Staphylococcus aureusStaphylococcus aureus

Ali Somily MD,FRCPCAli Somily MD,FRCPC

Gram Positive CocciGram Positive Cocci

Staphylococcus aureusStaphylococcus aureus Staphyloccocci - derived from Greek “stapyle” (bunch of Staphyloccocci - derived from Greek “stapyle” (bunch of

grapes)grapes) Gram Stain : Gram Positive CocciGram Stain : Gram Positive Cocci AerobicAerobic ExtracellularExtracellular FeaturesFeatures

• Morphology : CocciMorphology : Cocci• Arrangement : ClustersArrangement : Clusters• Colonies: White /yellow , rounded on blood agar plateColonies: White /yellow , rounded on blood agar plate

Non motile Non motile • Non motileNon motile

No capsuleNo capsule No glycocalyxNo glycocalyx

Virulence FactorsVirulence Factors ExotoxinsExotoxins ΒΒ-Lactamase-Lactamase

• Plasmid ,Penicillin resistantPlasmid ,Penicillin resistant Mutant Penicillin –Binding –Protein (PBP)Mutant Penicillin –Binding –Protein (PBP)

• MRSAMRSA CoagulaseCoagulase

• Free and boundFree and bound• Thrombin Thrombin Fibrin Fibrin

Protein AProtein A• Bind to Fc of IgG, Block complement and opsonizationBind to Fc of IgG, Block complement and opsonization

Other enzymesOther enzymes• Lipase, Protease, Hyaluronidase, Nuclease, FibrinolysinLipase, Protease, Hyaluronidase, Nuclease, Fibrinolysin

ExotoxinsExotoxins Hemolysins of RBCsHemolysins of RBCs

• Alpha toxin ( septic Shock and Dermonecrosis)Alpha toxin ( septic Shock and Dermonecrosis)• Beta toxin (Shingomyelinase)Beta toxin (Shingomyelinase)• Delta toxin (Leukocidin)Delta toxin (Leukocidin)• Gamma toxin (Tissue Necrosis)Gamma toxin (Tissue Necrosis)

Panton –Valentine Leukocidin (PMNs and Micros)Panton –Valentine Leukocidin (PMNs and Micros)• Influx of Ca++,Degranulation and LysisInflux of Ca++,Degranulation and Lysis

EnterotoxinsEnterotoxins• Toxin A (Food Poisoning) and F (Similar to TSST)Toxin A (Food Poisoning) and F (Similar to TSST)

Toxic Shock Syndrom Toxin(TSST)Toxic Shock Syndrom Toxin(TSST)• Release of IL2 CD4 T-cell and IL1Release of IL2 CD4 T-cell and IL1

Exfoliation ( Phage Group II , Epidermolytic; intraepithelial Exfoliation ( Phage Group II , Epidermolytic; intraepithelial Separation at Stratum Granulosum)Separation at Stratum Granulosum)

Laboratory TestsLaboratory Tests

Catalase : +veCatalase : +ve Coagulase: +veCoagulase: +ve DNase: +veDNase: +ve Mannitol: +veMannitol: +ve Hemolysis: BetaHemolysis: Beta 6.5 % NaCl : Growth6.5 % NaCl : Growth

Source and TransmissionSource and Transmission

ColonizationColonization• HumanHuman : Nose, Skin, Groin, Other moist area : Nose, Skin, Groin, Other moist area • Horizontal TransmissionHorizontal Transmission : Human contact, Sneeze : Human contact, Sneeze

and Contaminated environmentand Contaminated environment• Nosocomial TransmissionNosocomial Transmission: :

Clinical SyndromsClinical Syndroms Skin Infections (Furuncles, Boils, Carbuncles, Scalded Skin Skin Infections (Furuncles, Boils, Carbuncles, Scalded Skin

