Molecular determinants of antibiotic resistance in Salmonella enterica antibiotic resistance

Abstract

Nontyphoid strains of Salmonella enterica pose a great threat to human health. The problem of salmonellosis is aggravated compounded by the progressive spread of antibiotic resistance among clinical and agricultural strains of S. enterica. This literature review summarizes the current knowledge of the mechanisms of antibiotic resistance in S. enterica and illustrates the diversity and complexity of molecular systems providing antibiotic resistance. The spectrum of natural resistance is described and the adaptive (acquired) mechanisms of resistance to representatives of the main classes of antibiotics, including fluoroquinolones, aminoglycosides, tetracyclines, nitrofurans, sulfonamides, fosfomycin and chloramphenicol, are thoroughly characterized. Particular emphasis is placed on the analysis of the molecular genetic mechanisms of S. enterica resistance to representatives of the most important classes of antibiotics — β-lactams, and to reserve antibiotics — polymyxins (colistin). Genetic determinants of resistance, transmitted by a horizontal path route are also described. The review analyzes only those variants of the molecular mechanisms of antibiotic resistance where the clinical significance has been proven by a set of correct genetic (sequencing) and biochemical (confirmation of the spectrum of hydrolyzed β-lactams) studies. The main ways of regulating the expression of antibiotic resistance are also described. Many S. enterica strains exhibit a combination of different mechanisms of antibiotic resistance and have a multiple resistance. The question was raised about the heterogeneity of the distribution of resistance among different groups/serotypes within the S. enterica species. In particular, some clonal complexes with signs of resistance are more successful pathogens in humans and animals. Salmonella, like most other bacteria, exhibit a non-canonical type of antibiotic resistance — biofilm resistance, which is realized through several mechanisms, the main of which are the filtering/sorption capacity of the biofilm matrix and the transformation of biofilm cells into dormant and persistent forms.Despite the fact that the functional significance of the molecular assemblies that determine antibiotic resistance is the same for all enterobacteria, the specification of the mechanisms of resistance in Salmonella is a necessary link for the development of molecular diagnostic systems for assessing the sensitivity to antimicrobial drugs.