Deciphering Structure-Function Relationship Unveils Salt-Resistant Mode of Action of a Potent MRSA-Inhibiting Antimicrobial Peptide, RR14.

Multidrug-resistant (MDR) bacteria lead to considerable morbidity and mortality, threatening public health worldwide. In particular, infections of methicillin-resistant Staphylococcus aureus (MRSA) in hospital and community settings are becoming a serious health problem. Antimicrobial peptides (AMPs) are considered novel therapeutic targets against MDR bacteria. However, salt sensitivity reduces the bactericidal potency of AMPs, posing a major obstacle for their development as antibiotics. Thus, the design and development of salt-insensitive peptides with potent antibacterial activity is imperative. Here, we employed biochemical and biophysical examinations coupled with molecular modeling to systematically investigate the structure-function relationship of a novel salt-insensitive AMP, RR14. The secondary structure of RR14 was characterized as an apparent α-helix, a structure that confers strong membrane-permeabilizing ability targeting bacterial-mimetic membranes. Additionally, the bioactive structure of RR14 was determined in complex with dodecylphosphocholine (DPC) micelles, where it possesses a central α-helical segment comprising residues R4 to K13 (R4-K13). RR14 was observed to orient itself into the DPC micelle with its N terminus and the α-helical segment (I5-R10) buried inside the micelles, which is essential for membrane permeabilization and bactericidal activity. Moreover, the specific and featured arrangement of positively charged residues of RR14 on its amphipathic helical conformation has great potential to render its strong salt resistance ability. Our study explored the structure-function relationship of RR14, explaining its possible mode of action against MRSA and other microbes. The insights obtained are of great applicability for the development of new antibacterial agents. IMPORTANCE Many antimicrobial peptides have been observed to become inactive in the presence of high salt concentrations. To further develop new and novel AMPs with potent bactericidal activity and salt insensitivity, understanding the structural basis for salt resistance is important. Here, we employed biochemical and biophysical examinations to systematically investigate the structure-function relationship of a novel salt-insensitive AMP, RR14. RR14 was observed to orient itself into DPC micelles with the N terminus and the α-helical segment (I5-R10) buried inside the micelles, which is essential for membrane permeabilization and bactericidal activity. Moreover, the specific and featured arrangement of cationic residues of RR14 on its amphipathic helical conformation renders its strong salt resistance ability. The insights obtained are of great applicability for developing new antibacterial agents.

The Risks of Using Trimethoprim/Sulfamethoxazole in Patients with Renal and Cardiac Compromise.

The purpose of this article is to familiarize physicians with the risks of prescribing trimethoprim/sulfamethoxazole (TMP/SMX) for patients who have kidney or cardiac pathology, have hyperkalemia, or take other interacting medications. Although TMP/SMX is a drug that is frequently used to treat skin and soft-tissue infections of the leg and foot, particularly if methicillin-resistant Staphylococcus aureus is identified, it is not an innocuous antibiotic. Literature documenting the many adverse effects of TMP/SMX is reviewed. A case history is presented illustrating the association of TMP/SMX with the development of a life-threatening situation. Ways of avoiding these adverse events are discussed, and the use of safer antibiotics is recommended.

Antigen-Antibody Complex-Guided Exploration of the Hotspots Conferring the Immune-Escaping Ability of the SARS-CoV-2 RBD.

The COVID-19 pandemic resulting from the spread of SARS-CoV-2 spurred devastating health and economic crises around the world. Neutralizing antibodies and licensed vaccines were developed to combat COVID-19, but progress was slow. In addition, variants of the receptor-binding domain (RBD) of the spike protein confer resistance of SARS-CoV-2 to neutralizing antibodies, nullifying the possibility of human immunity. Therefore, investigations into the RBD mutations that disrupt neutralization through convalescent antibodies are urgently required. In this study, we comprehensively and systematically investigated the binding stability of RBD variants targeting convalescent antibodies and revealed that the RBD residues F456, F490, L452, L455, and K417 are immune-escaping hotspots, and E484, F486, and N501 are destabilizing residues. Our study also explored the possible modes of actions of emerging SARS-CoV-2 variants. All results are consistent with experimental observations of attenuated antibody neutralization and clinically emerging SARS-CoV-2 variants. We identified possible immune-escaping hotspots that could further promote resistance to convalescent antibodies. The results provide valuable information for developing and designing novel monoclonal antibody drugs to combat emerging SARS-CoV-2 variants.

An Evaluation of Off-Service Rotations in Podiatric Medicine and Surgery Residency Training.

Residency training in podiatric medicine and surgery includes 3years of comprehensive training. Complementing their podiatric medicine and surgery training, residents complete a series of required nonpodiatric, or off-service, rotations in a range of specialties. However, there has been a lack of formal investigation of these off-service rotation experiences. An online survey was developed and distributed to both program directors and residents nationwide. The survey instrument covered various aspects of off-service rotations, including rotation value, length, goals and objectives, activities, feedback, and resident satisfaction. In total, 122 of 222 directors responded and 151 of 243 residents responded. Resident responses reflected the impact of podiatric responsibilities during off-service rotations and the importance of hands-on, interactive, and dedicated learning opportunities during these rotations. Both similarities and differences were appreciated with regard to perceived rotation value between resident and director perspectives. Perceived satisfaction of certain rotations was correlated with rotation length, feedback, specific rotation activities, and whether residents received goals and objectives. Though perhaps neglected, the off-service rotation experience is an important part of the podiatric medical and surgical residency experience. Considering the perspectives of both directors and residents can be helpful in directing these experiences and in considering future changes.