Post on 11-Jan-2016
STAPHYLOCOCCAL INFECTIONS
-Bacterial invasion
- Distant diseases( SSSS-TSS)
- Toxin induced( food intoxication)
MICROBIOLOGY: non motile, facultative anaerobes
G+cocci
Catalase test
PositiveStaphylococci
NegativeStreptococci
Coagulase/Protein A
PositiveS. Aureus
NegativeCoNS
Novobiocin-susceptible
ResistantS.Saprophyticuc, S.Xylosus
SensitiveS.Epidrmidis,S.Haemolyticus,S.Homis,
S.Lugdunensis, S.Schleiferi
EPIDEMIOLOGY
Normal flora: Ant. Nares Skin( damaged) Vagina Axilla Perineum OropharynxPersistant/ Transient colonization: 25-50% higher in: Insulin dependent diabetics HIV+ IVDU Hemodialysis Skin damaged
Infection: Personal colonization
Other people( hand of hospital personnel)
Environment
Aerosol of respiratory/nasal secretion
S.Aureus: leading cause of nosocomial infection
CoNS: leading cause of primary bacteremia MRSA in community: prisoners
athletes
Drug users
( poor hygiene, close contact, contaminated material, damaged skin)
PATHOGENESIS
1. Inoculation and local colonization
2. Invasion
3. Evasion of host defense mechanisms
4. spreading
1- Inoculation and local colonization
Colonization in keratinized epithelium and mucin: - other resident normal flora
- nasal mucosal damage
- antimicrobial properties of nasal secretions
- host genetic factors (HLA) - S.aureus( fibronectin binding protein, clumping factor, collagen
binding protein), S,coagulase neg ( biofilm)
Inoculation: - minor abration
- administration of medication
- intravascular access with catheters
2- Invasion
Enzyme: Serine proteases
Hyaluronidases destruction of host’s tissue Thermoneucleases nutritional material
Lipases
Toxin: 1- cytotoxins:-Panton-Valentine Leukocidin (cytolytic effect on PMN, Mac, Mono.): skin, lung infection – VRSA in community
- α toxin ( pore formation in eukaryotic cells) 2- pyrogenic toxins: ( superantigen) TSS-1, enterotoxin 3- exfoliative toxins: ETA, ETB ( destroy desmosomes)
Cell wall: N-acetyl muramic acid
N-acetyl glucosamine inflammatory process Lipoteichoic acid
3- Evasion of host defense mechanismsPolysaccharide capsule: Antiphagocytic
polysaccharide microcapsule)
Protein A: FC portion of IgG so inhibit opsonophagoytosis of PMN
Intracellular: protection from immune system
small-colony variant(prolongred ab use, slow growing, chronic/recurrent infection, prolonged ab treatment)
4- Spreading
Groups at increased risk of infection
Diabetes: - colonization
- impaired leukocyte function
PMN defects: - neutropenia
- intracellular killing (CGD) - chemotaxis ( Job’s syn., Chediak-Higashi
syn.)
