Antimicrobial peptides often show broad-spectrum activity due to a mechanism based on bacterial membrane disruption, which also reduces development of permanent resistance, a desirable characteristic in view of the escalating multidrug resistance problem. Host cell toxicity however requires design of artificial variants of natural AMPs to increase selectivity and reduce side effects. Kiadins were designed using rules obtained from natural peptides active against E. coli and a validated computational algorithm based on a training set of such peptides, followed by rational conformational alterations. In vitro activity, tested against ESKAPE strains (ATCC and clinical isolates), revealed a varied activity spectrum and cytotoxicity that only in part correlated with conformational flexibility. Peptides with a higher proportion of Gly were generally less potent and caused less bacterial membrane alteration, as observed by flow cytometry and AFM, which correlate to structural characteristics as observed by circular dichroism spectroscopy and predicted by molecular dynamics calculations.

Volatile compounds of hedge mustard (Sysimbrium officinale) have been investigated for the first time. Forthy-two compounds were identified after hydrodistillation (without or upon autolysis) after gas chromatography and gas chromatography/mass spectrometry analyses. In addition, after decoction and hydrolysis of O-glycosides, 18 volatile O-aglycones were identified. In general, the main volatiles found in hydrodistillates were: isopropyl isothiocyanate (27.6-48.9%), 2-methylpropanenitrile (0.5-18.8%), (Z)-hex-3-en-1-ol (0.5-18.0%), sec-butyl isothiocyanate (4.9-9.4%), (E)-hex-2-enal (3.5-8.6%), (Z)-hex-2-en-1-ol (0.3-8.4%), octanoic (0.5-8.6%) and dodecanoic acid (0-5.0%), 2-methylbutanenitrile (0-4.6%), dibutyl phthalate (0-4.5%), and ethyl linolenate (0-3.6%). The main volatile O-aglycones were: 2-phenylethyl alcohol (21.5%), 6,7-dehydro-7,8-dihydro-3-oxo-alpha-ionol (9.3%), eugenol (8.3%), benzyl alcohol (7.0%), ethyl vanillate (5.2%), 6-(tert-butyl)-5-methylphenol (5.1%), vanillin acetone (4.7%), ethyl 4-hydroxybenzoate (4.3%), and 2-hydroxy-beta-ionone (3.8%). All hydrodistillates exhibited great potential of antibacterial activity against five Gram-positive bacteria, nine ampicillin-resistant Gram-negative bacteria, and four fungi at a concentration of 500 microg/ml using the disc diffusion method.

Some Acinetobacter species have emerged as very important opportunistic pathogens in humans. We investigated Acinetobacter spp. from the polluted urban riverine environment in Croatia in regard to species affiliation, antibiotic resistance pattern, and resistance mechanisms. Considerable number of isolates produced acquired extended-spectrum β-lactamase(s) (ESBLs), CTX-M-15 solely or with TEM-116. By Southern blot hybridization, bla TEM-116 was identified on plasmids ca. 10, 3, and 1.2 kb in Acinetobacter junii, A. gandensis, and A. johnsonii. The bla TEM-116-carrying plasmid in A. gandensis was successfully transferred by conjugation to azide-resistant Escherichia coli J53. A. radioresistens isolate also carried an intrinsic carbapenemase gene bla OXA-133 with ISAba1 insertion sequence present upstream to promote its expression. Majority of ESBL-producing isolates harbored integrases intI1 and/or intI2 and the sulfamethoxazole resistance gene sul1. Almost all isolates had overexpressed resistance-nodulation-cell division (RND) efflux system, indicating that this mechanism may have contributed to multidrug resistance phenotypes. This is the first report of environmental CTX-M-15-producing Acinetobacter spp. and the first identification of CTX-M-15 in A. johnsonii, A. junii, A. calcoaceticus, A. gandensis, A. haemolyticus, and A. radioresistens worldwide. We identified, also for the first time, the environmental Acinetobacter-producing TEM ESBLs, highlighting the potential risk for human health, and the role of these bacteria in maintenance and dissemination of clinically important antibiotic resistance genes in community through riverine environments.

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