Bacteriemia por Comamonas testosteroni e infección polimicrobiana intrahospitalaria luego de estancia prolongada. Reporte de caso

Comamonas testosteroni bacteremia and nosocomial polymicrobial infection following a prolonged hospital stay: A case report

Introducción. Comamonas testosteroni es un bacilo gramnegativo oportunista considerado un patógeno emergente. Aunque hasta 2022 se habían documentado pocos casos, recientemente se ha observado un aumento en los reportes, principalmente de bacteriemia.

Presentación del caso. Hombre de 58 años quien fue ingresado a la UCI de un hospital de Duitama, Colombia, debido a un ACV hemorrágico que requirió manejo con ventriculostomía y posterior craniectomía descompresiva por hipertensión intracraneal. Ante la presencia de neumonía por aspiración, se inició antibioticoterapia con ampicilina/sulbactam y clindamicina (7 días). En el día 10 de hospitalización se inició tratamiento con cefepima (10 días) debido a la presencia de fiebre intermitente; además, se realizaron una traqueostomía y una gastrostomía ya qué seguía requiriendo soporte respiratorio. El día 22, ante la persistencia de fiebre, se inició terapia con meropenem. En el día 24 se tomaron muestras para hemocultivos (secreción de herida de la ventriculostomía) y cultivo de bacteria (secreción de la traqueostomía), las cuales fueron positivas para Klebsiella pneumoniae productora de carbapenemasas y Proteus mirabilis productora de carbapenemasas, respectivamente, ajustando dosis de meropenem el día 27. En el día 40, ante la ausencia de mejoría clínica y la sospecha de flebitis en miembro superior izquierdo como origen de la infección, se inició tratamiento con trimetoprima/sulfametoxazol (160/800 mg oral cada 8 horas durante 7 días) y se solicitaron varias pruebas, incluyendo un hemocultivo y un urocultivo, este último positivo para P. mirabilis; también se retiró la traqueostomía. El día 46, dada la identificación de Bordetella bronchiseptica resistente a cefazolina y amikacina en el hemocultivo, se continuó la terapia antibiótica sin ajustes y se tomó una nueva muestra para hemocultivo con identificación de microorganismos mediante espectrometría de masas MALDI-TOF, donde se detectó C. testosteroni. No se ajustó el tratamiento antibiótico y el paciente fue dado de alta el día 56 luego de lograrse una mejora gradual de su condición clínica. En cita de control 12 días después del egreso, se retiró la gastrostomía y no se observaron signos de infección; sin embargo, tampoco se documentó mejoría neurológica.

Conclusión. A pesar de su baja virulencia, C. testosteroni debe considerarse en pacientes con infecciones nosocomiales, especialmente en estancias prolongadas.

Introduction: Comamonas testosteroni is an opportunistic Gram-negative bacillus considered an emerging pathogen. Although few cases had been documented until 2022, there has recently been an increase in reports, primarily involving bacteremia.

Case presentation: A 58-year-old male was admitted to the ICU of a hospital in Duitama, Colombia, due to a hemorrhagic stroke that required management with ventriculostomy and subsequent decompressive craniectomy for intracranial hypertension. Given the presence of aspiration pneumonia, antibiotic therapy with ampicillin/sulbactam and clindamycin was initiated for 7 days. On day 10 of hospitalization, cefepime treatment was started for 10 days due to intermittent fever. Additionally, tracheostomy and gastrostomy were performed as the patient continued to require respiratory support. On day 22, due to persistent fever, meropenem therapy was initiated. On day 24, samples were taken for blood cultures (ventriculostomy wound secretion) and bacterial culture (tracheostomy secretion), which were positive for carbapenemase-producing Klebsiella pneumoniae and carbapenemase-producing Proteus mirabilis, respectively, leading to the adjustment of meropenem on day 27. On day 40, given the lack of clinical improvement and suspected phlebitis in the left upper limb as the source of infection, treatment was started with trimethoprim/sulfamethoxazole (160/800 mg orally every 8 hours for 7 days). Several tests were requested, including a blood culture and a urine culture, the latter of which was positive for P. mirabilis; tracheostomy was removed. On day 46, following the identification of Bordetella bronchiseptica resistant to cefazolin and amikacin in the blood culture, antibiotic therapy continued without adjustments. A new blood culture sample was taken for microorganism identification using MALDI-TOF mass spectrometry, which detected C. testosteroni. No adjustments were made to the antibiotic treatment, and after gradual clinical improvement the patient was discharged on day 56. At a follow-up appointment 12 days after discharge, the gastrostomy was removed and no signs of infection were observed. However, no neurological improvement was documented.

