Clinical findings and treatment of disseminated ‘Mycobacterium avium subspecies hominissuis’ infection in a domestic cat

KANEGI, Ryoji; YASUGI, Mayo; NABETANI, Tomoyo; TANAKA, Toshiyuki; WADA, Yusuke; HIRAI, Kotaro; SUGIURA, Kikuya; HATOYA, Shingo

During combined administration of antibiotics, this case presented atonic seizures. As the possible causes of seizures, we considered MAH infiltration into central nervous systems, side effects of isoniazid, or other intracranial diseases. Chest X-ray and ultrasound imaging revealed the improvement of lung disease and jejunum lymph node swelling, which indicated the therapeutic response of MAH infection. Therefore, a side effect of isoniazid, whose recommended dosage range was 10 − 20 mg/kg every 24 hr [8] , was suspected as the cause of seizures. In human medicine, isoniazid administration for patients with concurrent diseases, such as chronic kidney disease and diabetes, sometimes causes atonic seizures, and these side effects can be prevented and treated Fig. 4 . hsp65 gene sequences from 12 nontuberculous Mycobacterium (NTM) species retrieved from GenBank belonging to codes 1 to 9, and 15 to 17 (accession numbers DQ284765−DQ284773, EU085419, AB453830, and AB453831, respectively), and from the present clinical isolate (strain MY332) were aligned using Mega7 [17] . Phylogenetic tree was constructed using the neighbor-joining method. with pyridoxal phosphate [7] . In the present case, there were no clinical findings to indicate concurrent diseases. However, we should consider the possibility that the multiple nodules in the liver potentially affected the metabolism of isoniazid even though isoniazid was administered at the minimum recommended dosage. Three cats were previously reported with MAH infection. Two were diagnosed at necropsy [3, 20] . One, which presented with chronic vomiting, diarrhea, weight loss, anorexia and an abdominal mass, was treated with combined antibiotics, including azithromycin, rifampicin and enrofloxacin [15] . However, after a short period of improvement of clinical symptoms, the cat was euthanized because of severe protein-losing enteropathy. Although treatment and prognosis of M. avium infection in domestic cats in Australia has been reported, Mycobacterium subspecies were not identified in these cases [2] . This is therefore the first case of MAH infection to be confirmed by gene analysis and to show recovery with combination antibiotic treatment. The poor prognosis in previous cases could be attributed to difficulties in the antemortem diagnosis and delayed start time for treatment of MAH infection after clinical symptoms were observed. This case demonstrates that combined antibiotic administration based on reports from human medicine is effective for MAH infection in cats, and early examinations, diagnosis and treatment will lead to a good result. Susceptibility testing revealed that the MAH isolate was resistant to most antitubercular drugs. However, we administered combined antibiotics including isoniazid and rifampicin, which the MAH isolate was resistant to, and clinical symptoms improved. Previous studies revealed that in vitro susceptibility testing for Mycobacterium species was of little or no value for predicting clinical efficacy [4, 11] . The present study indicated that it is difficult to predict therapeutic effects of antitubercular drugs for MAH depending on in vitro susceptibility testing in domestic cats.