Biology subjects

Rossen, J. W.

Publications and source records attributed to Rossen, J. W..

3 recordsLinked to original sources

bioRxiv2019

Detection of AmpC β-lactamases in Escherichia coli using different screening agars

The aim of this study was to determine the performance of both cefotaxime and ceftazidime containing agars on the specificity and sensitivity for chromosomal AmpC-hyperproducing and plasmid AmpC harboring Escherichia coli compared to ESBL-producing E. coli and E. coli without ESBL, pAmpC or cAmpC hyperproduction. Second, we evaluated the influence of adding cefoxitin to these agars for detection of both chromosomal AmpC-hyperproducing and plasmid AmpC harboring E. coli.\n\nFour different homemade screening agars with cefotaxime (1mg/L), ceftazidime (1mg/L), cefotaxime (1mg/L) with cefoxitin (8mg/L), and ceftazidime (1mg/L) with cefoxitin (8mg/L) were compared to each other for the identification of AmpC producing E. coli. A total of 40 isolates with plasmid encoded AmpC {beta}-lactamases, 40 isolates with alterations in the promoter/attenuator region of the AmpC gene leading to hyperproduction of the {beta}-lactamase, 40 isolates with ESBL genes and 39 isolates lacking both a AmpC and ESBL genotype were used to test the four agars.\n\nThe sensitivity and specificity were 100% (95% confidence interval (95% CI) 96.1% to 100%) and 48.1% (95% CI 38.6%-60.2%), respectively, for the cefotaxime agar; 100% (95% CI 96.1% to 100%) and 49.41% (95% CI 39.8%-61.4%), respectively, for the ceftazidime agar; 96.3% (95% CI 89.1% to 99.2%) and 77.2% (95% CI 66.7%-85.2%) respectively, for the cefotaxime with cefoxitin agar; 98.8% (95% CI) 92.6% to 99.6%) and 81.0% (95% CI 70.9%-88.3%) respectively, for the ceftazidime agar with cefoxitin. The main reason for false-positive results were ESBL-harboring strains that grew on various agars; therefore, the specificity of each agar reported here was influenced mainly by the proportion of ESBL isolates tested. In conclusion addition of cefoxitin to cefotaxime and ceftazidime containing agars had little influence on sensitivity, but increased specificity for the detection of AmpC in E. coli.

microbiology↗

bioRxiv2019

The global phylogenetic landscape and nosocomial spread of the multidrug-resistant opportunist Stenotrophomonas maltophilia

Recent studies portend a rising global spread and adaptation of human- or healthcare-associated pathogens. Here, we analysed an international collection of the emerging, multidrug-resistant, opportunistic pathogen Stenotrophomonas maltophilia from 22 countries to infer population structure and clonality at a global level. We show that the S. maltophilia complex is divided into 23 monophyletic lineages, most of which harboured strains of all degrees of human virulence. Lineage Sm6 comprised the highest rate of human-associated strains, linked to key virulence and resistance genes. Transmission analysis identified potential outbreak events of genetically closely related strains isolated within days or weeks in the same hospitals.\n\nOne Sentence SummaryThe S. maltophilia complex comprises genetically diverse, globally distributed lineages with evidence for intra-hospital transmission.

genomics↗

bioRxiv2019

Revealing virulence potential of clinical and environmental Aspergillus fumigatus isolates using Whole-genome sequencing

Aspergillus fumigatus is an opportunistic airborne pathogen and one of the most common causative agents of human fungal infections. A restricted number of virulence factors have been described but none of them lead to a differentiation of the virulence level among different strains. In this study, we analyzed the whole-genome sequence of a set of A. fumigatus isolates from clinical and environmental origin to compare their genomes and to determine their virulence profiles. For this purpose, a database containing 244 genes known to be associated with virulence was built. The genes were classified according to their biological function into factors involved in thermotolerance, resistance to immune responses, cell wall structure, toxins and secondary metabolites, allergens, nutrient uptake and signaling and regulation. No difference in virulence profiles was found between clinical isolates causing an infection and a colonizing clinical isolate, nor between isolates from clinical and environmental origin. We observed the presence of genetic repetitive elements located next to virulence related gene groups, which could potentially influence their regulation. In conclusion, our genomic analysis reveals that A. fumigatus, independently of their source of isolation, are potentially pathogenic at the genomic level, which may lead to fatal infections in vulnerable patients. However, other determinants such as genetic variations in virulence related genes and host-pathogen interactions most likely influence A. fumigatus pathogenicity and further studies should be performed.\n\nImportanceAspergillus spp. infections are among the most clinically relevant fungal infections also presenting treatment difficulties due to increasing antifungal resistance. The lack of key virulence factors and a broad genomic diversity complicates the development of targeted diagnosis and novel treatment strategies. A widely spread variability in virulence has been reported for experimental, clinical and environmental isolates. Here we provide supporting evidence that members of this species are fully capable of establishing an infection in immunosuppressed hosts according to their virulence content at the genomic level. Due to the possible clinical complications, studies are urgently required linking strains virulent phenotype with the genotype to better understand the virulence activation of this important fungal pathogen.

microbiology↗