Nocardiosis need prolonged treatment for cure and prolonged incubation for its culture growth.
A patient was admitted to the nephrology ward of TUTH with diagnosis of Nephrotic syndrome. He had pulmonary symptoms of fever, cough, chest pain and abscess in right thigh. He was under corticosteroid therapy for Nephrotic syndrome and under antibiotics for his pulmonary symptoms and abscess. He has taken 7 days course of broad-spectrum antibiotcs for two times. However, his symptoms were not improving.
His sputum sample was sent to microbiology laboratory for the evaluation of the cause of infection. Gram stain of sputum revealed branching filamentous gram variable bacilli suggestive of Nocardia species but culture revealed no significant growth on 24 hours of incubation at 37 degree celcius.
His abscess was not resolving despite broad spectrum antibiotics and culture of pus sample showed no growth after 24 hours of incubation at 37 degree celcius. In suspicion of Nocardia causing the abscess, we collected repeat pus sample and performed gram stain and modified Ziehl Neelsen stain. Gram stain revealed branching, filamentous, Gram variable structure. Modified Ziehl-Neelsen stain revealed branching filamentous acid fast structure suggestive of Nocardia species. Culture on Blood agar and MacConkey agar revealed no growth after 24 hours of incubation. However, after 72 hours of continue incubation, whitish dry colonies appeared on blood agar which on further incubation revealed colonies with “molar tooth” appearance. Branching filamentous acid fast structure and whitish molar tooth appearance colonies is a textbook rule for the diagnosis of Nocardia species. Antibiotic susceptibility testing was done and it was sensitive to Cotrimoxazole, Cefexime, Ceftriaxone, Imepenem and Meropenem.
The patient was then kept under cotrimoxazole therpy for a month after which he improved. Patient may be switched to other sensitive antibiotics. Nocardia is a pathogen to be considered in immunocompromised patients and it requires a prolonged course of antibiotics for complete cure. As Nocardia requires more than 48 hours for growth, it may be missed in routine culture which is done only for 24 hours. In suspicion of Nocardiosis, culture plates should be incubated for prolonged period and antibiotic therapy should be continue for one month for complete resolution.
Thanks to Dr. Dibya Singh Shah and Department of Nephrology for their support and guidance. A big thanks to Dr. Shusila khadka, Prof.Bharat Mani Pokharel, Prof. Jeevan Bahadur Sherchand, Prof. Basista Rijal and Hari Prasad Kattel for helping me to establish the diagnosis.