Actinomyces spp.

Actinomyces spp. are anaerobic, Gram-positive bacteria known for their filamentous, branching rods. 

These bacteria are part of the human commensal flora and are commonly found in the oropharynx, gastrointestinal tract, and urogenital tract. 

Related to genera such as Corynebacterium, Mycobacterium, and Nocardia, Actinomyces species are facultative anaerobes, with some requiring prolonged culture periods in anaerobic conditions. 

They contribute to biofilm formation on teeth and play roles in both health and disease by breaking down organic compounds and producing various substances. 

While generally non-pathogenic, Actinomyces can cause chronic infections like actinomycosis, characterized by granulomatous tissue and sulfur granules, particularly in immunocompromised individuals or those with mucosal damage.

What is Actinomyces spp.? [1., 5., 8.] 

Actinomyces spp. are anaerobic Gram-positive bacteria that form filamentous, branching rods and are part of the human commensal flora, commonly found in the oropharynx, gastrointestinal tract, and urogenital tract. 

They are related to other genera such as Corynebacterium, Mycobacterium, Nocardia, and Propionibacterium. These bacteria are facultative anaerobes, with some species being strictly anaerobic, requiring prolonged culture periods (up to 20 days) in anaerobic conditions for isolation. 

Morphologically, Actinomyces species are filamentous, branching, and non-spore-forming. 

Common species include Actinomyces israelii (which is the most prevalent), Actinomyces viscosus, Actinomyces meyeri, Actinomyces naeslundii, Actinomyces odontolyticus, Actinomyces gerencseriae, Actinomyces neuii, Actinomyces turicensis, and Actinomyces radingae. 

Actinomyces spp. In the Human Microbiome

Actinomyces are significant members of the human microbiome, particularly in the oral cavity, where they contribute to biofilm formation on teeth. They also colonize the gastrointestinal tract and play roles in both health and disease. 

Their metabolic activities include breaking down organic compounds and producing various substances such as formate, acetate, succinate, lactate, and antibiotics. [4.] 

Although not known to release exotoxins, Actinomyces can cause tissue damage through chronic inflammatory responses. [4.] 

Actinomyces spp. In Disease

Actinomyces spp. Infections

Clinically, Actinomyces spp. are implicated in various infections, including cervicofacial actinomycosis, pulmonary actinomycosis, abdominal actinomycosis, pelvic actinomycosis, central nervous system infections, and cutaneous actinomycosis. [5., 8.] 

Actinomyces spp. can cause chronic granulomatous infections characterized by the formation of sulfur granules, which are yellowish clumps composed of bacterial filaments and host material. These bacteria typically require a breach in mucosal barriers to cause infection. 

Actinomyces species have also been associated with various alimentary tract diseases, including periodontal disease, inflammatory bowel disease (IBD), and celiac disease. [4.] Infections caused by Actinomyces in the alimentary tract are rare and often occur in immunocompromised individuals or those with a history of mucosal damage or other infections. [4.] 

Actinomyces spp. has also been isolated from pap smears, primarily from IUD users.  Among women who tested positive for the presence of Actinomyces spp., two developed pelvic inflammatory disease, but neither case was associated with pelvic actinomycosis. [3.] 

They are often part of polymicrobial infections and require prolonged antibiotic therapy, usually with beta-lactams, for effective treatment. [5., 8.] 

Actinomyces in Depression [2.] 

Actinomyces, as part of the Actinobacteria phylum, is highlighted for its altered abundance in individuals with depression. 

One systematic review found inconsistencies in the abundance of major phyla, including Firmicutes, Bacteroidetes, and Proteobacteria. However, a consistently higher abundance of Actinobacteria, including Actinomyces, was observed in people with depression compared to healthy controls. [2.] 

Specifically, the studies reported a higher presence of Actinomycineae, which includes Actinomyces, suggesting a potential role of these bacteria in the pathophysiology of depression. [2.] 

The review notes that changes in gut microbiota, including an increased abundance of Actinomyces, may be linked to immune activation and inflammatory responses, which are known to contribute to depressive symptoms. 

This finding aligns with the broader hypothesis that gut microbiota alterations can affect brain function and mood through the production of metabolites and modulation of the immune system.

Laboratory Testing for Actinomyces spp.

Test Type, Sample Collection and Preparation

Actinomyces levels are commonly assessed in stool samples.  Stool samples may be collected from the comfort of home.  

With concern for infections, tissue or other sample cultures may be performed.

Testing may require avoidance of certain medications and/or supplements including probiotics prior to sample collection.  It is important to consult with the ordering provider for full test preparation instructions.  

Interpretation of Test Results

Optimal Levels of Actinomyces spp.

It is important to consult with the laboratory company used for test interpretation, and to interpret test results within the context of an individual’s symptom picture.

One lab company provides the following reference range for Actinomyces levels and reports this on a scale from -3 (very low prevalence of these organisms) to +3 (very high prevalence of these organisms). [6.]  

Optimal levels fall within the reference range at 0.

Clinical Significance of Elevated Actinomyces spp. 

Elevated levels of Actinomyces spp. should be interpreted in the context of an individual’s symptoms.  Elevated levels of Actinomyces are commonly seen with: 

Gut Microbiome Imbalance

Actinomyces spp. are important components of the normal human gut microbiome. Elevated levels could potentially indicate a disruption in the normal balance of gut bacteria.

