Outer Ear Canal Infection with Rhabditis sp. Nematodes in a Human

Abstract

Here we report the first human case of an outer ear canal infection with a free-living nematode of the genus Rhabditis. Otomicroscopy revealed viable worms in the outer ear canal of a patient suffering from chronic otorrhea and hearing loss. The nematode was identified by microscopy and internal transcribed spacer (ITS)-PCR. CASE REPORTA 37-year-old male presented with purulent otorrhea from both ears for 8 weeks in a tertiary care center. Additionally, he reported of mild hearing loss since the beginning of symptomatic disease. Both otorrhea and hearing loss were more pronounced for the right ear, on which the patient had undergone mastoidectomy 3 years earlier due to chronic otitis media. The patient reported no other underlying disease or recent travel history, owned a pet dog as well as a pet cat, and had been working in an industrial agriculture company. Macroscopic inspection and visualization by otomicroscopy of the outer ear canal confirmed otorrhea and revealed tympanostomy tubes and a retraction of the tympanic membranes on both sides. The tuning fork test according to Weber lateralized left, the tuning fork test according to Rinne was bilaterally negative, and no spontaneous nystagmus as a sign of disturbance of the vestibular system was detected. Pure-tone audiometry revealed a conductive hearing loss on both sides in combination with a mild sensorineural hearing loss of 20 dB hearing level (HL) in the middle frequencies on the right side. No other local or systemic signs of infection such as fever or enlarged cervical lymph nodes were detected.Because a chronic bacterial otitis media infection was suspected, local antibiotic ear drops containing ciprofloxacin (3 mg per ml) were prescribed. Bacterial swab cultures from the outer ear canal obtained prior to antibiotic therapy detected bacteria of the normal skin flora (coagulase-negative staphylococci, nonhemolytic streptococci, and Corynebacterium spp.) as well as Alcaligenes faecalis, none of which are typically associated with otitis media. At that time, surgery was considered in the event of persistent clinical symptoms to exclude cholesteatoma. Cholesteatoma represents a benign proliferation of keratinizing squamous epithelium, which can lead to local tissue destruction and secondary chronic infection.In a follow-up physical examination 4 weeks later, no regression of clinical symptoms was noted. Surprisingly, otomicroscopy of both outer ear canals under 25-fold magnification revealed a large number of viable, moving worm-like organisms (Fig. 1, arrow). Both external ear canals were rinsed with saline solution, and the lavage fluid was submitted for further parasitological examination. The patient was treated with repeated topical application of ethanol (dequaliniumchlorid [0.04 g], glycerin anhydricum, ethanol [90%] aa ad 20 g) twice a day. No blood tests for leukocytosis or eosinophilia were performed due to the absence of clinical symptoms of a general infection. Microscopy of the unstained lavage fluid revealed high numbers of viable, 500-to-...

Molecular characterization of human isolates of Strongyloides stercoralis and Rhabditis spp. based on mitochondrial cytochrome c oxidase subunit 1 (cox1)

“…Genus Rhabditis have been reported to infect human digestive system [10][11][12][13], urinary system [14,15,17], and even outer ear canal [16]; and excreting larvae in stool and urine. Identification of Rhabditis species using morphological criteria requires skillful microscopists.…”

“…On the other hand, discrimination of Rhabditis species from S. stercoralis is necessary due to importance of S. stercoralis in immunocompromised patients and differences of managements in case of infectivity with these nematodes. Presently, utilization of molecular-based methods in such discrimination is very rare in clinical settings [16]. Although studies comparing quantitative polymerase chain reaction (qPCR) with microscopy methods for soil-transmitted helminthes are imperfect, they do show a significant increase in sensitivity and specificity of qPCR compared with labor-intensive traditional microscopic techniques [20].…”

“…Human infections with Rhabditis nematodes (Rhabditida) have been reported from different parts of the world, for example from China [12], Korea [13], Japan [14], Brazil [11], Rhodesia [15], Germany [16] and Iran [10]. In the past, morphological criteria were used for discrimination of Rhabditis species from S. stercoralis [10][11][12][13][14][15]17].…”

Molecular characterization of human isolates of Strongyloides stercoralis and Rhabditis spp. based on mitochondrial cytochrome c oxidase subunit 1 (cox1)

“…Genus Rhabditis have been reported to infect human digestive system [12][13][14][15], urinary system [16,17,19], and even outer ear canal [18]; and excreting larvae in stool and urine. As the parasitological diagnosis of S. stercoralis is the detection of parasite larvae in stool exams and other biological materials such as such as sputum, duodenal aspirates, gastric biopsies, cervical smear or CSF liquid [6], therefore, this study pointing out to the challenge for discrimination between S. stercoralis and Rhabditis species.…”

“…Human infections with Rhabditis spp. nematodes have been reported as scattered sporadic reports from different parts of the world, for example from China [14], Korea [15], Japan [16], Brazil [13], Rhodesia [17], Germany [18] and Iran [12]. In the past, morphological criteria were used for discrimination of Rhabditis species from S. stercoralis [12][13][14][15][16][17]19].…”