Bacteria, Epidemiology, Infectious Diseases, Microbiology

Nocardiosis: ‘The Great Imitator’ That’s Often Misdiagnosed

Author Chandana Balasubramanian , 26-Mar-2024

Nocardiosis, labeled as ‘The Great Imitator,’ is a bacterial infection notorious for mimicking various other illnesses, complicating its diagnosis and treatment. 


Fortunately, early detection allows for effective treatment with antibiotics. However, if left untreated, nocardiosis can become a chronic infection and potentially invade the brain.


The culprits behind nocardiosis are bacteria known as Nocardia, with Nocardia asteroides and Nocardia brasiliensis being the main disease-causing types. Nocardiosis incidence is on the rise worldwide, so it’s essential to stay aware and continue researching this gram-positive, aerobic bacteria.


This article covers the history, epidemiology, symptoms, diagnosis, treatment, and ways to prevent nocardiosis.



Nocardiosis was first described by Edmond Nocard in 1888; Nocard was a French veterinarian and microbiologist investigating a disease in cattle called “Francine du boeuf.” 

A year later, Trevisan named this group of bacteria Nocardia in tribute to Nocard. Shortly after, the organism was isolated from the brain abscess of a 52-year-old patient. It was initially labeled Cladothrix asteroides but later known as Nocardia asteroides. This finding established Nocardia as the initial aerobic actinomycete (a group of gram-positive bacteria) identified to cause disease in humans.



Incidence of nocardiosis is poorly reported. It is estimated to be around 500-1000 cases per year in the United States.

At-risk demographics

People at the highest risk of contracting nocardiosis include those with weakened immune systems, such as individuals who have undergone organ transplantation, have cancer, diabetes mellitus, AIDS, autoimmune diseases, or have been on prolonged corticosteroid therapy.

Endemic regions

Nocardiosis is found worldwide, but some species, like N. brasiliensis, are found more in tropical and subtropical regions.

Notable Outbreaks

The epidemiology and incidence of nocardiosis are poorly described. This could be because the symptoms of nocardiosis are very similar to those of other infections. 

Also, since the disease does not spread rapidly from person to person, large-scale outbreaks may not have been reported.


How does it spread?

Nocardiosis is spread primarily through contaminated soil containing the Nocardia bacteria. There are no vectors that spread the infection. Nocardiosis is not transmitted from person to person but through direct contact with bacteria in the environment. 

It is also not a hospital-acquired infection, typically, but infections can happen if contaminated medical equipment introduces bacteria into a wound.

Nocardia bacteria can be found in contaminated soil, stagnant water, decaying plants, sewage, and plant and animal tissues. 

Humans can get nocardiosis when they inhale Nocardia bacteria found in the air or when contaminated soil or water gets into a cut or broken skin. For example, people who garden without gardening gloves may be at risk.


Biology of the disease

There is limited information regarding the precise method by which Nocardia bacteria infect the human body. The disease spreads through blood after entering the body through the lungs or skin.



Nocardiosis can affect different body parts, and symptoms vary depending on the site of infection.

According to the US CDC, nocardiosis symptoms include: 

  • Nocardiosis typically affects the lungs, presenting symptoms such as fever, weight loss, night sweats, cough, chest pain, and pneumonia. 
  • Lung infections can progress to involve the brain and spinal cord, resulting in symptoms like headache, weakness, confusion, and seizures. 
  • Skin infections may arise when soil containing Nocardia bacteria gets into open wounds or cuts. This can lead to skin ulcers or nodules that drain and have the potential to spread to lymph nodes.



Detecting nocardiosis requires tests to pinpoint the bacteria responsible for the infection. Healthcare providers will analyze bacterial cultures from samples taken from the infected site. Since the Nocardia bacteria grow very slowly, the laboratory must allow 3-5 days for them to grow before diagnosis can be confirmed.

If there is a lung infection is suspected, blood samples and a chest X-ray and CT may be required. If Nocardia is suspected, a CT or MRI scan of the brain can help. To detect meningitis, cerebrospinal fluid (CSF) testing will work best.



The primary treatment for the bacterial infection nocardiosis usually involves antibiotics. Depending on the infection type, a combination of antibiotics may be prescribed for an extended period. Therapy may range from months to a year to reduce the chance of recurrence.



There is no vaccine for nocardiosis, so prevention involves safety when working with soil. Wearing protective gear is important when wading through dirty or stagnant water. Covering cuts and scrapes when working in the garden can help mitigate the risk of getting a nocardiosis infection.



Nocardiosis poses a public health challenge due to its ability to mimic other illnesses, leading to misdiagnosis. Early detection and treatment with antibiotics can help prevent chronic infection and severe disease. Although antibiotic therapy is the standard of care, some strains of Nocardia bacteria are developing antibiotic resistance. As a result, awareness, research, and preventive measures remain vital in tackling the rising incidence of nocardiosis globally.


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Chandana Balasubramanian

Chandana Balasubramanian is an experienced healthcare executive who writes on the intersection of healthcare and technology. She is the President of Global Insight Advisory Network, and has a Masters degree in Biomedical Engineering from the University of Wisconsin-Madison, USA.

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