Scandinavian Journal of Infectious Diseases

ISSN: 0036-5548 (Print) 1651-1980 (Online) Journal homepage: http://www.tandfonline.com/loi/infd19

Mycobacterium abscessus: a rare cause of vascular graft infection Imran Umer, Satish Mocherla, Joseph Horvath, Suthep Arora & Yasir Ahmed To cite this article: Imran Umer, Satish Mocherla, Joseph Horvath, Suthep Arora & Yasir Ahmed (2014) Mycobacterium abscessus: a rare cause of vascular graft infection, Scandinavian Journal of Infectious Diseases, 46:11, 813-816 To link to this article: http://dx.doi.org/10.3109/00365548.2014.943284

Published online: 19 Aug 2014.

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Date: 05 November 2015, At: 17:48

Scandinavian Journal of Infectious Diseases, 2014; 46: 813–816

CASE REPORT

Mycobacterium abscessus: a rare cause of vascular graft infection

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IMRAN UMER1, SATISH MOCHERLA1, JOSEPH HORVATH2, SUTHEP ARORA1 & YASIR AHMED1 From the 1Internal Medicine Department and Infectious Diseases, Texas Tech University Health Science Center, Odessa, TX, and 2Infectious Disease Department, University of South Carolina, Columbia, SC, USA

Abstract Prosthetic vascular graft infection (PVGI) following vascular reconstructive surgery is an uncommon but serious complication and is associated with high morbidity as well as mortality rate. Staphylococcal species are the most common organisms causing PVGI. Mycobacterium abscessus is a very rare cause of PVGI and poses a significant diagnostic and management dilemma. To the best of our knowledge, we report the third documented case of M. abscessus vascular graft infection that was diagnosed with 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) scan and treated successfully.

Keywords: Prosthetic vascular graft infection, femoral graft infection, Mycobacterium abscessus, mycobacterial graft infection

Introduction Prosthetic vascular graft infection (PVGI) is an infrequent but serious complication of vascular reconstructive surgery. Its incidence varies from 1 to 5% and depends upon graft location [1]. Staphylococcus aureus is commonly seen in early PVGI (⬍ 4 months) and coagulase-negative Staphylococcus species are more likely seen in late PVGI (⬎ 4 months) [2]. Mycobacterium abscessus vascular graft infection is very rare and only two previous cases of M. abscessus (femoro-popliteal graft and hemodialysis arteriovenous graft) infection have been reported [3,4]. It poses a significant diagnostic challenge as well as a management dilemma. Here we report a third documented case of M. abscessus femoral vascular graft infection that was treated successfully.

Case report A 69-year-old male presented to an outlying facility with low grade fever, chills, weight loss, and skin rash on the right foot extending to the leg for 6 weeks. The patient had a significant medical history of coronary artery disease status post triple vessel

bypass, left carotid artery endarterectomy, and right to left femoral–femoral artery bypass, along with abdominal aortic aneurysm repair with stent placement 2.5 years ago. He was diagnosed with multiple sclerosis 5 months before presentation and received a short course of corticosteroid and daily subcutaneous injection of glatiramer for 39 days. Initial work-up included acid-fast bacilli (AFB) blood cultures which turned positive on the ninth day of incubation and were subsequently identified as M. abscessus by 16S RNA gene sequencing and internal transcribed spacer (ITS) PCR method at the national ARUP reference laboratory. Details on susceptibility are shown in Table I. Unfortunately further identification of M. abscessus subspecies was not obtained. He received oral ciprofloxacin and clarithromycin for 4 weeks but his symptoms were not resolved, so he was admitted to our facility. Examination revealed a pulse rate of 106, blood pressure of 112/68 mmHg, respiratory rate of 16/minute, and a temperature of 98.6°F. A mild papular rash was noted on the right foot extending to the lower leg with mild edema. The rest of the systemic examination was unremarkable. Routine blood tests were normal. After obtaining

Correspondence: Yasir Ahmed, MD, Assistant Professor Infectious Diseases, Internal Medicine Department, Texas Tech University Health Science Center, Permian Basin, 701 W 5th Street, Odessa, TX 79763, USA. Tel: ⫹ 1 432 703 5343. Fax: ⫹ 1 432 335 5262. E-mail: [email protected] (Received 2 April 2014 ; accepted 24 June 2014 ) ISSN 0036-5548 print/ISSN 1651-1980 online © 2014 Informa Healthcare DOI: 10.3109/00365548.2014.943284

