Yanan Li,1 Yahui Feng,2 Dongmei Li,3 Dongmei Shi,2,4 Guanzhi Chen1 

1Department of Dermatology, Affiliated Hospital of Qingdao University, Qingdao, People’s Republic of China; 2The Laboratory of Medical Mycology, Jining No. 1 People’s Hospital, Jining, Shandong, People’s Republic of China; 3Department of Microbiology & Immunology, Georgetown University Medical Center, Washington, DC, USA; 4Department of Dermatology, Jining No.1 People’s Hospital, Jining, Shandong, People’s Republic of China

Correspondence: Guanzhi Chen, Department of Dermatology, Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, 266000, People’s Republic of China, Email chenguanzhiqd@hotmail.com

Objective: The increasing incidence of chronic skin infections caused by Mycobacterium marinum, coupled with the time-consuming and low detection rates nature of traditional culture and histological-based diagnostic methods, underscores the need for an expedited approach. The study aims to develop a rapid and efficient method for detecting M. marinum with PCR technology.
Methods: We designed four pairs of primers based on DNA sequences from GeneBank and prior studies, we utilized both PCR and Real-time PCR to identify M. marinum. Specificity and sensitivity assessments were conducted in vitro by DNAs extracted from M. marinum and other bacterial or fungal cultures. Further validation was performed through the implementation of a mouse skin infection model to optimize and confirm the efficacy of the detection method in both fresh and paraffin-embedded skin tissues. The same PCR testing system was further confirmed with paraffin-embedded skin tissues samples from patients as well.
Results: The results of the study indicate promising outcomes for the four-pair primers system. It demonstrated 100% sensitivity in detecting M. marinum from purified cultures, including typical strains and nine clinical isolates, while achieving a specificity of 100%. This specificity was evidenced by the absence of PCR products from 12 bacterial species, 12 fungi species, and six other non-tuberculous mycobacterium (NTM) species. In the animal model, the PCR assay exhibited high detection efficacy for both infected fresh tissues and paraffin-embedded tissues, with a slight superiority observed in fresh tissues. However, the PCR assay exhibited high detection efficacy for clinical paraffin-embedded tissues. These findings collectively underscore the robust detection capabilities of our four-pair primers in both in vitro and in vivo settings.
Conclusion: A sensitive and highly specific rapid detection system has been successfully developed that can be used to detect M. marinum in both infected fresh tissues and paraffin-embedded tissues.

Keywords: Mycobacterium marinum, bacteria, infected tissue, paraffin-embedded tissue, PCR technique