Diagnosis of Infection in a Routine Testing Workflow: Effect of Bacterial Load and Virulence Factors.

Reliable diagnostic methods are mandatory for effective management of infection. Histology and culture are the most common invasive methods in current practice, even if molecular methods are gaining in importance. The performance of these conventional methods varies significantly. We conducted a retrospective study of 1540 adults and 504 children with gastric biopsies taken during endoscopy to assess the impact of bacterial load and the virulence factor on the performance of infection testing. The association between virulence and histology findings was also investigated. With 23S rRNA qPCR confirmed by amplification as the gold standard, culture and histology had lower sensitivity, 74.4% and 73.3%, respectively. However, their sensitivity was enhanced (>90%) in biopsies with high bacterial load (qPCR Ct < 30). Positive status of the strain was associated with high bacterial load (94.9%), thus resulting in more frequent positive culture (94.3%) and histology detection (91.7%) and more severe lesions on histology ( < 0.001). Conversely, the status of the strains was negative in 110/119 (92.4%) of biopsies with low bacterial load (qPCR Ct < 30), 82/90 (91.1%) with negative histology detection and 119/131 (90%) with negative culture findings ( < 0.001). This study highlights the low sensitivity of conventional culture and histology that may lead to false negative diagnosis if used alone. quantification associated with genotyping in routine workflow are essential for a sensitive and reliable diagnosis, to identify patients at high risk and to manage eradication therapies.