Mycobacterium marinum: A brief update for clinical purposes

Activation of host nucleic acid sensors by Mycobacterium: good for us or good for them?

Although the importance of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) sensors in controlling viral infection is well established, their role in promoting an effective immune response to pathogens other than viruses is less clear. This is particularly true for infections with mycobacteria, as studies point to both protective and detrimental roles for activation of nucleic acid sensors in controlling a mycobacterial infection. Some of the contradiction likely stems from the use of different model systems and different mycobacterial species/strains as well as from which nucleic acid sensors were studied and what downstream effectors were evaluated. In this review, we will describe the different nucleic acid sensors that have been studied in the context of mycobacterial infections, and how the different studies compare. We conclude with a section on how nucleic acid sensor agonists have been used therapeutically and what further information is needed to enhance their potential as therapeutic agents.

Characterization of microbial contamination in agricultural soil: A public health perspective

Soil is widely recognized as a reservoir of microbial contaminants including antibiotic resistance genes (ARGs) and human bacterial pathogens (HBPs), which are major public health concerns. Although the risks associated with soil safety in different soil habitats have been studied, the results are not comprehensive. In this study, dryland soils used for vegetable, corn, and soybean planting, and submerged soils used for rice planting and crab farming were collected and subjected to metagenomic sequencing to characterize HBPs, ARGs, and virulence factor genes (VFGs). The results showed that submerged soils had a higher abundance of HBP than dryland soils. In addition, the submerged soil microbiome acquired significantly higher levels of high-risk ARGs than the dryland soil microbiome and these ARGs were mainly assigned to bacA, sul1, and aadA genes submerged. Network analysis revealed that 11 HBPs, including Yersinia enterocolitica, Vibrio cholerae, Escherichia coli, and Leptospira interrogans, were high-risk because of their close association with ARGs, VFGs, and mobile genetic elements (MGEs). Procrustes and network analyses showed that HBPs and ARGs were more closely linked in submerged soil. This study confirms that submerged field has higher ecological environment risk and human health risk than dryland soil.

Environmental Sources and Transmission of Nontuberculous Mycobacteria

The field of environmental nontuberculous mycobacteria (NTM) is benefiting from a new era of genomics that has catapulted our understanding of preferred niches, transmission, and outbreak investigations. The ability to forecast environmental features that promote or reduce environmental NTM prevalence will greatly improve with coordinated environmental sampling and by elevating the necessity for uniform disease notifications. Studies that synergize environmental biology, isolate notifications, and comparative genomics in prospective, longitudinal studies, particularly during climate changes and weather events, will be useful to solve longstanding NTM public health quandaries.

Mycobacterium marinum: A Case-Based Narrative Review of Diagnosis and Management

Skin and soft tissue infections caused by non-tuberculous mycobacteria are occurring more frequently in recent years. However, chronic skin and soft tissue lesions present a challenge for clinicians, as the diagnostic work-up and definitive diagnosis require knowledge and available laboratory resources. We present here the case of a 66-year-old male patient who presented with painful abscess-like nodules on his right hand and forearm, which worsened after treatment with an anti-TNF-a agent. The fluid specimen taken from the lesion was positive for mycobacteria according to the acid-fast stain. Mycobacterium marinum was identified, first by next-generation sequencing and finally grown on culture, after eight weeks. Acknowledging the complexity of diagnosing and managing infections by non-tuberculous mycobacteria, and especially Mycobacterium marinum, we provide a review of the current epidemiology, clinical characteristics, diagnosis and management of Mycobacterium marinum infection.

Molecular epidemiology of nontuberculous mycobacteria isolated from tuberculosis-suspected patients

It is a growing problem around the world to deal with nontuberculous mycobacteria infection (NTM), but its clinical significance is still largely unknown. This study aims to investigate the epidemiology of NTM infections from various clinical samples and determine their clinical significance. From December 2020 to December 2021, 6125 clinical samples were collected. In addition to phenotypic detection, genotypic detection through multilocus sequence typing (hsp65, rpoB, and 16S rDNA genes) and sequencing was also conducted. Records of patients were consulted for clinical information, such as symptoms and radiological findings. Of the 6,125 patients, 351 (5.7%) were positive for acid-fast bacteria (AFB). Out of 351 AFB, 289 (82.3%) and 62 (17.7%) subjects were identified as M. tuberculosis complex (MTC) and NTM strains, respectively. Isolates of Mycobacterium simiae and M. fortuitum were the most frequent, followed by isolates of M. kansasii and M. marinum. We also isolated M. chelonae, M. canariasense, and M. jacuzzii, which are rarely reported. Symptoms (P = 0.048), radiographic findings (P = 0.013), and gender (P = 0.039) were associated with NTM isolates. M. Fortuitum, M. simiae, and M. kansasii presented with bronchiectasis, infiltration, and cavitary lesions most frequently, while cough was the most common symptom. In conclusion, Mycobacterium simiae and M. fortuitum were presented in seventeen and twelve NTM isolates from the collected samples. There is evidence that NTM infections in endemic settings may contribute to the dissemination of various diseases and the control of tuberculosis. In spite of this, further research is needed to evaluate the clinical significance of NTM isolates.

Comparative Evaluation of LAMP and Nested PCR for the Rapid Diagnosis of Mycobacterium marinum Infection

Purpose

Culture of Mycobacterium marinum is very time-consuming, taking several weeks to produce positive results. Seeking rapid and sensitive diagnostic methods for diagnosis can greatly improve patient treatment. Our study aimed to compare the rapid diagnostic abilities of polymerase chain reaction (PCR), nested PCR and loop mediated isothermal amplification (LAMP) of detecting M. marinum in skin samples from patients with M. marinum infection.

Methods

A total of 6 M. marinum strains and 6 skin samples with definite diagnosis of M. marinum infection were included in the study. We optimized LAMP performance for detection of M. marinum genomic DNA and confirmed the specificity of the primers. Then, the sensitivity of the LAMP and nested PCR assays were assessed by M. marinum strains and clinical samples.

Results

Nested PCR was 10-fold more sensitive than the LAMP assay by serial dilution of M. marinum DNA. PCR positive samples were all positive by LAMP detection of 6 clinical M. marinum strains. Out of 6 clinical skin specimens confirmed as M. marinum infection, 0 (0%), 3 (50%), 3 (50%), and 4 (66.6%) were positive by PCR, nested PCR, LAMP and culture. The LAMP shared the same sensitivity than nested PCR in M. marinum strains and clinical samples, but it was easy to perform and faster than nested PCR assay.

Conclusion

Compared with conventional PCR, LAMP and nested PCR are more sensitive and have a higher detection rate of M. marinum in clinical skin specimens. The LAMP assay proved to be more suitable for rapid diagnosis of M. marinum infection in a shorter time, especially in resource-limited settings.