Small proline-rich antimicrobial peptides (AMP) have attracted considerable interest, as they target specific intracellular bacterial components and do not act by lytic mechanisms. Here, a novel peptide, termed oncocin (VDKPPYLPRPRPPRRIYNR-NH(2)), is reported that was optimized for the treatment of Gram-negative pathogens. Its minimal inhibitory concentrations in tryptic soy broth medium ranged from 0.125 to 8 microg/mL for 34 different strains and clinical isolates of Enterobacteriaceae and nonfermenters, such as Escherichia coli , Pseudomonas aeruginosa , and Acinetobacter baumannii . Substitutions of two arginine residues by ornithine increased the half-lives in full mouse serum from about 20 min to greater than 180 min and the activity. Both optimized oncocin derivatives were neither toxic to human cell lines nor hemolytic to human erythrocytes. They could freely penetrate lipid membranes and were washed out completely without any sign of lytic activity, as assessed by quartz crystal microbalance. Fluorescence labeled peptides entered the periplasmic space within 20 min at room temperature and homogeneously stained E. coli within 50 min. In conclusion, the optimized oncocin represents a very promising candidate for future in vivo work and may serve as a novel lead compound for an antibacterial drug class.

The emergence of multiple-drug-resistant (MDR) bacterial pathogens in hospitals (nosocomial infections) presents a global threat of growing importance, especially for Gram-negative bacteria with extended spectrum β-lactamase (ESBL) or the novel New Delhi metallo-β-lactamase 1 (NDM-1) resistance. Starting from the antibacterial peptide apidaecin 1b, we have optimized the sequence to treat systemic infections with the most threatening human pathogens, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The lead compound Api88 enters bacteria without lytic effects at the membrane and inhibits chaperone DnaK at the substrate binding domain with a K(D) of 5 μmol/L. The Api88-DnaK crystal structure revealed that Api88 binds with a seven residue long sequence (PVYIPRP), in two different modes. Mice did not show any sign of toxicity when Api88 was injected four times intraperitoneally at a dose of 40 mg/kg body weight (BW) within 24 h, whereas three injections of 1.25 mg/kg BW and 5 mg/kg BW were sufficient to rescue all animals in lethal sepsis models using pathogenic E. coli strains ATCC 25922 and Neumann, respectively. Radioactive labeling showed that Api88 enters all organs investigated including the brain and is cleared through both the liver and kidneys at similar rates. In conclusion, Api88 is a novel, highly promising, 18-residue peptide lead compound with favorable in vitro and in vivo properties including a promising safety margin.

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BackgroundLyme disease, caused by various species of Borrelia, is transmitted by Ixodes ticks in North America and Europe. Studies have shown the genotype of Borrelia burgdorferi sensu stricto (s.s.) or the species of B. burgdorferi sensu lato (s.l.) affects the ability of the bacteria to cause local or disseminated infection in humans.Methodology/Principal FindingsWe used a multilocus PCR electrospray mass spectrometry assay to determine the species and genotype Borrelia from ticks collected in New York, Connecticut, Indiana, Southern Germany, and California and characterized isolates from parts of the United States and Europe. These analyses identified 53 distinct genotypes of B. burgdorferi sensu stricto with higher resolution than ospC typing. Genotypes of other members of the B. burgdorferi sensu lato complex were also identified and genotyped including B. afzelii, B. garinii, B. lusitaniae, B. spielmanii, and B. valaisiana. While each site in North America had genotypes unique to that location, we found genotypes shared between individual regions and two genotypes found across the United States. Significant B. burgdorferi s.s. genotypic diversity was observed between North America and Europe: only 6.6% of US genotypes (3 of 45) were found in Europe and 27% of the European genotypes (3 of 11) were observed in the US. Interestingly, 39% of adult Ixodes scapularis ticks from North America were infected with more than one genotype of B. burgdorferi s.s. and 22.2% of Ixodes ricinus ticks from Germany were infected with more than one genotype of B. burgdorferi s.l.Conclusions/SignificanceThe presence of multiple Borrelia genotypes in ticks increases the probability that a person will be infected with more than one genotype of B. burgdorferi, potentially increasing the risks of disseminated Lyme disease. Our study indicates that the genotypic diversity of Borrelia in ticks in both North America and Europe is higher then previously reported and can have potential clinical consequences.

Infection rates of Ixodes ticks with Borrelia miyamotoi in Europe and the United States vary greatly based upon location.