[Emergence of a multidrug-resistant tuberculosis through inadequate treatment of isoniazid monoresistance].

History:  We admitted a 65-year-old patient with suspected reactivation of a pulmonary tuberculosis for further diagnosis.

Findings and diagnosis:  14 months after completing a standard treatment course against pulmonary tuberculosis, the patient presented with cough and night sweat. A CT-scan revealed signs of a bipulmonary progress. Microbiological results proved multi-drug resistant tuberculosis (resistances against isoniazid and rifampicin). Reviewing the patient's old records uncovered a previous isoniazid-resistance at the start of the first treatment course, which had not been appropriately addressed.

Therapy and course:  The patient was started on oral therapy with Bedaquiline, Linezolid, Terizidon and Levofloxacin.

Conclusion:  Treating tuberculosis, considering drug resistances is crucial. To avoid ineffective therapy, molecular diagnostic methods are recommended, however, cultural testing remains essential. Diagnostic latency, rising rates of drug resistances and lengthy treatment courses contribute to the complexity of treatment. In Germany, specialized outpatient clinics are available since 2014 for diagnosis and treatment of patients with tuberculosis or non-tuberculous mycobacterial diseases, even in the event of mere suspicion.