Prevalence and characterization of azole-resistant Aspergillus fumigatus in patients with cystic fibrosis: a prospective multicentre study in Germany.

Objectives: Aspergillus fumigatus is the most prevalent filamentous fungus in the respiratory tract of patients with cystic fibrosis (CF). The aim of this prospective multicentre study was to investigate the prevalence of azole-resistant A. fumigatus (ARAF) in respiratory secretions from CF patients across Germany and to characterize ARAF isolates by phenotypic and molecular methods. Methods: Twelve tertiary care centres from Germany participated in the study. In total, 2888 A. fumigatus isolates from 961 CF patients were screened for ARAF by using azole-containing agar plates. Antifungal susceptibility testing of isolates was performed by broth microdilution according to EUCAST guidelines. Analysis of mutations mediating resistance was performed using PCR and sequencing of the cyp51A gene. Furthermore, genotyping by microsatellite PCR was performed. Results: Of a total of 2888 A. fumigatus isolates, 101 isolates from 51 CF patients were found to be azole resistant (prevalence per patient 5.3%). The Essen centre had the highest prevalence (9.1%) followed by Munich (7.8%), Münster (6.0%) and Hannover (5.2%). Most ARAF isolates (n = 89) carried the TR34/L98H mutation followed by eight G54E/R, one TR46/Y121F/T289A and one F219S mutation. In two isolates no mutation was found. Genotyping results showed no major clustering. Forty-five percent of CF patients with ARAF had previously received azole therapy. Conclusions: This is the first multicentre study analysing the prevalence of ARAF isolates in German CF patients. Because of a resistance rate of up to 9%, susceptibility testing of A. fumigatus isolates from CF patients receiving antifungal treatment should be part of standard diagnostic work-up.

In Vitro Activity of Isavuconazole against Rasamsonia Species.

The in vitro susceptibilities to the novel triazole isavuconazole and six other antifungal agents of a large collection of Rasamsonia isolates (n = 47) belonging to seven species were determined. Isavuconazole and voriconazole had no in vitro activity (MIC, >32 mg/liter) against isolates of the Rasamsonia argillacea species complex. The echinocandins were the most potent antifungal drugs against all of the isolates tested (minimum effective concentration, ≤0.19 mg/liter).

Adaptation of Stenotrophomonas maltophilia in cystic fibrosis: molecular diversity, mutation frequency and antibiotic resistance.

Due to the continuous exposure to a challenging environment and repeated antibiotic treatment courses, bacterial populations in cystic fibrosis (CF) patients experience selective pressure causing the emergence of mutator phenotypes. In this study we investigated the genotypic diversity, mutation frequency and antibiotic resistance of S. maltophilia isolates chronically colonizing CF patients. S. maltophilia was isolated from a total of 90 sputum samples, collected sequentially from 19 CF patients admitted between January 2008 and March 2012 at the University Hospital Essen, Germany. DNA fingerprinting by repetitive-sequence-based PCR revealed that 68.4% (n=13) of CF patients harbored different S. maltophilia genotypes during the 4-year study course. Out of 90 S. maltophilia isolates obtained from chronically colonized CF patients, 17.8% (n=16) were hypomutators, 27.7% (n=25), normomutators, 23.3% (n=21), weak hypermutators and 31.2% (n=28) strong hypermutators. We also found that mutation rates of the most clonally related genotypes varied over time with the tendency to become less mutable. Mutator isolates were found to have no significant increase in resistance against eight different antibiotics versus nonmutators. Sequencing of the mismatch repair genes mutL, mutS and uvrD revealed alterations that resulted in amino acid changes in their corresponding proteins. Here, we could demonstrate that several different S. maltophilia genotypes are present in CF patients and as a sign of adaption their mutation status switches over time to a less mutator phenotype without increasing resistance. These results suggest that S. maltophilia attempts to sustain its biological fitness as mechanism for long-term persistence in the CF lung.

In vitro activity of colistin as single agent and in combination with antifungals against filamentous fungi occurring in patients with cystic fibrosis.

