|Year : 2011 | Volume
| Issue : 2 | Page : 86-88
Otomastoiditis by Mycobacterium fortuitum: A rare case
Archana Wankhade, Dnyaneshwari Ghadage, Rupali Mali, Arvind Bhore
Department of Microbiology, Smt. Kashibai Navale Medical College and Hospital, Pune, Maharashtra, India
|Date of Web Publication||20-Dec-2011|
Department of Microbiology, Smt. Kashibai Navale Medical College and Hospital, Pune, Maharashtra
Source of Support: None, Conflict of Interest: None
We report a case of a 26-year-old female patient diagnosed with chronic otomastoiditis caused due to Mycobacterium fortuitum. Definitive identification of pathogen was done on the basis of growth characteristics and biochemical reaction. M. fortuitum was isolated from the lesion. M. fortuitum is a rarely reported cause of otitis media and mastoiditis. The isolate showed resistance to antitubercular drugs and sensitivity to amikacin, ciprofloxacin and imipenem.
Keywords: Mycobacterium fortuitum, Nontuberculous mycobacteria, Otomastoiditis
|How to cite this article:|
Wankhade A, Ghadage D, Mali R, Bhore A. Otomastoiditis by Mycobacterium fortuitum: A rare case. Indian J Otol 2011;17:86-8
| Introduction|| |
Infection of middle ear is a common problem. The usual pathogens causing middle ear infection are the bacteria. It is not well appreciated, however, that Mycobacterium is occasionally associated with middle ear infection. Cases of otitis media and mastoiditis due to nontuberculous mycobacteria (NTM) are very rare. NTM which include Mycobacterium fortuitum, Mycobacterium chelonae, Mycobacterium abcessus are rapidly growing mycobacteria and widely distributed in nature.  Identification and isolation of NTM is helpful for the management of patients as the treatment for M. tuberculosis and NTM varies.  A case of otomastoiditis due to M. fortuitum is reported in this study. M. fortuitum causes variety of cutaneous diseases, but rarely disseminated infection.
| Case Report|| |
A 26-year-old female presented with pain and discharge from the right ear since 3 months. The patient had symptoms of giddiness and severe headache. She had fever for 2 months, associated with giddiness, loss of appetite and loss of weight. On examination, the patient was febrile, without any significant local or regional lymphadenopathy. Clinically, it was diagnosed as chronic suppurative otitis media. X-ray examination showed the inflammatory signs in mastoid area. Chest X-ray was normal. Results of laboratory investigations were all normal including WBC count and erythrocyte sedimentation rate. Serostatus of the patient was normal.
Debridement of mastoid was done. Pus was aspirated from the mastoid under all aseptic precautions and was sent for culture and Ziehl-Neelsen (Z-N) staining in microbiology laboratory. Pus was yellowish in color and thick in consistency. Gram stain examination revealed plenty of pus cells with no organism. Z-N stain revealed acid-fast bacilli [Figure 1]. No growth was observed in routine culture for aerobic and anaerobic organisms. Sample was inoculated in duplicate on Lowenstein-Jenson's slopes (LJ slopes). LJ showed growth which was observed within 5 days [Figure 2]. Colonies were smooth white, creamy and easily emulsifable with no pigmentation. Z-N stain of the colony showed acid-fast bacilli. Gram stain of the colony showed no organism. The organism was presumptively identified as rapid grower, NTM. Further identification of the isolate was done on the basis of rate of growth, and colony morphology and biochemical test.
Subculture of the colony on LJ medium was done and incubated at 25°C and 45°C. Photochromic and scotochromic character was also observed by incubation in light and dark, respectively. There was growth at 25°C and 45°C. Pink-colored colonies were seen on subculture in MacConkey medium after 3 days of incubation at 37°C. Semi-quantitative catalase test was strongly positive; heat-stable catalase test and nitrate reductase test were also positive. In addition, iron uptake test, urease test and 5% salt tolerance test were positive, and niacin test was negative. These results confirmed the identification of organism to be M. fortuitum. Sensitivity was tested on Muller Hinton agar by Kirby Bauer disc diffusion method.  It was sensitive to ciprofloxacin (5 μg), amikacin (30 μg) and imipenem (10 μg), and was resistant to tetracycline (30 μg), linezolid (30 μg), and cefoxitin (30 μg), chloramphenicol (10 μg) and erythromycin (15 μg).
Consecutive samples taken at an interval of 1 week showed growth of M. fortuitum in culture. Repeated isolation confirmed the diagnosis of M. fortuitum. The patient was treated with amikacin and cefoxitin. No duration of therapy or outcome was reported.
| Discussion|| |
In a developing country, the incidence of infection due to NTM is still increasing, while in developing countries like India tuberculosis is still a major health problem.  Mycobacterium tuberculosis, Mycobacterium bovis and Mycobacterium leprae are the established pathogens.  Predominating human mycobacterial infections, NTM are increasingly being reported as etiological agents for human infections but rarely as the cause of otomasoiditis. 
Acute otomastoiditis is an inflammation process in the mastoid region, frequently complicated by acute or subacute otitis media. Cervical lymph node is the frequently invaded site of otolaryngological field by NTM, while middle ear space is rarely involved. 
Otomastoiditis due to NTM has been reported from patients of all age groups.  Conventional methods have been used for identification of the pathogen. Z-N stain cannot differentiate between M. tuberculosis and NTM. Culture is necessary for identification of NTM. Even if automated systems and molecular methods are available for the identification of NTM, in resource-limited centers, phenotypic methods are helpful for their identification and speciation.
Pseudomonas aeruginosa, Streptococcus pneumoniae, Streptococcus pyogenes and methicillin-resistant Staphylococcus aureus have been proved as the common pathogens causing otomasoiditis.  In our study, M. fortuitum was isolated from the specimen. Distribution of NTM and incidence of disease caused by them is not fully understood. M. fortuitum has been commonly reported to cause skin and soft tissue infections and wound infections and injection abscess. , Otomastoiditis due to M. tuberculosis has been reported. 
Even as the presence of acid-fast bacilli was reported on smear examination, a high degree of suspicion is needed to specifically identify whether the pathogen is M tuberculosis or NTM. NTM are resistant to antitubercular drugs like para-aminosalicylic acid, streptomycin and isoniazid. They are susceptible to amikacin, cefotaxin and often to tetracycline, but prolonged treatment for 5-6 months is essential to eradicate the infectious foci. The isolated M. fortuitum was resistant to tetracycline, linezolid, and cefoxitin, chloramphenicol and erythromycin, and was sensitive to ciprofloxacin, amikacin, and imipenem.
Our aim is to focus the attention of ENT specialists toward this pathological agent causing otomasoiditis. Efforts should be made to isolate and speciate NTM, as treatment is not same for all mycobacterial species. This case report illustrates the importance of microbiologic examination and culture.
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[Figure 1], [Figure 2]