1. Gram Positive Cocci: STAPHYLOCOCCUS EDWARD-BENGIE L. MAGSOMBOL, MD, FPCP, FPCC Department of Microbiology Fatima College of Medicine

2. Staphylococci: General Characteristics Greek: “staphyle”= bunch of grapes Greek: “staphyle”= bunch of grapes arranged in clusters, divides in many planes arranged in clusters, divides in many planes Gram positive Gram positive Catalase positive Catalase positive Grow best in aerobic conditions but may behave as facultative anaerobes Grow best in aerobic conditions but may behave as facultative anaerobes Grow in 7.5% NaCl Grow in 7.5% NaCl

3. Gram Positive cocci in clusters

4. Staphylococci: Classification S. aureus: most important pathogen S. aureus: most important pathogen responsible for most human infections responsible for most human infections S. epidermidis: opportunistic infections S. epidermidis: opportunistic infections S. saprophyticus: opportunistic infections, UTI in sexually active females S. saprophyticus: opportunistic infections, UTI in sexually active females

5. Staphylococci: Structure Cell wall teichoic acid Cell wall teichoic acid S. aureus= ribitol teichoic acid S. aureus= ribitol teichoic acid S. epidermidis= glycerol teichoic acid S. epidermidis= glycerol teichoic acid Peptidoglycan Peptidoglycan tetrapeptides attached to muramic acid tetrapeptides attached to muramic acid residues and linked by pentaglycine residues and linked by pentaglycine bridges bridges sensitive to lysostaphin (S. staphylolyticus) sensitive to lysostaphin (S. staphylolyticus)

6. Staphylococci: Determinants of Pathogenicity 1. Exotoxins a. pyrogenic exotoxins= interacts with a. pyrogenic exotoxins= interacts with both MHC-II of macrophages and both MHC-II of macrophages and specific variable regions on T-cells specific variable regions on T-cells “superantigens” “superantigens” release IL-1, TNF alpha, IL-6 release IL-1, TNF alpha, IL-6 fever, capillary leak, circulatory collapse fever, capillary leak, circulatory collapse and shock and shock

7. Staphylococci: Determinants of Pathogenicity 2. Types a. Enterotoxins= in 33% of S. aureus; a. Enterotoxins= in 33% of S. aureus; heat stable CHONs heat stable CHONs (1) Enterotoxin A= most common; (1) Enterotoxin A= most common; vomiting and diarrhea vomiting and diarrhea (2) Enterotoxin B-F= structure and (2) Enterotoxin B-F= structure and function same with A function same with A

8. Staphylococci: Determinants of Pathogenicity 2. Types b. TSST-1= fever, multiple organ b. TSST-1= fever, multiple organ dysfunction and shock dysfunction and shock structurally identical to enterotoxin structurally identical to enterotoxin F

9. Staphylococci: Determinants of Pathogenicity b. Leucocidin: kills PMNs and macrophages c. Exfoliatins: cleave stratum corneum coded by chromosomal gene or coded by chromosomal gene or plasmid plasmid immunogenic immunogenic

10. Staphylococci: Determinants of Pathogenicity 2. Hemolysins alpha, beta, gamma and sigma: lyse RBCs; facilitates tissue sigma: lyse RBCs; facilitates tissue destruction destruction 3. Protein A: surface CHON covalently bound to peptidoglycan covalently bound to peptidoglycan in >90% of isolates in >90% of isolates MOA: binds to Fc portion of IgG, MOA: binds to Fc portion of IgG, prevents Abs from binding to bacteria, prevents Abs from binding to bacteria, hinders opsonization hinders opsonization massive complement activation--shock massive complement activation--shock

11. Staphylococci: Determinants of Pathogenicity 4. Enzymes B-lacamase (penicillinase) B-lacamase (penicillinase) fibrinolysin (staphylokinase) fibrinolysin (staphylokinase) DNAse DNAse phospholipase phospholipase hyaluronidase hyaluronidase

12. Staphylococci: Clinical Disease 1. Superficial infections a. Pyoderma (impetigo) a. Pyoderma (impetigo) b. Folliculitis, furuncles (boils) and b. Folliculitis, furuncles (boils) and sties sties c. Abscesses and carbuncles c. Abscesses and carbuncles

13. Folliculitis

14. Carbuncle

15. Staphylococci: Clinical Disease 2. Deep infections a. Osteomyelitis a. Osteomyelitis b. Pneumonia b. Pneumonia c. Acute endocarditis c. Acute endocarditis d. Arthritis d. Arthritis e. Bacteremia, septicemia e. Bacteremia, septicemia f. Deep organ abscesses (brain, f. Deep organ abscesses (brain, kidney, lungs) kidney, lungs)

16. Brain abscess

17. Acute infective endocarditis

18. Staphylococci: Clinical Disease 3. Staphylococcal toxin diseases a. Scalded skin syndrome (SSS) a. Scalded skin syndrome (SSS) (1) bullous impetigo (1) bullous impetigo (2) staphylococcal scarlet fever (2) staphylococcal scarlet fever b. Staphylococcal food poisoning b. Staphylococcal food poisoning c. Toxic shock syndrome (TSS) c. Toxic shock syndrome (TSS)

19. Bullous impetigo

20. Staphylococci: Epidemiology Colonizes skin and mucous membranes of 30% of normal humans Colonizes skin and mucous membranes of 30% of normal humans Anterior nares: most common site Anterior nares: most common site Human to human transmission Human to human transmission Nosocomial infectious agent Nosocomial infectious agent Contamination of food by handlers Contamination of food by handlers Phage typing used to trace the source Phage typing used to trace the source

21. Staphylococci: Laboratory Diagnosis Microscopic: gram (+) cocci in clusters Microscopic: gram (+) cocci in clusters Culture: BAP, aerobic conditions Culture: BAP, aerobic conditions 7.5% NaCl, 40% bile, 7.5% NaCl, 40% bile, polymyxin polymyxin mannitol salt agar mannitol salt agar Identification: coagulase test Identification: coagulase test mannitol fermentation mannitol fermentation

22. Gram Positive cocci in clusters

23. S. epidermidis culture

24. Coagulase test

25. Staphylococci: Treatment Most isolates now resistant to penicillin Most isolates now resistant to penicillin Penicillinase-resistant penicillin (methicillin, oxacillin, nafcillin) Penicillinase-resistant penicillin (methicillin, oxacillin, nafcillin) First generation cephalosporin First generation cephalosporin Vancomycin: for MRSA Vancomycin: for MRSA Erythromycin, clindamycin, 1 st gen cephalosporin: for penicillin allergic pts Erythromycin, clindamycin, 1 st gen cephalosporin: for penicillin allergic pts

26. Staphylococci: Treatment Both superficial and deep infections need to be given antibiotics but deep infections need higher doses, IV route, and prolonged treatment Both superficial and deep infections need to be given antibiotics but deep infections need higher doses, IV route, and prolonged treatment Debridement or drainage may be needed Debridement or drainage may be needed

27. Staphylococci: Control and Prevention Suppress the carrier state Suppress the carrier state Diligent aseptic practices Diligent aseptic practices No vaccine available No vaccine available