Stepwise emergence of azole, echinocandin and amphotericin B multidrug resistance in vivo in Candida albicans orchestrated by multiple genetic alterations.

OBJECTIVES: The objective of this study was to characterize the underlying molecular mechanisms in consecutive clinical Candida albicans isolates from a single patient displaying stepwise-acquired multidrug resistance. METHODS: Nine clinical isolates (P-1 to P-9) were susceptibility tested by EUCAST EDef 7.2 and Etest. P-4, P-5, P-7, P-8 and P-9 were available for further studies. Relatedness was evaluated by MLST. Additional genes were analysed by sequencing (including FKS1, ERG11, ERG2 and TAC1) and gene expression by quantitative PCR (CDR1, CDR2 and ERG11). UV-spectrophotometry and GC-MS were used for sterol analyses. In vivo virulence was determined in the insect model Galleria mellonella and evaluated by log-rank Mantel-Cox tests. RESULTS: P-1 + P-2 were susceptible, P-3 + P-4 fluconazole resistant, P-5 pan-azole resistant, P-6 + P-7 pan-azole and echinocandin resistant and P-8 + P-9 MDR. MLST supported genetic relatedness among clinical isolates. P-4 harboured four changes in Erg11 (E266D, G307S, G450E and V488I), increased expression of ERG11 and CDR2 and a change in Tac1 (R688Q). P-5, P-7, P-8 and P-9 had an additional change in Erg11 (A61E), increased expression of CDR1, CDR2 and ERG11 (except for P-7) and a different amino acid change in Tac1 (R673L). Echinocandin-resistant isolates harboured the Fks1 S645P alteration. Polyene-resistant P-8 + P-9 lacked ergosterol and harboured a frameshift mutation in ERG2 (F105SfsX23). Virulence was attenuated (but equivalent) in the clinical isolates, but higher than in the azole- and echinocandin-resistant unrelated control strain. CONCLUSIONS: C. albicans demonstrates a diverse capacity to adapt to antifungal exposure. Potentially novel resistance-inducing mutations in TAC1, ERG11 and ERG2 require independent validation

Rapid in situ conversion of late-stage volcanic materials to halloysite implicated in catastrophic dam failure, Hawaii

Ka Loko Dam, in Kauai, Hawaii, failed suddenly and catastrophically on March 14, 2006. The resulting breachwas marked by three topographic benches, the lowest of which exposed native volcanic deposits once resident in the dam foundation. These deposits were found to contain outcrops of a waxy, gel-like material that appeared to result from in situ weathering processes. This unusual material was found to be highly enriched in halloysite. Gravel-size pieces in the hydraulic fill of the embankment derived from these materials also exhibited significant in situ weathering and significant halloysite content. Engineers and geologists generally recognize that bedrock materials weather progressively into soil constituents over ‘geological time’, and that this process is accelerated in tropical environments. Still, the strength, stiffness and durability of bedrock, earth and embankment materials are not expected to vary significantly over the geologically short life of a dam. In the case of Ka Loko Dam, however, the volcaniclastic sediments that comprise the local bedrock experienced substantial in situ weathering over its geologically brief 115-year operational lifetime. Prolonged exposure to seepage of anoxic water weathered the sediments completely to saprolite, including weak, sensitive, fine, spherical halloysite.Philip Shaller, David Sykora, Macan Doroudian and G. Jock Churchma

Assessment of site effects in the Kathmandu valley, Nepal, during the 2015 Mw 7.8 Gorkha earthquake sequence using 1D and 2D numerical modelling

The paper reports on the results of 1D and 2D site response analyses carried out in the Kathmandu Valley, Nepal, in order to investigate how site effects influenced the seismic response during the 2015 Mw 7.8 Gorkha earthquake sequence. The mainshock and a Mw 6.6 aftershock, for which recordings at both rock and soil sites are available, were considered. First, 1D analyses were carried out for the Pulchowk soft soil site, where a borehole was drilled. The shear wave velocity profile was defined using several 2D seismic array surveys carried out in the valley and constrained by noise measurements at Pulchowk site; the nonlinear soil behavior was characterized by means of cyclic simple shear tests carried out on undisturbed soil samples. Both equivalent and nonlinear approaches were adopted in the 1D analyses. Overall, the 1D model was capable to capture some relevant features shown by mainshock recordings such as the de-amplification of medium-to-high frequencies. On the contrary, the unusual high spectral amplification at long periods (3–6 s) recorded during the mainshock was better captured by the 2D finite element analyses carried out on a 20 km-large cross section of the entire valley, thus supporting the hypothesis of the occurrence of basin effects. The paper contributes to the understanding of site effects in Kathmandu Valley for the implementation of seismic risk mitigation strategies in the area