Identification of a novel drug-resistant community-acquired Nocardia spp. in a patient with bronchiectasis

Clinical screening of Nocardia in sputum smears based on neural networks

Objective

Nocardia is clinically rare but highly pathogenic in clinical practice. Due to the lack of Nocardia screening methods, Nocardia is often missed in diagnosis, leading to worsening the condition. Therefore, this paper proposes a Nocardia screening method based on neural networks, aiming at quick Nocardia detection in sputum specimens with low costs and thereby reducing the missed diagnosis rate.

Methods

Firstly, sputum specimens were collected from patients who were infected with Nocardia, and a part of the specimens were mixed with new sputum specimens from patients without Nocardia infection to enhance the data diversity. Secondly, the specimens were converted into smears with Gram staining. Images were captured under a microscope and subsequently annotated by experts, creating two datasets. Thirdly, each dataset was divided into three subsets: the training set, the validation set and the test set. The training and validation sets were used for training networks, while the test set was used for evaluating the effeteness of the trained networks. Finally, a neural network model was trained on this dataset, with an image of Gram-stained sputum smear as input, this model determines the presence and locations of Nocardia instances within the image.

Results

After training, the detection network was evaluated on two datasets, resulting in classification accuracies of 97.3% and 98.3%, respectively. This network can identify Nocardia instances in about 24 milliseconds per image on a personal computer. The detection metrics of mAP50 on both datasets were 0.780 and 0.841, respectively.

Conclusion

The Nocardia screening method can accurately and efficiently determine whether Nocardia exists in the images of Gram-stained sputum smears. Additionally, it can precisely locate the Nocardia instances, assisting doctors in confirming the presence of Nocardia.

Rapid diagnosis of fatal Nocardia kroppenstedtii bacteremic pneumonia and empyema thoracis by next-generation sequencing: a case report

Nocardia species do not replicate as rapidly as other pyogenic bacteria and nocardial infections can be highly fatal, particularly in immunocompromised patients. Here, we present the first report of fatal Nocardia kroppenstedtii bacteremic pneumonia and empyema thoracis diagnosed by next-generation sequencing (NGS) using the Oxford Nanopore Technologies' MinION device. The bacterium was not identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Due to its low equipment cost, short turn-around-time, and portable size, the Oxford Nanopore Technologies' MinION device is a useful platform for NGS in routine clinical microbiology laboratories.

Case report: Nocardia gipuzkoensis infection in an immunocompetent patient diagnosed by metagenomic next-generation sequencing and whole genome sequencing

The infection of Nocardia gipuzkoensis is a relatively uncommon form of pulmonary nocardiosis seen in clinical patients. In general, nocardiosis tends to occur in patients with immune deficiency. Here, we report a 23-year-old female who was admitted to the hospital due to cough and sputum production over 10 years, diagnosed with bronchiectasis. The N. gipuzkoensis infection was identified by metagenomic next-generation sequencing and whole genome sequencing. Imipenem/cilastatin and compound sulfamethoxazole tablets were used to control the infection and the pulmonary inflammation subsided gradually.