October 25, 2024

Adult Long-Term Fever, Chills, Weight Loss

By Med-Challenger · 2 minute read

A 22-year-old male college student originally from India presents with fever, chills, night sweats, and weight loss of 4 weeks' duration. He received the Bacille–Calmette–Guérin (BCG) vaccine as a child. He moved to the United States 9 years ago.

He has no past medical history. He had an HIV test 3 months ago that was negative. His chest x-ray shows a right upper lobe infiltrate and mild hilar lymphadenopathy. No cavities are noted.

Sputum sample was taken with acid-fast Ziehl–Neelsen stain (see Figure).

image (9)

What is the most likely organism?

Legionella pneumophilia
Mycobacterium tuberculosis
Streptococcus pneumoniae
Staphylococcus aureus

The correct answer is:

Mycobacterium tuberculosis

Educational Objective:

Diagnose active tuberculosis.

Key Point:

Clinical and radiologic suspicion should be confirmed in suspected cases of acute pulmonary tuberculosis by finding M tuberculosis bacteria in a sputum sample with acid-fast Ziehl–Neelsen stain.

Explanation:

This patient’s presentation is typical for pulmonary tuberculosis (TB). He comes from an area of the world with the highest incidence of TB (India). Approximately one-half of patients with pulmonary TB show acid-fast bacteria in the sputum on Ziehl–Neelsn stain. The yield is highest when 3 morning sputum samples are examined. The yield is higher when cavitary lesions are present.

The gold standard for the diagnosis of TB is evidence for growth in liquid or solid media. This usually takes several weeks; thus, early treatment, when based on the findings from acid fast stains, is indicative of good medical practice.

The first phase of treatment is for 2 months--using the 4-drug regimen of isoniazid, rifampin, ethambutol, and pyrazinamide--and is then followed by 4 months of continuation therapy with isoniazid and rifampin.

Drug-resistant TB is more difficult to cure than drug-susceptible TB. The management of such cases should be referred to specialists with extensive experience managing drug-resistant TB.

Streptococcal, Legionella, and staphylococcal respiratory infections are more acute and the positive Ziehl–Neelsen stain is definitive for the diagnosis of tuberculosis.

Reference:

Ellner JJ. Tuberculosis (chapter 324). In: Goldman L, Schafer A. Goldman-Cecil Medicine. 25th ed., 2016:2030-2039.

Key Facts about the BCG Vaccine:

Usage:
- The BCG vaccine is most widely used in countries where tuberculosis is common, such as parts of Africa, Asia, and Latin America.
- It is routinely given to newborns and infants in high-risk countries to protect them from severe forms of tuberculosis, such as TB meningitis and miliary TB, both of which are more common in young children.
- In countries with a low incidence of TB (e.g., the United States and most of Western Europe), the BCG vaccine is not routinely given due to low prevalence of the disease.
Efficacy:
- The BCG vaccine is particularly effective at preventing severe forms of TB in children, but its efficacy in preventing pulmonary TB (the most common and contagious form in adults) varies widely, with estimates ranging from 0% to 80% depending on the population and geographic location.
- Protection against TB often diminishes with age, so it is generally not as effective for preventing adult TB.
Mechanism of Action:
- The BCG vaccine stimulates the immune system to recognize and fight Mycobacterium tuberculosis if exposed. It does not, however, protect against latent TB infection or reactivation of latent TB in most cases.
- It also provides cross-protection against some other mycobacterial infections, like Mycobacterium leprae, the bacterium that causes leprosy.
Administration:
- The vaccine is given intradermally, usually in the upper arm.
- A small, localized reaction typically develops at the injection site, which may ulcerate and leave a small scar. This is a normal part of the healing process and evidence of the vaccine's administration.
Side Effects:
- Common side effects include a small, localized ulcer or abscess at the injection site.
- More serious side effects are rare but can include regional lymphadenitis (swelling of lymph nodes) or, in very rare cases, disseminated BCG infection, particularly in individuals with weakened immune systems.

This question appears in Med-Challenger Family Medicine Review with CME.

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