Journal of Medical Microbiology (2013), 62, 1245–1248
Case Report
DOI 10.1099/jmm.0.051698-0
Identification of Actinomyces meyeri actinomycosis
in middle ear and mastoid by 16S rRNA analysis
Risako Kakuta,1 Hiroshi Hidaka,1 Hisakazu Yano,2 Hiromitsu Miyazaki,1
Hiroshi Suzaki,3 Yasuhiro Nakamura,4 Hajime Kanamori,2 Shiro Endo,2
Yoichi Hirakata,2 Mitsuo Kaku2 and Toshimitsu Kobayashi1
1
Correspondence
Department of Otolaryngology, Head and Neck Surgery, Tohoku University School of Medicine,
Sendai, Japan
Hisakazu Yano
[email protected]
2
Department of Infection Control and Laboratory Diagnostics, Tohoku University Graduate School
of Medicine, Sendai, Japan
3
Suzaki ENT Clinic, Hachinohe, Japan
4
Department of Pathology, Tohoku University Graduate School of Medicine, Sendai, Japan
Received 30 August 2012
Accepted 1 May 2013
Actinomycosis of the middle ear and mastoid is extremely rare. Here, we report a unique case of
actinomycosis of the middle ear and mastoid caused by Actinomyces meyeri diagnosed by 16S
rRNA gene sequence analysis.
Actinomycosis is a rare, chronic and slowly progressive
granulomatous disease caused by filamentous, Grampositive, anaerobic, non-acid-fast bacteria of the Actinomycetaceae family (genus Actinomyces) (Wong et al., 2011).
Pathogenic Actinomyces species do not exist freely in nature,
but are commensals that inhabitant the oropharynx,
gastrointestinal tract and female genital tract of healthy
humans (Mehta et al., 2007). The most common site of
Actinomyces infection is the cervicofacial region (about
60 %) (Oostman & Smego, 2005), whereas actinomycosis of
the middle ear and mastoid is a rare entity. Difficulty in
diagnosing actinomycosis by bacterial cultures of clinical
specimens has been attributed to the fact that most species
are hard to grow on agar plates (Tarabichi & Schloss, 1993;
Olson et al., 1989). To date, almost all reported cases of
actinomycosis of the middle ear and mastoid have been
diagnosed by examination of histopathological features
(Budenz et al., 2010; Mehta et al., 2007; Shishegar et al.,
2009; Sivarajasingam & Rajan, 2007; Sobol et al., 2004;
Subha et al., 2004).
Bacterial identification using 16S ribosomal RNA (16S
rRNA) sequencing is particularly important when dealing
with unusual phenotypic profiles, rare, slow-growing or
uncultivable bacteria, and in patients with culture-negative
infections. Not only has use of this method provided insight
into aetiologies of various infectious diseases, but it
facilitates choice of appropriate antibiotics and infection
control procedures, as well as determination of treatment
duration (Woo et al., 2008). This report describes a unique
case of middle ear actinomycosis caused by Actinomyces
meyeri diagnosed using bacterial 16S rRNA gene sequence
analysis. To the best of our knowledge, this is the first report
of actinomycosis of the middle ear and mastoid caused by
A. meyeri.
051698 G 2013 SGM
Case report
A 55-year-old male presented to another institution’s ENT
(ear, nose and throat) clinic in January 2011 with chief
complaints of left otorrhoea and otalgia. The patient was
receiving medical treatment for diabetes. There had been
dental therapy a few years before and persistent otitis
media since childhood. On physical examination, the right
ear had no abnormalities, but in the left ear, a polypoid
mass that completely occluded the external auditory canal
was found. Histopathological examination of the polypoid
mass revealed inflammatory granulation. Bacterial cultures
of middle ear secretions were negative. Pure tone audiometry demonstrated conductive hearing loss on the left
side and a normal-hearing right ear. The patient’s
symptoms failed to respond to non-invasive treatment,
and a postauricular abscess developed. Pathological
analysis of a biopsy specimen from the abscess raised the
suspicion of actinomycosis; therefore, in July 2011, he was
referred to the ENT department of Tohoku University
Hospital.
Physical examination at this institution revealed purulent
discharge from the left ear, bulging of the posterior wall of
the posterior left external auditory canal, and a thickened
left tympanic membrane containing a large perforation.
Inflammatory granulation tissue extending from the
middle ear cavity was seen. There was no nystagmus,
fistula symptom or facial palsy. Bacterial cultures of middle
ear secretions were negative. Immediate surgery was
initially refused, and it was decided that intravenous
ampicillin 2000 mg daily would be administered. However,
dizziness and left hearing loss occurred in August, and
the patient was admitted in September 2011 to undergo
surgery. Pure tone audiometry demonstrated profound
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R. Kakuta and others
deafness on the left side. Computed tomography (CT) of the
temporal bone revealed complete opacification of the left
middle ear and mastoid. The incus seemed to have
disappeared and a bony defect of the left lateral semicircular
canal was suspected.
(Applied Biosystems) and the ABI3730xl Analyser (Applied
Biosystems). BLAST was used for sequence analysis (http://
blast.ncbi.nlm.nih.gov/Blast.cgi).
DNA sequencing revealed the presence of Fusobacterium
spp., detected by the universal primers. The amplicons
detected by the Actinomyces-specific primers from all four
samples were 100 % identical with those of A. meyeri.
