Influence of previous antimicrobial therapy on microbial results
acute infection, PJIs, chronic infection (N=75).In, infection
ACUTE INFECTIONS, INFECTION, CHRONIC INFECTIONS, ACUTE INFECTION
In the group with prior antimicrobial therapy, the positivity rate of mNGS was 88.2% (67 of 76), which was significantly higher than that of all cultures in all courses (synovial fluid and deep tissue) (58 of 76 [76.3%], p=0.004). In the group without prior antimicrobial therapy, the positivity rate of mNGS was 87.3% (48 of 55), which was significantly higher than that of all cultures in all courses (synovial fluid and deep tissue) (33 of 55 [60.0%], p= 0.013).Almost all non-microbiological and microbiological tests showed a higher positivity rate (with or without statistical difference) in the group with prior antimicrobial therapy compared to the group without prior antimicrobial therapy (Positivity rate of (non-) microbiologic tests according to prior antimicrobial therapy: with antibiotics (N=76) and without antibiotics (N=55).The rate of previous antimicrobial therapy was significantly higher in acute PJIs (39 of 56 cases [69.6%]) than in chronic PJIs (37 of 75 cases [49.3%], p=0.020). Comparison of positivity rate of microbiologic tests between acute infections and chronic infections in separate group with or without previous antimicrobial therapy are shown in Positivity rate of microbiologic tests according to classification of infection: acute infection (N=56) and chronic infection (N=75).In relation to the sequencing read counts which was regarded as a semi-quantitative indicator of the detected pathogens abundance, the average number of reads for the top known pathogen identified in cases with previous antimicrobial therapy and without previous antimicrobial therapy was comparable (453.4 ± 1407.3 vs 428.3 ± 660.2, p=0.079), as was that for acute PJIs in both groups (643.8 ± 1797.5 with previous antimicrobial therapy vs 685.1 ± 1015.1 without previous antimicrobial therapy, p=0.289). While, the average number of reads for the top known pathogen identified in chronic PJIs was significantly higher in cases without previous antimicrobial therapy than cases with previous antimicrobial therapy (311.5 ± 380.1 vs 226.1 ± 669.4, p=0.033).