Ok s. aureus mehre 92

STAPHYLOCOCCI

STAPHYLOCOCCUS

• Introduction• Classification• Antigenic Structure• Staphylococcal Enzymes• Staphylococcal Toxins• Pathogenesis• Resistance to antibiotics• Treatment

Staphylococcus

• F. Micrococcaceae

• G. Staphylococcus (facultative anaerobic)

• G. Micrococcus (only aerobic)

• G. Stomatococcus (facultative anaerobic)

• G. Planococcus (only aerobic)

•

INTRODUCTION

• Staphyloccocci - derived from Greek “stapyle” (bunch of grapes)

• Gram positive cocci arranged in clusters

• Hardy organisms surviving many non physiologic conditions

• Include a major human pathogen and skin commensals

Gram Stain of Staphylococcus Culture

Gram-positive cocci predominately in clusters

Doctor: Boil

Salesman: Carrier and Paronychia

Nurse(Carrier)

Son:Impetigo

Spread of Hospital Strain of Staphylococcus aureus

Species Catalase Coagulase Mannitol Novobiocin

S. aureus positive positive positive sensitive

S. epidermidis positive negative negative sensitive

S. saphrophyticus positive negative negative resistant

Properties of Staphylococcus species

Grouping for Clinical Purposes

• 1. Coagulase positive Staphylococci– Staphylococcus aureus

• 2. Coagulase negative Staphylococci– Staphylococcus epidermidis– Staphylococcus saprophyticus

A. Staphylococcus aureus

• Major human pathogen

• Habitat - part of normal flora in some humans and animals

• Source of organism - can be infected human host, carrier, or environment

2. Staphylococcus epidermidis• Skin commensal• Infection of an implanted device such as

heart valve, intravenus catheter.

• Ass. With infection of prosthetic• Causes urinary tract infection in

cathetarised patients• Usually resistant to many drugs.

3. Stapylococcus saprophyticus

• Skin commensal

• Imp. Cause of UTI in sexually active young women

• UTI in men (usually after age 50)

• Cystitis, pyelonephritis

Resistance to antibiotics– β- lactamase production - plasmid mediatedHas made S. aureus resistant to penicillin group

of antibiotics - 90% of S. aureus

• Resistance to Naficillin-Oxacillin-Methicillin

• (Chromosomal mediated)• Tolerance• Resistance to Tetracyclin- Erythromycin-

Aminoglycosides ( plasmid mediated )

• Tested in lab using methicillin• Referred to as methicillin resistant S. aureus (MRSA)• Emerging problem in the world• In Sri Lanka prevalence varies from 20- 40% in

hospitals• Drug of choice - vancomycin• In Japan emergence of VIRSA(vancomycin

intermediate resistant S. aureus)• No effective antibiotics discovered -We might have to

discover

Antigenic structure

• Capsule

• Peptidoglycan

• Teichoic acid

• Protein A

Staphylococcus Structural Virulence Factors

= peptidoglycan= capsule

= clumping factor= fibronectin binding protein

= collagen binding protein= protein A

= teichoic acid

= PNSG (biofilm)

Structural Carbohydrates and Virulence

Peptidoglycan Inflammatory

Teichoic Acid Inflammatory & allergen

Capsule* Anti-phagocytic

PNSG* Biofilm

* - Antibodies to these carbohydrates are protective

Staphylococcal binding sites

• The binding sites allow staphylococci to persist in areas where these substances abound.

• Fibronectin, • C1q• Lamanin (glycoprotein in mammalian

basement membranes)• Colagen

S. aureus Exoproteins and Virulence

Hemolysins: alpha-hemolysin beta-hemolysin tissue damage at gamma-hemolysin site of infection delta-hemolysinProteases tissue damageCoagulase correlates with virulence Hyaluronidase(s)StaphylokinaseLipase(s)Protease V8

spreading factors

destroy host defense

Staphylococcal Enzymes

• Coagulase

• Catalase

• Hyaluronidase

• Fibrinolysine

• Lipases

• Nucleases

• Penicillinase

Toxins

- Cytotoxins (α , β ,γ)

- Leukocidin

- Exfoliative toxins (ETA , ETB)

- Enterotoxins (A-F , G-I and three subtype C)

- SEB (super Ag)

- Toxic Shock Syndrom toxin-1 (super Ag)

α , β ,γ -hemolysin

• Toxic for :

• leukocytes , erythrocytes,

• macrophages and platelets

• Lymphocytes

DISEASES

• Due to direct effect of organism– Local lesions of

skin– Deep abscesses– Systemic infections

• Toxin mediated– Food poisoning– toxic shock

syndrome– Scalded skin

syndrome

EndocarditisScalded Skin Syndrome (toxin) Nasopharynx 4+

PneumoniaFood Poisoning (toxin)

