ok s. aureus mehre 92
DESCRIPTION
Bacteriology2, Session 1, 26bahman1392, Professor Havaii(PHD)TRANSCRIPT
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