Tuberculosis

Bacterial infection of the endocardial surface, usually a heart valve, producing vegetations that destroy the valve and embolize; diagnosis rests on the modified Duke criteria (blood cultures plus echocardiography) and treatment is a prolonged organism-directed intravenous antibiotic course, with valve surgery for heart failure, uncontrolled infection, or embolic recurrence.

Histoplasma capsulatum is an endemic dimorphic fungus, acquired by inhalation of conidia in the Mississippi and Ohio River valleys and other endemic regions, that most often causes asymptomatic or mild pulmonary infection but can disseminate in immunosuppressed hosts; diagnosis rests on the Histoplasma urinary antigen assay and treatment is itraconazole for mild to moderate disease or liposomal amphotericin B followed by itraconazole for severe or disseminated infection.

Coccidioidomycosis, or valley fever, is a dimorphic fungal infection acquired by inhaling Coccidioides arthroconidia in the southwestern United States, ranging from self-limited pneumonia to disseminated or meningeal disease, diagnosed by culture, histopathology, or serology and treated with fluconazole for symptomatic disease and lifelong fluconazole for meningitis.

Blastomycosis is a dimorphic fungal infection acquired by inhaling Blastomyces dermatitidis conidia in the Mississippi and Ohio River valleys, presenting as primary pulmonary infection that can mimic lung cancer or disseminate to skin and bone, diagnosed by direct fungal stain confirmed with culture, antigen, or serology, and treated with itraconazole for mild to moderate disease or liposomal amphotericin B for severe, disseminated, or CNS disease.

Nocardiosis is an opportunistic infection caused by aerobic, weakly acid-fast, branching gram-positive Nocardia species acquired from soil by inhalation or direct inoculation, most often producing necrotizing pulmonary disease with a strong tendency to hematogenously seed the brain, diagnosed by modified acid-fast stain and prolonged culture, and treated with high-dose trimethoprim-sulfamethoxazole, escalated with amikacin and imipenem for disseminated or CNS disease.

Community-acquired pneumonia is a lower respiratory tract infection diagnosed by fever with cough, dyspnea, or chest pain plus a new infiltrate on chest imaging, with Streptococcus pneumoniae, respiratory viruses, and atypical organisms as leading causes. Site of care is guided by the Pneumonia Severity Index or IDSA/ATS criteria, outpatient therapy is amoxicillin or doxycycline, and hospitalized patients receive a beta-lactam plus a macrolide or a respiratory fluoroquinolone, escalated to cover Pseudomonas or MRSA when risk factors are present.

Acute HIV infection, also called the acute retroviral syndrome, is the symptomatic viremic phase in the days to weeks after HIV acquisition, presenting with fever, fatigue, myalgia, rash, and pharyngitis at a time when antibody testing may still be negative. Diagnosis requires an HIV RNA viral load, and antiretroviral therapy should begin as soon as the patient is ready, regardless of CD4 count.

Isolation precautions pair standard precautions, used for every patient, with transmission-based precautions selected by a suspected or confirmed organism's dominant route: contact (gloves and gown), droplet (mask within 3 to 6 feet), or airborne (a negative-pressure room and a fit-tested N95 respirator). Hand hygiene and matching the barrier to the route are the core interventions.