*Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ.
†Arizona College of Podiatric Medicine, Midwestern University, Glendale, AZ.
J Am Podiatr Med Assoc. 2024 Jul-Aug;114(4). doi: 10.7547/23-134.
Mycobacterium abscessus complex (MAbc) is a rapidly growing nontuberculous mycobacterium that represents an increasingly prevalent cause of skin infections. This report describes an atypical presentation of MAbc to heighten physician awareness of the pathogen. A 69-year-old woman with immunocompromised status presented with a 4-month history of a solitary, nonhealing ulcer on her right lower extremity after an insect bite. After no improvement following oral amoxicillin/clavulanate and topical mupirocin for the initial diagnosis of cellulitis, biopsy and culture of the lesion revealed MAbc. Microscopic examination revealed reactive cutaneous inflammation without evidence of malignancy. Acid-fast bacteria (AFB) stain was negative, and no granulomas were noted histologically. Clarithromycin and doxycycline were initiated while awaiting susceptibility testing results. Final culture showed MAbc sensitive to amikacin, cefoxitin, and clarithromycin. Unfortunately, before antibiotic therapy could be modified, the patient died. The presentation of a solitary lower-extremity ulcer is rare compared with current literature. This case occurred after a suspected insect bite rather than instrumentation. In addition, this case demonstrated negative AFB stain and absence of granulomas on histologic analysis. The patient's death did not allow for evaluation of treatment efficacy. Existing literature characterizing MAbc is sparse. Most cases present as multiple papules, nodules, and abscesses with positive AFB staining and granulomas; it is possible for deviations to exist depending on host immune status. Considering the highly drug-resistant nature of M abscessus, prompt diagnosis and treatment are crucial. For this to occur, clinicians must maintain high clinical suspicion for M abscessus infection in any chronic, nonhealing wound failing to respond to initial treatment.
脓肿分枝杆菌复合体（MAbc）是一种快速生长的非结核分枝杆菌，是越来越常见的皮肤感染原因。本报告描述了 MAbc 的一种不典型表现，以提高医生对病原体的认识。一名 69 岁的免疫功能低下女性，在昆虫叮咬后右下肢出现 4 个月的单一、不愈合溃疡，来诊。最初诊断为蜂窝织炎，给予口服阿莫西林/克拉维酸和局部莫匹罗星治疗后未见改善，随后对病变进行活检和培养，结果显示为 MAbc。显微镜检查显示反应性皮肤炎症，无恶性肿瘤证据。抗酸杆菌（AFB）染色阴性，组织学未见肉芽肿。克拉霉素和强力霉素在等待药敏试验结果的同时开始使用。最终的培养显示 MAbc 对阿米卡星、头孢西丁和克拉霉素敏感。不幸的是，在抗生素治疗可以调整之前，患者死亡。与目前的文献相比，下肢单发溃疡的表现较为罕见。这种情况发生在疑似昆虫叮咬后，而不是器械操作后。此外，该病例的 AFB 染色阴性，组织学分析未见肉芽肿。患者的死亡不允许评估治疗效果。目前关于 MAbc 的文献描述较少。大多数病例表现为多发性丘疹、结节和脓肿，AFB 染色阳性和肉芽肿；根据宿主免疫状态的不同，可能存在偏差。考虑到 M 脓肿的高度耐药性，及时诊断和治疗至关重要。为了实现这一目标，临床医生必须对任何慢性、不愈合的伤口，在初始治疗后未能缓解时，保持对 M 脓肿感染的高度临床怀疑。
