Infection characteristics among <i>Serratia marcescens</i> capsule lineages

Bacteremia occurs when the host immune system fails to contain bacterial bloodstream replication following an initial inoculation event from either an internal or external source. Capsule polysaccharides play a protective role for <i>Serratia marcescens</i> during bacteremia, but there is abundant genetic diversity at the capsule-encoding locus within the species. This study compares the infection characteristics of <i>S. marcescens</i> isolates belonging to five capsule types and defines the contributions to infection fitness for each. By characterizing the differences in capsule dependence and infection potential between <i>S. marcescens</i> strains, efforts to combat these life-threatening infections can be focused toward identifying strategies that target the most critical genetic lineages of this important opportunistic pathogen.