- phagocytosis( Wiskot-Aldrich syn., Down syn.) - opsonization ( combined/selective
hypogamaglobulinemia)
Skin abnormality: Eczema
Prosthetic devices
DIAGNOSIS
Smear: cocci g+, single, pairs, clusterCultureBlood culturePCR
CLINICAL SYNDROMES
Skin/ Soft tissue infections1. skin dis.2. Damaged skin3. Injection4. Poor personal hygieneFolliulitis:Furucles:Carbuncles:Mastitis:Impetigo:Cellulitis:Hydradenitis suppurative:Surgical wound infection:
Skin Infection1- Folliculitis •-Involve hair follicle• -Central area of purulence• -Surrounding induration and erythema
Skin Infection2-Furuncles (boil)• painful•Hairy, moist region•Central purulence
Skin Infection3- Carbuncle•Lower neck•Severe/ painful•Extend to deeper layer•Pus discharge
Skin Infection4- Mastitis •1-3% of nursing mothers•2-3 w after delivery•Cellulitis to abscess •Systemic sign
Skin Infection5- Surgical wound infection•Progressive edema, erythema, pain
Skin Infection
6- Hidradenitis suppurativa•Apocrine sweat gland•Crops of furuncles•axillary., perineal, genital area•Spontaneous drainage•Hypertrophic scar
Skin Infection
7- Cellulitis•Pain, erythema, warmness
Musculoskeletal infections
Osteomyelitis:1-Hematogenous: Child: long bone, fever, bone pain,
claudicating, ESR, CRP, B/C (50%), bone biopsy, X-ray, Tc-phosphate, MRI
Adult: ( endocarditis, diabetes, IVDU, hemodialysis) vertebral, fever, back pain, epidural abscess, MRI
2-Contiguous: drainage, no healing, fistula, exposed bone, bone culture and biopsy
Arthritis: fever, swelling, pain, aspiration (>50,000 PMN, cluster g+cocci)
Pyomyositis: skeletal muscle, tropical region, trauma, fever, swelling, pain, aspiration (pus, WBC, cluster g+ cocci)
Respiratory tract
Newborn/infant: shortness of breath, fever, respiratory failure, CXR ( pneumatoceles), pneumotorax, empyema
Adult: nosocomial: fever, increased sputum, new infiltration
community-acquired: postviral( Influenza), septic pulmonary emboli( IVDU)
Bacteremia
SepsisEndocarditisVasculitisMetastatic seeding: bones, joints, kidney,
lungsHigh risk: community-acquried( except IVDI)
no primary source
Prosthetic device
Endocarditis
Increased recently: IV device
IVDU
hemodialysis
immunosuppression
New/changing cardiac valvular murmur, cutaneous evidence ( Osler’s node, Janeway lesion, embolic diseases)
Dignosis: B/C, Transtoracic/ transosophageal
echocardiography
Clinical setting
Right-sided (IVDU): fever, toxic clinical appearance, pleuretic chest pain, production of purulent( bloody) sputum, CXR (septic emboli)
Left-sided native valve: damaged valve
Prosthetic-valve: valvular insuifficency, myocardial abscess, need valvular replacement
Nosocomial
UTI
Ascending: instrumentationHematogen
Prosthetic device
IV catheterProsthetic valveOrthopedic devicePeritoneal catheterIntraventricular catheterVascular graftLeft-ventricular-assist device
- acute, progressive, pyogenic collection, early postimplantation
Toxic-mediated diseasesA:Toxic shock syndrome: - menstrual (TSS-1)
- nonmenstrual (Enterotoxin)
1-fever (T>38.9)
2- hypotension (BP<90mmHg, orthostatic hypotension)
3- diffuse macular rash with desquamation in 1-2 w
4- multisystem involvement: a) hepatic( Bil, ALT, AST>2X)
b) hematologic( plat.< 100,000)
c) renal ( BUN, Cr> 2X)
d) mucous( vaginal, oropharyngeal, conjunctival hyperemia) e) GI (vomiting, diarrhea)
f) muscular ( severe myalgia, CPK>2X)
g) CNS ( disorientation, alteration in conciousness without focal neurologic sign)
5- neg. serology for measles, leptospirosis, RMSF, ….
