Acanthamoeba Infection in a Hematopoietic Cell Transplant Recipient: Challenges in Diagnosis, Management, and Source Identification

Abstract

We report a case of Acanthamoeba infection in an HCT recipient with steroid-refractory GVHD. We highlight the multiple challenges that free-living ameba infections present to the clinician, the clinical laboratory, transplant infectious disease for review, hospital epidemiology if nosocomial transmission is considered, and public health officials, as exposure source identification can be a significant challenge. Transplant physicians should include Acanthamoeba infections in their differential diagnosis of a patient with skin, sinus, lung, and/or brain involvement.

Keywords: Acanthamoeba; HCT; free‐living ameba; nosocomial.

FIGURE 1

Timeline of Clinical Events.

FIGURE 2

Non‐contrast computed tomography (CT) chest on Day +52 and Day +55. Non‐contrast CT chest. CT chest demonstrated bilateral pulmonary nodules with ground glass opacities and consolidation in varying sizes, with interval worsening over a 3‐day period from (A) D + 52 to (B) D + 55.

FIGURE 3

Cytopathology and microbiology. Numerous ovoid to polygonal extracellular structures morphologically consistent with ameba organisms. (A) Stained Acanthamoeba cysts with lactophenol–aniline blue wet mount, and (B) Fungi–Fluor stain. The cysts appeared double‐walled and internal structures were poorly visible.

FIGURE 4

Lung biopsy demonstrated acute pneumonia with neutrophilic inflammation and extensive necrosis. Microorganisms in the forms of trophozoites and cysts present, positive with GMS stain, morphologically consistent with ameba organisms. Lung biopsy with H&E stain (A) and GMS stain (B) (both ×20 magnification). Image courtesy of Dilara Akbulut and Martha M. Quezado. GMS, Gomori methenamine silver; H&E, hematoxylin and eosin.

FIGURE 5

Further microbiology characteristics. Growth of Acanthamoeba on a lawn of Escherichia coli plated on a non‐nutrient agar. (A) Photomicrograph of culture plate demonstrating heavy growth of Acanthamoeba, (B) trichrome stained Acanthamoeba trophozoite, and (C) cyst growing on culture plate.

FIGURE 6

A midpoint‐rooted maximum likelihood tree (PhyML/3.3.20190321; iTOL) of Acanthamoeba 18S rRNA gene sequences from patient BAL (BAL1) and environmental samples (ENV1‐4). Remaining sequences as described in Qvarnstrom, Nerad, and Visvesvara et al. [21]. Asp, Acanthamoeba sp.; Atub, A. tubiashi; Aast, A. astronyxis; Acom, A. comandoni; Acas, A. castellanii.