RESUMEN
Pseudomonas aeruginosa, a leading cause of severe hospital-acquired pneumonia, causes infections with up to 50% mortality rates in mechanically ventilated patients. Despite some knowledge of virulence factors involved, it remains unclear how P. aeruginosa disseminates on mucosal surfaces and invades the tissue barrier. Using infection of human respiratory epithelium organoids, here we observed that P. aeruginosa colonization of apical surfaces is promoted by cyclic di-GMP-dependent asymmetric division. Infection with mutant strains revealed that Type 6 Secretion System activities promote preferential invasion of goblet cells. Type 3 Secretion System activity by intracellular bacteria induced goblet cell death and expulsion, leading to epithelial rupture which increased bacterial translocation and dissemination to the basolateral epithelium. These findings show that under physiological conditions, P. aeruginosa uses coordinated activity of a specific combination of virulence factors and behaviours to invade goblet cells and breach the epithelial barrier from within, revealing mechanistic insight into lung infection dynamics.
Asunto(s)
Células Caliciformes , Infecciones por Pseudomonas , Pseudomonas aeruginosa , Mucosa Respiratoria , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/patogenicidad , Pseudomonas aeruginosa/fisiología , Células Caliciformes/microbiología , Células Caliciformes/metabolismo , Humanos , Mucosa Respiratoria/microbiología , Mucosa Respiratoria/citología , Infecciones por Pseudomonas/microbiología , Sistemas de Secreción Tipo VI/genética , Sistemas de Secreción Tipo VI/metabolismo , Factores de Virulencia/metabolismo , Factores de Virulencia/genética , Sistemas de Secreción Tipo III/metabolismo , Sistemas de Secreción Tipo III/genética , GMP Cíclico/análogos & derivados , GMP Cíclico/metabolismo , Organoides/microbiología , Traslocación BacterianaRESUMEN
BACKGROUND: Diazabicyclooctanes (DBOs) are an increasingly important group of non ß-lactam ß-lactamase inhibitors, employed clinically in combinations such as ceftazidime/avibactam. The dose finding of such combinations is complicated using the traditional pharmacokinetic/pharmacodynamic (PK/PD) index approach, especially if the ß-lactamase inhibitor has an antibiotic effect of its own. OBJECTIVES: To develop a novel mechanism-based pharmacokinetic-pharmacodynamic (PKPD) model for ceftazidime/avibactam against Gram-negative pathogens, with the potential for combination dosage simulation. METHODS: Four ß-lactamase-producing Enterobacteriaceae, covering Ambler classes A, B and D, were exposed to ceftazidime and avibactam, alone and in combination, in static time-kill experiments. A PKPD model was developed and evaluated using internal and external evaluation, and combined with a population PK model and applied in dosage simulations. RESULTS: The developed PKPD model included the effects of ceftazidime alone, avibactam alone and an 'enhancer' effect of avibactam on ceftazidime in addition to the ß-lactamase inhibitory effect of avibactam. The model could describe an extensive external Pseudomonas aeruginosa data set with minor modifications to the enhancer effect, and the utility of the model for clinical dosage simulation was demonstrated by investigating the influence of the addition of avibactam. CONCLUSIONS: A novel mechanism-based PKPD model for the DBO/ß-lactam combination ceftazidime/avibactam was developed that enables future comparison of the effect of avibactam with other DBO/ß-lactam inhibitors in simulations, and may be an aid in translating PKPD results from in vitro to animals and humans.
Asunto(s)
Compuestos de Azabiciclo/farmacología , Compuestos de Azabiciclo/farmacocinética , Ceftazidima/farmacología , Ceftazidima/farmacocinética , Bacterias Gramnegativas/efectos de los fármacos , Antibacterianos/farmacocinética , Antibacterianos/farmacología , Combinación de Medicamentos , Bacterias Gramnegativas/enzimología , Pruebas de Sensibilidad Microbiana , Inhibidores de beta-Lactamasas/farmacocinética , Inhibidores de beta-Lactamasas/farmacología , beta-LactamasasRESUMEN
Numerous bacterial pathogens secrete multiple effectors to modulate host cellular functions. These effectors may interfere with each other to efficiently control the infection process. Bartonellae are Gram-negative, facultative intracellular bacteria using a VirB type IV secretion system to translocate a cocktail of Bartonella effector proteins (Beps) into host cells. Based on in vitro infection models we demonstrate here that BepE protects infected migratory cells from injurious effects triggered by BepC and is required for in vivo dissemination of bacteria from the dermal site of inoculation to blood. Human endothelial cells (HUVECs) infected with a ΔbepE mutant of B. henselae (Bhe) displayed a cell fragmentation phenotype resulting from Bep-dependent disturbance of rear edge detachment during migration. A ΔbepCE mutant did not show cell fragmentation, indicating that BepC is critical for triggering this deleterious phenotype. Complementation of ΔbepE with BepEBhe or its homologues from other Bartonella species abolished cell fragmentation. This cyto-protective activity is confined to the C-terminal Bartonella intracellular delivery (BID) domain of BepEBhe (BID2.EBhe). Ectopic expression of BID2.EBhe impeded the disruption of actin stress fibers by Rho Inhibitor 1, indicating that BepE restores normal cell migration via the RhoA signaling pathway, a major regulator of rear edge retraction. An intradermal (i.d.) model for B. tribocorum (Btr) infection in the rat reservoir host mimicking the natural route of infection by blood sucking arthropods allowed demonstrating a vital role for BepE in bacterial dissemination from derma to blood. While the Btr mutant ΔbepDE was abacteremic following i.d. inoculation, complementation with BepEBtr, BepEBhe or BIDs.EBhe restored bacteremia. Given that we observed a similar protective effect of BepEBhe on infected bone marrow-derived dendritic cells migrating through a monolayer of lymphatic endothelial cells we propose that infected dermal dendritic cells may be involved in disseminating Bartonella towards the blood stream in a BepE-dependent manner.