Persistent Pyelonephritis and Renal Abscess due to Mycoplasma hominis in an Immunocompromised Patient: A Case Report

Background: Mycoplasma hominis is a fastidious, cell wall-deficient bacterium commonly colonising the lower genitourinary tract. While usually commensal, it can cause opportunistic infections in immunocompromised patients. As it can be difficult to culture on standard mediums and is resistant to many first-line antimicrobials, diagnosis and treatment are often delayed.

Case presentation: We report the case of a 31-year-old woman with Stage IVA extranodal marginal zone lymphoma previously treated with bendamustine-rituximab, who presented with fever, suprapubic pain and haematuria in the setting of neutropenia. She developed acute kidney injury and was initially treated for neutropenic sepsis. Computed tomography revealed bilateral hydroureteronephrosis and, subsequently, a right renal lesion concerning for abscess. Despite broad-spectrum empirical therapy, she remained febrile with persistently elevated inflammatory markers. Blood cultures grew Streptococcus mitis in a single bottle, later considered a contaminant. Routine urine cultures were initially negative; M. hominis was identified only after prolonged incubation and directed testing on a urine culture collected on Day 5 of admission. On Day 10 of admission, urine culture identified Mycoplasma hominis. Directed therapy with intravenous clindamycin, doxycycline and levofloxacin led to clinical improvement. She was discharged after 17 days with a combination of oral doxycycline and levofloxacin. She was readmitted shortly afterwards with symptom recurrence and progression of renal abscesses but responded to re-initiation of clindamycin. At outpatient follow-up, she had transitioned to levofloxacin monotherapy with symptomatic improvement, radiological reduction of abscesses, downtrending inflammatory markers and recovery of renal function.

Conclusion: This case highlights M. hominis as a rare but important cause of upper urinary tract infection and renal abscess in immunocompromised hosts. Clinicians should suspect atypical pathogens in culture-negative urosepsis unresponsive to empirical antibiotics. Specialised diagnostics are essential for accurate detection, and timely targeted therapy can achieve favourable outcomes even when surgical drainage is not feasible.