Abstract
RATIONALE: Lawsonella clevelandensis is a gram-positive bacterium, partially acid-fast, strictly anaerobic, nonspore-forming, and catalase-positive. This microorganism was once overlooked in clinical microbiology due to its stringent growth requirements in laboratory cultures, but it has recently attracted recognition as a potential pathogen. Available reports implicate Lawsonella clevelandensis infection with abscess formation, including breast, spinal, abdominal, and deep soft tissue abscesses. Here, we present a case of recurrent breast abscess caused by Lawsonella clevelandensis infection. PATIENT CONCERNS: A 46-year-old female patient had a history of left breast abscess for 6 years, with recurrent episodes and persistent symptoms. DIAGNOSES: Three milliliters of pus obtained from abscess puncture were examined. The results were negative for tuberculosis, interferon-γ, the rifampicin resistance gene rpoB, and Mycobacterium tuberculosis complex. The Kingfield metagenomics capture (MetaCAP) test identified Lawsonella clevelandensis (sequence number 17,296) with a 99% confidence level and no detected resistance genes. INTERVENTIONS: Following abscess puncture and irrigation under ultrasound guidance, intravenous infusion of "piperacillin-tazobactam (4.5 g q8h)" was administered for 16 days, resulting in an improvement in the patient's condition. Oral treatment with "amoxicillin-clavulanate 2.0 g bid and metronidazole 1.2 g tid" was continued after discharge. OUTCOMES: One month after discharge, color Doppler ultrasound showed a significant reduction in the abscess size. At the 3-month telephone follow-up, the patient reported that she had not taken the medication for over a month and had experienced no symptoms of redness, swelling, or pain in the left breast. LESSONS: The clinical manifestations of Lawsonella clevelandensis infection are similar to those of other acid-fast bacilli (e.g., Nocardia and Mycobacterium tuberculosis), potentially leading to misdiagnosis and mistreatment, thereby delaying resolution of the condition. The methods used for treating infections by bacterial pathogens differ significantly, as do the prognoses, indicating the importance of precise diagnosis. Lawsonella clevelandensis should be included in the differential diagnosis of infections caused by acid-fast bacteria. Due to the extreme difficulty in culturing this bacterium in vitro, gene sequencing is used primarily for diagnosis. Overall, the prognosis of patients with Lawsonella clevelandensis infection is good. Timely debridement and drainage, combined with antibiotic treatment, can usually lead to a cure.