B:Food poisoning
Toxin resistant to heat1-6h after ingestionNausea, vomiting, diarheaRecovery in 8-10hD: detection of bacteria/ toxin in foodR: supportive
C: Staphylococcal Scalded-Skin Syndrome( Ritter’s disease) •Newborn/ child<1y•Nasal carriage of staff•Localized infection and toxin production•Fragile/ tender skin, thin-walled fluid-filled bullae, Nikolsky’s sign, fever, lethargy, irritability with poor feeding, dehydration•Without mucous membrane involvement
COAGULASE-NEGATIVE STAPHYLOCOCCUS (CoNS)S. Epidermidis: normal flora of skin, oropharynx, vagina
1-Implanted prosthetic material: coated with fibronectin/ fibrinogen
2-Surface-associated staphylococcal enzyme: autolyzin, fibrinogen-binding protein, cell wall teichoic acid
3-Extracellular polysaccharide (slime): protective biofilm
Prosthetic cardiac valve, prosthetic joint, vascular graft, intravascular device, CNS shunt infection
S. Saprophyticus: UTI in young womenD: culture ( 10-25% true bacteremia) 1- frequent isolation of 1 species from different site
2- growth <48h
3- growth in aerobic/ anaerobic media
TREATMENT
Antimicrobial agentSurgical incision and drainageRemoval of deviceProlonged therapy (4-8w) 1- immunocompetent
2- primary focus that was removed 2w
Antibiotics
Penicillin: ( P.G. 4mu/4h, Naficillin2g/4h, Oxacillin 2g/4h) < 5%
- Penicillinase
Methicillin: (PRP)( naficillin/Oxacillin, Cefazolin, Vancomycin, Imipenem)
- Penicillin binding protein 2 a
Vancomycin: ( MRSA), ( TMP-SMX, Ciprofloxacin, Levofloxacin, Quinupristin/dalfopristin, Linezolid, Daptomycin ) 40-50%
- Abnormal cell wall
Intermediate/ complete resistant to vancomycin ( VISA/VRSA)
Empirical : ( Vancomycin)
Synergistic effect
Β-lactam + aminoglicosideVancomycin + GentamycinVancomycin + Gentamycin + RifampinVancomycin + Rifampin
Endocarditis: native-valve: PRP + Aminoglicoside 4-6w
Prosthetic-valve: PRP + Aminoglicoside + Rifampin + surgery
Osteomyelitis/ arthritis: 4-6w
chronic: surgical debridement joint: repeated aspiration prosthetic joint: Ciprofloxacin + Rifampin
TSS: Fluid + Pressors + PRP + Clindamycin+ IVIG SSSS: supportive + PRP
PREVENTION
Hand washingIsolation proceduresTopical antibiotic agents: muciprocinVaccine: - capsular polysaccharide protein
- Ligand-binding domain of MSCRAMMS
Streptococcal infections
Normal human flora: respiratory, GI, GUG+cocci in chainsFacultative anaerobe/strict anaerobeClassification: β-hemolysis: Lancefield group A, B, C, G
α-hemolysis: Pneumococci
Viridance
γ-hemolytic Enterococcal: Faecalis, Faecum
Pharyngitis•Respiratory droplet, food-borne•20-40% exudative pharyngitis in children.•Rare under 3 y. fever, malaise, without exudative pharyngitis•Incubation period: 1-4d•Sore throat, fever, chills, malaise, abdominal pain, vomiting, erythema and swelling of pharyngeal mucosa, purulent exudates, enlarged tender ant. cervical LAP•Throat culture, Rapid test ( latex, ELISA) (specificity>90%, sensitivity<55-90%)
•P.B. 1.2mu IM, P.V. 250mg/ tds 10d Erythromycin, Azithromycin
Complications
Suppurative Cervical lymphadenitis Peritonsillar/retropharyngeal abscess Sinusitis Otitis media Meningitis Bacteremia Endocarditis Pneumonia
o Nonsuppurative ARF(throat infection, preventable with ab) PSGN(throat and skin infection, unpreventable)
Asymptomatic carrier state (20%)Bacteriologic treatment failure
If it is a potential source of infection to others
Pharyngeal colonization: P.V. 500mg/6h 10d + Rif 600mg/12h 4d
Rectal colonization: Vanco. 250mg/6h po+ Rif 600mg/12h 10d
Scarlet fever•Strep.pyrogenic exotoxic A,B,C•Pharyngitis •Rash: 1-2 d, upper trunk, extremities ( exept palms and soles), sandpaper•Circumoral pallor•Strawberry tongue•Pastia’s lines•6-9d desquamation
Impetigo•Strep.A/ S.aureus•Young children•Warm months•Tropical climate•Poor hygiene•Face, legs•Red papule, vesicle, pustule, honey-comb crust, thick •No fever, no pain•Treatment: same as pharyngitis
cephalexin, cloxacillin 250mg/6h
mupirocin
•Complication: glomerulonephritis
Erysipelas•Strep. A, C, G•Bright red skin, sharply demarcated•Warm, tender, shiny, swollen•2-3d superficial bullae•Fever, chills•Molar area of face, lower extremities
Cellulitis•Disruption in lymphatic drainage: cellulitis, mastectomy, DVT, chronic lymphedema, CAB G•Fissure, tinea pedis, surgical wound (24h)•lymphangitis•Treatment: P.