Introduction:

Nocardia are soil-borne, aerobic microorganisms, which are often causes of opportunistic infections in immunocompromised patients. There are 92 identified Nocardia species out of which 54 of them have been identified to infect humans, Nocardia beijingenesis being one of them. It can manifest as pulmonary, disseminated, or cutaneous infection. Early diagnosis and prompt treatment are vital in the overall prognosis of patients. We present a case of a young male with HIV who had Nocardiosis without travel history outside of the United States.

Case description:

A 37-year-old man, diagnosed with HIV two years ago and currently not on antiretroviral therapy, presented with flu-like symptoms and weight loss over the last two months and confusion for two days. The patient denied any international travel outside the United States. On presentation, although hemodynamically stable, he was found to have severe hyperkalemia, metabolic acidosis, and acute kidney injury. The patient underwent emergent hemodialysis. CT scan of the lungs without contrast showed multifocal pneumonia, suspicious for necrotizing pneumonia on the left with dense consolidation, cavitation, and air bronchograms with mild involvement of the right lung. CT head and MRI brain did not reveal any intracranial abnormalities. Imipenem-cilastin and minocycline were started initially along with atovaquone for Pneumocystis jiroveci pneumonia prophylaxis. Although blood cultures were negative, the aspergillus galactomannan assay was positive. Next-generation sequencing as well as the culture of bronchoalveolar lavage detected Nocardia beijingensis. The antibiotics were later tailored to ceftriaxone, minocycline, and linezolid to be continued for a minimum of three months, followed by monotherapy for at least six months which is to be guided by susceptibilities results in the outpatient setting. 

Discussion:

Nocardia, an aerobic, weakly gram-positive opportunistic bacteria, primarily affects immunocompromised individuals, including those with HIV. One of its less common species, Nocardia beijingensis, was initially reported in the US in 2014. This infection may present as pulmonary, cutaneous, or disseminated nocardiosis. Pulmonary nocardiosis, the most common form, manifests with chest pain, coughing, sputum production, and sometimes hemoptysis resembling tuberculosis, aspergillosis, or bacterial pneumonia. Skin infections by Nocardia beijingensis may present with cellulitis, draining lesions, or nodules. Dissemination occurs in about 45% of cases, commonly via the bloodstream, affecting various organs. The central nervous system is often involved, that presents with headaches, nausea, altered mental status, and seizures. Nocardia beijingensis, due to diagnostic complexities, is associated with numerous

complications, notably abscesses in the lungs, skin, brain, adrenal glands, subretinal space, and muscles. It can also lead to rare complications like superior vena cava syndrome and cardiac tamponade. Due to its high mortality rate, early diagnosis is crucial but challenging due to nonspecific symptoms. Diagnosis involves gram staining, modified acid-fast staining, and cultures from clinical specimens. Advanced molecular techniques such as gene sequencing of the 16SrRNA, PCR, and restriction gene analysis are also commonly used for species identification. Although trimethoprim-sulfamethoxazole (TMP-SMX) is a common treatment, resistance has led to a preference for combination therapy, especially in severe, disseminated cases, or those with central nervous system involvement. Antibiotic susceptibilities vary among Nocardia species, with many responsive to TMP-SMX, ceftriaxone, minocycline, and linezolid. The duration of treatment, usually lasting 6 to 12 months is determined on expert recommendations as there are no trials establishing a definitive timeframe. TMP-SMX also offers prophylaxis to Nocardia infections which is beneficial as it is commonly used in HIV patients for prophylaxis of pneumocystis infections.