Complete genome analysis of clinical Shigella strains reveals plasmid pSS1653 with resistance determinants: a triumph of hybrid approach

Diagnosis and treatment of refractory infectious diseases using nanopore sequencing technology: Three case reports

BACKGROUND

Infectious diseases are still one of the greatest threats to human health, and the etiology of 20% of cases of clinical fever is unknown; therefore, rapid identification of pathogens is highly important. Traditional culture methods are only able to detect a limited number of pathogens and are time-consuming; serologic detection has window periods, false-positive and false-negative problems; and nucleic acid molecular detection methods can detect several known pathogens only once. Three-generation nanopore sequencing technology provides new options for identifying pathogens.

CASE SUMMARY

Case 1: The patient was admitted to the hospital with abdominal pain for three days and cessation of defecation for five days, accompanied by cough and sputum. Nanopore sequencing of the drainage fluid revealed the presence of oral-like bacteria, leading to a clinical diagnosis of bronchopleural fistula. Cefoperazone sodium sulbactam treatment was effective. Case 2: The patient was admitted to the hospital with fever and headache, and CT revealed lung inflammation. Antibiotic treatment for Streptococcus pneumoniae, identified through nanopore sequencing of cerebrospinal fluid, was effective. Case 3: The patient was admitted to our hospital with intermittent fever and an enlarged neck mass that had persisted for more than six months. Despite antibacterial treatment, her symptoms worsened. The nanopore sequencing results indicate that voriconazole treatment is effective for Aspergillus brookii. The patient was diagnosed with mixed cell type classical Hodgkin's lymphoma with infection.

CONCLUSION

Three-generation nanopore sequencing technology allows for rapid and accurate detection of pathogens in human infectious diseases.

CRISPR-cas heterogeneity and plasmid incompatibility types in relation to virulence determinants of Shigella

Introduction. Virulence factors (VFs) are the most potent weapon in the molecular armoury of Shigella . In bacteria, the mobile genetic elements (MGEs) are contributors to the evolution of different types of clustered regularly interspaced short palindromic repeats-CRISPR associated genes (CRISPR-cas) variants and plasmid incompatibility types. The present study explored the virulence potential of Shigella in relation to the CRISPR-cas pattern and incompatibility types among the isolates.

Hypothesis/Gap Statement. The profile of the CRISPR-cas systems among clinical isolates of Shigella in India has not been reported earlier. Limited knowledge is available on the pattern of plasmid incompatibility groups among clinical isolates Shigella . The bias is always towards studying the genetic elements associated with AMR, but the present study highlights CRISPR-cas and incompatibility types among Shigella in association with virulence.

Aim. We aimed to investigate the distribution of virulence factors, CRISPR-cas pattern followed by plasmid incompatibility types among Shigella isolates.

Methodology. Between 2012–2017, a total of 187 isolates of Shigella were included in the study. The virulence genes' distribution was carried out. CRISPR-cas profiling followed by analysis of the repeats and spacers was carried out. PCR-based replicon typing was used to determine the incompatibility types. The interplay was statistically determined using STATA.

Results. The distribution of virulence genes showed varied pattern with ipaH present in all the isolates followed by ompA (93.6 %), virF (66.8 %), ial and sen (60.4 %), set1A (39.6 %) and set1B (39 %). CRISPR 1, CRISPR 3 and Cas6-Cas5 region were dominantly conserved. Twenty-two types of spacers were identified. The CRISPR3 repeat appeared to have a highly conserved sequence. CRISPR2 being the least common CRISPR type showed a strong association with an array of virulence genes (ial-set1A-set1B-virF) while CRISPR1 being the most dominant showed the least association with virulence genes (sen-virF). The dominant plasmids were found to be belonging to the inc FII group. The incompatibility groups FII, IncIγ, U, FIIS, FIIK, K, A/C, I1alpha was found to be associated with a greater number of virulence genes.