Possible Link to Depression in IBS Patients

High levels of Acinetomycetales have been linked to depression and IBS. [2.] 

‍Dietary Influence

A strict vegetarian diet may increase the total count of Actinomyces spp. compared to a Western diet. This indicates that diet can influence Actinomyces spp. levels, though the clinical significance of this is not clear. [7.] 

Potential for Infections 

Some Actinomyces spp. species can cause infections such as actinomycosis, a rare but serious infection characterized by abscess formation, often occurring as a cervicofacial or dental infection.  

However, it's important to note that the presence of these bacteria doesn't necessarily indicate an infection, as many are part of the normal flora.

Decreased Levels of Actinomyces spp.

Low levels of Actinomyces spp. should be interpreted within the context of an individual’s symptoms.  Low levels may indicate:

Gut Microbiome Imbalance

Some Actinomyces spp. are important components of the normal human gut microbiome. 

Low levels could potentially indicate a disruption in the normal balance of gut bacteria, especially if an individual presents with symptoms including gas, bloating, digestive discomfort, and/or systemic symptoms such as fatigue, brain fog, and body pains.

Potential Impact on Immune Function

Actinomyces spp. play a role in maintaining gut health and immune function. Low levels might potentially affect these processes, though more research would be needed to confirm this.

Dietary Influence

Since a strict vegetarian diet may increase the total count of Actinomyces spp. compared to a Western diet, low levels might potentially be associated with certain dietary patterns such as the standard American diet.

Biomarkers Related to Actinomyces spp.

Microbial Community Analysis

The presence of Actinomyces spp. within the context of the broader microbial community can provide insights into microbiome health and assess for dysbiosis.  

Techniques like 16S rRNA gene sequencing and metagenomics can be used to analyze the composition and functional potential of the microbiome in various body sites such as the oral cavity, respiratory tract, or gastrointestinal tract.

Short-Chain Fatty Acids (SCFAs)

Short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate, are products of microbial fermentation of dietary fibers in the gut. Actinomyces spp. participate in the production of SCFAs through the degradation of polysaccharides. 

Measuring SCFA levels in conjunction with Actinomyces spp. provides insights into the functional activity of the gut microbiome and its impact on host health. 

SCFAs have anti-inflammatory properties and contribute to gut barrier integrity and energy metabolism. Alterations in SCFA levels can indicate dysbiosis and have been linked to conditions such as IBD, IBS, and metabolic syndrome. 

By integrating SCFA measurements with Actinomyces spp. levels, clinicians can better assess gut health and develop targeted nutritional or probiotic therapies.

Inflammatory Markers

Inflammatory markers, such as C-reactive protein (CRP) and interleukins (e.g., IL-6), are commonly used to assess systemic inflammation and immune responses. 

Since the gut microbiome plays a critical role in modulating inflammation, measuring inflammatory markers alongside Actinomyces spp. levels can provide valuable information about the interaction between the gut microbiota and the immune system. 

FAQ: Understanding Actinomyces spp. 

Actinomyces spp. are a group of bacteria that can be found in various parts of the human body and are sometimes associated with infections.

What is Actinomyces spp.?

Actinomyces spp. (species) are a group of Gram-positive bacteria that are part of the normal flora of the human oral cavity, gastrointestinal tract, and female genital tract. 

They are known for their filamentous structure, which resembles fungal hyphae, and can sometimes cause chronic infections known as actinomycosis.

What Is the Significance of Actinomyces spp. in a Pap Smear?

The presence of Actinomyces spp. in a pap smear can indicate a possible infection, particularly in women using intrauterine devices (IUDs). 

While Actinomyces spp. are part of the normal vaginal flora, their overgrowth or presence in significant numbers may require further evaluation to rule out an infection or other gynecological issues.

What Are the Symptoms of an Actinomyces spp. Infection?

Symptoms of an Actinomyces spp. infection can vary depending on the site of infection but may include:

• Chronic, slow-developing infections

• Swelling and formation of abscesses

• Sinus tract formation that can drain pus

• Fever and general malaise

How Is an Actinomyces spp. Infection Diagnosed?

Diagnosis typically involves microbiological culture and microscopic examination of samples from the infected site. Imaging studies may also be used to identify the extent of the infection, especially in deeper tissues.

How Is an Actinomyces spp. Infection Treated?

Treatment of Actinomyces spp. infections usually involves prolonged antibiotic therapy, often with penicillin or other beta-lactam antibiotics. In some cases, surgical intervention may be necessary to drain abscesses or remove infected tissue.

Can Actinomyces spp. Be Prevented?

Preventing Actinomyces spp. infections involves good oral hygiene, proper care and monitoring of IUDs, and prompt treatment of any infections that may arise. Regular medical check-ups can help detect and manage any potential issues early.

How Common are Actinomyces spp. Infections?

Actinomyces spp. infections are relatively rare but can be serious when they occur. They are more common in individuals with poor oral hygiene, those using IUDs, or people with weakened immune systems.

When Should I Consult a Healthcare Provider About Actinomyces spp.?

You should consult a healthcare provider if you have symptoms of a chronic infection, particularly if you have risk factors such as an IUD, poor oral hygiene, or a compromised immune system. Early diagnosis and treatment are essential for managing Actinomyces spp. infections effectively.

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