Syndrom (SSS), Burn and Wound)Syndrom (SSS), Burn and Wound) Food Poisoning (Enterotoxin A, No Bacteria, N&V)Food Poisoning (Enterotoxin A, No Bacteria, N&V) Toxic Shock Syndrom (Tampons, Wound, Nasal Packing)Toxic Shock Syndrom (Tampons, Wound, Nasal Packing) Oseomyelitis (Most Common Cause, Meta in Childern and Oseomyelitis (Most Common Cause, Meta in Childern and

Epiphysis in Adult, Truma or Hematogenous)Epiphysis in Adult, Truma or Hematogenous) Infective Artheritis (Most Common Cause in Adult)Infective Artheritis (Most Common Cause in Adult) Acute Endocarditis (Most Common Cause Normal Abnormal Acute Endocarditis (Most Common Cause Normal Abnormal

and Prosthetic Valves )and Prosthetic Valves ) Post viral lobar Pneumonia ( Especially Flu)Post viral lobar Pneumonia ( Especially Flu) Bacteremia and Sepsis (Most Common Cause ,Community Bacteremia and Sepsis (Most Common Cause ,Community

Acquired)Acquired) Parotitis ( Gland and Duct of Stensen)Parotitis ( Gland and Duct of Stensen)

TOXIN MEDIATED DISEASESTOXIN MEDIATED DISEASES

1. Staphylococcal food poisoning1. Staphylococcal food poisoning• Due to production of entero toxinsDue to production of entero toxins• heat stable entero toxin acts on gutheat stable entero toxin acts on gut• produces severe vomiting following a very short produces severe vomiting following a very short

incubation periodincubation period• Resolves on its own within about 24 hoursResolves on its own within about 24 hours

2. Toxic shock syndrome2. Toxic shock syndrome

High fever, diarrhoea, shock and erythematous High fever, diarrhoea, shock and erythematous skin rash which desquamateskin rash which desquamate

Mediated via ‘toxic shock syndrome toxin’Mediated via ‘toxic shock syndrome toxin’ 10% mortality rate10% mortality rate Described in two groups of patientsDescribed in two groups of patients

• Associated With young women using tampones during Associated With young women using tampones during menstruationmenstruation

• Described in young children and menDescribed in young children and men

3. Scalded skin syndrome3. Scalded skin syndrome

Disease of young childrenDisease of young children Mediated through minor Staphylococcal Mediated through minor Staphylococcal

infection by ‘epidermolytic toxin’ producing infection by ‘epidermolytic toxin’ producing strainsstrains

Mild erythema and blistering of skin Mild erythema and blistering of skin followed by shedding of sheets of epidermisfollowed by shedding of sheets of epidermis

Children are otherwise healthy and most Children are otherwise healthy and most eventually recovereventually recover

Pustular impetigo

Hordeolum-furuncle

Bacteremia-hemorrhage

Bacteremia-gangrene

Host Defense and ImmunityHost Defense and Immunity

Opsonization (IgG, C3b or IgM +C3b)Opsonization (IgG, C3b or IgM +C3b) Phagocytosis (by PMNs)Phagocytosis (by PMNs) Cytokines (By CD4+T-Cells)Cytokines (By CD4+T-Cells)

No Immunity Gained by InfectionNo Immunity Gained by Infection

TreatmentTreatment

Methicillin : Drug of ChiceMethicillin : Drug of Chice Penicillin : If sensitivePenicillin : If sensitive Vancomycin: If MRSAVancomycin: If MRSA Linazolid : If vancomycin RsistantLinazolid : If vancomycin Rsistant Cephalosporins : First GenerationCephalosporins : First Generation Bacitricin : TopicalBacitricin : Topical Special Special

Situation :Rifampin ,Doxycyclin ,TrimethopriSituation :Rifampin ,Doxycyclin ,Trimethoprime / Sulphamethoxazoleme / Sulphamethoxazole

PreventionPrevention

MRSAMRSA Infection controlInfection control Isolation, Treatment , DecolonizationIsolation, Treatment , Decolonization Contact percussionContact percussion

