Screening under infection-relevant conditions reveals chemical sensitivity in multidrug-resistant invasive non-typhoidal Salmonella (iNTS)

Abstract

Bloodstream infections caused by invasive, non-typhoidal salmonellae (iNTS) are a major global health concern. These infections are especially problematic in sub-Saharan Africa, where the sequence type (ST) 313 of invasive non-typhoidal Salmonella Typhimurium (iNTS) is dominant. Unlike S. Typhimurium strains that cause mild gastroenteritis, iNTS strains are resistant to multiple first-line antibiotics and have higher extraintestinal invasiveness, limiting current treatment options. Here, we performed multiple small molecule screens under infection-relevant conditions to reveal chemical sensitivities in ST313 as entry points to drug discovery to combat the clinical burden of iNTS. By screening the invasive ST313 sequence type under host-mimicking conditions, we identified the antimicrobial activity of the nucleoside analog 3-azido-3-deoxythymidine, which required bacterial thymidine kinase activity for its antimicrobial activity. In a parallel macrophage-based screening platform, we also identified three host-directed compounds (amodiaquine, berbamine, and indatraline) that significantly restricted intracellular replication of ST313 in macrophages without directly impacting bacterial viability. This work provides evidence that despite elevated invasiveness and multidrug resistance, iNTS S. Typhimurium remains susceptible to unconventional drug discovery approaches.