ve cocci in clusters, catalase positive. Other gram positive cocci include Streptococci and Micrococci Differences between Staphylococci , Micrococci and Streptococci. Character Staphylococci Streptococci

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STAPHYLOCOCCI

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  1. STAPHYLOCOCCI PROF AM KAMBAL

  2. Staphylococci Definition: Gram +ve cocci in clusters, catalase positive. Other gram positive cocci include Streptococci and Micrococci Differences between Staphylococci, Micrococci and Streptococci

  3. CharacterStaphylococciStreptococci (& Micrococci) Gram Stain Positive Positive Arrangement Clusters Chains (Micrococci) in Fours) Size Large 1 um Smaller 0.5 – 1 um Catalase Positive Negative H2O2Catalase H2O + O2

  4. Staphylococci are similar to Micrococci in shape • ButStaphylococci can be: a) Pathogenic b) Commensals (Normal Flora) c) Oxidative & fermentative

  5. 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

  6. Gram Positive Cocci In Clusters Species : • S.aureus : main pathogen • S.epidermidis (S.albus) : opportunistic • S.saprophyticus : UTI

  7. Laboratory Characteristics Morphology: • Culture: ordinary media,aerobic/ non aerobic, positive catalase reaction. Colonies : • S.aureus : golden yellow-white • S.epidermidis : white, no pigment • Both tolerate 5-10 % NaCL.

  8. Staphylococci are divided into two main groups: 1) Coagulase +ve 2) Coagulase negative i.e. Staphylococcus aureus a) Staphylococcus epidermidis b) Staphylococcus saprophyticus

  9. Differentiating Tests • Coagulase test : main test • S.aureus : coagulase positive • S. epidermidis and albus : coagulase negative • Two types of coagulase tests: • Tube coagulase • Slide coagulase

  10. Coagulase Test • Enzyme secreted by Staphylococcus aureus. • Differentiate between Staphylococcus aureus and other Staphylococci • Coagulates Plasma Fibrinogen to Fibrin in clot form • Tested By: 1. Slide test for bound coagulase or clumping factor 2. Tube test free coagulase test

  11. DNAse test Phosphatase test Mannitol fermentation Novobiocin sensitivity to differentiate between S.epid. and S. saproph. which is resistant Other Tests

  12. Staphylococci are divided into two main groups: 1) Coagulase +ve 2) Coagulase negative i.e. Staphylococcus aureus a) Staphylococcus epidermidis b) Staphylococcus saprophyticus

  13. Staph. aureusStaph. epidermidis HabitatCertain areas All skin of skin surface (see diagram) Colour Mainly golden White yellow (on Blood (on Blood agar) agar medium) Catalase +ve +ve

  14. (Continued) Staph aureus Staph epidermidis Coagulase +ve -ve Dnase +ve -ve Phosphalase +ve -ve Growth on Yellow Red Mannitol salt agar due to fermentation of mannitol Phage typing availableNot available Groups I, II, III

  15. Staphylococcus aureus • Carried by 20 – 50 % of healthy people on the skin mainly in a. Nose b. Axilla c. Perineum d. Throat e. Gut

  16. Human Staphylococcal Species most important are: 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

  17. 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-

  18. 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 Plasma Fibronolysin Digests fibrin Leucoccidin Kills leucocytes Hyaluronidase Breaks down hyaluronic acid DNAase Hydrolysis DNA

  19. Virulence Factors: (Continued) Toxins Activity Lipase Lipolytic (produces opacity in egg-yolk medium) Protein A Antiphagocytic Epidermolytic toxins Epidermal splitting and exfoliation A and B Enterotoxin(s) Causes vomiting and diarrhoea Toxic shock syndrome Shock, rash, desquamation toxin - 1 • Other virulence factors include: 1. Peptidoglycan of the cell wall 2. Teichoic acid

  20. Pathogenecity Or Infections Caused By: Staph. aureus • 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

  21. 2) Skin Exfoliation • Toxic epidermal necrocysis • S.S.S.S. = Staphylococcus Scalded Skin Syndrome 3) Deep Infections • Septicaemia, • Endocarditis • Pyaemia • Osteomyelitis – Infection of bone • Pneumonia 4) Food Poisoning • Due to an enterotoxin produced in the food before ingestion. • An intoxication not infection 5) Toxic Shock Syndrome

  22. 1l – 1 = Interlukin I TNF = Tumour necrosis factor

  23. 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

  24. 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.

  25. 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.

  26. M.R.S.A • Methicillin and cloxacillin resistant S.aureus. • Due to mec A gene which codes for PBP 2a with low affinity to beta lactam antibiotics nosocomial infections. • Treatment: vancomycin for systemic infections only.

  27. 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. Polysaccharide b. Techoic acid enhanced by presence of fibrinogen. • This makes them sticky on biomaterial like catheters. Sticky material called is Biofilm.

  28. They Cause: 1. Endocarditis in artificial valves “shunts”. 2. Infections of spitz holter valves connecting brain ventricle with jugular vein 3. Infection of cannulae 4. Infection of Intravenous catheters 5. Infections of prosthesis e.g.Artificial valves (heart) Orthopaedic fixing nails 6. Infection in premature babies (Bacteriaemia) 7. Infection in Oncology patients 8. Staphylococcus saprophyticus causes urinary infection in young females

  29. Treatment of Coagulase Negative Staphylococci “Staphylococcus epidermidis” and others : • Depends on testing antibiotics sensitivity on the isolates • But Vancomycin is the drug of choice for severe serious infection

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