Adaptation in a Fibronectin Binding Autolysin of Staphylococcus saprophyticus

Abstract

Staphylococcus saprophyticus is an important cause of urinary tract infections (UTI) in women; such UTI are common, can be severe, and are associated with significant impacts to public health. In addition to being a cause of human UTI, S. saprophyticus can be found in the environment, in food, and associated with animals. After discovering that UTI strains of S. saprophyticus are for the most part closely related to each other, we sought to determine whether these strains are specially adapted to cause disease in humans. We found evidence suggesting that a mutation in the gene aas is advantageous in the context of human infection. We hypothesize that the mutation allows S. saprophyticus to survive better in the human urinary tract. These results show how bacteria found in the environment can evolve to cause disease.

Foodborne Origin and Local and Global Spread of Staphylococcus saprophyticus Causing Human Urinary Tract Infections

“…SNP-based phylogenetic analysis with a tree-rooted at the midpoint showed that most (91%; 95/104) slaughterhouse isolates belonged to lineage G ( Figure 2 , panels A, B) and that a strain from slaughterhouse equipment was at the base of this lineage (bootstrap 100). In addition, the phylogenetic reconstruction including isolates from this study and other isolates from production and companion animals (including 2 pigs, 2 bovine, and 1 canine) and food ( 8 ) showed that most (3/5) animal isolates clustered together at a basal clade of lineage G (bootstrap 100) ( Appendix 2 Figure 2). Some clusters in the phylogenetic tree (e.g., G9) had slaughterhouse isolates at the base and UTI isolates at the tip.…”

“…The global S. saprophyticus collection we used included 299 isolates from humans collected in 7 countries during 1997–2017: 286 from UTIs, 12 from invasive disease, and 1 from colonization ( Appendix 1 Table 1). We also analyzed the genomes of S. saprophyticus for 38 isolates from 5 other countries: 35 isolates from human UTIs ( 8 ), 2 from human hand swabs ( 8 ), an isolate from Byzantine Troy ( 8 ), and ATCC 15305 ( 9 ), a previously investigated human UTI-causing isolate.…”

“…The local collection included isolates collected in Lisbon, Portugal, during 2016–2017: 128 human UTI isolates collected in 3 hospitals and 104 slaughterhouse isolates collected from equipment, pork samples, workers’ hands, and a pig’s rectum. In addition, we included 5 isolates from animals and 12 isolates from food used in other studies ( 8 ) ( Appendix 2 ).…”

“…Moreover, given the frequent bacterial contamination of meat through the meat-processing chain, meat and food are speculated to be sources of human gut colonization and human S. saprophyticus infection ( 6 ). Some studies have reported high genetic diversity among isolates from human infections, food products, and other sources ( 5 , 7 , 8 ). However, previous studies were performed with a limited number of isolates, which prevented the description of the global and local molecular epidemiology of S. saprophyticus .…”

Host-specialized fibrinogen-binding by a bacterial surface protein promotes biofilm formation and innate immune evasion

“…For example, uropathogenic Escherichia coli virulence has arisen due to mutations in the fimbrial adhesin FimH, promoting high affinity binding to the urinary epithelium [3]. Similarly, a single non-synonymous mutation in a fibronectin-binding autolysin of Staphylococcus saprophyticus , associated with a selective sweep, has been linked to the pathogenesis of urinary tract infection in humans [4]. Additionally, single amino acid substitutions in the fibronectin-binding protein A (FnBPA) of Staphylococcus aureus , are associated with cardiac device infections and bacteremia in humans due to increased binding affinity for fibronectin [5–7].…”