What is the Difference Between Nocardia and Actinomyces

The main difference between Nocardia and Actinomyces is that Nocardia is a saprophytic organism with a worldwide distribution in the soil whereas Actinomyces is a part of the normal flora of the mouth and gastrointestinal tract.

Nocardia and Actinomyces are two genera of bacteria that can be virulent to humans. Both are Gram-positive, rod-shaped bacteria. Nocardia infections occur through the inhalation of the bacteria or through a traumatic introduction, while Actinomyces causes painless “Lumpy jaws”.

Key Areas Covered

1. What is Nocardia
   • Definition, Features, Importance
2. What is Actinomyces
   • Definition, Features, Importance
3. Similarities Between Nocardia and Actinomyces
   • Outline of Common Features
4. Difference Between Nocardia and Actinomyces 
   • Comparison of Key Differences

Key Terms

Nocardia, Actinomyces

What is Nocardia

Nocardia is a genus of weakly staining Gram-positive, rod-shaped bacteria, forming partially acid-fast beaded branching filaments. Around 25 species occur in this genus. They usually occur worldwide in rich soil and organic matter. In addition, they are oral microflora found in healthy gingiva, as well as in periodontal pockets. Although some species are non-pathogenic, others cause nocardiosis. Nocardia infections are acquired by inhalation of the bacteria or through its traumatic introduction. However, Nocardia is low virulence.

Figure 1: Nocardia

Furthermore, Nocardia colonies have a variable appearance, but most species appear to have aerial hyphae. They grow slowly on nonselective culture media and are strict aerobes with the ability to grow in a wide temperature range. In those with a weak immune system, Nocardia causes opportunistic infections. Nocardiosis is a disease caused by the bacterium, and it affects the lungs, brain, and skin.

What is Actinomyces

Actinomyces is another genus of Gram-positive, rod-shaped bacteria. It is a facultative anaerobic bacterium that grows best in anaerobic conditions. Although individual bacterium is rod-shaped, Actinomyces forms endospores. Actinomyces colonies form fungus-like branched networks of hyphae. This bacterium generally occurs in soil and, it is a part of the human microbiota. In soil, Actinomyces helps to degrade organic plant material, lignin, and chitin by their extracellular enzymes.

Figure 2: Actinomyces

Moreover, Actinomyces is commensal in the skin flora, oral flora, gut flora, and vaginal flora of humans and livestock. It can also form opportunistic infections. They are generally present in the gums and are the most common cause of infection in dental procedures and oral abscesses.   

Similarities Between Nocardia and Actinomyces

• Nocardia and Actinomyces are two genera of rod-shaped bacteria.
• Both are Gram-positive.
• Moreover, their branching filament formation is similar to each other.
• They grow in soil.
• Both bacteria can be virulent to humans.

Difference Between Nocardia and Actinomyces

Definition

Nocardia refers to a genus of aerobic Gram‐positive bacteria that forms filamentous cells that fragment into rod‐shaped or coccoid elements or L‐forms, while actinomyces refers to any of a genus of filamentous or rod-shaped bacteria that includes usually commensal and sometimes pathogenic.

Significance

Nocardia is a saprophytic organism with a worldwide distribution in the soil while Actinomyces is a part of the normal flora of the mouth and gastrointestinal tract.

Respiration

Nocardia is an aerobic bacterium while Actinomyces is a facultative anaerobic bacterium.

Infections

Moreover, Nocardia infections are acquired by inhalation of the bacteria or through a traumatic introduction while Actinomyces cause opportunistic infections.

Diseases

Nocardiosis is the disease caused by Nocardia while Actinomyces cause painless “Lumpy jaws”.

Conclusion

In brief, Nocardia and Actinomyces are two genera of bacteria. Both bacteria are Gram-positive and live in the soil. Although both bacteria can cause opportunistic infections, only Nocardia is a part of the human microbiota. Both Nocardia and Actinomyces are similarly filamentous. Nocardiosis is a disease caused by the Nocardia bacterium. In contrast, Actinomyces causes painless “Lumpy jaws”. Thus, this is the main difference between Nocardia and Actinomyces.

References:

1. Wikimedia Foundation. (2022, August 24). Nocardia. Wikipedia. Retrieved August 28, 2022
2. Wikimedia Foundation. (2022, May 11). Actinomyces. Wikipedia. Retrieved August 28, 2022

Image Courtesy:

1. “Nocardia species close-up detail” By Michaelphillipr – Own Work (CC BY-SA 4.0) via Commons Wikimedia
2. “Actinomyces israelii” By Graham Beards at English Wikipedia – Own Work (CC BY 3.0) via Commons Wikimedia