Comparative genomics reveals diverse capsular polysaccharide synthesis gene clusters in emerging Raoultella planticola

Whole Genome Sequencing of an Extensively Drug-Resistant Raoultella planticola Isolate Containing blaKPC-2, blaNDM-1, and blaCTX-M-15

Raoultella planticola harboring genes that confer resistance to antimicrobials, such as carbapenems, have been associated with severe infections in immunocompromised patients. In this study, we reported the first whole genome sequence of a Brazilian isolate of R. planticola and the genomic context of antibiotic resistance markers. By whole-genome sequencing (WGS) of a carbapenem-resistant R. planticola isolate, RpHUM1, we found 23 resistance-encoding genes belonging to 9 classes of antibiotics (aminoglycosides, β-lactams, fluoroquinolones, fosfomycin, macrolides, phenicols, sulfonamides, tetracycline, and diaminopyrimidine derivatives) and 3 plasmids (RpHUM1pEaer-4382s, RpHUM1_pFDAARGOS_440, and RpHUM1pRSF1010). This isolate coharbored the genes blaKPC-2, which is carried by the plasmid RpHUM1pEaer-4382s, and blaNDM-1 and blaCTX-M-15 all located in the accessory genome. In addition, these genes were associated with, at least, one mobile genetic element. This comprehensive knowledge is of great importance for implementation of control measures to prevent the rapid dissemination of this neglected microorganism and their genetic resistance background.

An X1α plasmid from a Salmonella enterica serovar Ohio isolate carrying a novel IS26-bounded tet(C) pseudo-compound transposon

The sequence of a conjugative plasmid, pSRC22-2, found in a multiply antibiotic resistant Salmonella enterica serovar Ohio isolate SRC22 originally cultured from swine in 1999, was determined. Plasmid pSRC22-2 has a copy number of approximately 40 and transfers tetracycline resistance at very high frequency. It was typed as IncX1 using the three typing schemes proposed for X-type plasmids, which utilize the replication region, iteron region and taxC conjugation gene and pSRC22-2 belongs to the X1α subgroup. The plasmid backbone, derived by removing mobile elements, is shared with pOLA52, which was the first fully sequenced IncX1 plasmid, and five other X1α plasmids. The pSRC22-2 backbone is interrupted by a complete copy of an IS903 isoform, partial copies of IS1 and IS903 on either side of a 5930 bp IS26-bounded pseudo-compound transposon (PCT), and a novel 256 bp miniature inverted repeat transposable element (MITE). The MITE belongs to the Tn3 family and was named MITESen1. The PCT, which carries a tet(C) tetracycline resistance determinant, is bounded by copies of a novel IS26 variant, IS26-v4, and was designated PTn6184. Comparison of PTn6184 with other tet(C)-carrying PCTs revealed that it can be derived from the largest, PTntet(C), via a two-step process that re-orders the central fragment and involves both an IS26-mediated event and homologous recombination. IS26-v4, which encodes a variant transposase, Tnp26 G184D, has appeared in only 46 entries in the GenBank non-redundant database.

Comparative Genomics Reveals Pathogenicity-Related Loci in Shewanella algae

Shewanella algae is an emerging marine zoonotic pathogen and accounts for considerable mortality and morbidity in compromised hosts. However, there is scarce literature related to the understanding of the genetic background of virulence determinants in S. algae. In this study, we aim to determine the occurrence of common virulence genes in S. algae using whole-genome sequence and comparative genomic analysis. Comparative genomics reveals putative-virulence genes related to bile resistance, chemotaxis, hemolysis, and motility. We detected the existence of hlyA, hlyD, and hlyIII involved in hemolysis. We also found chemotaxis gene cluster cheYZA operon and cheW gene. The results provide insights into the genetic basis underlying pathogenicity in S. algae.

Genomic investigation of emerging zoonotic pathogen Shewanella xiamenensis

Objective:

Shewanella xiamenensis is an emerging zoonotic pathogen commonly found in aquatic ecosystem. Clustered regularly interspaced short palindromic repeats (CRISPR) and (CRISPR)-associated gene systems act as adaptive immune system of prokaryotes. Recently, growing evidence suggested their role in bacterial virulence and resistance. Despite its medical importance, little is known about the genomic characteristics of S. xiamenensis.

Materials and Methods:

Strain ZYW6 was isolated from Epinephelus awoara. We sequenced the 16S rRNA gene and blast against the GenBank bacterial database. Antibiotic susceptibility tests and interpretation were performed by automatic VITEK 2 system. We extracted the genomic DNA with QIAGEN Genomic-tip 100/G kit and QIAGEN Genomic DNA Buffer Set. Whole-genome shotgun sequencing was performed using the Illumina MiSeq sequencer. To identify the CRISPR-Cas System in the genome of S. xiamenensis ZYW6, the Integrated Microbial Genomes and Microbiomes and CRISPRFinder were used.

Results:

We characterized the genome of a S. xiamenensis strain. The genome is 4,765,190 bp in length and encodes 4262 open-reading frames. Type I CRISPR-Cas system and serine biosynthesis genes were identified.

Conclusion:

Our results demonstrate the genetic structure of CRISPR-Cas system, l-serine synthesis, and oxacillinase in S. xiamenensis. The report of antibiotics resistance genes in the study might indicate a possible reservoir of antimicrobial drug resistance determinants in food animal, resulting in potential infection source. The findings provide insights into the structure and composition of CRISPR-Cas system in S. xiamenensis and foundation for future biological validation.