Nocardia acididurans sp. nov., an acid-tolerant actinobacterium isolated from bio-fertilizer of Musa species

A novel acid-tolerant actinobacterium (strain LPG 2T), which formed fragmented substrate mycelia, was isolated from bio-fertiliser of Musa spp. collected from Lampang Province, Thailand. Its morphological and chemotaxonomic properties, e.g., the presence of mycolic acid and MK-8 (H4ω-cycl) in the cells, showed that strain LPG 2T was a member of the genus Nocardia . 16S rRNA gene sequence analysis revealed that this strain was closely related to Nocardia otitidiscaviarum NBRC 14405T (98.7 %). The low average nucleotide identity–blast and digital DNA–DNA hybridization values (<78.6 and <24.0 %, respectively), and several phenotypic differences between strain LPG 2T and its related Nocardia type strains, indicated that the strain merits classification as representing a novel species of the genus Nocardia , for which we propose the name Nocardia acididurans sp. nov. The type strain is LPG 2T (=TBRC 11242T=NBRC 114293T).

Molecular identification and antibiotic resistance pattern of actinomycetes isolates among immunocompromised patients in Iran, emerging of new infections

Recent advancements in DNA-based approaches have led to the identification of uncommon and rare bacterial pathogens. In this study, by utilizing a DNA-based approach, a total of 1043 clinical specimens were processed for the identification of actinobacteria targeting the 16S rRNA and gyrB genes. Drug susceptibility testing was also conducted using micro-broth dilution and PCR. Two isolates of Nocardia flavorosea and Rhodococcus erythropolis were reported for the first time in Iran. Also, Nocardiopsis dassonvillei, Streptomyces olivaceus, and Streptomyces griseus were reported for the first time in Asia. Infections caused by Nocardia caishijiensis and Prauserella muralis have also been reported in this study. The first Asian case of pulmonary infection caused by Nocardia ignorata and the first global case of brain abscess caused by Nocardia ninae and Nocardia neocaledoniensis have been reported in this study. Overall 30 isolates belonging to 6 genera (Nocardia, Streptomyces, Rodoccoccus, Nocardiopsis, Rothia, and Prauserella) were detected in 30 patients. All 30 isolates were susceptible to amikacin and linezolid. Three isolates including Nocardia otitidiscaviarum (n = 2) and Nocardia flavorosea (n = 1) were resistant to trimethoprim-sulfamethoxazole which were the first trimethoprim-sulfamethoxazole resistant clinical actinomycetes in Iran. Isolation of rare species of actinomycetes particularly Nocardia spp. requires urgent action before they spread clinically particularly among immunocompromised patients.

Fatal pulmonary infection by trimethoprim-sulfamethoxazole resistant Nocardia otitidiscaviarum: report of two cases and review

Introduction: Nocardia otitidiscaviarum is a rare cause of human infections, mostly causing cutaneous and lymphocutaneous infections of mild severity. We report two cases of fatal pulmonary infection caused by Nocardia otitidiscaviarum in elderly patients. Methodology: Case 1: A 70-year old woman presented with fever and cough with expectoration for a month. On physical examination, she had tachypnea and inspiratory crepitations in bilateral basal regions. Case 2: A 74-year old man presented with productive cough with foul smelling expectoration, fever and shortness of breath for one week. On examination, he had tachypnea, bilateral wheezing and inspiratory crepitations. In both cases, sputum was sent to microbiology laboratory. On direct microscopy Gram-positive, finely branching filaments were observed which were acid fast with 1% sulphuric acid. Chalky white opaque wrinkled colonies with musty basement type odour were seen on blood agar. Both patients were treated empirically with trimethoprim-sulfamethoxazole for Nocardia infection after notification of microscopy findings however both expired on Day 2 and Day 5 of admission, respectively. Both isolates were susceptible to amikacin, linezolid, ciprofloxacin and gentamicin. They were resistant to trimethoprim-sulfamethoxazole, ampicillin, amoxicillin-clavulanic acid, erythromycin, and imipenem. Based on biochemical identification and antimicrobial susceptibility pattern, the organism was identified as Nocardia otitidiscaviarum. The identification was confirmed using MALDI-TOF (Vitek MS, Biomerieux, France). Conclusion: Our report highlights the importance of early identification of Nocardia to species level to improve treatment outcomes especially in critically ill patients. Mass spectrometry can become an integral part of diagnostic algorithms for nocardiosis.