Background: Klebsiella variicola and K. quasipneumoniae are new species distinguishable from K. pneumoniae but they are often misidentified as K. pneumoniae in clinical settings. Several reports have demonstrated the possibility that the virulence factors and clinical features differ among these three phylogroups. In this study, we aimed to clarify whether there were differences in clinical and bacterial features between the three phylogroups isolated from patients with bloodstream infections (BSIs) in Japan. Methods: Isolates from all patients with BSIs caused by K. pneumoniae admitted to two hospitals between 2014 and 2017 (n = 119) were included in the study. Bacterial species were identified via sequence analysis, and their virulence factors and serotypes were analyzed via multiplex PCR results. Clinical data were retrieved from medical records. Results: Of the 119 isolates, 21 (17.7%) were identified as K. variicola and 11 (9.2%) as K. quasipneumoniae; K1 serotype was found in 16 (13.4%), and K2 serotype in 13 (10.9%). Significant differences in the prevalence of rmpA, iutA, ybtS, entB and kfu (p < 0.001), and allS genes (p < 0.05) were found between the three phylogroups. However, there were no significant differences in clinical features, including the 30-day mortality rate, between the three organisms, although K. variicola was more frequently detected in patients over 80 years old compared with other Klebsiella species (p < 0.005), and K. quasipneumoniae more frequently occurred in patients with malignancy (p < 0.05). Conclusions: Our findings demonstrated the differences in bacterial pathogenicity and clinical features among these three phylogroups. Further epidemiological studies into BSI caused by Klebsiella species are warranted.

Purpose . The new third-generation sequencing platform MinION is an attractive maintenance-free and disposable portable tool that can perform long-read and real-time sequencing. In this study, we validated this technology for the identification of pathogens from positive blood culture (BC) bottles. Methodology . A total of 38 positive BC bottles were collected from patients with bloodstream infections, and 18 isolates of Gram-negative (GN) bacteria and 20 isolates of Gram-positive (GP) bacteria were identified from these using 16S rRNA sequencing and then used in this study. DNA was extracted from each aliquot using an extraction protocol that combined glass bead beating and chemical lysis. Up to 200 ng of each purified DNA sample was processed for library preparation and whole-genome sequencing was performed on up to 12 samples through a single MinION flow cell. Results . All GN bacteria identifications made by MinION sequencing for 30 min using the What’s In My Pot? (WIMP) workflow via EPI2ME on the basis of the most frequent classified reads were consistent with those made by 16S rRNA sequencing. On the other hand, for GP bacteria specimens, the identification results for 16S rRNA sequencing and MinION were only in agreement in 12 out of 20 (60.0 %) cases. ARMA analysis was able to detect extended-spectrum β-lactamase (ESBL)-associated genes among various antimicrobial resistance-related genes. Conclusion . We demonstrated the potential of the MinION sequencer for the identification of GN bacteria from positive BC bottles and the confirmation of an ESBL phenotype. This innovative sequence technology and its application could lead to a breakthrough in the diagnosis of infectious diseases.

We herein report the first case of infective endocarditis attributable to Rothia aeria, which had a fatal outcome after cerebral hemorrhagic infarction and was not susceptible to vancomycin. If Gram-positive bacillary or filamentous bacteria that form white, coarse, dry colonies are detected, keeping the possibility of Rothia species in mind is advisable because members of this species can cause severe infections.

Differentiation between mitis group streptococci (MGS) bacteria in routine laboratory tests has become important for obtaining accurate epidemiological information on the characteristics of MGS and understanding their clinical significance. The most reliable method of MGS species identification is multilocus sequence analysis (MLSA) with seven house-keeping genes; however, because this method is time-consuming, it is deemed unsuitable for use in most clinical laboratories. In this study, we established a scheme for identifying 12 species of MGS (S. pneumoniae, S. pseudopneumoniae, S. mitis, S. oralis, S. peroris, S. infantis, S. australis, S. parasanguinis, S. sinensis, S. sanguinis, S. gordonii, and S. cristatus) using the MinION nanopore sequencer (Oxford Nanopore Technologies, Oxford, UK) with the taxonomic aligner “What's in My Pot?” (WIMP; Oxford Nanopore's cloud-based analysis platform) and Kraken2 pipeline with the custom database adjusted for MGS species identification. The identities of the species in reference genomes (n = 514), clinical isolates (n = 31), and reference strains (n = 4) were confirmed via MLSA. The nanopore simulation reads were generated from reference genomes, and the optimal cut-off values for MGS species identification were determined. For 31 clinical isolates (S. pneumoniae = 8, S. mitis = 17 and S. oralis = 6) and 4 reference strains (S. pneumoniae = 1, S. mitis = 1, S. oralis = 1, and S. pseudopneumoniae = 1), a sequence library was constructed via a Rapid Barcoding Sequencing Kit for multiplex and real-time MinION sequencing. The optimal cut-off values for the identification of MGS species for analysis by WIMP and Kraken2 pipeline were determined. The workflow using Kraken2 pipeline with a custom database identified all 12 species of MGS, and WIMP identified 8 MGS bacteria except S. infantis, S. australis, S. peroris, and S. sinensis. The results obtained by MinION with WIMP and Kraken2 pipeline were consistent with the MGS species identified by MLSA analysis. The practical advantage of whole genome analysis using the MinION nanopore sequencer is that it can aid in MGS surveillance. We concluded that MinION sequencing with the taxonomic aligner enables accurate MGS species identification and could contribute to further epidemiological surveys.

β-Lactamase-negative ampicillin-resistant Haemophilus influenzae is a common opportunistic pathogen of hospital- and community-acquired infections, harboring multiple single nucleotide polymorphisms in the ftsI gene, which codes for penicillin-binding protein-3. The objectives of this study were to perform comprehensive genetic analyses of whole regions of the penicillin-binding proteins in H. influenzae and to identify additional single nucleotide polymorphisms related to antibiotic resistance, especially to ampicillin and other cephalosporins. In this genome analysis of the ftsI gene in 27 strains of H. influenzae, 10 of 23 (43.5%) specimens of group III genotype β-lactamase-negative ampicillin-resistant H. influenzae were paradoxically classified as ampicillin-sensitive phenotypes. Unfortunately, we could not identify any novel mutations that were significantly associated with ampicillin minimum inhibitory concentrations in other regions of the penicillin-binding proteins, and we reconfirmed that susceptibility to β-lactam antibiotics was mainly defined by previously reported SNPs in the ftsI gene. We should also consider detailed changes in expression that lead to antibiotic resistance in the future because the acquisition of resistance to antimicrobials can be predicted by the expression levels of a small number of genes.