OBJECTIVE: Klebsiella aerogenes is a largely understudied opportunistic pathogen that can cause sepsis and lead to high mortality rates. In this study, we reported the occurrence of carbapenem-resistant blaOXA-181-carrying Klebsiella aerogenes from swine in China and elucidate their genomic characteristics.
METHODS: A total of 126 samples, including 109 swine fecal swabs, 14 environmental samples, and three feed samples were collected from a pig farm in China. The samples were enriched with LB broth culture and then inoculated into MacConkey agar plates for bacterial isolation. After PCR detection of carbapenemases genes, the blaOXA-181-carrying isolates were subjected to antimicrobial susceptibility testing, and whole-genome sequence analysis.
RESULTS: Four Klebsiella aerogenes isolates carrying the blaOXA-181 gene were obtained from swine faecal samples. All the 4 strains were belonged to ST438. The blaOXA-181 genes were located in IncX3-ColKP3 hybrid plasmids with the core genetic structure of IS26-ΔIS3000-ΔISEcp1-blaOXA-181-ΔlysR-ΔereA-ΔrepA-ISKpn19-tinR-qnrS1-ΔIS2-IS26, which suggests the potential for horizontal transfer and further dissemination of this resistance gene among Enterobacteriaceae and other sources.
CONCLUSIONS: This study represents the first instance of OXA-181-producing K. aerogenes being identified from swine faeces in China. It is crucial to maintain continuous monitoring and ongoing attention to the detection of K. aerogenes carrying blaOXA-181 and other resistance genes in pigs.

Escherichia coli is regarded as one of the most commonly isolated Gram-negative pathogens from bloodstream infections. Increasing antimicrobial resistance (AMR) among E. coli is a threat to disease management as well as further dissemination of AMR genes to other clinically important pathogens. Here we report the genome of a multidrug-resistant (MDR) E. coli (BA22372) from a bloodstream infection belonging to ST410 B4/H24RxC subtype from India.
Genomic DNA of E. coli BA22372 was sequenced using Ion Torrent™ PGM™ and MinION™ sequencing. Hybrid genome assembly was performed using short and long reads from both methods to achieve accurate and complete genome data.
Here we report the genome of MDR E. coli BA22372 harbouring blaOXA-181 and blaCTX-M-15 in two individual plasmids, namely pOXA181_22372 (IncX3) and pCTX-M-15_22372 (IncF). The pCTX-M-15 plasmid is well known to co-harbour blaNDM-5, which was not seen in the studied isolate here.
To the best of our knowledge, this is the first report of B4/H24RxC MDR E. coli from India co-harbouring blaCTX-M-15 and blaOXA-181 along with other AMR genes. Information from this genome data revealed the possession of AMR genes in two individual plasmids and their potential for rapid dissemination. This isolate is of high health concern as it harbours a plasmid with replicatory mechanisms capable of acquiring blaNDM-5, which is a great threat for rapid dissemination of AMR. This study enhances our understanding of the AMR mechanisms among different clones of E. coli.

Carbapenem-resistant Enterobacterales are a global problem, however little is known about the burden and origin of carbapenem resistance in Africa. The objectives of this study were to determine the proportion of carbapenem-resistant isolates among extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), to identify the underlying mechanisms of resistance and to assess the population structure of carbapenem-resistant isolates from Nigeria.
ESBL-E isolates (n = 175) from infections were collected at four hospitals in Lagos, Nigeria, from July 2016 to January 2018 and were screened for carbapenem resistance using a VITEK®2 automated system. All carbapenem-resistant ESBL-E (CRE) were screened for blaKPC, blaCTX-M, blaCMY-2, blaNDM, blaVIM, blaIMP, blaOXA-181 and blaOXA-48 genes. Genotyping of randomly selected isolates was performed by whole-genome sequencing.
The isolates included Escherichia coli (n = 113; 64.6%) and Klebsiella pneumoniae (n = 62; 35.4%). Of the 175 ESBL-E isolates, 48 (27.4%) were resistant to carbapenems (15 E. coli and 33 K. pneumoniae). CRE isolates carried blaNDM (n = 30; 62.5%), blaNDM + blaOXA-181 (n = 10; 20.8%), blaOXA-181 (n = 2; 4.2%) and blaNDM + blaOXA-48 (n = 1; 2.1%); no carbapenemase gene was detected in 5 isolates (10.4%). The isolates showed low diversity and were mainly associated with multilocus sequence typing (MLST) sequence types ST410 for E. coli and ST395 and ST147 for K. pneumoniae.
Carbapenem resistance is frequent among ESBL-E in Nigeria and is mainly associated with blaNDM. Genotyping suggested that the observed clones possibly originated from Southeast Asia.

