Bacteriophage-Resistant Salmonella rissen: An In Vitro Mitigated Inflammatory Response.

Rosanna Capparelli,Cristina Pagano,Marina Papaianni,Paola Cuomo,Domenico Iannelli,Annarita Ricciardelli,Angela Michela Immacolata Montone

doi:10.3390/v13122468

Abstract

Non-typhoid Salmonella (NTS) represents one of the major causes of foodborne diseases, which are made worse by the increasing emergence of antibiotic resistance. Thus, NTS are a significant and common public health concern. The purpose of this study is to investigate whether selection for phage-resistance alters bacterial phenotype, making this approach suitable for candidate vaccine preparation. We therefore compared two strains of Salmonella enterica serovar Rissen: RR (the phage-resistant strain) and RW (the phage-sensitive strain) in order to investigate a potential cost associated with the bacterium virulence. We tested the ability of both RR and RW to infect phagocytic and non-phagocytic cell lines, the activity of virulence factors associated with the main Type-3 secretory system (T3SS), as well as the canonic inflammatory mediators. The mutant RR strain—compared to the wildtype RW strain—induced in the host a weaker innate immune response. We suggest that the mitigated inflammatory response very likely is due to structural modifications of the lipopolysaccharide (LPS). Our results indicate that phage-resistance might be exploited as a means for the development of LPS-based antibacterial vaccines.

Highlights

Salmonella enterica (S. enterica) is a Gram-negative bacterium, causing salmonellosis, one of the major threats to human health
Non-typhoid Salmonella enterica subsp. enterica serovar Rissen strain RW, Salmonella bongori, Salmonella nottingham and Salmonella typhimurium were isolated from a food matrix and characterized by Istituto Zooprofilattico Sperimentale Del Mezzogiorno (Portici, Naples, Italy)
Recent studies have shown that, in bacteria, acquisition of phage resistance is often associated with loss of antibiotic resistance [27]

Summary

Introduction

Salmonella enterica (S. enterica) is a Gram-negative bacterium, causing salmonellosis, one of the major threats to human health. 2500 Salmonella serovars have been identified [1] and classified as typhoid or non-typhoid strains, according to host specificity and clinical manifestation [2,3]. Typhimurium or Enteritidis— are the most frequent cause of worldwide foodborne gastroenteritis, causing 155,000 deaths every year [4]. Even though self-limiting gastroenteritis is the main clinical manifestation of Salmonella infection, more severe complications—such as extra-intestinal infections or bacteremia—can occur in immunocompromised patients [5]. The increased resistance of Salmonella to traditional antimicrobial drugs makes it difficult to prevent Salmonella infections. In this context, vaccination may represent a valid alternative

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