Materials and Methods
Bacterial isolation and identification were conducted according to the third edition of the National Guide for Clinical Laboratory Procedures. Bcterial analyzers and identification cards were used for the isolation and identification of pathogens. Before the patient received anti-infective therapy upon admission, an anopharyngeal swab was tested for coronavirus nucleic acid, and sputum, suction sputum, tracheal secretions, and deep tracheal secretions were also obtained and immediately sent to the laboratory for bacterial culture. The laboratory conducted a preliminary screening by microscopy, Gram staining and low-power observation of single-field squamous epithelial cells less than 10 and more than 25 neutrophils were considered qualified sputum specimens. Qualified sputum specimens were inoculated on Blood agar plates and cultured in a 35°C incubator for 24-48 hours to isolate and purify the dominant bacteria and make an identification. Microorganisms were identified performing a VITEK 2 identification system.
The control strains used: Staphylococcus aureus ATCC 25923,Escherichia coli ATCC 25922, Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853 were all obtained from the Fujian Provincial Inspection Center. The coronavirus nucleic acid test was performed by RT-PCR, and the reagents, positive and negative control reagents, automatic nucleic acid extractor, and fluorescent PCR instrument were all provided by Xi’an Tianlong Gene Co., Ltd. Ct values (cycle threshold values) less than 40 were judged as positive results.
Data processing was performed using the SPSS version 22.0 software (SPSS Inc., Chicago, IL, United States), and the count data was expressed as percentages. The Chi-square test (χ 2) or Fisher’s exact test was used for inter-group comparison. Fisher’s exact test was applied as numbers in one or more categories were <5. Testing of data for normal distribution was performed by means of Kolmogorov-Smirmov test. For metric data that had passed the normality test, the median and quartiles (P25-P75) were used to represent the data. Mann-Whitney U test (non-parametric test) was used for data comparison. In all tests, a P <0.05 was considered statistically significant.