This study reported the resistome content of sewage sludge-isolated carbapenem-resistant Citrobacter koseri (C. koseri) carrying blaOXA-181. It also provided a general phylogenomic analysis highlighting antibiotic resistance genes (ARGs), plasmids and pathogenicity of C. koseri genomes.
The carbapenem-resistantC. koseri AS1 strain was isolated from sewage sludge on CHROMagar™ mSuperCARBA™ media. Whole genome sequencing of C. koseri AS1 was performed using an HiSeq X™ Ten instrument. Additional C. koseri genomes were downloaded from National Center for Biotechnology Information (NCBI). Phylogenomic analysis was established through CSI Phylogeny. ARGs, plasmids and pathogenicity were identified using ResFinder 3.1, PlasmidFinder 2.0 and PathogenFinder 1.1, respectively.
The phylogenomic tree indicated a polyclonal pattern ofC. koseri genomes. Resistome analysis of C. koseri AS1 revealed β-lactam resistance genes (blaMAL-1 and blaOXA-181) as well as a fosfomycin resistance gene (fosA7). Three plasmids (ColKP3, ColRNAI and IncX30) were identified in the C. koseri AS1 genome. In addition, 25 ARGs were found in downloaded genomes. Of these, clinically significant ARGs such as blaKPC-2 and blaOXA-48 were found in two and four genomes, respectively. Assessment of the genomes using PathogenFinder revealed all genomes as putative human pathogens.
It is believed that noC. koseri genome has been reported to carry blaOXA-181; therefore, C. koseri AS1 is the first of its kind. This study also highlighted the resistome contents of C. koseri genomes.

The aim of this study was to investigate the prevalence and characterisation of OXA-48-like-producing Enterobacteriaceae in Henan Province, China.
A total of 339 carbapenem-non-susceptible clinical Enterobacteriaceae isolates [imipenem or meropenem minimum inhibitory concentration (MIC) of >1μg/mL] obtained between January 2013 and December 2016 were screened for the presence of the blaOXA-48-like gene by PCR and sequencing. Antimicrobial susceptibility to various antimicrobials agents was examined by MIC testing. Multilocus sequence typing (MLST) was performed for bacterial genotyping. The plasmid pEC21-OXA-181 was transformed into Escherichia coli DH5α by electroporation and was sequenced using an Illumina MiSeq platform, followed by subsequent annotation and genetic analysis.
Among the 339 carbapenem-non-susceptible Enterobacteriaceae isolates, only one (0.3%) E. coli strain EC21, belonging to ST410, was positive for blaOXA-181, a variant of blaOXA-48. This OXA-181-producing E. coli, recovered from a patient without a history of foreign travel, was obtained earlier than the first reported blaOXA-181-positive E. coli (WCHEC14828) in Sichuan Province, China. Plasmid analysis revealed that blaOXA-181 together with the quinolone resistance gene qnrS1 was carried by an IS26-flanked composite transposon on a 51-kb IncX3-type plasmid.
These findings indicate the emergence of OXA-181-producing E. coli in China earlier than previously thought. The blaOXA-181 gene is associated with the widely disseminated potentially endemic E. coli ST410 clone and is carried by an IncX3 plasmid, a common vehicle for spreading NDM-type carbapenemases, which might promote the further dissemination of blaOXA-181 among the Enterobacteriaceae in China.

Carbapenemase-producing Aeromonas spp. are of great concern in healthcare settings and are also known to acquire clinically relevant resistance genes. In this study, carbapenem-non-susceptible Aeromonas isolates were characterised for their molecular mechanisms of resistance.
Among 180 Aeromonas isolates, 10 carbapenem-non-susceptible isolates were selected based on their antimicrobial susceptibility profile. Carbapenemase production was investigated by the CarbaNP test. ESBL-, AmpC- and carbapenemase-encoding genes were screened by PCR. Isolates VBF557 and VBF856 with high MICs for imipenem were selected for whole-genome sequencing (WGS). Conjugation experiments were performed to determine the transmissibility of resistance.
WGS remarkably revealed the presence of class D β-lactamases (AmpS/AmpH), class C β-lactamases and class B2 metallo-β-lactamase (cphA3) in VBF557. In contrast, VBF856 had multiple resistance genes coding for aminoglycoside, sulphonamide, carbapenem (blaOXA-181 class D β-lactamase), macrolide, fluoroquinolone, rifampicin, phenicol, tetracycline and trimethoprim resistance. This is the first global report of blaOXA-181 in Aeromonas spp. Interestingly, blaOXA-181 was identified in association with transposon Tn2013 in plasmid pKP3-A. Additionally, an IncQ2 plasmid with qnrS2 was identified. Among the tested isolates, VBF1116 and VBF888 possessed blaNDM and blaVEB, respectively, by PCR. None of the other isolates harboured any tested β-lactamase genes. The resistance gene was transmissible in the presence of imipenem.
Presence of such resistance genes in plasmids further adds complexity for control of spread of carbapenem resistance. This study reveals the emergence of carbapenem resistance among Aeromonas spp. and the importance of mobile genetic elements such as plasmids in interchanging resistance determinants between species.