In the world of infectious disease, even the most common soil organism can become a formidable foe when the body's defenses are down.
Imagine a meticulously planned kidney transplant, a life-saving procedure that offers a new lease on life. Now, picture a stealthy invader, a bacterium commonly found in soil, launching an attack on this precious new organ. This is not a fictional scenario but a documented medical reality involving a pathogen known as Gordonia terrae.
For patients who have undergone organ transplants, the very medications that prevent organ rejection also open a door to opportunistic infections. Among these, a rare but serious threat can emerge from an unexpected source in our environment, leading to complex challenges for both diagnosis and treatment.
Gordonia terrae is an aerobic, Gram-positive bacterium belonging to a group of bacteria known as actinomycetes. Commonly residing in soil and water, it is one of over 50 known species in the Gordonia genus 4 8 . While most of its relatives are environmental, a handful have been identified as opportunistic pathogens in humans, with G. terrae being one of the more prominent ones, alongside G. sputi and G. bronchialis 4 7 9 .
In the clinical setting, this organism is a master of disguise. It is a Gram-positive bacillus (rod-shaped) that is weakly acid-fast, characteristics it shares with its more notorious cousins like Mycobacterium, Nocardia, and Rhodococcus 6 7 9 . This similarity is a primary source of diagnostic confusion, often leading to initial misidentification and, consequently, delays in providing the correct treatment.
Bacillus shape
Similar to Mycobacterium
Environmental origin
>48 hours incubation
Organ transplant recipients exist in a state of carefully managed immunosuppression. Drugs like tacrolimus and mycophenolate mofetil, which are standard anti-rejection therapy, work by deliberately suppressing the immune system's T-cells 2 . This prevents the body from attacking the new organ, but it also lowers its defenses against a wide array of infections.
In this immunocompromised state, organisms like Gordonia terrae, which would be swiftly eliminated by a healthy immune system, find an opportunity to cause disease. The risk is further amplified by the presence of indwelling medical devices, such as central venous catheters, which can serve as a physical portal for the bacterium to enter the bloodstream 2 4 . The combination of a suppressed immune system and a potential entry point creates the "perfect storm" for an invasive Gordonia infection.
Anti-rejection drugs deliberately weaken the immune system
Catheters and other devices provide entry points
Environmental bacteria become dangerous invaders
The first known case of a Gordonia terrae-induced kidney graft abscess was reported in 2014 and serves as a telling example of the challenges this infection presents 1 .
The patient was a renal transplant recipient who developed a perirenal abscess surrounding the donated kidney. Complicating the situation, the patient was also simultaneously fighting pulmonary tuberculosis. This co-infection highlights the vulnerability of immunosuppressed patients to multiple opportunistic pathogens at once 1 .
In this landmark case, doctors successfully treated the infection with a course of the carbapenem antibiotic imipenem, alongside a standard regimen of anti-tuberculosis drugs 1 . This dual approach addressed both the abscess and the coexisting tuberculosis, ultimately leading to a cure for the patient.
The bacterium is a slow-grower, requiring more than 48 hours of incubation to form visible colonies on culture plates 6 . These colonies are often dry, wrinkled, and light to dark brown 6 .
While the kidney graft abscess is a dramatic manifestation, Gordonia terrae can cause a variety of other infections, particularly in susceptible individuals. A large study in Spain found that respiratory tract infections were the most common, followed by bacteremia (bloodstream infections) and soft tissue infections 4 8 .
| Infection Type | Description |
|---|---|
| Peritoneal Dialysis-Related Peritonitis | Infection of the abdominal cavity in patients undergoing peritoneal dialysis, with cases proving difficult to treat and sometimes fatal . |
| Spontaneous Bacterial Peritonitis | Infection of ascitic fluid in patients with liver cirrhosis, as reported in a patient with Hepatitis C cirrhosis 6 . |
| Bacteremia/Bloodstream Infection | Often associated with central venous catheters, where the bacterium forms biofilms on the catheter line 2 4 . |
| Soft Tissue/Bone Infections | Includes post-surgical wound infections and other soft tissue involvements 4 . |
Diagnosing a Gordonia terrae infection requires a multi-pronged approach. The following table details the key tools and reagents essential for researchers and clinical microbiologists working to identify this organism.
| Tool/Reagent | Function |
|---|---|
| 16S rRNA Gene Sequencing | Considered the most reliable method; provides precise genetic identification by comparing the bacterial 16S ribosomal RNA gene sequence to a database 2 4 . |
| MALDI-TOF Mass Spectrometry | A faster technique that identifies bacteria by analyzing their unique protein profiles; however, its accuracy depends on having an updated database 2 6 . |
| Modified Ziehl-Neelsen Stain | A staining technique used to detect the "weakly acid-fast" property of G. terrae, helping to distinguish it from other bacteria 6 . |
| Blood Culture Systems (e.g., BACTEC™) | Automated systems used to detect bacteria in blood or other sterile fluids; G. terrae typically grows only in aerobic bottles and can take several days to signal positive 2 6 . |
| Columbia Blood Agar & Chocolate Agar | Enriched culture media that provide the necessary nutrients to support the slow growth of G. terrae in a 5% CO2 environment 6 . |
Unlike common infections, there are no standardized treatment guidelines for Gordonia terrae infections. Therapy is typically guided by antimicrobial susceptibility testing performed on the isolated strain. The good news is that G. terrae generally has a wide antimicrobial susceptibility profile.
| Antibiotic | Susceptibility Pattern | Clinical Context |
|---|---|---|
| Imipenem | Susceptible | Successfully used to cure the first reported kidney graft abscess 1 . |
| Ciprofloxacin | Susceptible | Often used in combination therapy for complicated infections like bacteremia 2 . |
| Vancomycin | Susceptible | A common choice for Gram-positive infections, especially when the central line is involved 2 . |
| Amikacin | Susceptible | An aminoglycoside with good activity; often part of a combination regimen 7 9 . |
| Cefoxitin | Variable Resistance (~36%) | Resistance can occur, highlighting the need for susceptibility testing 4 8 . |
| Amoxicillin-Clavulanate | Variable Resistance (~21%) | Resistance has been reported in some strains 4 8 . |
A systematic review on the related species G. bronchialis found that successful treatment often involves antibiotics like fluoroquinolones (e.g., ciprofloxacin), vancomycin, and carbapenems, frequently for a prolonged course of several weeks 7 9 . For device-related infections, such as those involving a catheter, removal of the device is often a critical step for achieving a cure 2 .
Gordonia terrae remains a rare but significant pathogen, a reminder of the delicate balance in transplant medicine. Its ability to masquerade as other bacteria and its slow-growing nature demand a high degree of clinical suspicion and sophisticated laboratory techniques for accurate identification. As the number of immunocompromised patients and the use of medical devices grow, the medical community's awareness of and preparedness for such opportunistic invaders must keep pace. Through continued reporting of cases and research into its biology, the fight against this uncommon but consequential soil bacterium continues.