Lecture 4: Mycobacteria and Endocarditis Flashcards
Mycobacteria: Management
- Isolated in negative pressure room
- Treatment with 4 drug therapy initiated: Isoniazid, Rifampin, Pyrazinamide, Ethambutol
- For treatment resistant mtb: Amikacin and Moxifloxacin
Mtb: Primary Infection
- Ghon complex is lung involvement with lymphadenopathy
- Over next 2 to 6 weeks cell mediated immunity may control infection. If not, expanding lesion and lung destruction with caseating necrosis
- Hematogenous spread with miliary disease and seeding of distant sites (brain, bone, liver, kidney, bowel, nodes)
- Erosion into airways results in infectivity to others via droplets small enough for airborne transmission
- Mortality rate up to 80% in untreated disease
Mtb: Reactivation Disease
- Proliferation of dormant bacteria from initial blood seeding
- Host immunity is key for reactivation
- Risk relative to person with positive TB skin test and no risk factors
- » AIDS: 110 to 170 x
- » HIV: 50 to 110 x
- » Transplant: 20 to 70 x
- » Head and neck cancer 40 x
- » Silicosis: 30 x
- » Hemodialysis: 10 to 25 x
- » Exposure within last 2 years: 15 x
- » TB scarring on x-ray (upper lobe fibronodular) 6 to 19 x
- » Tumor necrosis factor inhibitors: 1.7 to 9 x
- Other risk factors with less than 6 x risk include diabetes, smoking, corticosteroid use > 15 mg / day, gastrectomy, malnutrition (less than 85% ideal body weight)
Mtb: Reactivation Disease Age Risk
– Infants (ages ≤1 years): 50 percent
– Children (ages 1 to 2): 12 to 25 percent – Children (ages 2 to 5): 5 percent
– Children (ages 5 to 10): 2 percent
– Age >10 years: 1 to 2 percent
- Reactivation often in apices of lungs
- Less caseation and regional lymph node involvement
- May reactivate in disseminated sites with symptoms related to involved organs
Mtb: Clinical features
- Primary, latent and reactivation pathophysiology described earlier
- Socioeconomic factors (homeless, IVDU, TB endemic area) all increase risk of disease
- Fever, cough, weight loss , night sweats, malaise
- – Sputum may be purulent or have hemoptysis
- Symptoms are often chronic lasting several weeks before diagnosis
- Big problem in HIV patients in Africa
Mtb DDx
Similar symptoms with presence of granulomas (list is longer)
– Other Mycobacteria (M. avium complex)
– Sarcoidosis
– Endemic fungal infections (Histoplasmosis, Blastomycosis, Coccidiodomycosis)
– Q-fever (Coxiella burnetii)
– Lymphoma
– Foreign body vasculitis from IVDU
– HIV infection with AIDS
Mycobacterium leprae
– Involves skin and peripheral nerves
– Mostly found in developing countries
– Transmission is via respiratory route
– Risk factors
- Close contact with active case (lepromatous or multibacillary)
- Exposure to nine banded armadillo in North America
- Older age
- Genetic factors which influence type of leprosy experienced
Sx:
- Hypopigmentation or reddish discoloration
- Loss of sensation in skin lesion
- Peripheral neuropathy (paraesthesias)
- Painless burns or wounds on feet or hands
- Lumps or swelling of earlobes or face
- Enlarged peripheral nerve
Other mycobacteria
- Organisms ubiquitous in environment
- 4 spectra of infection
- Lymphadenopathy in children (M. scrofulaceum)
- Skin lesions by direct inoculation (M. marinum)
- Infection in lung in elderly (Mycobacterium avium complex)
- Disease in immunocompromised host
thin, IV drug use marks on right and left forearms. No skin findings endocarditis. 2/6 systolic murmur right sternal border. Scattered crackles in lungs. Uterus palpable above umbilicus
– WBC 17.3, Hg 101, platelets 95
– Creatinine 75
– CXR bilateral pneumonia
Dx: Endocarditis
Endocarditis: Clinical Features
Sx
- Fever, fatigue, myalgias, arthralgias, weight loss, exercise intolerance, diaphoresis
- Evidence of embolic phenomena
- Septic arthritis, brain abscess or stroke, splenic abscess
- Generalized arthralgias
- Right sided emboli go to the lung – pleuritic chest pain, cough, shortness of breath
Note: Right sided endocarditis will have the embolic phenomena in the lung so usual peripheral exam findings are often absent unless coincident left sided disease
Dx: FROM Josh C
- Eyes: Roth spots
- CVS: new regurgitant murmur, muffled prosthetic valve,
- pericardial rub, signs of heart failure
- RESP: signs of septic pulmonary infarcts
- ABDO: tender splenomegaly
- Extremities: petechiae, splinter hemorrhages, Janeway lesions, Osler’s nodes
- NEURO: Focal neurologic deficits
Endocarditis: Modified Duke’s Criteria
Major Criteria
- Persistent positive blood cultures with organism typical for endocarditis
- Evidence of endocardial involvement
- Positive echocardiogram
- New valvular regurgitation
- Serologic or culture evidence of Coxiella burnetii infection
Minor Criteria
- Predisposition: prosthetic heart valve, structural heart disease, IVDU
- Fever
- Vascular phenomena - major arterial emboli, septic pulmonary emboli, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhage, Janeway lesions
- Immunologic phenomena - GN, Osler’s nodes, Roth spots, RF
- Intermittent bacteremia/fungemia
Definite endocarditis
- Direct evidence on histology or gram stain of vegetation or infected cardiac tissue
- 2 major criteria
- 1 major criteria and 3 minor
- 5 minor criteria
Possible
- 1 major and 1 or 2 minor criteria
- 3 minor criteria
Endocarditis: Investigations
- Blood cultures x 3
- over 1 hour (prior to empiric antibiotic therapy if possible) from 3 different sites.
- If subacute presentation can hold off antibiotics while investigating.
- If rapid onset and unwell initiate therapy after cultures collected
- ESR/CRP -> elevated
- CBC + peripheral blood smear -> leukocytosis, normochromic normocytic
- anemia, thrombocytosis or thrombocytopenia
- Rheumatoid Factor -> elevated
- Urinalysis -> RBC casts: indicates Glomerulonephritis (GN)
- ECG
- – Ischemic changes may indicate emboli to the coronary circulation
- – New heart block or conduction delay may indicate extension of infection to valve annulus or septum
- CXR -> focal infiltrates often with central cavitation may indicate septic pulmonary emboli
- Echocardiogram
Endocarditis: When to consult for valve replacement
– Heart failure related to valve dysfunction
– Severe aortic or mitral valve regurgitation
– Endocarditis due to fungi or highly resistant organisms
– Perivalvular infection with abscess or fistula
– Embolization in spite of antibiotic therapy (weak)
– Vegetation size > 10mm (15mm in Europe) (weakest)
Endocarditis: Predictors of Mortality
- S. aureus infection
- Heart failure
- Diabetes
- Embolic events
- Perivalvular abscess
- Large vegetation size
- Contraindication to surgery
- Female gender
- Persistent bacteremia
