BI18: Mycobacterium marinum bacteraemia: a complication worth fishing for

Abstract

Opportunistic fungal infection with Alternaria in the immunosuppressed H. Wace, N. McEntyre, I. Elliott and R. Matin Departments of Dermatology, Pathology and Infectious Diseases, Oxford University Hospitals NHS Trust, Oxford, UK Alternaria is a rare cause of fungal infection in the human host but has emerged as an increasing source of morbidity in the iatrogenically immunosuppressed, in particular solid organ transplant recipients (OTRs). This ubiquitous soil saprophyte is a common plant pathogen responsible for leaf blight and leaf spot on a wide variety of crops. It is a phaeohyphomycosis (melanin-producing fungus) and can manifest as a cutaneous infection, which poses both diagnostic and therapeutic challenges. We report a case of cutaneous alternariosis in a 69-year-old farmer 20 months after renal transplantation for diabetic nephropathy. Current immunosuppressive medications included mycophenolate mofetil and tacrolimus. He presented to dermatology with a 6-month history of two well-circumscribed, smooth, violaceous nodules (approximately 0 5 and 2 cm in diameter, respectively) on the right thigh. These were asymptomatic and had remained static in size since onset. There was no preceding history of trauma or inoculation at the site. The patient was systemically well. Examination revealed no associated lymphadenopathy. Routine blood tests, including inflammatory markers, were normal. Excision biopsy of one nodule revealed a dermal abscess with necrotizing granulomatous inflammation. Periodic acid–Schiff with diastase and Grocott stains showed numerous hyaline septated fungal hyphae with acute angle branching. Culture identified Alternaria spp. sensitive to itraconazole and posaconazole, intermediate to voriconazole. Definitive management with surgical excision of the second nodule and a 6-month course of oral posaconazole was initiated. Alternariosis occurs more frequently in immunocompromised individuals as Alternaria spp. are weakly pathogenic. Localized disease has been reported to manifest with rhinosinusitis, ocular infections, onychomycosis and cutaneous/subcutaneous infections. Cutaneous presentations are most frequent and can be variable, ranging from macules to violaceous nodules/plaques and ulcers. Disseminated disease is rare but if undiagnosed it can be fatal. We present a case of localized disease with no obvious entry site for inoculation, although the patient’s occupation is likely to be relevant. Treatment remains a challenge in OTRs owing to drug–drug interactions through inhibition of cytochrome P450 enzymes. Posaconazole has an improved side-effect profile and more consistent bioavailability than itraconazole. Surgical excision is reported to be successful in reducing the burden of infection. Close surveillance is required to identify recurrence as early as possible. This case highlights the differential of rare fungal infections in OTRs presenting with nodules clinically suspicious of skin cancers and the management challenge it poses. BI18 Mycobacterium marinum bacteraemia: a complication worth fishing for B. Rooke, E. Justice, M. O’Shea and H.M. Lewis Dermatology Department and Infectious Diseases Department, University Hospitals Birmingham, Birmingham, UK Mycobacterium marinum infection, commonly referred to as fish tank granuloma, develops following cutaneous exposure to a contaminated aquatic environment. Mycobacterium marinum growth is optimal at 30 °C, and inhibited at 37 °C; hence, human infection typically manifests as cutaneous nodules affecting an extremity. Complicated M. marinum infection is uncommon, presenting with tenosynovitis, septic arthritis, osteomyelitis or haematogenous dissemination. We report a case of M. marinum bacteraemia in an elderly patient with diabetes, presenting as localized cutaneous nodules. An 83-yearold man who kept tropical fish presented with a 3-month history of discharging nodules on the left hand, with sporotrichoid spread along the left upper limb. His medical history included poorly controlled type 2 diabetes mellitus (HbA1c 74 mmol mol), chronic kidney disease stage 3B, atrial fibrillation, ulcerative colitis and proctocolectomy. He was previously independent, but he had become frail, confused and less mobile since developing the nodules. This general decline prompted an investigative workup to exclude disseminated infection. Skin and blood cultures isolated acid-fast bacilli; whole-genome sequencing identified M. marinum. Repeated blood cultures, obtained on separate occasions and from different sites, confirmed M. marinum bacteraemia. Whole-body computed tomography revealed a 5-cm multiloculated cystic lesion within the right hepatic lobe, with associated right portal vein thrombosis. Ultrasound-guided core liver biopsy demonstrated coagulative necrosis with no granulomas or malignancy. Further imaging to monitor the liver lesion is planned. Treatment is ongoing with clarithromycin, ethambutol and rifampin. Early during treatment, new cutaneous nodules developed on his forehead; however, at the 5-week follow-up, his cutaneous disease has improved. Mycobacterium marinum bacteraemia is exceptionally rare, with only nine culture-proven cases reported to our knowledge. All reported patients with M. marinum bacteraemia had demonstrable immunocompromise, specifically immunosuppressive therapy (n = 6), AIDS (n = 2) and severe combined immunodeficiency (n = 1). In our patient, we hypothesized that immunosenescence and diabetic immune dysfunction facilitated haematogenous dissemination. Mycobacterium marinum bacteraemia is usually associated with widespread cutaneous lesions, but two of nine previously reported cases were associated with cutaneous lesions localized to a limb. Seven of nine cases of M. marinum bacteraemia were fatal, and in four of these seven fatal cases M. marinum bacteraemia was first confirmed postmortem. Our case highlights that haematogenous dissemination of M. marinum can occur with fish tank granuloma, and atrisk patients may include those not classically considered immunocompromised. Clinicians should have a low threshold for including mycobacterial blood cultures in the investigative