Methicillin-resistant Staphylococcus aureus (MRSA) is a World Health Organization’s high priority pathogen organism, with an estimated > 100,000 deaths worldwide in 2019. Thus, there is an unmet medical need for novel and resistance-breaking anti-infectives. The natural product Co-rallopyronin A (CorA), currently in preclinical development for filariasis, is efficacious against MRSA in vitro. In this study, we evaluated the pharmacokinetics of CorA after dosing in mice. Furthermore, we determined compound concentrations in target compartments, such as lung, kidney and thigh tissue, using LC-MS/MS. Based on the pharmacokinetic results, we evaluated the pharmacodynamic profile of CorA using the standard neutropenic thigh and lung infection models. We demonstrate that CorA is effective in both standard pharmacodynamic models. In addition to reaching effective levels in the lung and muscle, CorA was detected at high levels in the thigh bone. The data presented herein encourage the further exploration of the additional CorA indications treatment of MRSA- and methicillin-sensitive S. aureus- (MSSA) related infections.

Buried explosive material, e.g., landmines, represent a severe issue for human safety all over the world. Most explosives consist of environmentally hazardous chemicals like 2,4,6-trinitrotoluene (TNT), carcinogenic 2,4-dinitrotoluene (2,4-DNT) and related compounds. Vapors leaking from buried landmines offer a detection marker for landmines, presenting an option to detect landmines without relying on metal detection. 2,4-Dinitrotoluene (DNT), an impurity and byproduct of common TNT synthesis, is a feasible detection marker since it is extremely volatile. We report on the construction of a wireless, handy and cost effective 2,4-dinitrotoluene biosensor combining recombinant bioluminescent bacterial cells and a compact, portable optical detection device. This biosensor could serve as a potential alternative to the current detection technique. The influence of temperature, oxygen and different immobilization procedures on bioluminescence were tested. Oxygen penetration depth in agarose gels was investigated, and showed that aeration with molecular oxygen is necessary to maintain bioluminescence activity at higher cell densities. Bioluminescence was low even at high cell densities and 2,4-DNT concentrations, hence optimization of different prototypes was carried out regarding radiation surface of the gels used for immobilization. These findings were applied to sensor construction, and 50 ppb gaseous 2,4-DNT was successfully detected.

Corallopyronin A (CorA) is active against Gram-positive bacteria and targets the switch region of RNA polymerase. Because of the high frequency of mutation (FoM) leading to rifampicin resistance, we determined the CorA FoM in S. aureus using fluctuation analysis at 4 × minimum inhibitory concentration (MIC). Resistant mutants were characterized. S. aureus strains HG001, Mu50, N315, and USA300 had an MIC of 0.25 mg/L. The median FoM for CorA resistance was 1.5 × 10⁻⁸, 4.5-fold lower than the median FoM of 6.7 × 10⁻⁸ for rifampicin, and was reflected in a 4-fold lower mutation rate for CorA than rifampicin (6 × 10⁻⁹ for CorA vs. 2.5 × 10⁻⁸ for rifampicin). In CorA-resistant/rifampicin-sensitive strains, the majority of amino acid exchanges were S1127L in RpoB or K334N in RpoC. S. aureus Mu50, a rifampicin-resistant clinical isolate, yielded two further exchanges targeting amino acids L1131 and E1048 of the RpoB subunit. The plating of >10¹¹ cells on agar containing a combination of 4 × MIC of rifampicin and 4 × MIC of CorA did not yield any growth. In conclusion, with proper usage, e.g., in combination therapy and good antibiotic stewardship, CorA is a potential antibiotic for treating S. aureus infections.

Tyromyces floriformis, a potent fungal sesquiterpene producer, was grown Cerrena unicolor, as a model organism in submerged culture to search for chemicals affecting sesquiterpene biosynthesis in vitro. Thirty-one sesquiterpenes and sesquiterpenoids were identified in the supernatant, among them the fruity α-ylangene as the main volatile. Additives, such as some polysaccharides or lipids, did not affect the qualitative product spectrum but strongly affected the quantitative synthesis. Rye arabinoxylan and other polysaccharides, such as chitin, starch, and agarose, almost blocked the synthesis of α-ylangene. Single addition of the building blocks of arabinoxylan, arabinose, xylose, or ferulic acid showed no inhibitory effect, whereas 0.05% (w/v) 3²-α-l-arabinofuranosyl-xylobiose and larger oligosaccharides resulted in a significant suppression. In contrast, addition of acetyl donors boosted the α-ylangene concentration by 1 order of magnitude up to >40 mg L⁻¹. Both increased as well as decreased α-ylangene concentrations correlated with the intracellular sesquiterpene cyclase activity. Similar experiments using submerged cultured Cerrena unicolor, Postia placenta, and Coprinopsis cinerea showed that the additives affected fungal sesquiterpenoid synthesis differently. Whereas the addition of acetyl donors boosted the synthesis in all biphasic cultures, it was inhibited by polysaccharides in fungi preferably interacting with lignified plants. In contrast, Cerrena unicolor, known for a symbiotic lifestyle with wasps, responded by forming higher concentrations of the possibly insect-attracting sesquiterpenes.