Objective:To investigate the factors influencing phytohemagglutinin (PHA) response in the detection of Mycobacterium tuberculosis infection by gamma interferon release assay (IGRA). Methods:A retrospective case-control study was conducted on 360 hospitalized patients who received IGRA in West China Hospital of Sichuan University from January 2019 to December 2021. According to PHA response (IFN-γ level), they were divided into three groups: negative mitogen response group (IFN-γ<2 pg/ml), weak positive mitogen response group (IFN-γ: 2-100 pg/ml), and normal mitogen response group (IFN-γ>400 pg/ml).Results:Immune diseases were independently associated with negative (OR=0.34, 95%CI: 0.17-0.72, P=0.004) and weak positive mitogen responses (OR=0.29, 95%CI: 0.16-0.55, P<0.001). Infections caused by pathogens other than Mycobacterium tuberculosis was independently associated with negative mitogen response (OR=0.266, 95%CI: 0.09-0.83, P=0.023), while immunodeficiency was independently associated with weak positive mitogen response (OR=0.280, 95%CI: 0.12-0.63, P=0.002). Mitogen response was significantly correlated with the levels of albumin and hemoglobin in serum and the counts of neutrophils and lymphocytes ( P<0.001). Conclusions:Immune diseases and immunodeficiency can affect mitogen response. Therefore, clinicians should give attention to mitogen response in the interpretation of IGRA test results to prevent misdiagnosis and underdiagnosis. Besides, to a certain extent, mitogen response can reflect the infection status of hospitalized patients.

Objective: To retrospectively analyze the distribution of non-fermentative bacteria causing bloodstream infection in hospitalized patients in Sichuan Province and their drug susceptibility to common antibiotics for better understanding their epidemiological characteristics. Methods: From January 1, 2015 to December 31, 2017, all of the non-fermentative bacteria isolated from patients with bloodstream infection in nine hospitals in Sichuan Province were collected. Species distribution and drug resistance test results were retrospectively analyzed. Results: A total of 6 291 strains of pathogenic bacteria were isolated, including 3 674 strains of gram-negative bacteria (58.4%) and 2 617 strains of gram-positive bacteria (41.6%). The gram-positive bacteria were 1 895 strains of Staphylococcus (30.1%), 372 strains of Streptococcus (5.9%), 317 strains of Enterococcus (5.1%) and 33 strains of other gram-positive bacteria (0.5%). The gram-negative bacteria were 3 191 Enterobacteriaceae strains (50.7%), 389 non-fermentative strains (6.2%) and 94 other gram-negative strains (1.5%). The isolated non-fermentative bacteria were mainly Pseudomonas aeruginosa (136 strains, 35.0%), Acinetobacter baumannii (126 strains, 32.0%) and Stenotrophomonas maltophilia (33 strains, 8.5%). There were 167 (42.9%), 112 (28.8%) and 82 (21.1%) non-fermentative bacteria isolated in internal medicine departments, ICUs and surgery departments, respectively. The drug resistance rates of Pseudomonas aeruginosa to cefepime, ciprofloxacin and gentamicin were 16.5%, 10.7% and 9.9%, respectively. Carbapenems-resistant Pseudomonas aeruginosa (CR-PA) accounted for 13.6%. No polymyxin-resistant Pseudomonas aeruginosa was found. The resistance rates of Acinetobacter baumannii to all antibiotics were over 30% except for minocycline and polymyxin and 75.7% of carbapenem-resistant Acinetobacter baumannii (CR-AB) were isolated. The drug resistance rates to levofloxacin, trimethoprim/sulfamethoxazole and ceftazidime were 0%, 0% and 37.0% in Stenotrophomonas maltophilia isolates and 10.5%, 4.2% and 19% in Burkholderia cepacia isolates, respectively. Conclusions Non-fermentative bacteria causing 6.2% of bloodstream infection in Sichuan, mainly by Pseudomonas aeruginosa and Acinetobacter baumannii. There were significant differences in the isolation rate of non-fermentative bacteria in different departments and most of the strains were isolated in internal medicine departments. The detection rate of Acinetobacter baumannii with multiple drug resistance was high, while other non-fermentative bacteria had good sensitivity to antibiotics.