Li Jiang,1– 3,* Lili Wei,1– 3,* Xiuying Li,1– 3 Dongyan Zheng,1– 3 Cunwei Cao,1– 3 Meng Li2,4 

1Department of Dermatology and Venereology, the First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, People’s Republic of China; 2Guangxi Key Laboratory of Mycosis Prevention and Treatment, Nanning, Guangxi, People’s Republic of China; 3Fangchenggang Wanqing Institute of Mycosis Prevention and Control, Fangchenggang, People’s Republic of China; 4Department of Clinical Laboratory,the First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Meng Li, Department of Clinical Laboratory, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, 530021, People’s Republic of China, Tel +86 771 5356052, Email gxmulimeng@foxmail.com Cunwei Cao, Department of Dermatology and Venereology, the First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, 530021, People’s Republic of China, Tel +86 771 5356514, Email caocunwei@yeah.net

Abstract: Protothecawickerhamii (P. wickerhamii) and Mycobacteriumhaemophilum (M. haemophilum) are both opportunistic pathogens that could cause infections in immunocompromised populations. However, these infections rarely occur in individuals with normal immunity. We reported a 39-year-old immunocompetent man presented with recurrent subcutaneous abscess on fingers who developed a co-infection of P. wickerhamii and M. haemophilum. To our knowledge, this is the first reported co-infection involving P. wickerhamii and M. haemophilum. The diagnosis was complicated by mNGS misidentifying M. haemophilum as Mycobacterium leprae (M. leprae) (98% sequence similarity) and overlooking P. wickerhamii. This case underscores the critical need to correlate mNGS results with clinical features and use complementary diagnostic methods to avoid errors. The combination of traditional and molecular methods can improve diagnostic accuracy.

Keywords: metagenomic next-generation sequencing, Prototheca wickerhamii, Mycobacterium haemophilum, co-infection