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For calculated initial antifungal therapy, knowledge on parallel and cross-resistances are vitally important particularly in the case of multiresistant isolates. Based on a strain collection of 1,062 yeast isolates from a German/Austrian multicentre study, susceptibility pattern analysis (SPA) was used to determine the proportion of parallel and cross-resistances to eight antifungal agents (AFAs) encompassing flucytosine, amphotericin B, azoles (fluconazole, voriconazole and posaconazole) and echinocandins (caspofungin, micafungin and anidulafungin). A total of 414 (39.0%) isolates were resistant for one or more of the AFAs. Resistance to one AFA was shown for 18.1% of all isolates. For 222 isolates (20.9%), resistance to two to seven AFAs was noted (7.7%; 7.7%; 3.6%; 1.0%; 0.7% and 0.2% to 2, 3, 4, 5, 6 and 7 antifungal compounds, respectively). Partial parallel resistances within the azole and echinocandin classes, respectively, were found for 81 (7.6%) and 70 (6.6%) isolates. Complete parallel resistances for azoles, echinocandins and combined for both classes were exhibited by 93 (8.8%), 18 (1.7%) and 6 (0.6%) isolates, respectively. Isolates displaying cross-resistances between azoles and echinocandins were infrequently found. Highly resistant isolates (resistance to ≥6 AFAs) were almost exclusively represented by Candida albicans. Highly standardized testing of AFAs in parallel and from the same inocula followed by SPA allows detailed insights in the prevalence and distribution of susceptibility patterns of microbial isolates., GMS Infectious Diseases; 4:Doc02

4,860 clinical yeast isolates (25 genera, 47 species) were tested in parallel to fluconazole, itraconazole, ketoconazole, and voriconazole. After re-evaluation of all species according to their current valid taxonomic denominations, the range of the top four of the dermatology, gynaecology and paediatrics associated species from superficial infections was similar to those isolated from other wards with mainly systemic/invasive infections. Candida albicans (44.7%) was the most frequent pathogen followed by C. glabrata, C. tropicalis, and C. parapsilosis. The MIC-assessment revealed for the ten-year test period an overall azole-susceptibility of about 75%, and ~80% for their associated ICUs. The overall susceptibility of the isolates from systemic and superficial infections to the four azoles was 79% and 80% respectively, and demonstrates a high in vitro activity. When two test periods (1998-2001 and 2002-2008) were compared by characteristic MIC values and multi-azole resistance, no significant increase could be detected in azole susceptibility/resistance over the two periods, respectively, over the total investigation period of ten years. This holds true when the characteristic MIC values were compared with those from different azole susceptibility studies from similar time periods and from different investigators around the world (1991 to 2010). With a new method, susceptibility pattern analysis for fungi, detailed information of multi-resistant microorganism populations could be obtained, and different characteristic resistance patterns in clinical yeast species detected. Although at a relatively low level, multi-resistance was seen in individual species populations demonstrating resistance to two (6.7%), three (4.4%), or all four (4%) azoles tested. A level of 4% and 2% fourfold parallel resistance was also determined in Candia spp. and non-Candida spp. derived of blood culture isolates.

Due to the Fourier-Transform Infrared Spectroscopy (FT-IR) of strain specific traits demonstrated to be a suitable and efficient method for diagnostic and epidemiological determinations for the yeasts Candida albicans, Exophiala dermatitidis and the chlorophylless algae of the genus Prototheca. FT-IR leads in a rapid and economical way to reproducible results according to the spectral differences of intact cells (IR-fingerprints). Different genera, species and sub-species respectively, different strains can be recognized and grouped into different clusters and subclusters. The FT-IR analysis of Candida albicans isolates (n = 150) of 22 newborns-at-risk of an intensive care unit showed, that 86% of the children were colonised with several (2-4) different strains in the oral cavities and faeces. Stationary cross-infections could definitely be determined. Exophiala dermatitidis isolates (n = 31), mostly isolated repetitively within a period of 3 years from sputa of patients suffering from cystic fibrosis could be characterized and grouped patient-specifically over the total sampling period. Of 6 from 8 patients (75%) their individual strains remain the same and could be tracked over the three years. Cross-infections during the stationary treatment could be clearly identified by FT-IR. The Prototheca isolate (n = 43) from live-stock and farm environment showed clear distinguishable clusters differentiating the species P. wickerhamii, P. zopfii and P. stagnora. In addition, the biotypes of P. zopfii could be distinguished, especially the subclusters of variants II and III. It could be demonstrated, that FT-IR is suitable for the routine identification and differentiation of yeasts and algae. However, in spite of the gain of knowledge by using FT-IR for the characterization of microorganisms, the conventional phenotyping and/or genetic analysis of yeast or algae strains cannot be replaced completely. For a final taxonomic classification a combination of conventional methods on FT-IR together with more sophisticated molecular genetic procedures is necessary.

Twenty-six hop bitter resins, some hitherto not investigated, were tested for antimicrobial activities. Gram-positive bacteria were much more sensitive than Gram-negative ones. The inhibitory effect against Bacillus subtilis 168 was measured by several methods and the general rule could be established that the antibiotic properties are mainly dependent on the hydrophobic parts of the molecules. Thus the acyl-lupuphenones (2-acyl-3, 5-4, 4′, 6-tri(3-methyl-2-butenyl)-cyclohexane-triones (1, 3, 5)) having three prenyl and one acyl side chain are the most active substances. Their minimum inhibitory concentration (MIC) increases from the capro (0.5 μM) to the aceto derivative (11 μM). Any substitution with hydrophilic functions or loss of hydrophobic groups causes reductions in biological activity. This is most evident with the corresponding acyl-phloroglucine precursors (2-acyl-1, 3, 5-trihydroxybenzenes) which lack the three prenyl side chains (MIC, 110 to 5050 μM respectively). Conversion of the central six-membered ring structure into a five-membered one results in additional losses of antimicrobial activity. These findings support the proposal that the lipophilic region of the cell membrane represents the target site for the hop bitter resins.

The bactericidal activity of the hop constituents lupulone, humulone, isohumulone and humulinic acid against Bacillus subtilis 168 is shown to result from primary membrane leakage. This process leads to complete inhibition of active transport of α-methyl-d-glucopyranoside and several amino acids into whole bacteria and isolated membrane vesicles within 5 min at 37°C at the corresponding minimal inhibitory concentrations of 1, 2, 25 and 250 μg/ml, respectively. Inhibition of the respiratory chain, of protein, RNA and DNA synthesis seems to be a secondary event.