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I. Umer et al. Table I. Mycobacterium abscessus blood cultures and graft tissue cultures with susceptibility and relevant minimum inhibitory concentration (MIC) level for different antibiotics. Blood culture MIC (mg/L)

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Antibiotics Trimethoprim/ sulfamethoxazole Ciprofloxacin Moxifloxacin Cefoxitin Amikacin Doxycycline Minocycline Clarithromycin Linezolid Imipenem Tigecycline

Outlying hospital

Admission

Hospital day 5

Re-admission

⬎ 8/152 R

⬎ 16/304 R

NA

⬎ 16/304 R

⬎4 R ⬎8 R 32 I 16 S ⬎ 16 R NA 1 16 I 16 I 0.50

⬎8 R ⬎ 16 R 32 I 16 S ⬎ 32 R ⬎ 16 R ⬎ 32 R 32 R 16 I 0.25

NA NA NA NA NA NA NA NA NA NA

⬎8 R ⬎ 16 R 64 I 16 S ⬎ 32 R ⬎ 16 R ⬎ 32 R 16 I 16 I 0.25

Graft tissue culture MIC (mg/L) ⬎ 16/304 R ⬎8 R ⬎ 16 R 64 I 16 S ⬎ 32 R ⬎ 16 R ⬎ 32 R 16 I 16 I 0.25

I, intermediate; NA, not available; R, resistant; S, susceptible.

blood cultures, intravenous (i.v.) amikacin and tigecycline were started. Blood cultures from both admission and on hospital day 5 remained positive (same incubation period; 9 days) for M. abscessus (Table I). Due to persistent bacteremia he underwent extensive work-up including transthoracic and transesophageal echocardiogram; computed tomography (CT) scan of the chest, abdomen, and pelvis; and technetium-labeled white blood cell scan (WBC scan). All these tests were negative. On hospital day 19 the patient developed increasing somnolence and confusion. A lumbar puncture revealed cerebrospinal fluid (CSF) WBCs: 197/ mm3 with 86% lymphocytes, protein 44.1 mg/dl, glucose 47 m/dl, and the corresponding serum glucose was 121 mg/dl. Intravenous imipenem was added to the above regimen. However, CSF AFB culture remained negative at 8 weeks of incubation. Blood AFB cultures were repeated after 4 weeks of the three-drug regimen (imipenem, tigecycline, and amikacin) and these remained negative. Lumbar puncture was repeated after 10 weeks of treatment and CSF analysis was normal. The patient showed clinical improvement, hence all antibiotics were stopped at 13 weeks of treatment; however, 4 weeks later, the patient was readmitted to hospital with recurrence of fever up to 101°F. Blood cultures were repeated, which became positive for M. abscessus again (Table I). Lumbar puncture was repeated and CSF analysis was normal. CT examination of the abdomen and pelvis remained negative. Arterial graft infection continued to be the suspected source, thus an 18F-fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT) was performed and it showed high uptake in the femoral graft only (Figure 1). The patient immediately underwent

debridement with removal of infected graft and placement of a new graft. Culture of the graft tissue was positive for M. abscessus (Table I). Postoperatively, he was treated initially with i.v. imipenem and tigecycline daily and amikacin (three times per week) along with cefoxitin for the first 4 weeks. Subsequently, imipenem, tigecycline, and amikacin were continued for about 14 weeks after removal of the graft. The patient did develop hearing loss at 4 weeks of treatment that was thought to be amikacininduced but because of the lack of therapeutic options amikacin was continued. Surveillance blood AFB cultures obtained at 2, 4, and 8 weeks after completion of i.v. antibiotics remained negative. The patient was followed for 6 months and remained symptom-free. Discussion PVGI is an infrequent but serious complication with associated mortality up to 75% for intra-abdominal aortic grafts and limb amputation rates up to 70% for lower extremities grafts [5,6]. Infection is thought to occur during the intraoperative or early postoperative period in the majority of patients. The risk factors for PVGI are groin incisions, emergent surgery, history of multiple invasive interventions before or after graft placement, and contiguous infection in the graft area or presence of bacteremia at the time of graft placement [7]. Comorbid conditions including diabetes mellitus, chronic renal disease, obesity, and other immunocompromised conditions also appear to predispose to PVGI [8,9]. In our case the portal of entry was not clear. Staphylococcal species are the most common organisms causing PVGI and account for more than

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M. abscessus as rare cause of vascular graft infection

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Figure 1. 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) scan; arrow shows moderately intense FDG uptake in femoral–femoral bypass vascular graft.

