Pulmonary Fungus and Tuberculosis

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2. Fungal Infections of the Lung
The three major mycotic infections are histoplasmosis, coccidiomycosis, and blastomycosis
The fungal agent in each case is dimorphic: exists in nature as mycelium (mold) that bears infectious spores, which enter host and develop into a yeast-like phase that is the tissue pathogen
These fungi require special staining and culture methods
Amphotericin B is primary therapy for all three fungal infections

3. Histoplasmosis
Systemic disease caused by H. capsulatum, which is found in soil with high concentration of fecal material of chickens, pigeons and bats
Endemic areas are the valleys of Ohio, Missouri, and Mississippi rivers
Occurs as an intracellular yeast and is seen best on silver stain
Farmers, construction workers, and people who enjoy outdoor activities are the most at risk by inhaling spores
1 in 2000 people will develop chronic pulmonary disease
Most cases of primary histoplasmosis are asymptomatic or mild flu-like syndrome
Progressive pulmonary disease associated with chronic lung disease occurs in middle-aged men
CXR demonstrates dense nodules with central calcification
Chronic cavitary histoplasmosis is less common
Mediastinal histoplasmosis results in fibrosing mediastinitis, which is the most frequent benign etiology of SVC obstruction
Healed histoplasmosis causes a solitary pulmonary nodule, which can be confused with carcinoma

Indications for surgery:
A. Chronic cavitary pulmonary disease - persistent thick-walled cavity after 2g to 3g course of Amphotericin B for 2-3 months
B. Fibrosing mediastinitis with middle lobe syndrome
C. SVC syndrome

4. Coccidiomycosis
Causative agent is C. immitis
Endemic areas are the Southwestern USA and Mexico
The spherules have a thin wall containing endospores which are seen on wet mount slides
Infection occurs after spore inhalation and 60% of patients are asymptomatic
Acute valley fever is characterized by pneumonitis, erythema nodosum, and arthralgias
Only 5% of patients with symptomatic pulmonary disease develop irreversible bronchiectasis, pulmonary nodules, pulmonary abscesses or residual cavities
The most frequent long-term complication is a chronic cavitary lesion (solitary, thin-walled)
CXR demonstrates nonspecific infiltrates, hilar adenopathy, or pleural effusions
Diagnosis is made by serologic testing for IgM or IgG antibodies; a rising titer suggests possible dissemination
The most important extra pulmonary manifestation is meningitis
Most patients require no therapy
Amphotericin B is indicated if there is severe, prolonged pulmonary disease; primary disease with risk of dissemination (pregnancy, immunosuppression); symptomatic, chronic cavitary disease; and as an adjuvant to surgical resection

Indications for surgery:
A. Enlarging cavitary lesion
B. Hemoptysis
C. Secondary infection
Peri-operative Amphotericin B is recommended for these patients

5. Blastomycosis
Causative agent is B. dermatitides
The endemic areas are the southeastern and southwestern USA, mostly the Ohio and Mississippi river valleys and the Great Lakes area
Classically seen as a round, thick-walled single yeast cell on staining
Acute infection typically involves the lower lobes and is asymptomatic, or can result in influenza-like syndrome
Chronic infection typically involves the upper lobes and results in a pyogranulomatous process
The most common extrapulmonary manifestation is cutaneous ulcers
Chronic, disseminated disease typically involves the skin and ribs
Primary treatment is typically Amphotericin B - 2 to 2.5g over 2-3 months or ketoconazole as an alternative agent

Indications for surgery:
A. Rule out malignancy
B. Drainage of large cavitary abscesses
C. Closure of bronchopleural fistulas

6. Other Fungal and Opportunistic Infections of the Lung
A. Cryptococcosis
Caused by C. neoformans, found in soil contaminated by pigeon droppings
India ink staining reveals round, budding yeast which has gelatinous polysaccharide capsule
Primarily involves the bronchopulmonary tree, with special predilection for the meninges
Lesions often involve the lower lobes and are solid
Amphotericin B and 5-fluorocytosine are both effective medical treatment
Always examine CSF if C. neoformans is isolated from sputum or surgical specimen
10% of patients develop cryptococcal meningitis after resection of a pulmonary lesion

B. Aspergillosis
Most are caused by A. fumigatus, an organism found in hay and grains
Appears as mixture of coarse, fragmented hyphae and ball-like clusters on histology
Three clinical syndromes occurs: aspergillar bronchitis, aspergilloma, and invasive aspergillosis
Aspergillomas are the most common surgically resected lesion of this type and usually occur in a upper lobe cavity
These may be asymptomatic for years or cause hemoptysis
Hemoptysis occurs in 50% of patients with Aspergilloma, in 10% the hemoptysis is severe and recurrent
Once hemoptysis develops, the aspergilloma should be resected
Medical therapy usually not effective because Amphotericin penetrates aspergillus cavities poorly
Prophylactic resection in asymptomatic patients is generally not indicated because of significant complication rate