Because published reports indicate that the antibiotic colistin (COL) has antifungal properties, this study investigated the antifungal in vitro activity of COL as single agent and in combination with the antifungal compounds voriconazole (VRC), caspofungin (CAS) and amphotericin B (AMB) against Scedosporium/Pseudallescheria spp., Exophiala dermatitidis and Geosmithia argillacea. In total, susceptibility was determined for 77 Scedosporium/Pseudallescheria spp., 82 E. dermatitidis and 17 G. argillacea isolates. The minimal inhibitory concentrations (MICs) of COL and the antifungals as single compound and in combination were determined with MIC test strips. Drug interactions were detected by crossing the MIC test strips at a 90º angle. The fractional inhibitory concentration index was used to categorise the drugs' interaction. The MIC50 value of COL was 12 µg ml(-1) for S. prolificans, 16 µg ml(-1) for P. apiosperma, 16 µg ml(-1) for P. boydii, 12 µg ml(-1) for E. dermatiditis and 6 µg ml(-1) for G. argillacea. VRC was the most active drug in combination without any antagonism with the exception of few P. boydii isolates. COL as single agent and in most combinations with antifungals exhibits in vitro antifungal activity against filamentous ascomycetes occurring in cystic fibrosis patients and may offer a novel therapeutic option, especially for multidrug-resistant S. prolificans.

Growth of aligned MWNT arrays using a micrometer scale local-heater at low ambient temperature.

Ambient room temperature growth of aligned multi-walled carbon nanotube arrays on micrometer scale local heaters is demonstrated. High growth rates of up to 8.8 microm per second have been achieved and the growth has been monitored in situ using optical microscopy. The growth starts and ends abruptly over the length of the local heater. The terminal length of the nanotubes shows a clear dependence on growth temperature and small inhomogeneities in temperature across the heater are seen to lead to interesting microstructure of the arrays. The activation energy for growth was seen to be consistent with earlier reports for acetylene growth of nanotubes on iron catalysts.

Practical modeling of Bayesian decision problems - exploiting deterministic relations.

The widespread use of influence diagrams to represent and solve Bayesian decision problems is still limited by the inflexibility and rather restrictive semantics of influence diagrams. We propose a number of extensions and adjustments to the definition of influence diagrams in order to make the practical use of influence diagrams more flexible and less restrictive. In particular, we describe how deterministic relations can be exploited to increase the flexibility and efficiency of representing and solving Bayesian decision problems. The issues addressed in the paper were motivated by the construction of a decision support system for mission management of unmanned underwater vehicles (UUVs).

Loss to follow-up among infants in a study of isoniazid prophylaxis (P1041) in South Africa.

OBJECTIVE: To assess risk factors for loss to follow-up (LFU) from the IMPAACT P1041 study, an isoniazid (INH) prophylaxis study conducted in southern Africa. DESIGN: Infants in two cohorts, human immunodeficiency virus-infected (HIV+) and HIV-exposed but non-infected (HIV-), were randomized to INH or placebo for 96 weeks. LFU was evaluated at week 96. RESULTS: Of 1351 infants, 12.9% were LFU (10.4% HIV+, 14.7% HIV-); 65% of the HIV+ cohort was asymptomatic. Among HIV+ infants, large household size (>6 vs. <4 members, P = 0.035) and presence of an elder (≥55 years, P = 0.05) were associated with better retention. Although attenuated in adjusted analysis, these associations held among HIV- infants. Among HIV- infants, having a younger mother increased the risk (P = 0.008) and maternal history of TB reduced the risk of LFU, the latter by nearly 70% (P = 0.048 univariate, 0.09 adjusted). LFU was largely due to inability to contact the participant (58% HIV+, 30% HIV-), and inability to attend the clinic and withdrawal of consent (HIV-). CONCLUSIONS: Household support was an important factor in participant retention, particularly for the non-HIV-infected cohort, as young maternal age was a risk factor for LFU. Retaining study participants from this mobile population can be challenging and may warrant additional support.