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.