Conclusion. Despite its low virulence, C. testosteroni should be considered in patients with nosocomial infections, especially during prolonged stays.

Case report

Carlos Arturo Álvarez-Moreno1,2,3,4 Gladys Cecilia Gordillo-Navas1 Jimmy Harvey Bello-Torres1 Juan Pablo Sánchez-Aguirre3,4,5

1 E.S.E. Hospital Regional de Duitama - Epidemiology Unit - Duitama, Boyacá - Colombia.

2 Universidad Nacional de Colombia - Bogotá Campus - Faculty of Medicine - Department of Internal Medicine - Infectious Diseases Unit - Bogotá D.C. - Colombia.

3 Clinica Colsanitas - Vice presidency of Innovation and Scientific Development - Bogotá D.C. - Colombia.

4 Clinica Colsanitas - One Health in Infectious Diseases, Keralty - Bogotá D.C. - Colombia.

5 Universidad del Bosque - Urology Unit - Bogotá D.C. - Colombia.

Open access

Received: 29/12/2024

Accepted: 14/10/2025

Corresponding author: Juan Pablo Sánchez-Aguirre. Vice presidency of Innovation and Scientific Development, Clinica Colsanitas. Bogotá D.C. Colombia. E-mail: jpsanchezag@unal.edu.co.

Keywords: Bacteremia; Comamonas testosteroni; Cross Infection; Drug Resistance, Bacterial; Case reports (MeSH).

Palabras clave: Bacteriemia; Comamonas testosteroni; Infección Hospitalaria; Farmacorresistencia Bacteriana, Informes de caso (DeCS).

How to cite: Álvarez-Moreno CA, Gordillo-Navas GC, Bello-Torres JH, Sánchez-Aguirre JP. Comamonas testosteroni bacteremia and nosocomial polymicrobial infection following a prolonged hospital stay: A case report. Rev. Fac. Med. 2026;74:e117795. English. doi: https://doi.org/10.15446/revfacmed.v74.117795.

Cómo citar: Álvarez-Moreno CA, Gordillo-Navas GC, Bello-Torres JH, Sánchez-Aguirre JP. [Bacteriemia por Comamonas testosteroni e infección polimicrobiana intrahospitalaria luego de estancia prolongada. Reporte de caso]. Rev. Fac. Med. 2026;74:e117795. English. doi: https://doi.org/10.15446/revfacmed.v74.117795.

Copyright: ©2026 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, as long as the original author and source are credited.

Abstract

Resumen

Introduction

Comamonas testosteroni, a Gram-negative bacillus of the Comamonas genus,1,2 is an aerobic, motile, non-hemolytic, non-fermenting, rod-shaped bacterium.1,3 Although it has a low virulence, it can cause infections, including serious conditions such as septicemia or endocarditis, in immunocompetent individuals.1,2 This bacillus was initially classified within the Pseudomonas genus and was known as Pseudomonas testosteroni; however, it was renamed and reclassified into the Comamonas genus in 1987.1,2 These microorganisms are found in water, soil, mud, and plants. Although infrequent, they can cause diseases in immunocompromised individuals and immunocompetent hospitalized patients, leading them to be considered opportunistic pathogens.1,2

Documented reports of human infections by C. testosteroni are scarce. According to a recent review article, only 52 cases of infections associated with this bacterium were reported in the literature between 1987 and 2022. Nevertheless, a considerable increase in the reports of these infections has been observed since late 2022, with 12 new cases.1,4-6

