1. Staphylococcus aureus
Gram Positive Cocci
Staphylococcus aureus
Ali Somily MD,FRCPC

2. Staphylococcus aureus
Staphyloccocci - derived from Greek “stapyle” (bunch of grapes)
Gram Stain : Gram Positive Cocci
Aerobic
Extracellular
Features
Morphology : Cocci
Arrangement : Clusters
Colonies: White /yellow , rounded on blood agar plate
Non motile
No capsule
No glycocalyx

4. Virulence Factors Exotoxins Β-Lactamase
Plasmid ,Penicillin resistant
Mutant Penicillin –Binding –Protein (PBP)
MRSA
Coagulase
Free and bound
Thrombin  Fibrin
Protein A
Bind to Fc of IgG, Block complement and opsonization
Other enzymes
Lipase, Protease, Hyaluronidase, Nuclease, Fibrinolysin

5. Exotoxins Hemolysins of RBCs
Alpha toxin ( septic Shock and Dermonecrosis)
Beta toxin (Shingomyelinase)
Delta toxin (Leukocidin)
Gamma toxin (Tissue Necrosis)
Panton –Valentine Leukocidin (PMNs and Micros)
Influx of Ca++,Degranulation and Lysis
Enterotoxins
Toxin A (Food Poisoning) and F (Similar to TSST)
Toxic Shock Syndrom Toxin(TSST)
Release of IL2 CD4 T-cell and IL1
Exfoliation ( Phage Group II , Epidermolytic; intraepithelial Separation at Stratum Granulosum)

6. Laboratory Tests Catalase : +ve Coagulase: +ve DNase: +ve
Mannitol: +ve
Hemolysis: Beta
6.5 % NaCl : Growth

7. Source and Transmission
Colonization
Human : Nose, Skin, Groin, Other moist area
Horizontal Transmission : Human contact, Sneeze and Contaminated environment
Nosocomial Transmission:

8. Clinical Syndroms
Skin Infections (Furuncles, Boils, Carbuncles, Scalded Skin Syndrom (SSS), Burn and Wound)
Food Poisoning (Enterotoxin A, No Bacteria, N&V)
Toxic Shock Syndrom (Tampons, Wound, Nasal Packing)
Oseomyelitis (Most Common Cause, Meta in Childern and Epiphysis in Adult, Truma or Hematogenous)
Infective Artheritis (Most Common Cause in Adult)
Acute Endocarditis (Most Common Cause Normal Abnormal and Prosthetic Valves )
Post viral lobar Pneumonia ( Especially Flu)
Bacteremia and Sepsis (Most Common Cause ,Community Acquired)
Parotitis ( Gland and Duct of Stensen)

9. TOXIN MEDIATED DISEASES
1. Staphylococcal food poisoning
Due to production of entero toxins
heat stable entero toxin acts on gut
produces severe vomiting following a very short incubation period
Resolves on its own within about 24 hours

10. 2. Toxic shock syndrome
High fever, diarrhoea, shock and erythematous skin rash which desquamate
Mediated via ‘toxic shock syndrome toxin’
10% mortality rate
Described in two groups of patients
Associated With young women using tampones during menstruation
Described in young children and men

12. 3. Scalded skin syndrome Disease of young children
Mediated through minor Staphylococcal infection by ‘epidermolytic toxin’ producing strains
Mild erythema and blistering of skin followed by shedding of sheets of epidermis
Children are otherwise healthy and most eventually recover

13. Pustular impetigo
Hordeolum-furuncle

14. Bacteremia-hemorrhage

15. Bacteremia-gangrene

16. Host Defense and Immunity
Opsonization (IgG, C3b or IgM +C3b)
Phagocytosis (by PMNs)
Cytokines (By CD4+T-Cells)
No Immunity Gained by Infection

17. Treatment Methicillin : Drug of Chice Penicillin : If sensitive
Vancomycin: If MRSA
Linazolid : If vancomycin Rsistant
Cephalosporins : First Generation
Bacitricin : Topical
Special Situation :Rifampin ,Doxycyclin ,Trimethoprime / Sulphamethoxazole

18. Prevention MRSA Infection control
Isolation, Treatment , Decolonization
Contact percussion
Vaccine and Toxoid : Not Available yet

19. Staphylococcus epidermidis
Gram Stain : Gram Positive Cocci
Aerobic
Extracellular
Features
Morphology : Cocci
Arrangement : Clusters, Tetrads
Colonies: White/yellow , rounded on blood agar plate
Non motile
No capsule
Glycocalyx : Exopolysaccharide

20. Virulence Factors
Glycocalyx
Β- Lactamase
Mutant PBP
Exotoxins : None

21. Laboratory Tests Catalase : +ve Coagulase: -ve DNase: -ve
Mannitol: -ve
Hemolysis: None
Novobiocin : Susceptible

22. Source and Transimission
Normal Flora : Skin and Mucous membrane
Infections : Trauma and Foreign bodies

23. Clinical Bacteremia and Sepsis Subacte Endocarditis
Neonatal Bacteremia

24. Host Defense and Immunity
Opsonization
Phagocytosis
Cytokines
No Immunity Gained by Infection

25. Treatment Vancomycin Cephalosporins : First generation if Sensitive
Vaccine and Toxoid : Not Available yet

26. Staphylococcus saprophyticus
Gram Stain : Gram Positive Cocci
Aerobic
Extracellular
Features
Morphology : Cocci
Arrangement : Clusters, Tetrads
Colonies: White /yellow , rounded on blood agar plate
Non motile
No capsule
No Glycocalyx

27. Virulence Factors Multiple Drug Resistant
Hemagglutinin proteins and Surface Proteins
Urease
Exotoxins : None

28. Laboratory Tests Catalase : +ve Coagulase: -ve DNase: -ve
Mannitol: -ve
Hemolysis: None
Novobiocin : Resistant

29. Source and Transimission
Normal Flora : of genitourinary Skin
Poor Hygiene : Sexual Activity Urinary Tract

30. Clinical Urinary Tract Infection (UTI)
Healthy, young, sexual active women
Cystitis (Lower UTI) or Pyelonephritis (upper UTI)
Pyuria : Most cases

31. Host Defense and Immunity
Opsonization
Phagocytosis
Cytokines
No Immunity Gained by Infection

32. Treatment Trimethoprime / Sulphamethoxazole (TMP-SMZ)
Ciprofluxacin : Alternative
Vaccine and Toxoid : Not Available yet