Conclusion. The isolates showed increasing diversity in their gene content that contributes to increasing heterogeneity among the isolates, which is a known virulence strategy among pathogens.

First Comparative Analysis of Clostridium septicum Genomes Provides Insights Into the Taxonomy, Species Genetic Diversity, and Virulence Related to Gas Gangrene

Clostridium septicum is a Gram-positive, toxin-producing, and spore-forming bacterium that is recognized, together with C. perfringens, as the most important etiologic agent of progressive gas gangrene. Clostridium septicum infections are almost always fatal in humans and animals. Despite its clinical and agricultural relevance, there is currently limited knowledge of the diversity and genome structure of C. septicum. This study presents the complete genome sequence of C. septicum DSM 7534T type strain as well as the first comparative analysis of five C. septicum genomes. The taxonomy of C. septicum, as revealed by 16S rRNA analysis as well as by genomic wide indices such as protein-based phylogeny, average nucleotide identity, and digital DNA–DNA hybridization indicates a stable clade. The composition and presence of prophages, CRISPR elements and accessory genetic material was variable in the investigated genomes. This is in contrast to the limited genetic variability described for the phylogenetically and phenotypically related species Clostridium chauvoei. The restriction-modification (RM) systems between two C. septicum genomes were heterogeneous for the RM types they encoded. C. septicum has an open pangenome with 2,311 genes representing the core genes and 1,429 accessory genes. The core genome SNP divergence between genome pairs varied up to 4,886 pairwise SNPs. A vast arsenal of potential virulence genes was detected in the genomes studied. Sequence analysis of these genes revealed that sialidase, hemolysin, and collagenase genes are conserved compared to the α-toxin and hyaluronidase genes. In addition, a conserved gene found in all C. septicum genomes was predicted to encode a leucocidin homolog (beta-channel forming cytolysin) similar (71.10% protein identity) to Clostridium chauvoei toxin A (CctA), which is a potent toxin. In conclusion, our results provide first, valuable insights into strain relatedness and genomic plasticity of C. septicum and contribute to our understanding of the virulence mechanisms of this important human and animal pathogen.

Acquisition and loss of CTX-M plasmids in Shigella species associated with MSM transmission in the UK

Shigellosis in men who have sex with men (MSM) is caused by multidrug resistant Shigellae, exhibiting resistance to antimicrobials including azithromycin, ciprofloxacin and more recently the third-generation cephalosporins. We sequenced four bla_CTX-M-27-positive MSM Shigella isolates (2018–20) using Oxford Nanopore Technologies; three S. sonnei (identified as two MSM clade 2, one MSM clade 5) and one S. flexneri 3a, to explore AMR context. All S. sonnei isolates harboured Tn7/Int2 chromosomal integrons, whereas S. flexneri 3a contained the Shigella Resistance Locus. All strains harboured IncFII pKSR100-like plasmids (67-83kbp); where present bla_CTX-M-27 was located on these plasmids flanked by IS26 and IS903B, however bla_CTX-M-27 was lost in S. flexneri 3a during storage between Illumina and Nanopore sequencing. IncFII AMR regions were mosaic and likely reorganised by IS26; three of the four plasmids contained azithromycin-resistance genes erm(B) and mph(A) and one harboured the pKSR100 integron. Additionally, all S. sonnei isolates possessed a large IncB/O/K/Z plasmid, two of which carried aph(3’)-Ib/aph(6)-Id/sul2 and tet(A). Monitoring the transmission of mobile genetic elements with co-located AMR determinants is necessary to inform empirical treatment guidance and clinical management of MSM-associated shigellosis.

Complete Genome Analysis of Campylobacter jejuni subsp. jejuni Isolated from Bloodstream Infection

We report here the complete genome analysis of a clinical Campylobacter jejuni strain sequenced by a hybrid assembly approach. A hybrid assembly approach provided a complete genome sequence of C. jejuni that contains a 1,681,375-bp chromosome and 47,467-bp plasmid carrying various virulence and antimicrobial resistance determinants.