First Human Isolate of Mycobacterium poriferae in the Sputum of a Patient with Chronic Bronchitis

LETTER

Mycobacterium poriferae was described in 1987 by Padgitt and Moshier (6), who reported its isolation from cell suspensions of the marine sponge Halichondria bowerbanski. The microorganism consists of rapidly growing, strongly acid-fast, Gram-positive rods. Optimal growth occurs between 28 and 30°C, and it is an orange scotochromogen (3, 6). There had not been further identification in other organisms until 1996, when Tortoli et al. (8) identified it in granulomatous lesions in the viscera of a cultured freshwater fish (Channa striatus). These types of lesions are not unusual in fish and are a typical feature of tuberculosis. The present letter reports, to the best of our knowledge and for the first time, the isolation of M. poriferae from a human.

In April 2010, a 53-year-old woman was admitted to the Emergency Unit of the Hospital Universitari Sant Joan de Reus (Catalunya, Spain) with hemoptysis. She reported having had a cough with purulent sputum for 7 days. Also, bloody sputum was observed on occasion during this period. The patient had an 8-year history of chronic bronchitis with sporadic hemoptoic sputum and was an active smoker. She had no fever. On physical examination, she was eupneic but had pulmonary rhonchi. Standard biochemical and hematological tests were normal. Legionella pneumophila and Streptococcus pneumoniae antigenuria tests were negative. Chest X-ray showed chronic fibrosis in the upper right lobe. Ziehl-Neelsen staining of sputum was negative. A culture was negative for bacterial respiratory pathogens. A diagnosis of acute bronchitis was made, and the patient was treated with amoxicillin-clavulanate. She was referred to her general practitioner for monitoring and improved. A second sputum sample was not obtained because the hemoptysis disappeared. Concurrently, the sputum sample was cultured in the microbiology laboratory and 10 days later, orange colony growth was observed on Lowenstein-Jensen medium with and without pyruvate. The colonies were 1 mm in diameter and composed of acid-fast and Gram-positive rods which were identified using 16S rRNA gene sequencing (1) and phenotypic methods in a reference laboratory (Hospital Universitari de Bellvitge) as M. poriferae (GenBank accession number NR_025235.1). In vitro activities of several antimicrobial agents against these colonies of M. poriferae were tested by standard methods (5), and the results are shown in Table 1.

Table 1.

In vitro activities of several antimicrobial agents against M. poriferae isolate

Antimicrobial agent(s)	MIC(s)a (μg/ml)
Amikacin	≤1
Amoxicillin-clavulanate	≤2, 1
Cefoxitin	≤4
Ciprofloxacin	≤0.12
Clarithromycin	≤0.06
Doxycycline	≤0.12
Imipenem	≤2
Linezolid	≤1
Minocycline	≤1
Moxifloxacin	≤0.25
Tigecycline	0.12
Tobramycin	2
Trimethoprim-sulfamethoxazole	≤0.25, 4.75

^aTested with Sensititre RAPMYCO plates (Trek Diagnostic Systems Inc., Cleveland, OH).

The source of this M. poriferae infection could not be ascertained from the patient or from the data available in her medical history. However, her work involved the human and animal food-processing industry. Contamination of foods by other Mycobacterium species has been widely reported in industries related to fish handling (2, 4, 7). A direct causal relationship between the presence of this bacterium and the patient's symptoms cannot be assumed.