Serratia marcescens antibiotic resistance mechanisms of an opportunistic pathogen: a literature review

Abstract

Serratia marcescens is a ubiquitous bacterium from order Enterobacterales displaying a high genetic plasticity that allows it to adapt and persist in multiple niches including soil, water, plants, and nosocomial environments. Recently, S. marcescens has gained attention as an emerging pathogen worldwide, provoking infections and outbreaks in debilitated individuals, particularly newborns and patients in intensive care units. S. marcescens isolates recovered from clinical settings are frequently described as multidrug resistant. High levels of antibiotic resistance across Serratia species are a consequence of the combined activity of intrinsic, acquired, and adaptive resistance elements. In this review, we will discuss recent advances in the understanding of mechanisms guiding resistance in this opportunistic pathogen.

Keywords: Acquired resistance; Antimicrobial resistance; Intrinsic resistance; Opportunistic pathogen; Serratia marcescens.

Figure 1. S. marcescens, beneficial and pathogenic effects.

S. marcescens is distributed worldwide and it has positive environmental effects, it can produce antimicrobial compounds such as prodigiosin, as well as factors that promote plant growth. Some member of Serratia genus can degrade a wide variety of compounds including chitin and pollutants as heavy metals, therefore they can be considered as biological control agents. In counterpart, a significant phytosanitary risk can be associated to S. marcescens, based on its potential to damage several crops, including cucurbits, maize, pepper, sunflower, among others. This bacterium is particularly relevant as an opportunistic human pathogen displaying multi-resistant against several classes of antibiotics.

Figure 2. Mechanisms of antibiotic resistance in S. marcescens can be divided as intrinsic, acquired, and adaptive resistance.

S. marcescens intrinsic resistance is related with ARG inherently found in the chromosome (e.g., β-lactamases and efflux pumps), along with lipopolysaccharide (LPS) modifications (pale green rectangle). Acquired resistance is associated with HGT, genetic material transfer between species could derivate in antibiotic resistance and propagation of such phenotype beyond interspecies (lime green square). Adaptive resistance often arises due to pressures from the ecological niche inducing changes in cell permeability and biofilm formation (dark green square). Concerted activity of these mechanisms migth lead in synergistic drug resistance in S. marcescens. Each antibiotic resistance mechanisms is discussed in the appropriate subsection of this review.