Characteristics of CD4⁺T-cell reduction and pulmonary infections in critically ill immunocompromised patients

The CD4⁺T-cell count is a key indicator for evaluating immunosuppression. Infections significantly influence the survival and prognosis of critically ill patients. This study aims to systematically evaluate the association between reduced CD4⁺ T-cell counts and lung infections in immunosuppressed ICU patients, offering clinical evidence to guide the management of lung infections in this population.

This retrospective, single-center study included 40 immunocompromised patients admitted to the ICU from January 1, 2021, to June 30, 2023. All participants underwent metagenomic next-generation sequencing. Patients with suspected lung infections based on their CD4⁺T-cell counts were divided into mild (350/µL+T-cell count<500/µL), moderate (200 /µL+T-cell count ≤ 350/µL), and severe (CD4⁺T-cell count ≤200/µL) groups. Microecological analysis was performed on each group. Intergroup comparisons were conducted for 28-day mortality, hospital length of stay, and ICU length of stay.

Amang these forty immunosuppressed patients, 8 were assigned to the mild group, 16 to the moderate group, and 16 to the severe group. Streptococcus pneumoniae was almost all distributed in moderate patients (75.0%), while severe patients had a higher proportion of fungi detected (25.7%). Respiratory microbiome analysis identified Acinetobacter baumannii, Human alphaherpesvirus 1, and Klebsiella pneumoniae as the most abundant species. Although no significant difference in the alpha diversity index was found among the groups, index values were lower in the severe group than in the moderate group. Beta diversity analysis showed that the microbial community structure did not significantly differ among the three groups. A total of 27 microbial markers were obtained, with multiple streptococcal species showing enrichment in moderate group and Candida tropicalis in severe group. By day 28, four patients (50.0%) in the mild group had died compared with six (37.5%) in the moderate group and nine (56.3%) in the severe group. There were no significant difference in the duration of ICU or hospital stays.

This study on ICU-admitted immunocompromised patients identified the prevalent pathogens and microbiome features associated with pulmonary infections, as well as their relationship with CD4⁺T-cell depletion. These findings are valuable for optimizing clinical diagnosis and treatment strategies and may contribute to improving patient outcomes.