Complementary detection of respiratory pathogens and antimicrobial-resistance markers by multiplex PCR alongside culture in a High-AMR Egyptian cohort

Abstract Aim Lower respiratory tract infections frequently involve polymicrobial disease and antimicrobial-resistant pathogens, yet conventional culture may provide an incomplete and delayed microbiological picture. This study evaluated the complementary contribution of multiplex molecular testing and conventional culture in a high-AMR cohort in Egypt. Methods This retrospective cross-sectional study included 133 specimens collected at Souad Kafafi University Hospital, Egypt, during 2022–2023: 98 sputum records tested using the BioFire FilmArray Pneumonia Plus Panel and conventional culture with VITEK 2 susceptibility testing, and 35 blood-culture records evaluated using routine culture and BCID2 Panel. Paired molecular and culture results, descriptive analyses and multivariable logistic regression were performed. Results Among 133 specimen records, at least one pathogen was recorded at 58.6% (single-organism detection, 26.3%; mixed detection, 32.3%). Gram-negative bacteria predominated among organism-category detections (47.1%), followed by viruses (27.5%) and Gram-positive bacteria (25.5%). At least one AMR marker was detected in 51 records (38.3%), with blaCTX-M and blaNDM being the most frequent (each 27.8%). Among 98 paired sputum specimens, BioFire detected at least one target in 71.4%, compared with 51.0% by culture; the specimen-level PPA for any-target detection was 84.0%. Any degree of organism-level bacterial agreement was observed in 41.8%, while 58.2% showed complete discordance. Among 72 AMR-marker-positive observations with a matched cultured isolate and relevant susceptibility result, 64 demonstrated expected resistant phenotype (88.9% positive agreement). Both carbapenemases and Gram-negative detection were independently associated with phenotypic resistance. Conclusions Integration of multiplex PCR and conventional culture expanded pathogen detection and provided valuable AMR profiling in resource-limited, high-resistance settings.