Case 8

The patient was a 55-year-old male with a 2-month history of fevers, night sweats, increased cough with sputum production, and a 25-lb weight loss. The patient denied intravenous drug use or homosexual activity. He had had multiple sexual encounters, “sipped” a pint of gin a day, was jailed 2 years ago in New York City, and had a history of gunshot and stab wounds. His physical examination was significant for bilateral anterior cervical and axillary adenopathy and a temperature of 39.4°C. His chest radiograph showed paratracheal adenopathy and bilateral interstitial infiltrates. His laboratory findings were significant for a positive HIV serology and a low absolute CD4 lymphocyte count.

1. Bronchoalveolar lavage fluid. BALF is the fluid or secretion that is

obtained from the alveolar and bronchial airspaces. This fluid is washed with sterile saline water during the obtaining of the sample.

BALF is obtained by placing a small fiberoptic scope into the lung of the patient and injecting sterile saline water into the lung and removing the fluid.

Its value as a diagnostic specimen is limiting because of the large range of normal values.

2. The organism that can be positive for an acid-fast stain are:

Mycobacterium. Nocardia. Corynebacterium.

3. According to medical history, the most likely organism to be causing his infection is:

Mycobacterium tuberculosis.

The patient is HIV positive, this predisposes the patient to present the disease because this patient is immunocompromised.

Also, when the immune system responds to TB, it increases HIV levels, and HIV disease may progress more quickly.

4. The important factors in his medical history that are important in his contracting this infection with an acid-fast bacterium are:

- weight loss. - cough with sputum production. - he was jailed 2 years ago. - “sipped” a pint of gin a day. - history of gunshot and stab wound.

5. PPD test. The purified protein derivative is an

antigen that is injected into the most superficial layer under the skin resulting in a blister of the skin in positive cases.

The blister is measured and millimeters.

- 5mm : positive in individuals with HIV or individual on steroid therapy - 10mm: positive for individuals with diabetes, renal failure, and health care workers. - 15 mm: positive for individuals with no known risks for TB.

The value of PPD in this patient is limiting since he is positive HIV and we may obtain a false negative response.

The negative response is due to his affected immune system.

A chest x-ray should be ordered additionally to detect lesions in the lung.

Positive PPD test

6. The control measures of this patient are:

- Annual TB skin test is recommended. - DOT (directly observed therapy) is recommended. - Patients should be managed by physicians to reduce drugs interaction.

Mycobacterium tuberculosis

Classification

Family: Mycobacteriaceae Genus: Mycobacterium Specie: tuberculosis

M. tuberculosis is an obligate aerobe.The organism is a facultative intracellular parasite. It can survive in a dry phase for weeks but can grow only within a host organism.

Acid-fast Gram(+) rods: The organism presents a thick waxy

cell wall and rich in mycolic acid. It is considered a Gram (+) due to

lack of outer membrane. Heat is needed for stain penetration

because of the waxy cell wall.

The high concentration of lipids in the cell wall gives:

1. Impermeability to stains and dyes. 2. Resistance to many antibiotics. 3. Resistance to osmotic lysis. 4. Resistance to acidic and alkaline compounds.

Acid fast staining

According to Runyon division, Mycobacterium tuberculosis belongs to Non-photochromagen group:

May produce a white to yellow pigment that can be intensified by the exposition to light.

M. tuberculosis colonies are rough, granular, dry, and nopigmented.

Diseases.

The disease caused by M. tuberculosis is Tuberculosis.

May have different names depending where the organism is causing disease.

Scrofula : affect lymphatic system and results in swollen neck glands.

Tabes mesenterica: TB of the abdomen. Lupus vulgaris: TB of the skin. Milliary TB: When infection invades circulatory system.

Clinical Presentation

The organism is spread from person to person through the air in droplets nuclei.A person can be infected but disease can be absent.

Predisposing factors for TB infection include:

- HIV infection. - Immunodeficiency. - Malnutrition. - Alcoholism. - IV drug use. - Contact with large population of people:

prisons, dormitories, nursing homes, etc.

Symptoms: In early phases the patient will

present not symptoms. Also, if they have latent TB infection.

Latent infection : organism is present but dormant.

Early infection symptoms: - Fever. - Sweating. - Chills. - Weight loss. - Weakness. - Fatigue.

Symptoms of chronic lung infection: - persistent cough. - chest pain. - coughing up bloody sputum. - weight loss. - breathing difficulty.

Diagnosis.

A complete medical evaluation for TB include:Medical History:

- Ask about the patient’s history of TB exposure, infection, or disease.

Physical examination: - Determine whether the patient has medical conditions, especially HIV infection. HIV infection increases the risk of latent TB infection progressing to TB disease.

Skin Tests. 1. Mantoux tuberculin skin test. The purified protein derivative (PPD) is an antigen that leads to a sensitivity response. This response can occur if someone currently has TB or they were exposed to it in the past.

2. QuantiFERON-TB Gold Test. It is a blood test that measures the patient’s immune system reaction to M. tuberculosis.

Chest X-ray. If skin test gives positive, then a

chest X-ray is ordered to detect lesions anywhere in the lungs. These lesions may suggest TB but cannot be used to diagnose TB.

Microbiological diagnosis. - Acid-fast staining: Ziehl – Neelsen.- application of heat is needed. Kinyon.- uses higher content of phenol. Auramine-rhodamine fluorochrome. fluorescent stain.

- Cultural identification: Lowenstein-Jensen. Middlebrook 7H10 and 7H11. - PCR.

Virulence Factors - cord factor. - mycolic acid. - intracellular growth. - iron capturing ability.

Treatment

The treatment consists of three drugs that are effective against the organism. They include:

- Isoniazid. - Rifampin. - Pyrazinamide. - Streptomycin. - Ethambutol.

The treatment for TB is very complex because it lasts 6 to 18 months.Multidrug resistance may appear, which make the disease very difficult to treat.

Prevention

BCG vaccine.Tuberculine skin test. Preventive antibiotic treatment if someone is in contact with a TB patient.Preventive therapy of household members

References

Centers for Disease Control and Prevention (CDC), Department of Health and Human Services, Division of Tuberculosis Elimination: http://www.cdc.gov/nchstp/tb/faqs/qa.htmGinesu, F., P. Pirina, L.A. Sechi, P. Molicotti, L. Santoru, L. Porcu, A. Fois, P. Arghittu, S. Zanetti, and G. Fadda. 1998. Microbiological diagnosis of tuberculosis: a comparison of old and new methods. Journal of Chemotherapy 10: 295-300.Singh, V. 2006. TB in developing countries: diagnosis and treatment. Paediatric Respiratory Reviews 7: 132-135.