With the widespread use of antibacterial drugs and increasing number of immunocompromised patients, pulmonary fungal infections are becoming more common. However, the incidence of pulmonary fungal and bacterial co-infection is rarely reported. In this study, 119 patients definitively diagnosed with pulmonary fungal infections between July 2018 and March 2020 were assessed using metagenomic next-generation sequencing (mNGS) as well as traditional pathogen detection to gauge the incidence of fungal and bacterial co-infection and evaluate the associated risk factors. We found that of the 119 patients with fungal infections, 48 (40.3%) had pulmonary fungal and bacterial co-infection. We identified immunocompromised status and the presence of one or more pulmonary cavities as risk factors associated with fungal and bacterial co-infection. The most commonly isolated fungi species were Aspergillus, Pneumocystis, and Rhizopus. The most commonly isolated bacterial species were Pseudomonas aeruginosa, Acinetobacter baumannii, and Stenotrophomonas maltophilia. Seventy-nine (66.4%) patients had received empirical antibiotic treatment before their pathogenic test results became available, and 41.7% (fungal infection group) and 38.7% (fungal and bacterial co-infection group) of the patients had their antibacterial drug dosage changed accordingly. This mNGS-based study showed that the incidence of fungal and bacterial co-infection is significant. Our research outcomes can, thus, guide the use of antibacterial drugs in the treatment of clinical fungal infections.

Purpose: Metagenomic next-generation sequencing (mNGS) is widely used for pulmonary infection; nonetheless, the experience from its clinical use in diagnosing pulmonary fungal infections is sparse. This study aimed to compare mNGS results from lung biopsy and bronchoalveolar lavage fluid (BALF) and determine their clinical diagnostic efficacy. Patients and Methods: A total of 106 patients with suspected pulmonary fungal infection from May 2018 to January 2020 were included in this retrospective study. All patients' lung biopsy and BALF specimens were collected through bronchoscopy. Overall, 45 (42.5%) patients had pulmonary fungal infection. The performance of lung biopsy and BALF used for mNGS in diagnosing pulmonary fungal infections and identifying pathogens was compared. Additionally, mNGS was compared with conventional tests (pathology, galactomannan test, and cultures) with respect to the diagnosis of pulmonary fungal infections. Results: Lung biopsy-mNGS and BALF-mNGS exhibited no difference in terms of sensitivity (80.0% vs 84.4%, P=0.754) and specificity (91.8% vs 85.3%, P=0.39). Additionally, there was no difference in specificity between mNGS and conventional tests; however, the sensitivity of mNGS (lung biopsy, BALF) in diagnosing pulmonary fungal infections was significantly higher than that of conventional tests (conventional tests vs biopsy-mNGS: 44.4% vs 80.0%, P<0.05; conventional tests vs BALF-mNGS: 44.4% vs 84.4%, P<0.05). Among 32 patients with positive mNGS results for both biopsy and BALF specimens, 23 (71.9%) cases of consistency between the two tests for the detected fungi and nine (28.1%) cases of a partial match were identified. Receiver operating curve analysis revealed that the area under the curve for the combination of biopsy and BALF was significantly higher than that for BALF-mNGS (P=0.018). Conclusion:We recommend biopsy-based or BALF-based mNGS for diagnosing pulmonary fungal infections because of their diagnostic advantages over conventional tests. The combination of biopsy and BALF for mNGS can be considered when higher diagnostic efficacy is required.