Shigella(2) sublethal leptospirosis.(1) bacterial artificial chromosome(1) bacterial cultivation(1) replicon packaging(1) intracellular pathogen(1) Virus quantification(1) enteroid(1) natural transmission routes(1) coronavirus(1) Shigella flexneri(1) picornaviruses(1) Bacteria(1) tissue culture(1) mouse model(1) COVID-19(1) infectious clone(1) RNA replication(1) macrophages(1) monocyte-derived macrophage(1) Propagation(1) physiologic route of infection(1) reverse genetics(1) Replicon assay(1) Salmonella(1) Isolation(1) plaque(1) Leptospira(1) SARS-CoV-2(1) virus rescue.(1)