Hypervirulent Klebsiella pneumoniae (hvKp) is a variant that has been increasingly linked to severe, life-threatening infections including pyogenic liver abscess and bloodstream infections. HvKps belonging to the capsular serotypes K1 and K2 have been reported worldwide, however, very scarce studies are available on their genomics and virulence. In the current study, we report four hypermucoviscous extended-spectrum β-lactamase-producing hvKp clinical strains of capsular serotype K1 and K2 isolated from pus and urine of critically ill patients in tertiary care hospitals in Oman. These strains belong to diverse sequence types (STs), namely ST-23(K1), ST-231(K2), ST-881(K2), and ST-14(K2). To study their virulence, a Galleria mellonella model and resistance to human serum killing were used. The G. mellonella model revealed that the K1/ST-23 isolate was the most virulent, as 50% of the larvae died in the first day, followed by isolate K2/ST-231 and K2/ST-14, for which 75% and 50% of the larvae died in the second day, respectively. Resistance to human serum killing showed there was complete inhibition of bacterial growth of all four isolates by the end of the first hour and up to the third hour. Whole genome sequencing (WGS) revealed that hvKp strains display a unique genetic arrangement of k-loci. Whole-genome single-nucleotide polymorphism-based phylogenetic analysis revealed that these hvKp isolates were phylogenetically distinct, belonging to diverse clades, and belonged to different STs in comparison to global isolates. For ST-23(K1), ST-231(K2), ST-881(K2), and ST-14(K2), there was a gradual decrease in the number of colonies up to the second to third hour, which indicates neutralization of bacterial cells by the serum components. However, this was followed by a sudden increase of bacterial growth, indicating possible resistance of bacteria against human serum bactericidal activity. This is the first report from Oman detailing the WGS of hvKp clinical isolates and assessing their resistance and virulence genomics, which reinforce our understanding of their epidemiology and dissemination in clinical settings.

The genus Micropsalliota is a group of saprotrophic mushrooms, characterized by small to medium-sized basidiomata with fibrillose-squamulose or glabrous pilei, ellipsoid to amygdaliform or cymbiform basidiospores and cheilocystidia that vary in shape from clavate to ventricose or lageniform with more or less a capitate apex. In this study, we described a new species of Micropsalliota from southern Oman. Species description is based on morphological features of basidiomata and phylogenetic analyses of nuc ribosomal DNA internal transcribed spacer (ITS) and D1–D2 domains of the 28S region. The new species Micropsalliota ventricocystidiata is characterized by a medium-sized basidiomata, with plano-convex pileus, covered with reddish-brown squamules and basidiospores are ellipsoid to amygdaliform with acute apex in side view and oblong in face view, measuring 7.5–8.5 × 4.5–5 µm. Morphological comparison of M. ventricocystidiata with respect to other species of the genus is provided. We discussed that species of the genus can be divided into two groups based on their pileus morphology and basidiospores size.

Fuscoporia is a large genus with approximately 80 known species, distributed in various climates from subtropical to temperate, across the all continents except Antarctica. Divergence times of Fuscoporia was estimated for the first time, using BEAST v. 1.8.4, with three internal calibration points. Using three DNA regions: internal transcribed spacers (ITS1-5.8S-ITS2 = ITS), D1/D2 domain of large subunit of nuclear ribosomal DNA (28S) and translation elongation factor 1 alpha gene (TEF1α), the ancestral age of the genus was estimated around 77 Myr (million years). Molecular clock analyses also indicate the presence of six major clades, and the stem ages of each were estimated below 50 Myr. These six clades could be used for infrageneric classification of Fuscoporia. Further, we also discussed the distribution of Fuscoporia species in various climates. We hypothesized that the ancestral species of the genus evolved during late Cretaceous period with resupinate fruiting body in subtropics of Southern Asia. Furthermore, we also described a new species in the genus, Fuscoporia dhofarensis from Dhofar region, located in the southern part of Oman. Species description is based on morphological characteristics of fruiting body and phylogenetic analyses of ITS, 28S and TEF1α regions. The new species is characterized by a pileate fruiting body, with dimitic hyphal system, broadly ellipsoid basidiospores.

Staphylococcus epidermidis has been recently recognized as an emerging nosocomial pathogen. There are concerns over the increasing virulence potential of this commensal due to the capabilities of transferring mobile genetic elements to Staphylococcus aureus through staphylococcal chromosomal cassette (SCCmec) and the closely related arginine catabolic mobile element (ACME) and the copper and mercury resistance island (COMER). The potential pathogenicity of S. epidermidis, particularly from blood stream infections, has been poorly investigated. In this study, 24 S. epidermidis isolated from blood stream infections from Oman were investigated using whole genome sequence analysis. Core genome phylogenetic trees revealed one third of the isolates belong to the multidrug resistance ST-2. Genomic analysis unraveled a common occurrence of SCCmec type IV and ACME element predominantly type I arranged in a composite island. The genetic composition of ACME was highly variable among isolates of same or different STs. The COMER-like island was absent in all of our isolates. Reduced copper susceptibility was observed among isolates of ST-2 and ACME type I, followed by ACME type V. In conclusion, in this work, we identify a prevalent occurrence of highly variable ACME elements in different hospital STs of S. epidermidis in Oman, thus strongly suggesting the hypothesis that ACME types evolved from closely related STs.

Hypervirulent Klebsiella pneumoniae (hvKp) is a variant that has been increasingly linked to severe, life threatening infections including pyogenic liver abscess and bloodstream infections. HvKp belonging to the capsular serotypes K1 and K2 have been reported worldwide, however very scarce studies are available on the their genomics and virulence. In the current study we report four hypermucoviscous hvKp ESBL clinical strains of capsular serotype K1 and K2 isolated from pus and urine of critically ill patients in tertiary care hospitals in Oman. These strains belong to diverse sequence types (STs) namely ST-23(K1), ST-231(K2), ST-881(K2), and ST-14(K2). To study their virulence, Galleria Mellonella model and resistance to human serum killing were used. The G. mellonella model revealed that the K1/ST-23 isolate is the most virulent as 50% of the larvae died in the first day, followed by isolate K2/ST-231 for which 75% of the larvae died in the second day and isolate K2/ST-14 for which 50% of the larvae died in the second day. Resistance to human serum killing showed there was complete inhibition of bacterial growth of all four isolates by the end of the first hour and up to the third hour. For ST-23(K1), ST-231(K2), ST-881(K2), and ST-14(K2), there was a gradual decrease in the number of colonies up to the second to third hour, which indicates neutralization of bacterial cells by the serum components. However, this was followed by sudden increase of bacterial growth, indicating possible resistance of bacteria against human serum bactericidal activity. Whole genome sequencing (WGS) revealed that hvKp strains display unique genetic arrangement of k-loci. Whole genome SNP-based phylogenetic analysis revealed that these hvKp isolates are phylogenetically distinct, belonging to diverse clades and belong to different STs in comparison to global isolates. This is the first report from Oman detailing the WGS of hvKp clinical isolates and assessing their resistance and virulence genomics, which reinforce our understanding of their epidemiology and dissemination in clinical settings.