Abstract: Objective To discuss the changes of infectious pathogens and lymphocyte subsets in patients with perianal necrotizing fasciitis. Methods From January 2022 to December 2022, 98 cases of patients with perianal necrotizing fasciitis diagnosed in a certain hospital were selected as the study subjects. All patients were given infection related microbial detection and surgical treatment, and the prognosis were observed. Investigated the general information of all patients, Detected and correlation analyzed of changes in lymphocyte subsets. Results Infection-related microorganisms were detected in all patients, included 54 cases of gram-positive bacteria, 39 cases of gram-negative bacteria and 5 cases of fungi. The main microorganisms were Staphylococcus haemolyticus, Escherichia coli, Enterococcus faecium, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa. All patients were successfully completed the treatment, with 12 cases of complications and 9 cases of deaths (death group). The incidence rates of complications and mortality were 12.24% and 9.18% respectively. The proportion of CD3⁺T cells, CD8⁺T cells and NK cells in dead patients were significantly higher than that in living patients, while the proportion of B lymphocytes were significantly lower than that in living patients (P<0.05). Spearman correlation analysis showed that the death of patients with perianal necrotizing fasciitis were positively correlated with the proportion of CD3⁺T cells, CD8⁺T cells and NK cells, and were negatively correlated with the proportion of B lymphocytes (P<0.05). Logistic regression analysis showed that the proportion of CD3⁺T cells, CD8⁺T cells and NK cells were the main factors leading to the death of patients (P<0.05). Conclusion The infection microorganism of patients with perianal necrotizing fasciitis are mainly Staphylococcus haemolyticus, Escherichia coli and Enterococcus faecium. The incidence of complications and mortality after treatment are still relatively high. The changes of lymphocyte subsets are correlated with the prognosis of patients.

Key words: perianal necrotizing fasciitis, infectious microorganism, staphylococcus haemolyticus, relevance