A case of actinomycosis of the middle ear and a review of the literature

1. Introduction 

Actinomycosis is a granulomatous suppurative infection caused by an anaerobic, filamentous Gram-positive bacillus, belonging to the Actinomycetaceae family [1]. This is a rare disease, especially in children, and diagnosis is difficult to make. It is principally found in the cervicofacial region (50%) but we can also find it in the abdomen (25%) and thorax (15%) [2]. Usually, the disease reveals itself with tumefaction of the perimaxillar region, which infiltrate the skin and adjacent tissues. The color of the skin becomes bluish-purple. There is no associated adenopathy. The lesion evolves slowly often into an abscess or a fistula [3].

Rarely, actinomycosis can develop in the middle ear. The English language literature has reported fewer than 30 cases of tympano-mastoid infection. In this article, we reports the case of a child affected by actinomycosis of the right middle ear. We are going to develop the diagnosis, the treatment and the results.

2. Case report 

An 8-year-old child arrived in the ENT department of General Hospital of Dijon with a 9-month history of intermittent otorrhea of the right ear. A myringotomy has been done 3 months ago. The bacteriological cultures were sterile.

Otoscopy showed a bulging eardrum, with a voluminous inflammatory granuloma obstructing the anterior part of the external auditory canal (Fig. 1). The audiogram revealed a right 50dB conductive hearing loss. The CT scan showed a complete opacity of the middle ear cavities (Fig. 2). There was no associated bone erosion.

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Figure 1. Bulging eardrum with a granuloma in the anterior part of the external auditory canal.

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Figure 2. CT scan showing soft tissue involving all the middle ear.

Under suspicion of cholesteatoma of the middle ear, a surgery was planned. Since the middle ear cavities were congested, a retroauricular incision was used to perform the mastoidectomy. All the tympanic cavities were filled with granulomatous tissue which surrounded the ossicles and involved the tympanic membrane created a perforation. The tissue was excised and sent to the pathology department for analysis. Some of the tissue remained around the ossicles, which were both intact and mobile. Myringoplasty using a graft of fascia temporalis was performed.

The pathological analysis found sulfur granules containing actinomyces confirming the diagnosis of actinomycosis of the middle ear (Fig. 3). An antibiotic therapy with amoxicillin was prescribed for 3 weeks and at the end of this period, we noticed a normalization of the eardrum and the hearing. Four months later, the infection reappeared with purulent otorrhea in the right ear and renewed conduction-hearing loss of 30dB. A 2-month course of antibiotherapy with amoxicillin was implemented. The improvement was sensitive but incomplete at the end of the treatment. Deterioration with otorrhea forced the patient to renew his antibiotic therapy with amoxicillin for 3 months and a combination of amoxicillin and pristinamycine for 2 months. A restoration of the eardrum and the hearing was obtained. No relapse has been noticed in 2 years.

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Figure 3. Histology slide showing the branching filamentous aspect of actinomyces.

3. Discussion 

Actinomycosis has been described in 1877 in veterinary pathology by Bollinger [2]. In 1878, Israel described the first human case [2]. He reported the anaerobic nature of these bacteria and identified actinomyces israelli as the germ responsible for most human forms of actinomycosis. In 1906, Beck described, for the first time the otologic signs of the disease [2]. Afterwards, and before the antibiotic age, several actinomycosis cases of the middle ear were published. All of the patients, except one, were dead owing to an intracranial involvement. The diagnosis has to be done during the autopsy [4].

This infection is due to a germ member of the Actinomycetaceae family. This is a filamentous, branching, anaerobic, non-acid-fast, Gram-positive bacillus [2]. These germs have been very often confused with fungi because of their fungus-like morphology [3].

Actinomyces are members of the commensal oral flora of humans and animals. We can find them close to the tonsils, gums, and carious teeth [3]. In a study, Pransky reported the presence of actinomyces in the pathological analysis of 18.3% of surgical pieces from tonsillectomies and adenoidectomies [5].

