Mycobacterium senegalense is a non-tuberculous mycobacterium (NTM) that was first reported to cause bovine farcy in sub-Saharan Africa, exhibiting chronic granulomatous inflammation of skin lymphatics and draining lymph nodes of zebu cattle (1). However, human infections with M. senegalense are rare, and its zoonotic potential is unknown.

NTM is a complex pathogen that is usually a commensal or saprophytic organism. It is extensively found in the environment such as in soil and water sources, leading to high human–pathogen exposure (2), although only a few species infect humans. NTM is an opportunistic pathogen that usually infects immunocompromised patients with intractable conditions such as those with underlying lung diseases, human immunodeficiency virus infections, and cancers, as well as those receiving chemotherapy (3). NTM can be divided into two groups based on how long they take to grow in a culture: rapid-growing and slow-growing species. The most common pathogen among the slow-growing NTM species is M. avium-intracellulare, which primarily causes pulmonary infection (4). M. fortuitum is the most common pathogen among the rapid-growing NTM species, which usually causes colonized or transient infections in the respiratory tract, in addition to disseminated disease, lymphadenitis, and skin and soft tissue infections (5, 6). Although M. senegalense belongs to the same group as M. fortuitum, it rarely infects humans.

So far, only seven cases of humans being infected by M. senegalense have been described; however, none of them appear to have occurred in China. In this study, we report the first case of M. senegalense infection after laparoscopic cholecystectomy in China. mNGS test identified that the patient was infected with M. senegalense, even though routine diagnostic tests were negative. The patient's condition improved, and the wound healed after quadruple therapy with clarithromycin, moxifloxacin, rifampicin, and doxycycline.

We present a unique case of a patient with chronic incision site infections who underwent laparoscopic cholecystectomy and re-surgery, after which he was diagnosed as having an infection caused by an unusual NTM species.

Rapid-growing NTM species, such as M. fortuitum, have increasingly gained recognition during the last two decades because of their ability to thrive even in the harshest environments. In an immunosuppressed patient, these pathogens cause serious infections, such as bacteremia (5). M. senegalense is a rapid-growing NTM, belongs to the same group as M. fortuitum, and was first isolated from a bovine source (6). Infection with M. senegalense affects the sinus tracts and is characterized by multiple abscesses and granuloma formation. Only 7 cases about human infection with M. senegalense have been reported, the recent report found it to cause skin infections in immunocompetent patients (7). Most patients had minimal history of contact with animals and travel to areas where M. senegalense infection was more commonly endemic (8–10). And most of those cases were identified by various sequencing techniques. The first case of human infection by M. senegalense was described in 2005 (11). The patient had non-Hodgkin's lymphoma and was treated with R-CHOP. Her physical examination revealed high fever of 39.8°C, although she had no contact with any animal- or bovine-specific sources. Although it was difficult to diagnose, 16S rRNA gene, rpoB, and 16S-23S rRNA gene internal transcribed spacer sequence analyses finally revealed M. senegalense infection. Another case reported M. senegalense infection in a healthy girl with no prior history of serious illness or hospitalization (12). The patient was scratched by fish tank debris, following which the wound was sterilized and sutured. After 2 weeks, the wound failed to heal and appeared reddened and indurated. 16S gene sequencing and biochemical testing was used to diagnose the M. senegalense infection, which was the first infection reported in humans without immunodeficiency. This also indicated that immunocompetent individuals were also at a risk of infection.

It is worth mentioning that the patient had no history of contact with animals, and the patient's body temperature, routine blood test results, and other data indicated that infection was absent. These indicators were not present in previous cases, suggesting that M. senegalense may not cause changes in infection indicators. According to current literature, the prevalence and incidence of NTM infections continue to increase (11, 13). Rapid identification and subsequent drug susceptibility testing are essential for sleeting appropriate antibiotics against NTM. In addition, it is necessary to be vigilant about NTM infections, even if individuals have no contact history with animals, no travel history, and no infection-negative routine blood test results with recurrent infections at laparoscopic incision sites.

Because of the scarcity of literature on M. senegalense, we draw on treatment guidelines for NTM infections (14, 15). From the literature review, we found that the management of NTM infections is quite difficult. First, NTM infections possess several internal antimicrobial resistance mechanisms such as an impermeable cell wall and formation of granulomas, which reduces antimicrobial influx. Second, the long-term treatment of NTM infections leads to the development of drug resistance (16). According to the American Thoracic Society, Infectious Diseases Society of America, and Clinical and Laboratory Standards Institute, the latest recommended NTM drugs include macrolides, clofazimine, quinolones, sulfonamides, linezolid, aminoglycosides, bedaquiline, and tetracyclines (17). Additionally, the success rate of treatment for NTM infection is species specific. Usually, a combination of three or four drugs are administered to avoid the development of resistance to monotherapy. Based on previous experience combined with this patient's condition, we administered clarithromycin (500 mg, twice daily), moxifloxacin (400 mg, once daily), rifampicin (450 mg, once daily), and doxycycline (100 mg, once every 12 h). With this combination of therapy, the patient achieved good clinical efficacy. The case report provides a reference for the treatment of M. senegalense.

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding authors.

Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

HY, FLG, and SLZ collected and analyzed patient data. HLZ, HY, YFY, and HDL wrote the manuscript. HDL and JJL provided supervision. All authors reviewed, edited, and approved the final manuscript.

This study was supported by National Natural Science Foundation of China (82073260 to HDL).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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