The patient underwent left intact canal wall tympanomastoidectomy, which revealed that the tympanum and
mastoid were occupied by granulation tissue. The incus
had disappeared and a fistula was found at the lateral
semicircular canal. Although there was no lymphorrhoea,
the interior of the semicircular canal was also invaded by
granulation tissue. Presumably, inflammation could have
spread to the inner ear from this fistula. Histopathological
examination of the surgical specimen revealed Grampositive, non-acid-fast bacterial colonies surrounded by
inflammatory cells, consistent with a diagnosis of actinomycosis (Fig. 1).
Discussion
Pus from the external auditory canal, middle ear cavity and
mastoid, as well as granulation tissue from the mastoid were
obtained intraoperatively; DNA from these samples was
extracted using the QIAamp DNA Mini kit (Qiagen).
PCR amplifications were performed using universal
(Baker et al., 2003; Johansson et al., 2004) and Actinomycesspecific primers (Xia & Baumgartner, 2003) of 16S rRNA.
PCR amplicons were purified with a QIA quick PCR
Purification kit (Qiagen), followed by DNA sequencing using
the ABI BigDye Terminator v3.1 Cycle Sequencing kit
Actinomycosis usually occurs in immunocompetent persons, but may also afflict persons with diminished host
defences. Actinomyces species are generally of low pathogenicity, and usually cause disease only in the setting of
antecedent tissue injury (Oostman & Smego, 2005). In the
current case, dental therapy might have triggered the
development of actinomycosis. The route of spread was
believed to be from the oropharynx via the Eustachian tube
to the middle ear and mastoid (Mehta et al., 2007). Of 30
known Actinomyces species, A. israelii and A. gerencseriae
The patient was treated with intravenous ampicillin
3000 mg daily for 7 days, followed by oral amoxicillin
1500 mg daily for 5 weeks. At the 18 month follow-up
examination, the left ear was dry and the patient was
asymptomatic, except for having permanent hearing loss in
that ear.
50 mm
Fig. 1. Histopathological findings. Actinomyces colony surrounded by inflammatory cells (arrows). Bar, 50 mm (haematoxylin–
eosin stain).
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Journal of Medical Microbiology 62
Actinomycosis in middle ear
have been found in almost 70 % of orocervicofacial
actinomycosis (Wong et al., 2011). The diagnosis of
actinomycosis is most accurately made by isolation of
Actinomyces species in cultures of clinical specimens or in
histopathological tissue sections.
For cervicofacial infection, parenteral administration of
penicillin G may be followed by oral penicillin V. Adequate
drainage is indicated if abscesses are present. The prognosis
for cervicofacial actinomycosis is generally good; full
recovery occurs in more than 90 % of patients managed
by antimicrobial treatment alone (Oostman & Smego,
2005). In the current case, prior to surgery, hearing loss
had progressed severely and dizziness had developed,
presumably secondary to the lateral semicircular canal
fistula. Symptoms progressed in spite of antibiotic therapy,
so earlier surgical treatment might have resulted in a better
hearing outcome.
To the best of our knowledge, only 17 cases of middle ear
actinomycosis have previously been reported in the English
literature during the modern antibiotic era (Ajal et al.,
1997; Böör et al., 1998; Budenz et al., 2010; Fletcher, 1956;
Hoshino et al., 1996; Leek, 1974; Lester & Juhasz, 1990;
Mehta et al., 2007; Miglets & Branson, 1983; Olson et al.,
1989; Shelton & Brackmann, 1988; Shishegar et al., 2009;
Sivarajasingam & Rajan, 2007; Sobol et al., 2004; Subha et
al., 2004; Tarabichi & Schloss, 1993). The diagnosis of
middle ear actinomycosis in all previously reported cases
was confirmed by histopathological features. In the current
case, actinomycosis was first suspected after pathological
analysis of a biopsy specimen obtained 5 months after
initial presentation to the first clinic. Among the 17
previously reported cases, only two (Hoshino et al., 1996;
Lester & Juhasz, 1990) were diagnosed as actinomycosis by
biopsy examination, which preceded surgical extraction.
While one case (Lester & Juhasz, 1990) suffered from
purulent discharge and mastoid opacification like the
others, the infection resolved without surgery. It is possible
that early diagnosis may facilitate successful non-surgical
treatment of actinomycosis.
Cultures are negative in up to 70 % of actinomycosis
infections (Mehta et al., 2007); only 10 % are correctly
diagnosed at initial presentation (Oostman & Smego,
2005). Therefore, 16S rRNA gene sequence analysis for
genetic identification of bacterial pathogens is a useful
diagnostic tool, as illustrated in the current report. In this
study, we used two pairs of universal primers, one
universal for bacteria (Baker et al., 2003; Johansson et al.,
2004) and the other specific for Actinomyces (Xia &
Baumgartner, 2003). The former detected Fusobacterium
and the latter A. meyeri. The current patient’s course
suggests that chronic A. meyeri infection was followed by
secondary infection with Fusobacterium in the anaerobic
environment of the middle ear cavity, where an acute
inflammatory reaction subsequently developed. A. meyeri is
rarely isolated in patients with actinomycosis. Previously
http://jmm.sgmjournals.org
reported sites of infection, in order of frequency, include
lung, skin, long bones, liver, brain and muscle (Apothéloz
& Regamey, 1996). To the best of our knowledge, this is the
first report of a case of middle ear actinomycosis caused by
A. meyeri being diagnosed using 16S rRNA gene sequence
analysis. It is hoped that widespread use of this diagnostic
tool for patients with culture-negative infections might
lead to earlier diagnosis and more success with nonsurgical treatment regimens.
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