Central catheter-related Gordonia bronchialis bacteremia in an immunocompromised patient: A case report, and literature review

Gordonia is a rarely reported organism causing central line-associated bloodstream infection (CLABSI). This article reports an acute myeloid leukemia (AML) case in which the patient developed febrile neutropenia and was later found to have Gordonia bronchialis (G. bronchialis) CLABSI. The patient received a two-week ceftriaxone regimen, based on susceptibility. The microbiologic diagnosis of this organism is considered challenging due to its resemblance with other organisms; however, more sophisticated methods of diagnosis (such as gene sequencing) can aid in differentiation.


Introduction
Gordonia is a genus of gram-positive bacteria that belongs to the family Gordoniaceae, which was previously classified in the Rhodococcus genus [1,2]. It is rarely reported as a human pathogen in local and systemic diseases. The latter is more commonly described in immunocompromised cases, particularly those with indwelling catheters [3,4]. Furthermore, it poses a diagnostic challenge due to its prolonged incubation time and the need for advanced microbiological investigations to be detected [5]. This article reports a case of central line infection caused by Gordonia in an immunocompromised patient with acute myeloid leukemia (AML). In addition, we reviewed the literature for the previously reported cases of Gordonia-related line infection and summarized the findings in the Table 1.

Case report
A 46-year-old gentleman with a past medical history of AML was admitted to our hospital as a case of AML relapse for salvage chemotherapy. During his hospital stay, the patient developed febrile neutropenia. On physical examination found to have perianal swelling, which was tender with overlying red skin. Magnetic Resonance Imaging (MRI) of the pelvis was done, which showed an underlying perianal collection of 0.4 × 0.8 × 1.8 cm; that developed left-sided perianal fistula with cutaneous communication (with the lower third of the anal canal at 4:00 o ′ clock), traversing the external anal sphincter (Fig. 1).
In the beginning, the patient was treated empirically with meropenem and tigecycline. Later, blood culture results were positive for Extended Spectrum Beta Lactamase (ESBL) Klebsiella pneumoniae organism, and tigecycline was discontinued while the patient was kept on meropenem. Meanwhile, the patient's condition improved clinically as he had no more fever spikes, and laboratory test results showed a decrease in inflammatory markers (C-Reactive protein from 95 to 8 mg/ dL, Procalcitonin 2.08-0.35 ng/mL). Later, the patient underwent incision and drainage of the perianal abscess due to persistent perianal pain. The drained pus was sent for culture and showed mixed growth of anaerobic organisms.
Ten days after drainage, the patient developed another spike of highgrade fever (Temperature 39.4 C oral). At that time, the patient had no complaints. A full septic workup was conducted, including blood cultures from both peripheral and central lines taken simultaneously, and the patient was restarted on tigecycline. A complete blood count (CBC) test showed improvement in his absolute neutrophil count (ANC) to 0.8 × 10 3 cells/mm 3  three days from the last fever spike, an aerobic blood culture from a peripherally inserted central catheter (PICC) line grew G. bronchialis; However, peripheral blood cultures (one aerobic and one anerobic) did not grow any organism. Transthoracic Echocardiogram was done and demonstrated no valvular vegetations. With this positive culture, it was decided to remove his PICC line. Susceptibility tests showed that the identified organism was resistant to trimethoprim-sulfamethoxazole but was sensitive to all other tested antibiotics: amoxicillin-clavulanate, ciprofloxacin, and clarithromycin. The patient was then started on ceftriaxone, based on susceptibility. The patient received 14 days of a two-gram daily dose of ceftriaxone. He was doing very well after that, with no relapse, and is currently planning a bone marrow transplant (BMT) from a related donor.

Discussion
Gordonia organism is a weak acid-fast bacterium rod-shaped with cord-like colony formation, and it was first identified in the sputum of diseased pulmonary cases, particularly those with bronchiectasis or lung cavities. This type of bacteria has mixed characteristics of both Mycobacterium and Nocardia [6,7]. Gordonia organisms are known for their ability to form a biofilm called gordonan, an acidic polysaccharide that induces cell aggregation, increases their pathogenicity and ability to cause bacteremia, particularly in patients with indwelling devices, such as central lines, peritoneal dialysis catheters, and cardiac devices [8].
The genus includes 28 species; however, only 9 species have been reported to cause infections in humans [7,9]. The systemic disease caused by Gordonia is described mainly in immunocompromised patients, such as those with malignancy, diabetes, cardiovascular disease, and autoimmune conditions [5].
The lack of a precise diagnostic pathway, the prolonged incubation period of three to four days, and the need for thorough biochemical and morphological identification tests, make the diagnosis of Gordonia challenging. This organism can be identified using advanced nonphenotypic methods of identification, such as 16 S ribosomal RNA (rRNA) gene sequencing or matrix-assisted laser desorption/ionizationtime of flight mass spectrometry (MALDI-TOF MS) [5,9].
In one antibiotics susceptibility study involving 31 strains of Gordonia, all strains showed sensitivity to aminoglycosides (such as tobramycin, amikacin, and gentamicin). Besides, ampicillin was effective in all cases except in three strains: one bronchialis and two sputi [9]. Currently, there are no clear guidelines for the duration of antibiotics to cover this organism. In one case series, all pediatric patients used a four-to-six-week period of antibiotics and showed good outcomes; however, a two-week duration of both meropenem and gentamicin was used for one subject, later the patient developed a recurrence of infection [10]. Villanueva et al. used a two-week regimen of meropenem for one patient; however, the patient was re-admitted after two weeks and found to be infected with the same organism. The other case showed persistent bacteremia even after three weeks of proper antibiotics [11].

Conclusion
Gordonia is a rare, emerging human microorganism that causes a wide range of infectious diseases, particularly debilitating sepsis in cancer patients. Blood cultures that show gram-positive bacilli are often overlooked as potential diphtheroid contaminants. Phenotypic methods are not sufficient for detecting these pathogens, and it is essential to use more sophisticated genotypic identification methods. By increasing awareness of Gordonia species, clinical practice among physicians and microbiologists will improve, leading to better survival outcomes for patients.  Further multi-center studies are necessary to identify the organism's