Cutaneous Tuberculosis Masked by Pseudomonas Co-Infection in Chronic Ulcer Case

A diagnostically challenging case report published in BMC Infectious Diseases describes culture-confirmed cutaneous tuberculosis co-infected with Pseudomonas aeruginosa within a chronic granulomatous ulcer. The clinical case details how initial empirical antimicrobial therapy generated partial improvement, obscuring the underlying mycobacterial disease until post-discharge cultures confirmed Mycobacterium tuberculosis.

The patient, a 71-year-old man, presented to clinicians with a three-year history of recurrent ulcers located on his right thigh. Clinical evaluation documented an extensive shallow ulcer measuring approximately 20 by 15 centimeters, which was accompanied by surrounding pustules.

Histopathological assessment of the patient’s wound tissue demonstrated epithelioid cell granulomas. Consecutive wound cultures performed at admission grew exclusively Pseudomonas aeruginosa, a known common colonizer of chronic wounds that is rarely considered a direct cause of granulomatous inflammation. While cutaneous infectious granulomas are generally recognized as arising from pathogens such as fungi, parasites, atypical mycobacteria, or Mycobacterium tuberculosis, initial cultures identified only the bacterial colonizer.

In response to the clinical presentation and bacterial cultures, the patient received empirical antimicrobial therapy comprising intravenous piperacillin-tazobactam and linezolid for 16 days during inpatient hospitalization. Following discharge, the patient completed 15 additional days of oral linezolid therapy. This empirical regimen resulted in partial clinical improvement during his hospital stay and culminated in complete wound healing within approximately one month.

The diagnostic picture shifted after discharge when mycobacterial culture of the wound tissue turned positive for Mycobacterium tuberculosis, prompting clinicians to revise the diagnosis to cutaneous tuberculosis with P. aeruginosa co-infection. The authors noted that the patient’s favorable clinical healing response may have been partly attributable to the anti-tuberculous activity of linezolid rather than solely to the antibacterial management of P. aeruginosa.

Over an 18-month telephone follow-up, the patient reported that the ulcer remained completely healed with no new or recurrent skin lesions. However, because no objective reassessment was conducted in person, the authors emphasized that microbiological cure cannot be confirmed. The authors concluded that linezolid, as a second-line anti-tuberculous agent, can create a diagnostic pitfall by producing partial healing falsely attributed to bacterial coverage alone, reinforcing that standard combination anti-tuberculosis therapy remains the treatment of choice once diagnosis is established.

Subject of Research: Cutaneous tuberculosis and Pseudomonas aeruginosa co-infection in chronic ulcers

Article Title: Cutaneous tuberculosis co-infected with Pseudomonas aeruginosa in a chronic granulomatous ulcer: a diagnostically challenging case report

Article References: Yang, Z., Duan, Z., Li, M., Chen, H., Xiang, Z., & Li, C. (2026). Cutaneous tuberculosis co-infected with Pseudomonas aeruginosa in a chronic granulomatous ulcer: a diagnostically challenging case report. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14777-3

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14777-3

Keywords: cutaneous tuberculosis, Pseudomonas aeruginosa, chronic ulcer, granulomatous inflammation, linezolid, case report, mycobacterial infection, diagnostic delay, Cutaneous, tuberculosis, co-infected, Pseudomonas