A stroke occurs when blood flow to a part of the brain stops.7 There are two main types of stroke. Ischemic strokes occur when a blood vessel supplying the brain is blocked by a blood clot, preventing blood flow from reaching the brain; in this scenario, brain cells do not receive oxygen or nutrients and begin to die within minutes. On the other hand, hemorrhagic strokes occur when a blood vessel in a part of the brain weakens and ruptures, causing sudden bleeding in the brain; the blood leaking from the vessels creates pressure and damages brain cells.7,8 Hemorrhagic strokes represent only 10-20% of all strokes.9

Nosocomial infection by C. testosteroni in patients with a history of stroke is quite rare. In fact, of the 64 infections associated with this bacterium reported in the literature to the time of writing this report,1,2,4-6 only one patient presents these characteristics: an 83-year-old Turkish man with a history of hypertension and ischemic stroke in whom this bacterium was isolated during his stay in the ICU.2 Notwithstanding the above, there are also two additional cases of C. testosteroni infection in patients with cerebrovascular disease.1

The following is the case of a patient admitted to the ICU for a hemorrhagic stroke who developed C. testosteroni bacteremia and polymicrobial infection with Klebsiella pneumoniae, Proteus mirabilis, and Bordetella bronchiseptica during a prolonged hospital stay (>40 days). This is the first case of C. testosteroni infection described in our country.

Case presentation

A 58-year-old male, a poultry farmer from a rural area with uncontrolled arterial hypertension, was brought to the emergency department of a tertiary care hospital in Duitama, Colombia, due to dysarthria. Physical examination findings included agitation and disorientation, with eye-opening to verbal command (Glasgow Coma Scale score 12/15, arterial hypertension (180/120 mmHg), anisocoria, central facial palsy, left hemiparesis, aphasia, and dysarthria. A non-contrast head CT scan was performed, revealing a right-hemisphere basal ganglia hemorrhage.

Based on these findings, a hemorrhagic stroke was diagnosed. After securing the airway through endotracheal intubation, a ventriculostomy with a ventriculoperitoneal shunt and intracranial pressure monitoring was performed, followed by transfer to the intensive care unit (ICU). During the immediate postoperative period (12 hours after the procedure), a decompressive craniectomy was required due to intracranial hypertension. During the intervention, a right parietal intracerebral hematoma secondary to subarachnoid hemorrhage was found and drained. Notably, the complete blood count upon ICU admission showed no leukemoid reaction or other significant alterations.

On hospital day 2, given the presence of food debris in the oral cavity, tachypnea, and right-base pulmonary infiltrates on chest X-ray, the patient was diagnosed with aspiration pneumonia. Antibiotic therapy was initiated with ampicillin/sulbactam (1.5 g IV every 6 hours) and clindamycin (600 mg IV every 6 hours) for 7 days. Subsequently, on day 10, cefepime (1 g IV every 8 hours for 10 days) was started due to intermittent fever and suspected ventilator-associated pneumonia.

The following studies were also performed: urinalysis (no signs of inflammation: negative leukocyturia, nitrites, and esterase), chest CT (small bilateral pleural effusion and bilateral basal atelectasis), procalcitonin (PCT) test (0.18 ng/mL, not suggestive of sepsis), and C-reactive protein (elevated at 103.8 mg/dL). Additionally, since the patient required ongoing respiratory support, a tracheostomy and gastrostomy were performed to prevent further airway compromise. No neurological improvement was observed (Glasgow Coma Scale score 9/15).

On day 22, the patient was discharged from the ICU to the general ward. Due to persistent fever, meropenem therapy was initiated (1 g IV every 8 hours for 7 days). On day 24, thick bloody discharge was identified at the ventriculostomy surgical site, and a culture sample was collected. A tracheal secretion culture was also obtained. Three days later, reports confirmed carbapenemase-producing K. pneumoniae (KPC) in the surgical site culture and carbapenemase-producing P. mirabilis in the tracheal sample. Consequently, and due to impaired renal function (estimated glomerular filtration rate: 34 mL/min/1.73 m2) the meropenem dose was adjusted to 500 mg every 8 hours. Furthermore, despite slightly elevated PCT levels (0.17 ng/mL), tigecycline was started (loading dose: 100 mg bolus; maintenance dose: 50 mg every 12 hours for 7 days).