C. Actinomyocis
Causative agent is usually A. israelii, a microaerophilic organism
Appears as branching hyphae which contain "sulfur granules"
Thoracic infection occurs after aspiration of oropharyngeal organisms
Presents as empyema, infiltrate, consolidation, or hilar mass
Treatment of choice is high dose penicillin for 1-3 months

D. Nocardiosis
Causative agent is N. asteroides
Appears as long-branching filaments that can be confused with M. tuberculosis
Opportunistic infection which occurs in immunocompromised patients
CXR shows solitary nodules, nonspecific infiltrates, or cavitations
Chest wall sinus tracts and empyema may occur, as well as CNS dissemination
Treatment of choice is sulfadiazine, sulfisoxasolem, minocycline, or Bactrim for 2-3 months

E. Candidiasis
Causative agent is C. albicans, which is normal flora in GI tract, oral cavity, and female genital tract
Most common fungal infection in humans
Becomes invasive in immunocompromised host
Can cause deep thoracic infections or endocarditis
Treatment of choice is Amphotericin B

F. Protozoal Infections
Most common causative agent is P. carinii
Occurs as a diffuse interstitial pneumonitis in immunocompromised patients
CXR shows diffuse infiltrates radiating from the hilum
Often causes hypoxemia, hypocapnia, and pneumothoraces
Open lung biopsy may be required to establish diagnosis
Treatment of choice is pentamidine or Bactrim

G. Pulmonary Echinococcosis
Causitive agent is T. echinococcus, a small tapeworm
Reults in intrathoracic cyst that can rupture, causing asphyxiation or allergic reaction
CXR shows homogenous, oval shaped densities with clearly defined borders
Surgical therapy involves cystectomy or pericystectomy with instillation of formalin or 10% NaCl solution
Some success has been reported with medical treatment using benzimidazole derivatives

PULMONARY TUBERCULOSIS
1. Etiology
M. tuberculosis is a virulent organism transmitted by airborne droplets that can rapidly destroy lung tissue if left untreated
Three million deaths occur worldwide due to TB
The incidence had been declining until 1985 and is now rising
Resectional therapy is becoming increasingly utilized with the rise in multidrug resistant organisms

2. Diagnosis
Classic symptoms include night sweats, fever, cough, and occasionally hemoptysis
Tuberculosis is most common cause of severe hemoptysis
Asphyxiation rather than hypovolemia is usual cause of death from hemoptysis
The diagnosis is made by acid-fast staining and culture of the sputum
The Ghon complex is characterized by a peripheral lesion with associated hilar adenopathy
Other forms of mycobacterium, most commonly M. avium, can cause indolent infections that attack diseased pulmonary tissue

3. Medical Therapy
First line drug therapy includes isoniazid, ethambutol, pyrazinamide, and streptomycin
A minimum of 3 drugs should be initiated when the diagnosis is made
The preferred regimen is isoniazid and rifampin for 6 months, with pyrazinamide for 2 months
If the sputum is positive after 3 months of treatment, either the patient is noncompliant or the organism is an uncommon mycobacterium or is resistant; the patient should be recultured
Pure tuberculous effusions almost always resolve spontaneously or respond promptly to chemotherapy
Tube thoracostomy rarely provides a cure because dense pleural reaction interferes with full re-expansion of the underlying lung

4. Indications for Surgical Resection
Persistently positive sputum cultures with cavitation after 5-6 months of continuous optimal chemotherapy with 2 or more drugs
Localized pulmonary disease cause by M. avium-intracellulare; other atypical mycobacterium or M. tuberculosis which is drug resistant
Mass lesion of the lung in an area of tuberculous involvement
Massive life-threatening hemoptysis or recurrent severe hemoptysis (massive = 600 cc or more/24 hr, severe = 200 cc/24 hr)
Bronchopleural fistula in association with mycobacterial infection that does not respond to tube thoracostomy

5. Contraindications to Resection in TB
Widespread pulmonary or endobronchial disease
Children with mycobacterial disease
FEV1 less than 800-1,000 cc
Active endobronchial disease, as this interferes with healing of bronchial stump (pre-op bronchoscopy in all patients prior to resection)

6. Operative Management
Lobectomy or pneumonectomy usually necessary with active mycobacterial disease
Extrapleural pneumonectomy for extensive pulmonary parenchymal disease with chronic empyema (rare)
Complications of resection include empyema with or without broncho-pleural fistula and bronchogenic spread of mycobacterial disease
Both complications aremore frequent when the sputum is positive at the time of operation