Vaccine and Toxoid : Not Available yet Vaccine and Toxoid : Not Available yet

Staphylococcus epidermidisStaphylococcus epidermidis

Gram Stain : Gram Positive CocciGram Stain : Gram Positive Cocci AerobicAerobic ExtracellularExtracellular FeaturesFeatures

• Morphology : CocciMorphology : Cocci• Arrangement : Clusters, TetradsArrangement : Clusters, Tetrads• Colonies: White/yellow , rounded on blood agar plateColonies: White/yellow , rounded on blood agar plate

Non motile Non motile No capsuleNo capsule Glycocalyx : ExopolysaccharideGlycocalyx : Exopolysaccharide

Virulence FactorsVirulence Factors

GlycocalyxGlycocalyx ΒΒ- Lactamase- Lactamase Mutant PBPMutant PBP

Exotoxins : NoneExotoxins : None

Laboratory TestsLaboratory Tests

Catalase : +veCatalase : +ve Coagulase: -veCoagulase: -ve DNase: -veDNase: -ve Mannitol: -veMannitol: -ve Hemolysis: NoneHemolysis: None Novobiocin : SusceptibleNovobiocin : Susceptible

Source and TransimissionSource and Transimission

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

ClinicalClinical

Bacteremia and SepsisBacteremia and Sepsis Subacte EndocarditisSubacte Endocarditis Neonatal BacteremiaNeonatal Bacteremia

Host Defense and ImmunityHost Defense and Immunity

OpsonizationOpsonization PhagocytosisPhagocytosis Cytokines Cytokines

No Immunity Gained by InfectionNo Immunity Gained by Infection

TreatmentTreatment

VancomycinVancomycin Cephalosporins : First generation if SensitiveCephalosporins : First generation if Sensitive

Vaccine and Toxoid : Not Available yet Vaccine and Toxoid : Not Available yet

Staphylococcus saprophyticusStaphylococcus saprophyticus

Gram Stain : Gram Positive CocciGram Stain : Gram Positive Cocci AerobicAerobic ExtracellularExtracellular FeaturesFeatures

• Morphology : CocciMorphology : Cocci• Arrangement : Clusters, TetradsArrangement : Clusters, Tetrads• Colonies: White /yellow , rounded on blood agar plateColonies: White /yellow , rounded on blood agar plate

Non motile Non motile No capsuleNo capsule No Glycocalyx No Glycocalyx

Virulence FactorsVirulence Factors

Multiple Drug ResistantMultiple Drug Resistant Hemagglutinin proteins and Surface ProteinsHemagglutinin proteins and Surface Proteins UreaseUrease

Exotoxins : NoneExotoxins : None

Laboratory TestsLaboratory Tests

Catalase : +veCatalase : +ve Coagulase: -veCoagulase: -ve DNase: -veDNase: -ve Mannitol: -veMannitol: -ve Hemolysis: NoneHemolysis: None Novobiocin : ResistantNovobiocin : Resistant

Source and TransimissionSource and Transimission

Normal Flora : of genitourinary SkinNormal Flora : of genitourinary Skin Poor Hygiene : Sexual ActivityPoor Hygiene : Sexual Activity Urinary Urinary

Tract Tract

ClinicalClinical

Urinary Tract Infection (UTI)Urinary Tract Infection (UTI)• Healthy, young, sexual active womenHealthy, young, sexual active women• Cystitis (Lower UTI) or Pyelonephritis (upper Cystitis (Lower UTI) or Pyelonephritis (upper

UTI) UTI) • Pyuria : Most casesPyuria : Most cases

Host Defense and ImmunityHost Defense and Immunity

OpsonizationOpsonization PhagocytosisPhagocytosis Cytokines Cytokines

No Immunity Gained by InfectionNo Immunity Gained by Infection

TreatmentTreatment

Trimethoprime / Sulphamethoxazole (TMP-Trimethoprime / Sulphamethoxazole (TMP-SMZ)SMZ)

Ciprofluxacin : AlternativeCiprofluxacin : Alternative

Vaccine and Toxoid : Not Available yet Vaccine and Toxoid : Not Available yet