Potent, specific MEPicides for treatment of zoonotic staphylococci

Abstract

Coagulase-positive staphylococci, which frequently colonize the mucosal surfaces of animals, also cause a spectrum of opportunistic infections including skin and soft tissue infections, urinary tract infections, pneumonia, and bacteremia. However, recent advances in bacterial identification have revealed that these common veterinary pathogens are in fact zoonoses that cause serious infections in human patients. The global spread of multidrugresistant zoonotic staphylococci, in particular the emergence of methicillin-resistant organisms, is now a serious threat to both animal and human welfare. Accordingly, new therapeutic targets that can be exploited to combat staphylococcal infections are urgently needed. Enzymes of the methylerythritol phosphate pathway (MEP) of isoprenoid biosynthesis represent potential targets for treating zoonotic staphylococci. Here we demonstrate that fosmidomycin (FSM) inhibits the first step of the isoprenoid biosynthetic pathway catalyzed by deoxyxylulose phosphate reductoisomerase (DXR) in staphylococci. In addition, we have both enzymatically and structurally determined the mechanism by which FSM elicits its effect. Using a forward genetic screen, the glycerol-3-phosphate transporter GlpT that facilitates FSM uptake was identified in two zoonotic staphylococci, Staphylococcus schleiferi and Staphylococcus pseudintermedius. A series of lipophilic ester prodrugs (termed PLOS PATHOGENS

Antimicrobial Prodrug Activation by the Staphylococcal Glyoxalase GloB

“…Lipophilic carboxy ester prodrug modification of these phosphonates dramatically increases antistaphylococcal potency, presumably through increased cellular penetration (Figure A,B). However, prodrug modifications block the direct engagement of inhibitors with their enzyme target . For this reason, we hypothesized that one or more staphylococcal esterases were required for intracellular prodrug activation (Figure A).…”

“…In our strategy, we took advantage of inhibitor pairs with the same target engagement with and without prodrug modification. We employed the phosphonate antibiotic ERJ, which selectively inhibits the intracellular enzyme deoxyxylulose phosphate reductoisomerase (DXR), and POM-ERJ, the bis-pivaloyloxymethyl prodrug form of ERJ, which inhibits intracellular DXR even though it has been shown to lack direct activity against purified recombinant DXR in vitro . We sought to enrich for staphylococcal strains that were resistant to prodrugged inhibitors (e.g., POM-ERJ) but remained sensitive to the parent phosphonate ERJ itself .…”

“…Similarly, nucleoside analogues are generally cell-impermeable, but their cognate prodrugs have much improved cellular penetration and antiviral efficacy, as seen in remdesivir (SARS-CoV-2), tenofovir disoproxil (HIV), and sofosbuvir (hepatitis C virus, HCV). − We have recently employed lipophilic prodrugging strategies to increase the efficacy of broad-spectrum antimicrobial phosphonate antibiotics. Notably, POM ester modification of a phosphonate isoprenoid biosynthesis inhibitor (ERJ) increases antistaphyloccal activity by 200- and 500-fold for S. schleiferi and S. pseudintermedius , respectively (Figure A,B) . Similar dramatic potency gains are observed for the same class of compounds against Mycobacterium tuberculosis , Yersinia pestis , Franciscella novicida , and the malaria parasite Plasmodium falciparum . ,− , …”

“…In our previous study, we identified phosphonate antibiotics with activity against zoonotic Staphylococci ( S. schleiferi and S. pseudintermedius ) . Lipophilic carboxy ester prodrug modification of these phosphonates dramatically increases antistaphylococcal potency, presumably through increased cellular penetration (Figure A,B).…”

From canines to humans: Clinical importance of Staphylococcus pseudintermedius

“…Additional areas of investigation involve repurposing antimicrobials ( e.g. , fosmidomycin) [ 61 ], and appropriation of nonantimicrobial agents has also garnered interest. For example, carprofen, a nonsteroidal anti-inflammatory drug, appears to restore doxycycline susceptibility in MRSP isolates carrying tetK , while chemotherapeutic agents commonly used in veterinary oncology ( e.g.…”