Despite pharmacological management, the patient’s condition failed to improve. He presented with tachycardia, rapid shallow breathing with accessory muscle use, lethargy, anasarca, disseminated rhonchi, and decreased neurological response (Glasgow Coma Scale score 8/15). Given these findings and the recurrence of fever on hospital day 40, the following laboratory and imaging tests were performed: blood culture (Gram-negative bacilli), urine culture (positive for P. mirabilis with a count of 80 000 CFU), PCT (elevated at 7.41 ng/mL), complete blood count (normal results), and high-resolution chest CT (normal findings). Suspecting phlebitis in the left upper limb as the possible infectious source, treatment with trimethoprim/sulfamethoxazole (160/800 mg orally every 8 hours for 7 days) was initiated. On day 41, neurological improvement was observed (Glasgow Coma Scale score 11/15) and the fever subsided. The tracheostomy was removed on day 43.

On hospital day 46, the blood culture performed six days earlier reported the presence of B. bronchiseptica resistant to cefazolin and amikacin. Given the favorable clinical response, the medical team continued trimethoprim/sulfamethoxazole therapy without adjustments. A new blood culture sample was collected for microorganism identification using MALDI-TOF mass spectrometry (VITEK® 2 system), which reported the presence of C. testosteroni (Figure 1).

Figure 1. A) Comamonas testosteroni colonies on chocolate agar; B) Comamonas testosteroni colonies on blood agar.

Source: Images obtained while treating the patient.

On hospital day 49, the patient showed gradual improvement in clinical status and consciousness (Glasgow Coma Scale score 15/15). The patient was discharged on day 56 with the following neurological sequelae: total dependence, bilateral amaurosis, right facial paresis, and left hemiparesis. The gastrostomy tube was removed in an outpatient setting 12 days after discharge; however, no neurological improvement was observed. No further follow-up data are available after this event. Table 1 presents the timeline of the patient’s care.

Table 1. Timeline of infections and antibiotic treatments.

Hospital day	Clinical event / Diagnostic suspicion	Microorganism(s)	Antibiotic(s)	Dosage and frequency	Duration
0-1	ICU admission due to intraparenchymal hemorrhage; endotracheal intubation	—	—	—	—
2	Aspiration pneumonia	— (no isolate)	Ampicillin/sulbactam and clindamycin	1.5 g IV q6 h + 600 mg IV q6 h	7 days
10	Intermittent fever; suspected VAP	— (no isolate)	Cefepime	1 g IV q8 h	10 days
12-14	Persistent fever; progression of pulmonary involvement	—	Cefepime (continued)	—	—
18-20	Suspected persistent respiratory infection	—	Cefepime (completing regimen)	—	—
22	Tracheostomy	—	Meropenem (initiation)	1 g IV q8 h	—
24	Purulent tracheal secretion; persistent fever	Carbapenemase-producing Proteus mirabilis	Tigecycline + Meropenem (adjusted)	Tigecycline: loading 100 mg IV bolus; maintenance 50 mg IV q12 h + meropenem 500 mg IV q 8h	7 days
24	Thick bloody discharge from ventriculostomy wound	KPC
25-31	Targeted therapy against KPC and P. mirabilis	KPC	Tigecycline + Meropenem	As described above	7 days
33-37	Persistent fever; systemic deterioration	—	—	—	—
38-40	Preliminary positive blood cultures	Gram-negative bacilli	—	—	—
40	Positive blood culture	Bordetella bronchiseptica	Trimethoprim/sulfamethoxazole	160/800 mg PO	7 days
40	Urine culture	P. mirabilis (80 000 CFU)
40	Fever due to left upper limb phlebitis (clinical suspicion)	—
41-43	Neurological and systemic improvement	—	—	—	—
43	Tracheostomy removal	—	—	—	—
46	Confirmatory identification by MALDI-TOF	Comamonas testosteroni	Trimethoprim/sulfamethoxazole (no adjustment)	160/800 mg PO	(Ongoing regimen)
49	Normalization of GCS score and systemic stability	—	—	—	—
56	Hospital discharge	—	—	—	—

VAP: ventilator-associated pneumonia; KPC: carbapenemase-producing Klebsiella pneumoniae; IV: intravenous; PO: per os (oral).

