IS 1294 Reorganizes Plasmids in a Multidrug-Resistant Escherichia coli Strain

The increasing resistance to β-lactams and aminoglycoside antibiotics, mainly due to extended-spectrum β-lactamases (ESBLs) and 16S rRNA methylase genes, is becoming a serious problem in Gram-negative bacteria. Plasmids, as the vehicles for resistance gene capture and horizontal gene transfer, serve a key role in terms of antibiotic resistance emergence and transmission.

First Report of an Extensively Drug-Resistant ST23 Klebsiella pneumoniae of Capsular Serotype K1 Co-Producing CTX-M-15, OXA-48 and ArmA in Spain

An extensively drug-resistant (XDR) Klebsiella pneumoniae isolate MS3802 from a tracheostomy exudate was whole-genome sequenced using MiSeq and Oxford Nanopore MinION platforms in order to identify the antimicrobial resistance and virulence determinates and their genomic context. Isolate MS3802 belonged to the clone ST23 and presented a capsular serotype K1, associated with hypervirulent K. pneumoniae (hvKp) isolates. The isolate harboured a chromosomally encoded blaCTX-M-15 gene and contained a large IncHI1B hybrid virulence/resistance plasmid carrying another copy of the blaCTX-M-15 and the virulence factors iucABCD-iutA, iroBCDN, rmpA and rmpA2. The carbapenemase gene blaOXA-48 was found in a Tn1999-like transposon and the 16S rRNA methylase armA gen located in the vicinity of other antibiotic-resistant genes on an IncM2 plasmid. This study represents, to the best of our knowledge, the first description of a blaCTX-M-15-, blaOXA-48- and armA-harbouring K. pneumoniae of ST23 and capsular serotype K1 in Spain. Our report emphasizes the importance of implementing new surveillance strategies to monitor the risk of emergence and spread of such XDR and hypervirulent K. pneumoniae isolates.

Emergence of 16S rRNA Methylase Gene rmtB in Salmonella Enterica Serovar London and Evolution of RmtB-Producing Plasmid Mediated by IS26

This study aimed to characterize 16S rRNA methylase genes among Salmonella and to elucidate the structure and evolution of rmtB-carrying plasmids. One hundred fifty-eight Salmonella isolates from one pig slaughterhouse were detected as containing 16S rRNA methylase genes; two (1.27%) Salmonella London isolates from slaughtered pigs were identified to carry rmtB. They were resistant to gentamicin, amikacin, streptomycin, ampicillin, tetracycline, florfenicol, ciprofloxacin, and sulfamethoxazole/trimethoprim. The complete sequences of RmtB-producing isolates were obtained by PacBio single-molecule real-time sequencing. The isolate HA1-SP5 harbored plasmids pYUHAP5-1 and pYUHAP5-2. pYUHAP5-1 belonged to the IncFIBK plasmid and showed high similarity to multiple IncFIBK plasmids from Salmonella London in China. The rmtB-carrying plasmid pYUHAP5-2 contained a typical IncN-type backbone; the variable region comprising several resistance genes and an IncX1 plasmid segment was inserted in the resolvase gene resP and bounded by IS26. The sole plasmid in HA3-IN1 designated as pYUHAP1 was a cointegrate of plasmids from pYUHAP5-1-like and pYUHAP5-2-like, possibly mediated by IS26 via homologous recombination or conservative transposition. The structure differences between pYUHAP1 and its corresponding part of pYUHAP5-1 and pYUHAP5-2 may result from insertion, deletion, or recombination events mediated by mobile elements (IS26, ISCR1, and ISKpn43). This is the first report of rmtB in Salmonella London. IncN plasmids are efficient vectors for rmtB distribution and are capable of evolving by reorganization and cointegration. Our results further highlight the important role of mobile elements, particularly IS26, in the dissemination of resistance genes and plasmid evolution.

SCREENING FOR 16S RIBOSOMAL RNA METHYLASES (armA, RmtB & RmtC) GENE IN CLINICAL ISOLATES OF ENTEROBACTERIAECEAE FROM A TERTIARY CARE HOSPITAL IN SOUTH INDIA

Gram-negative bacilli may commonly produce aminoglycoside modifying enzymes. However, any one of these enzymes alone cannot confer resistance to all commonly used aminoglycosides because of their narrower substrate specificities(3,13).But ,the mechanism of resistance mediated by 16S rRNA methylases that methylates residue G1405 is the very high level of resistance to all parenterally formulated aminoglycosides (MIC>128ug/ml) commonly used (16). Screening for 16S rRNA methylase producing organisms has become an essential measure to be taken for epidemiological as well as diagnostic purposes when nosocomial spread of such bacteriae is suspected. Only by early identification of these resistant determinants (armA, rmtB and rmtC) by molecular methods can help us to design appropriate antibiotic and infection-control policies which are necessary to limit the nosocomial spread of these resistance organisms (2).

Highly multidrug-resistant Morganella morganii clinical isolates from Nepal co-producing NDM-type metallo-β-lactamases and the 16S rRNA methylase ArmA

Morganella morganii can harbour extended-spectrum β-lactamases and carbapenemases, resulting in increased resistance to multiple antibiotics and a high mortality rate. This study describes the emergence of highly multidrug-resistant clinical isolates of M. morganii from Nepal co-producing NDM-type metallo-β-lactamases, including NDM-1 and NDM-5, and the 16S rRNA methylase ArmA. This is the first report of M. morganii clinical isolates from Nepal co-producing NDM-1/-5 and ArmA. It is important to establish infection control systems and effective treatments against multidrug-resistant M. morganii .