Spontaneously their pathogenicity is low but some factors such as dental treatments, maxillofacial trauma, poor dental hygiene, foster the development of cervicofacial actinomycosis. Breaching of the mucosal barrier occurring in such circumstances may lead to the spread and development of theses germs [6].

Three routes for contamination of the middle ear are possible [2]:

We have to notice that we cannot find actinomyces in newborns and predentate infants. This could be why we cannot find actinomycosis otomastoiditis in this population [1].

Clinically speaking, actinomycosis is generally described like a chronic otitis. The infection is indolent; the otorrhea is intermittent, resistant to several antibiotic treatments [6]. Other forms have been described (serous otitis and sinusitis) [7]. These aspecific clinical features result in long delays to diagnosis, generally between 5 months depending on the study [7]. Before the antibiotic age, the issue was very often fatal due to the intracranial involvement of actinomycosis (petrous apecitis, subdural abscess, and sinus thrombosis) [6].

Certain diagnosis from otoscopy alone is difficult. Once again, we find very often an eardrum with increased vascularity, red, pink or gray, sometimes bulging or even with a perforation with eventual presence of granuloma or inflammatory polyps [4]. The CT scan is not enough to make the diagnosis showing a thick eardrum and presence of soft tissue in the middle ear [1], [10], [11]. Surgery is often decided from the association of the non-specific clinical and paraclinical pictures, together with the slow evolution and the absence of any improvement after well-managed treatment.

Generally, surgery reveals granulomatous tissue covered with yellow secretions in the whole mastoid and tympanic cavity [1], [10].

The pathological examination of this granulomatous tissue confirms the diagnosis in majority of the cases [10] finding the presence of sulfur granules. These granules comprise a mass of actinomyces included in a complex of polysaccharides, proteins and calcium. They are truly visible in standard coloration and able to be colored by PAS. The granules are surrounded by only slightly vascularised granulomatous inflammatory tissue. This reaction can increase the anaerobic conditions and the development of the germs [3].

The culture of the germ is very difficult because of its sensitivity to oxygen. It is negative in 70% of cases [6]. It needs to be realized at 37°C in anaerobic conditions [4]. For this reason, the bacteriologist must be informed when actinomycosis is suspected.

Because culture is difficult, the diagnosis is based most likely on the histological examination of the granulomatous tissue removed during the surgery. Hoshino et al. reported an actinomycosis diagnosis based on infected mucus taken after a myringotomy. But such instances are exceptions [12].

In case of chronic otorrhea without germ discovered in usual bacteriological cultures conditions, several differential diagnoses can be made:

The treatment of the actinomycosis otomastoidis combines surgery and long-term antibiotic therapy. Since actinomycosis is anaerobic, surgery will aerate all the tympano-mastoid surfaces.

The benefit of surgery needs to be consolidated by the implementation of long-term antibiotherapy in order to ensure permanent sterilization of the inner ear [2]. Penicillin is the first choice antibiotic. Although penicillin is often enough it must be done for a long time (3–6 months) [3], [10]. In case of allergy, other antibiotics such as tetracycline, erythromycine, clindamycine, and chloramphenicol have been used with success [6]. To our knowledge, the combination of pristinamycine and amoxicillin that we used with our patient has never been reported in the literature. It seems to have been effective in our case. This antibiotic was chosen for its spectrum and its ability to penetrate to the middle ear.

In the case of our patient, the first two courses of treatment, 3 weeks and 2 months, were far too short to prevent relapse, which reinforces the idea that long-term therapy is necessary.

4. Conclusion 

Actynomycosis of the middle ear is a rare disease and its diagnosis is difficult. We have to think of it in case of chronic otitis with otorrhea resistant to many successive antibiotic therapies. So, we can involve a right treatment with long-term penicillin therapy combined with middle ear surgery. A normal tympanic membrane and hearing are the evidence of a total recovery but a long follow up is necessary to affirm it.