Source: Own elaboration.

Discussion

Reports of human infections caused by C. testosteroni are scarce in the literature, with only 64 cases reported to date.1,2,4 C. testosteroni is an opportunistic pathogen that infects patients receiving hospital treatment (i.e., nosocomial infection) and immunocompromised individuals in non-hospital settings.2 Most of these infections are nosocomial, considering that of the 64 documented cases, 55 occurred during hospital stays, 6 in immunocompromised patients (cancer and HIV), 2 prior to hospital admission, and 1 in a possibly immunocompromised woman (pregnancy). In our case, it was determined that the infection was nosocomial because, although the patient could have been exposed to this bacterium on a daily basis (he was a poultry farmer living in a rural area), he was immunocompetent and the bacterium was detected in a blood culture performed on the 40th day of hospitalization, despite not being identified in previous cultures.

Regarding the type of infection caused by C. testosteroni, Ryan et al.,2 in their literature review, reported that among the 52 cases identified up to 2022, bacteremia was the most frequent diagnosis (32.69%; n=17). Similarly, Ozbay et al.,1 in a study conducted in Turkey involving 8 patients with C. testosteroni, reported that 75% were diagnosed with bacteremia. In our case, the bacterium was isolated from a blood culture; therefore, the patient was also diagnosed with C. testosteroni bacteremia, with persistent fever as the sole symptom.

Regarding the identification of this bacterium, Ozbay et al.1 report that the detection method used was MALDI-TOF mass spectrometry (VITEK 2), yielding a 99.9% probability for C. Testoroni. Since this same method was employed in our patient, it can be affirmed that the present report constitutes the sixty-fifth case of infection by this pathogen documented in the global literature.1,2,7

There is no standardized treatment for C. testosteroni infections. However, in their systematic review, Ryan et al.2 report that various antibiotics have been used with favorable clinical outcomes, achieving full recovery in up to 85% of cases. Nevertheless, it is important to note that the reported resistance rates for C. testosteroni to cefazolin and trimethoprim-sulfamethoxazole are 1.92% and 7.69%,2 respectively, while resistance to amikacin varies between 9.61%2 and 50%.1 In the present case, the isolate showed resistance to amikacin and cefazolin, but the patient had a favorable clinical response to trimethoprim-sulfamethoxazole.

Although the patient did not achieve full neurological recovery due to the stroke sequelae, the treatment for bacteremia was considered effective based on the resolution of fever and the return to full consciousness. A limitation of this case was the lack of microbiological follow-up after discharge.

The present case highlights the incidence of polymicrobial infections caused by multidrug-resistant agents in patients with prolonged hospital stays. The coexistence of multiple opportunistic pathogens in critically ill patients underscores the complexity of management and the necessity for a multidisciplinary approach to infection control.

It is important to note the significant similarities between B. bronchiseptica and C. testosteroni, since both are Gram-negative, strictly aerobic, motile, non-fermenting bacilli. They are considered opportunistic pathogens capable of causing human infections under specific clinical conditions.10,11

Conclusion

The present case report underscores the importance of considering C. testosteroni in unexplained nosocomial infections, especially in patients with prolonged hospital stays, and employing modern diagnostic methods for early identification since, including our patient, 13 new cases have been reported since late 2022. Additionally, this case is notable for occurring in a patient with a hemorrhagic stroke, a condition not previously reported as a history or comorbidity in the 64 documented cases of C. testosteroni infection to date.

Ethical considerations

Informed consent was obtained from the patient for the preparation of this case report.

Conflicts of interests

None stated by the authors.

Funding

None stated by the authors.

Acknowledgments

None stated by the authors.

References

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