Toxic Shock Syndrome vagina 4+

Pyoderma

Bone/Joint Infection

Brain and Eye Infections

Sites of Staphylococcus Infections and Toxic Reactions

Conditions Leading to S. aureus Infections

Skin damage: burns, cuts, sutures

Reduced Chemotaxis: burns, diabetes, cancer

Reduced Phagocytosis: diabetes, complement deficiency, immunoglobulin deficiency, genetic defect in phagocytes Age: very young or very old

Staphylococcus aureus PyodermasImpetigo - crusting vesicle formation of the skin

Folliculitis - hair follicles infected

Furnuncles - boil

Carbuncle - multiple skin lesions connected by sinuses in the connective tissue

Paronychia - infection of the nail bed

Cellulitis - spreading connective tissue infection

Eye Infections -

Staphylococcus aureus: Bulbus Impetigo

Staphylococcus aureus: Bulbous Impetigo

Staphylococcus aureus: Pustular Impetigo

Folliculitis

• Superficial folliculitis

• Infection of hair follicles

• Commonly caused by staph. aureus

• Children

• Scalp & limb

• Rarely painful

• Heals in a week

Photo of Arm Showing Folliculitis

Folliculitis Caused by Staphylococcus aureus

Staphylococcus aureus: Folliculitis

Furuncle (Boil)

• Acute

• Staph. aureus

• Small, follicular noduler -- Pustule--

necrotic--discharge pus

• Painful

• Constitutional symptoms تاثیر بدن تمام روی که عالئمی

میگذارند

Furuncle Caused by Staphylococcus aureus

Furuncle (Boil) Caused by Staphylococcus aureus

Staphylococcus aureus: Furuncle on Back of Neck

Carbuncle

• Extensive infection of a group of contagious follicles

• Staph. aureus

• Middle or old age

• Predisposing factors

– Diabetes

– Malnutrition

– During prolonged steroid therapy

• Painful, hard lump

• Suppuration begins after 5-7 days

• Pus discharge from multiple follicular

orificies

• Large deep ulcer

Staphylococcus aureus: Carbuncle on Chin

Staphylococcus aureus: paryonchia

Pus

Blepharitis Caused by Staphylococcus aureus

Staphylococcus aureus: Leading Cause of Blepharitis

Keratitis Caused by Staphylococcus aureus

Staphylococcus aureus: Keratitis

Systemic Infections• 1. With obvious focus

– Osteomyelitis, arthritis

• 2. No obvious focus• heart (infective endocarditis)

• Brain(brain abscesses)

Staphylococcus aureus: Osteomyelitis

Day 0 = No changes Day 35 = destruction of L2 ( , ), exotoses of L2 & L3 ( ), compression ( )

L2

L3

B. TOXIN MEDIATED DISEASES

• 1. Staphylococcal food poisoning– Due to production of entero toxins– (A-F, G-I, K-M) SEB (super Ag)– heat stable entero toxin acts on gut– produces severe vomiting following a very

short incubation period– Resolves on its own within about 24 hours

Staphylococcus

C. perfringens

SalmonellaShigellaC. botulinum

Other

UNKNOWN

Chemical

Parasitic Viral

Causes of Food Poisoning - - circa 1980

2. Toxic shock syndrome

• High fever, diarrhoea,vomiting, shock and erythematous skin rash which desquamate

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

– ass. With young women using tampones during menstruation

– Described in young children and men

Staphylococcus TSST Causes Desquamation

Rash Associated with TSST

Notice: men get toxic shock syndrome, only ~20% are due to vaginal infection

Erythomatous Membranes of Toxic Shock Syndrome

Toxic Shock Syndrome: Cutaneous and Soft Tissue Involvement

Woman’s side showing extensivetissue rash due toTSST.

3. Scalded skin syndrome

• Disease of young children

• Mediated via exfoliative toxins

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

• Heals 7 - 14 day

• Don’t grow staph. from blister fluid

Properties Exfoliative Exfoliative Toxin A Toxin B

Size (Daltons) 24,000 24, 000

Temperature stable 100C labile 60C

EDTA labile stable

DNA chromosome plasmid

Staphylococcus Exfoliative Toxin

Scalded Skin Syndrome Involving Exfoliative Toxin

Peeling skin

Staphylococcus aureus: Scalded Skin Syndrome

Scalded-Skin Syndrome: S. aureus Exfoliative Toxin

Toxin produced during rather limited infection from either plasmid or chromosomal toxin gene.

This condition is typically reversible with antibiotic therapy.

Thanks for your attention