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

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

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

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)

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

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

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)

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

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

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

Pustular impetigo Hordeolum-furuncle

Bacteremia-hemorrhage

Bacteremia-gangrene

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

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

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

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

Virulence Factors Glycocalyx Β- Lactamase Mutant PBP Exotoxins : None

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

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

Clinical Bacteremia and Sepsis Subacte Endocarditis Neonatal Bacteremia

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

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

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

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

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

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

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

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

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