Disseminated Infection of Nocardia farcinica in an Immunocompetent Adult: Mistaken for Tuberculosis Bacilli in Acid-Fast Staining of Bronchoalveolar Lavage Fluid

Research on improved YOLOv8s model for detecting mycobacterium tuberculosis

Accurate identification of Mycobacterium tuberculosis (M. tuberculosis) is a critical step in the diagnosis of tuberculosis. Existing object detection methods struggle with the challenges posed by the varied morphology and size of M. tuberculosis in sputum smear images, which makes precise targeting difficult. To solve these problems, an improved YOLOv8s model is proposed. Specifically, an additional detection head is added to focus on small target information. Second, a multi-scale feature fusion module is introduced to adapt the model to different sizes of M. tuberculosis. In addition, a convolutional layer is added to the Coordinate Attention (CA) module to extract more advanced semantic features. Finally, a self-attention mechanism is added after the CA module to enhance the model's ability to accurately understand and localize the varied morphology of M. tuberculosis. Our model performed well with an average precision of 85.7 % when tested on a publicly available dataset. This clearly demonstrates the effectiveness of our proposed model in M. tuberculosis detection.

Nocardia farcinica infection presenting as a solitary bronchial neoplasm in an immunocompetent adult: a case report

Nocardia species are gram-positive, acid-fast, saprophytic, aerobic bacilli, predominantly resulting in opportunistic infections in immunocompromised individuals. Here, we reported a case of Nocardia infection in a 27-year-old woman with normal immunocompetence, who presented as a solitary neoplasm in the left principal bronchus with a chief complaint of postural dyspnea. By electrotomy via bronchoscopy, the neoplasm was successfully removed, and it was further identified as Nocardia farcinica by metagenomic next-generation sequencing.

Cerebral Abscess Infected by Nocardia gipuzkoensis

Purpose

Nocardia gipuzkoensis is a novel species that solely identified in patients with pulmonary infections by far. Growing evidence showed the excellent performance of metagenomics next-generation sequencing (mNGS) on pathogenic identification, especially for new species. Here, we described the first case of an elderly female patient suddenly suffering from neurological disorders owing to N. gipuzkoensis infection. And linezolid could effectively treat N. gipuzkoensis infection.

Patients and Methods

The results of imaging, laboratory cultures, and mNGS, as well as therapeutic process are shared.

Results

An elderly female patient suddenly suffered from neurological disorders with dysphasia and right limb trembles under no obvious causes. Subsequently, she was diagnosed as intracranial space-occupying lesions by magnetic resonance imaging (MRI). The isolate from brain secretion was further identified as N. gipuzkoensis through mNGS. The targeted therapy with linezolid according to the antimicrobial susceptibility was used to treat cerebral abscess induced by N. gipuzkoensis. During the follow-up, no relapse was observed for the patient after surgery for 104 days.

Conclusion

Cerebral abscess induced by N. gipuzkoensis is rare disorder with high mortality. mNGS has been identified as a promising tool in pathogen diagnosis for timely therapy. Linezolid as one of the antimicrobial drugs could effectively treat N. gipuzkoensis infection and prevent adverse outcomes.

Otomastoiditis Caused by Nocardia Farcinica: A Case Report and Literature Review

Nocardia farcinica usually infects people with impaired immune status and usually manifests in the lungs. Otomastoiditis caused by Nocardia infection is extremely rare, with only 4 cases reported to date. This report describes a case of otomastoid N. farcinica infection in an immunocompetent patient. The case was a 10-month-old immunocompetent infant who presented with an approximately 3-month history of right ear discharge for which treatment with various antibiotics had not resulted in significant improvement. Multiple cultures of secretions and pathologic examination failed to identify the causative organism. The patient then underwent right mastoidectomy. Finally, metagenomic next-generation sequencing identified the pathogen to be N. farcinica. The patient was infection-free at the 6-month follow-up but had developed labyrinthitis ossificans. Otomastoid Nocardia infection has characteristic clinical features, namely, formation of a large amount of granulation tissue and coexistence of bone destruction and new bone formation. Traditionally, Nocardia is challenging to diagnose. Metagenomic next-generation sequencing of lesions is helpful. Complete local debridement and free drainage are key to treatment.