New synthetic antibiotics for the treatment of Enterococcus and Campylobacter infection

Berkeleylactones and a Citreohybriddione Analogue from Penicillium turbatum

In 2017 we reported the isolation and characterization of berkeleylactones A-H and A26771B from a coculture of two extremophilic Penicillium sp. isolated from an acid mine waste lake. Berkeleylactone A exhibited potent activity against several strains of multi-drug-resistant Staphylococcus aureus and Bacillus anthracis. A26771B, which is related to the berkeleylactones, also exhibited antibiotic activity. Although the berkeleylactones were novel compounds, A26771B was originally isolated by scientists at Eli Lilly Company from P. turbatum and reported in1977. We recently obtained P. turbatum and grew it in axenic culture. We isolated five new berkeleylactones (2 and 4-7), two berkeley-γ-lactones (8 and 9), and citreohybriddional (10), as well as the known compounds A26771B (1), berkeleylactone E (3), and gliovictin. The structures of the novel compounds were deduced from analysis of spectral data. Compounds 2 and 4 -7 are 16-membered macrolides, while 8 and 9 are γ-lactones that share the hexadecanoic acid skeleton. A26771B (1) and berkeleylactone I (2) were active against several strains of Staphylococcus aureus, including four multi-drug-resistant strains. Berkeleylactone N (8) was active only against Streptococcus pyogenes.

In vitro activity of fosfomycin against Campylobacter isolates from poultry and wild birds

Fosfomycin is a broad-spectrum antibiotic with the activity against both Gram-positive and Gram-negative pathogens by inhibiting the bacterial cell wall synthesis. Given the potential therapeutic efficacy of fosfomycin against Campylobacter spp., the aim of the present study was to determine the in vitro fosfomycin susceptibility of Campylobacter isolates from avian sources including poultry and wild birds. A total of eight (1.8%) strains of Campylobacter including five C. jejuni strains isolated from ducks and three C. coli strains isolated from chickens and duck showed resistance to fosfomycin, with MICs ranging from 64 to ≥ 256 μg/mL. The extent of fosfomycin resistance was 0%, 0.9% and 3.9% in wild birds, chicken and ducks respectively. The MIC50, MIC90, and MIC100 values were 8, 32, and 32 μg/mL respectively in wild bird, 32, 32, and 64 μg/mL respectively in chicken, and 32, 32, and ≥ 256 μg/mL respectively in ducks. All eight fosfomycin-resistant Campylobacter strains were multidrug resistant; six were also resistant to fluoroquinolones, ampicillin, and tetracycline, and two were also resistant to fluoroquinolones, ampicillin, tetracycline, and macrolides. However, the fosfomycin resistance gene fosXCC was not detected in the eight fosfomycin-resistant strains. Because food animals can harbor fosfomycin-resistant Campylobacter and transmit them to humans, greater efforts are needed to monitor the prevalence of fosfomycin resistance in Campylobacter strains isolated from such animals.

The Berkeleylactones, Antibiotic Macrolides from Fungal Coculture

A carefully timed coculture fermentation of Penicillium fuscum and P. camembertii/clavigerum yielded eight new 16-membered-ring macrolides, berkeleylactones A-H (1, 4, 6-9, 12, 13), as well as the known antibiotic macrolide A26771B (5), patulin, and citrinin. There was no evidence of the production of the berkeleylactones or A26771B (5) by either fungus when grown as axenic cultures. The structures were deduced from analyses of spectral data, and the absolute configurations of compounds 1 and 9 were determined by single-crystal X-ray crystallography. Berkeleylactone A (1) exhibited the most potent antimicrobial activity of the macrolide series, with low micromolar activity (MIC = 1-2 μg/mL) against four MRSA strains, as well as Bacillus anthracis, Streptococcus pyogenes, Candida albicans, and Candida glabrata. Mode of action studies have shown that, unlike other macrolide antibiotics, berkeleylactone A (1) does not inhibit protein synthesis nor target the ribosome, which suggests a novel mode of action for its antibiotic activity.

Synthesis and antibacterial evaluation of some teicoplanin pseudoaglycon derivatives containing alkyl- and arylthiosubstituted maleimides

Bis-alkylthio maleimido derivatives have been prepared from teicoplanin pseudoaglycon by reaction of its primary amino group with N-ethoxycarbonyl bis-alkylthiomaleimides. Some of the new derivatives displayed excellent antibacterial activity against resistant bacteria.