In this slide, I will teach you about first-gram positive cocci which staphylococcus aureus. I will tell you about its diseases, transmission, pathogenesis, characteristics, lab diagnosis, treatment, and prevention

2. Staphylococcus Aureus
Mubashar Ata

3. Gram Positive Staphylococci
Staphylococcus Aureus
Staphylococcus Epidermidis
Staphylococcus Saprophyticus

4. Gram Positive Streptococci
Streptococcus Pyogenes (Group A Streptococci)
Streptococcus Agalactiae (Group B Streptococci)
Streptococcus Pneumoniae (Pneumococcus)
Streptococcus Viridans (Streptococci Sanguis, Streptococci Mutans)
Enterococcus Faecalis

5. Diseases
Most Common cause human infections
Hospital Acquired Pneumonia(Nosocomial- 48 to 72h)
Post viral bacterial pneumonia
Osteomyelitis (painful joint)
Septic Arthritis (moving ability loss)

7. Local Skin infections
 Pyogenic (Abscesses containing pus foot and many organs)
 (Central raised area or necrosis whitish pus surround by erythema)
 Furuncles and boils (infection hair follicle)
 Carbuncle
 Multi headed abscess under skin on back of neck, yellow pus near center lesion.
 Surgical Wound infection
 Due poor skin hygiene or absence of aseptic measures.
 Impetigo
 Crops of vesicles with honey colored crust (S. pyogenes)
 Folliculitis
 Multiple small pustules with pus on chin & neck

9. Disseminated infections
 Endocarditis
 Due IV drug use.
 Sepsis
 Due IV drug use. Multiple organ failure.
 Kawasaki disease
 (Inflammation of vessels and lymph nodes)
 Aneurysm of coronary arteries.
 (Abnormal dilation )

10. Exotoxin mediated diseases
Gastroenteritis
Food Poisoning due improper food storage.
Toxic shock syndrome
(Due Vaginal & nasal tampon use for absorb blood )
Scaled Skin syndrome
(Rolled up desquamated skin or peeling in infants)

12. Habitat & Transmission
Habitat
Nose and Skin
Transmission
By Hands

13. Pathogenesis
 Toxic shock syndrome toxin
 Super antigen stimulate helper T cells to release Large amount of lymphokines i.e IL2
 Enterotoxin
 Super antigen has short incubation period(symptom). Present in meats and myonies
 Scaled Skin syndrome toxin
 Exfoliatin ,Protease cleave desmoglein in tight junctions in the skin.
 Alpha toxin
 Membrane disrupt Necrosis of skin and hemolysis.

14. Pathogenesis
 Protein A ,
 Virulent factor bind heavy chain IgG to prevent activation of complement.
 Prevent phagocytosis.
 Teichoic acids
 Polymer of ribitol phosphate, help in adherence to mucosal cells)
 Lipoteichoic acid
 Surface adhesion molecule Induce septic shock by cytokines i.e IL1 and TNF from macrophages.
 P-V leukocidin, (panton valentine)
 Pore forming toxin kill WBC by damaging cell membrane.

15. Predisposing Factors
Break in the skin
Foreign Bodies (sutures)
Intravenous drug use (right side endocarditis)
Tampon use (toxic shock syndrome)
Neutrophill Level below 500/uL

16. Characteristics
Grapes like Clusters
Neutrophil with pink segmented nuclei
B hemolytic
Produce B lactamases

18. Laboratory Diagnosis
 Gram stained smear and culture (crystal violet)
 Yellow or gold colonies in blood agar due Staphyloxanthin (carotenoid pigment)
 Ferment mannitol agar yellow (due enzymes)
 Coagulase positive
 (Tube inoculated form clotted plasma ,Fibrinogen into fibrin &
 prothrombin to thrombin)
 Catalase positive (H202 into o2 and H20)
 Patchy infiltrate at X-ray (normal aerated and infected lung lobules)

20. Treatment
 Penicillin G for sensitive isolates by pencillin binding proteins on cell membrane.
 Nafcillin for plasma encoded B lactamase resistant isolates (85%)
 Vancomycin for resistant to nafcillin by change in plasma binding proteins(NRSA)
 MRSA ( methicillin resistant staphylococci)
 Rare vancomycin resistant, Genes located in transposons on plasmid encode enzymes
substitute D-lactate fro D-alanine into peptidoglycan.
 Exhibit tolerance, inhibited by antibiotics but not killed.
 Incision & drainage (I &D) for skin abscess.

21. Prevention
Cefazolin to prevent surgical infections
Hand washing
Cleanliness
Reduce IV drug use
Reduce time of tampon use
Reduce nasal carriage
Refrigate food
No Vaccine

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