ABSTRACT
The threat of antibiotic resistance warrants the discovery of agents with novel antimicrobial mechanisms. Antimicrobial peptides (AMPs) directly disrupting bacterial membranes may overcome resistance to traditional antibiotics. AMP development for clinical use has been mostly limited to topical application to date. We developed a rational framework for systematically addressing this challenge using libraries composed of 86 novel Trp- and Arg-rich engineered peptides tested against clinical strains of the most common multidrug-resistant bacteria known as ESKAPE pathogens. Structure-function correlations revealed minimum lengths (as low as 16 residues) and Trp positioning for maximum antibacterial potency with mean minimum inhibitory concentration (MIC) of 2-4 µM and corresponding negligible toxicity to mammalian cells. Twelve peptides were selected based on broad-spectrum activity against both gram-negative and -positive bacteria and <25% toxicity to mammalian cells at maximum test concentrations. Most of the selected PAX remained active against the colistin-resistant clinical strains. Of the selected peptides, the shortest (the 16-residue E35) was further investigated for antibacterial mechanism and proof-of-concept in vivo efficacy. E35 killed an extensively-resistant isolate of Pseudomonas aeruginosa (PA239 from the CDC, also resistant to colistin) by irreversibly disrupting the cell membranes as shown by propidium iodide incorporation, using flow cytometry and live cell imaging. As proof of concept, in vivo toxicity studies showed that mice tolerated a systemic dose of up to 30 mg/kg peptide and were protected with a single 5 mg/kg intravenous (IV) dose against an otherwise lethal intraperitoneal injection of PA239. Efficacy was also demonstrated in an immune-compromised Klebsiella pneumoniae infection model using a daily dose of 4mg/kg E35 systemically for 2 days. This framework defines the determinants of efficacy of helical AMPs composed of only cationic and hydrophobic amino acids and provides a path for a potential departure from the restriction to topical use of AMPs toward systemic application.
ABSTRACT
In the era of a pandemic, the utilization of telemedicine is growing at a rapid speed. This new and necessary adaption in medicine is a threat to the basics of medicine which include the physical exam. A 72-year-old woman presents for a 1-week history of cervical neck discomfort. The patient was found to be febrile with initial physical exam nonrevealing due to patient preference of not taking off hospital gown. After blood cultures grew group A beta-hemolytic streptococcus and a computed tomography scan of the abdomen and pelvis with contrast demonstrated subtle bilateral renal hypodensities suggesting possible septic emboli, a more thorough physical exam was sought out which revealed a large rodent ulcer which the patient had been hiding from her family for 2 years. Transthoracic echocardiography was done which demonstrated a vegetation on the mitral valve confirming the diagnosis of endocarditis. The source of infection was the ulcer which was biopsied and found to be basal cell carcinoma. We present a unique case of endocarditis that was reliant on the physical exam to reveal the source of infection which was a rodent basal cell carcinoma ulcer. This case reminds physicians that at the forefront of telemedicine, the physical exam should not be forgotten.
