Modulation of the activity of moxifloxacin and solithromycin in an in vitro pharmacodynamic model of Streptococcus pneumoniae naive and induced biofilms

Insights into the molecular interactions between urease subunit gamma from MRSA and drugs: an integrative approach by STD-NMR and molecular docking studies

Staphylococcus aureus, an important human pathogen, is developing resistance against a wide range of antibiotics. The antibiotic resistance in S. aureus has created the need to identify new drug targets, and to develop new drugs candidates. In the current study, urease subunit gamma from Methicillin Resistant Staphylococcus aureus (MRSA 252) was studied as a potential drug target, through protein-ligand interactions. Urease is the main virulence factor of MRSA, it catalyzes the conversion of urea into ammonia that is required for the survival of bacteria during acid stress. Its subunits and accessory proteins can serve as targets for drug discovery and development. Present study describes the cloning, expression, and purification of urease subunit gamma from MRSA 252. This was followed by screening of 100 US-FDA approved drugs against this protein using STD-NMR spectroscopy and among them, 15 drugs showed significant STD effects. In silico studies predicted that these drugs interacted mainly via non-covalent interactions, such as hydrogen bond, aromatic hydrogen bonding, π-π stacking, π-cation interactions, salt bridges, and halogen bonding. The thermal stability of UreA in the presence of these interacting drugs was evaluated using differential scanning fluorimetry (DSF), which revealed a significant effect on the T m of UreA. Additionally, the inhibitory effects of these drugs on urease activity were assessed using a urease inhibition assay with Jack bean urease. The results showed that these drugs possess enzyme inhibitory activity, potentially impacting the survival of S. aureus. These hits need further biochemical and mechanistic studies to validate their therapeutic potential against the MRSA infections.

Widening the antimicrobial spectrum of esters of bicyclic amines: In vitro effect on gram-positive Streptococcus pneumoniae and gram-negative non-typeable Haemophilus influenzae biofilms

Antibiotic resistance is a global current threat of increasing importance. Moreover, biofilms represent a medical challenge since the inherent antibiotic resistance of their producers demands the use of high doses of antibiotics over prolonged periods. Frequently, these therapeutic measures fail, contributing to bacterial persistence, therefore demanding the development of novel antimicrobials. Esters of bicyclic amines (EBAs), which are strong inhibitors of Streptococcus pneumoniae growth, were initially designed as inhibitors of pneumococcal choline-binding proteins on the basis of their structural analogy to the choline residues in the cell wall. However, instead of mimicking the characteristic cell chaining phenotype caused by exogenously added choline on planktonic cultures of pneumococcal cells, EBAs showed an unexpected lytic activity. In this work we demonstrate that EBAs display a second, and even more important, function as cell membrane destabilizers. We then assayed the inhibitory and disintegrating activity of these molecules on pneumococcal biofilms. The selected compound (EBA 31) produced the highest effect on S. pneumoniae (encapsulated and non-encapsulated) biofilms at very low concentrations. EBA 31 was also effective on mixed biofilms of non-encapsulated S. pneumoniae plus non-typeable Haemophilus influenzae, two pathogens frequently forming a self-produced biofilm in the human nasopharynx. These results support the role of EBAs as a promising alternative for the development of novel, broad-range antimicrobial drugs encompassing both Gram-positive and Gram-negative pathogens.

Modulating antibiotic activity towards respiratory bacterial pathogens by co-medications: a multi-target approach

Non-antibiotic drugs can modulate bacterial physiology and/or antibiotic activity, opening perspectives for innovative therapeutic strategies. Focusing on respiratory pathogens and considering in vitro, in vivo, and clinical data, here we examine the effect of these drugs on the expression of resistance mechanisms, biofilm formation, and intracellular survival, as well as their influence on the activity of antibiotics on bacteria. Beyond the description of the effects observed, we also comment on concentrations that are active and discuss the mechanisms of drug-drug or drug-target interactions. This discussion should be helpful in defining useful targets for adjuvant therapy and establishing the corresponding pharmacophores for further drug fine-tuning.