50% of cases. Other gram-positive cocci, gram-negative bacilli, and fungi, particularly Candida species, cause a minority of PVGIs [9]. Nontuberculous mycobacteria (NTM) such as M. abscessus are rarely responsible for vascular graft infection. M. abscessus is a rapidly growing AFB that is commonly present in water and soil like other NTM [10]. It can be differentiated from other mycobacteria on the basis of its rapid growth features, biochemical tests, gasliquid chromatography of metabolic products, and PCR analysis [11]. It is endemic in the southeastern United States from Florida to Texas. M. abscessus can cause infection in both immunocompetent and immunocompromised hosts. Clinically it presents as pulmonary infection, skin and soft tissue abscesses, otitis, osteomyelitis, and disseminated infection [12]. Endovascular infection including vascular graft infection with M. abscessus is very uncommon. It is highly resistant to most commonly used antibacterial agents. The diagnosis of PVGI requires detailed history; physical examination of the affected site; bacterial, fungal, and AFB cultures of blood and/or wound; and imaging studies. The most common imaging studies used to evaluate vascular graft infections

include ultrasound and contrast-enhanced CT angiography [13]. 18F-FDG-PET/CT may have special value in localizing endovascular infection. A recent study of 39 patients with suspected vascular graft infection reported that FDG-PET/CT showed a sensitivity, specificity, positive predictive value, and negative predictive value of 93%, 91%, 88%, and 96%, respectively. The latter study did not specify the microorganisms causing the infection [14]. In our case it was particularly helpful as more than one vascular site was at risk Marion et al. reported the first case of M. abscessus vascular graft (femoral) infection that was successfully treated with graft removal and clarithromycin and minocycline for 1 year [3]. Similar to the above case report, our patient’s vascular graft infection was not detected on conventional CT and WBC scan and was eventually diagnosed with an FDG-PET/CT scan, which eventually led to cure with both long duration i.v. antibiotics and removal of the infected femoral graft. Kang et al. reported a second case of M. abscessus vascular graft (arteriovenous) infection in a patient with end stage renal disease who unfortunately did not survive despite the appropriate treatment [4].

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In the absence of data from randomized controlled trials, guidelines for management of PVGI generally involve removal of the infected vascular graft if possible, along with antimicrobial therapy. The duration of antimicrobial therapy is determined by the identification of the exact microorganism and the severity and extent of infection. Due to the rarity of M. abscessus vascular graft infection, the optimal duration of antimycobacterial therapy is unknown. Generally M. abscessus infection is treated with clarithromycin, amikacin, and cefoxitin. Other antibiotics include linezolid, imipenem, tigecycline, doxycycline; quinolones and azithromycin have also been used. Although the clinical correlation of susceptibility testing remains imprecise, the American Thoracic Society guidelines recommend susceptibility testing of clinically significant M. abscessus isolates. Usually a macrolide along with the addition of two or more drugs is the recommended treatment for disseminated M. abscessus infection [15]. Our patient had resistance to clarithromycin, quinolones, and doxycycline, yet was successfully treated with 14 weeks of intravenous antibiotics including imipenem, amikacin, and tigecycline after removal of the infected vascular graft. Unlike the previously reported case by Marion et al. [3], no further antibiotics were given after 14 weeks after removal of the graft. The patient remained symptom-free at 6 months follow-up. In summary, PVGI is a very uncommon but devastating complication of reconstructive vascular surgery. M. abscessus is a very rare cause of PVGI and poses a significant diagnostic and management dilemma. It requires prompt diagnosis for better outcome. An FDG-PET/CT scan can be useful in confirming the presence and location of such infection, especially when conventional imaging fails to localize the source of infection. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

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