Gordonia araii is a species of Gram-positive, aerobic, non-motile, and partially acid-fast bacterium belonging to the genus Gordonia. It is recognized as an opportunistic pathogen in humans, capable of causing various infections, particularly in immunocompromised individuals.
Taxonomy
- Domain: Bacteria
- Phylum: Actinomycetota (formerly Actinobacteria)
- Class: Actinomycetia
- Order: Corynebacteriales
- Family: Gordoniaceae
- Genus: Gordonia
- Species: Gordonia araii
Characteristics
- Morphology: Gordonia araii typically appears as rod-shaped or coccoid cells. It is characterized by its ability to form short, branched mycelial structures that readily fragment into coccobacillary or diphtheroid forms.
- Staining: It is Gram-positive and partially acid-fast, meaning it retains some of the carbolfuchsin stain after decolorization with acid-alcohol, similar to mycobacteria and nocardiae, which can lead to misidentification.
- Physiology: As an obligate aerobe, it requires oxygen for growth. It is catalase-positive and urease-positive. Its growth can be relatively slow on conventional culture media.
- Cell Wall: The cell wall contains meso-diaminopimelic acid, arabinose, and galactose, which are characteristic of the Gordonia genus and related actinomycetes. Mycolic acids are also present, contributing to its partial acid-fastness.
Habitat and Isolation Gordonia araii was initially described from clinical specimens and has been isolated from various human sources, including sputum, pus, catheter tips, cerebrospinal fluid, and blood. While its primary environmental reservoirs are not as extensively studied as some other Gordonia species (which are often found in soil, water, and petroleum-contaminated environments), its presence in clinical settings indicates its potential as a human pathogen.
Clinical Significance Gordonia araii is an opportunistic pathogen, meaning it primarily causes disease in individuals with weakened immune systems or those with pre-existing medical conditions, such as:
- Bacteremia: Bloodstream infections, often associated with indwelling catheters.
- Catheter-related infections: Colonization and infection of central venous catheters.
- Skin and soft tissue infections: Including cellulitis, abscesses, and wound infections.
- Respiratory tract infections: Such as pneumonia or bronchitis, especially in patients with underlying lung disease.
- Other infections: Less commonly, it has been implicated in meningitis, endocarditis, and osteomyelitis.
Due to its morphological and staining similarities with other actinomycetes like Nocardia and Mycobacterium, Gordonia araii infections can be challenging to diagnose accurately and may be initially misidentified. Definitive identification often requires molecular methods, such as 16S rRNA gene sequencing, in addition to conventional biochemical tests.
Diagnosis and Treatment Diagnosis typically involves culturing the bacterium from appropriate clinical samples. Differentiation from other Gordonia species and related genera relies on a combination of biochemical tests, fatty acid profiles, and molecular identification (e.g., 16S rRNA gene sequencing).
Treatment for Gordonia araii infections usually involves appropriate antibiotic therapy. Susceptibility patterns can vary, but isolates often show susceptibility to a range of antibiotics, including amikacin, imipenem, linezolid, ciprofloxacin, and trimethoprim-sulfamethoxazole. However, resistance to certain antibiotics (e.g., penicillin, macrolides) can occur, necessitating susceptibility testing to guide treatment.
Etymology The species epithet "araii" was given in honor of Dr. T. Arai, a distinguished Japanese microbiologist, in recognition of his significant contributions to the study of actinomycetes.