Lawsonella clevelandensis: a normal flora that bites deep

Since its formal description in 2016, Lawsonella clevelandensis-a strictly anaerobic, partially acid-fast bacterium-has been increasingly recognized as a cause of deep-seated abscesses, yet its fastidious nature and absence from routine diagnostic databases contribute to significant underdiagnosis. This narrative review synthesizes current knowledge on its microbiology, expanding clinical spectrum, diagnostic strategies, and treatment, based on a literature search of PubMed and Web of Science up to April 2026. Analysis of 27 documented publications, comprising 18 clinical cases, reveals a potential association with host risk factors including diabetes, immunosuppression, and prior surgical procedures, alongside a notable predilection for fat-rich tissues such as the breast and abdomen. While metagenomic next-generation sequencing and 16S rRNA gene amplification have become indispensable for definitive identification, antimicrobial susceptibility data-derived primarily from a single strain-demonstrate uniformly low minimum inhibitory concentrations for penicillins, carbapenems, clindamycin, and metronidazole, with no acquired resistance genes identified by whole-genome sequencing. However, the absence of established clinical breakpoints and limited tested isolates precludes definitive conclusions about universal susceptibility. Clinicians should maintain a high index of suspicion for L. clevelandensis in culture-negative deep abscesses, particularly those with acid-fast rods, as prompt diagnosis and empirical therapy with β-lactam/β-lactamase inhibitors or carbapenems appear reasonable based on current in vitro and clinical evidence, though further susceptibility surveillance is essential.