Menu

Auto Tag: clinical isolates

April 21, 2020  |  

Methicillin-Resistant Staphylococcus aureus Blood Isolates Harboring a Novel Pseudo-staphylococcal Cassette Chromosome mec Element.

The aim of this work was to assess a novel pseudo-staphylococcal cassette chromosome mec (?SCCmec) element in methicillin-resistant Staphylococcus aureus (MRSA) blood isolates. Community-associated MRSA E16SA093 and healthcare-associated MRSA F17SA003 isolates were recovered from the blood specimens of patients with S. aureus bacteremia in 2016 and in 2017, respectively. Antimicrobial susceptibility was determined via the disk diffusion method, and SCCmec typing was conducted by multiplex polymerase chain reaction. Whole genome sequencing was carried out by single molecule real-time long-read sequencing. Both isolates belonged to sequence type 72 and agr-type I, and they were negative for Panton-Valentine leukocidin and toxic shock syndrome toxin. The spa-types of E16SA093 and F17SA003 were t324 and t2460, respectively. They had a SCCmec IV-like element devoid of the cassette chromosome recombinase (ccr) gene complex, designated as ?SCCmecE16SA093. The element was manufactured from SCCmec type IV and the deletion of the ccr gene complex and a 7.0- and 31.9-kb portion of each chromosome. The deficiency of the ccr gene complex in the SCCmec unit is likely resulting in mobility loss, which would be an adaptive evolutionary mechanism. The dissemination of this clone should be monitored closely.

Read more
April 21, 2020  |  

Virulence characteristics and an action mode of antibiotic resistance in multidrug-resistant Pseudomonas aeruginosa.

Pseudomonas aeruginosa displays intrinsic resistance to many antibiotics and known to acquire actively genetic mutations for further resistance. In this study, we attempted to understand genomic and transcriptomic landscapes of P. aeruginosa clinical isolates that are highly resistant to multiple antibiotics. We also aimed to reveal a mode of antibiotic resistance by elucidating transcriptional response of genes conferring antibiotic resistance. To this end, we sequenced the whole genomes and profiled genome-wide RNA transcripts of three different multi-drug resistant (MDR) clinical isolates that are phylogenetically distant from one another. Multi-layered genome comparisons with genomes of antibiotic-susceptible P. aeruginosa strains and 70 other antibiotic-resistance strains revealed both well-characterized conserved gene mutations and distinct distribution of antibiotic-resistant genes (ARGs) among strains. Transcriptions of genes involved in quorum sensing and type VI secretion systems were invariably downregulated in the MDR strains. Virulence-associated phenotypes were further examined and results indicate that our MDR strains are clearly avirulent. Transcriptions of 64 genes, logically selected to be related with antibiotic resistance in MDR strains, were active under normal growth conditions and remained unchanged during antibiotic treatment. These results propose that antibiotic resistance is achieved by a “constitutive” response scheme, where ARGs are actively expressed even in the absence of antibiotic stress, rather than a “reactive” response. Bacterial responses explored at the transcriptomic level in conjunction with their genome repertoires provided novel insights into (i) the virulence-associated phenotypes and (ii) a mode of antibiotic resistance in MDR P. aeruginosa strains.

Read more
April 21, 2020  |  

ICESsuHN105, a Novel Multiple Antibiotic Resistant ICE in Streptococcus suis Serotype 5 Strain HN105.

Streptococcussuis serotype 5, an emerging zoonosis bacterial pathogen, has been isolated from infections in both pigs and humans. In this study, we sequenced the first complete genome of a virulent, multidrug-resistant SS5 strain HN105. The strain HN105 displayed enhanced pathogenicity in zebrafish and BABL/c mouse infection models. Comparative genome analysis identified a novel 80K integrative conjugative element (ICE), ICESsuHN105, as required for the multidrug resistance phenotype. Six corresponding antibiotic resistance genes in this ICE were identified, namely tet (O), tet (M), erm (two copies), aph, and spc. Phylogenetic analysis classified the element as a homolog of the ICESa2603 family, containing the typical family backbone and insertion DNA. DNA hybrids mediated by natural transformation between HN105 and ZY05719 verified the antibiotic resistant genes of ICESsuHN105 that could be transferred successfully, while they were dispersedly inserted with a single gene in different genomic locations of ZY05719(HN105) transformants. To further identify the horizontal transfer of ICESsuHN105 as a whole mobile genetic element, a circular intermediate form of ICESsuHN105 was detected by PCR. However, the effective conjugation using serotype 2 S. suis as recipients was not observed in current assays in vitro. Further studies confirmed the presence of the complete lantibiotic locus encoded in ICESsuHN105 that effectively inhibits the growth of other streptococci. In summary, this study demonstrated the presence of antibiotic resistance genes in ICE that are able to transfer between different clinical isolates and adapt to a broader range of Streptococcus serotype or species.

Read more
April 21, 2020  |  

Characterization of an NDM-5 carbapenemase-producing Escherichia coli ST156 isolate from a poultry farm in Zhejiang, China.

The emergence of carbapenem-resistant Enterobacteriaceae strains has posed a severe threat to public health in recent years. The mobile elements carrying the New Delhi metallo-ß-lactqtamase (NDM) gene have been regarded as the major mechanism leading to the rapid increase of carbapenem-resistant Enterobacteriaceae strains isolated from clinics and animals.We describe an NDM-5-producing Escherichia coli strain, ECCRA-119 (sequence type 156 [ST156]), isolated from a poultry farm in Zhejiang, China. ECCRA-119 is a multidrug-resistant (MDR) isolate that exhibited resistance to 27 antimicrobial compounds, including imipenem and meropenem, as detected by antimicrobial susceptibility testing (AST). The complete genome sequence of the ECCRA-119 isolate was also obtained using the PacBio RS II platform. Eleven acquired resistance genes were identified in the chromosome; four were detected in plasmid pTB201, while six were detected in plasmid pTB202. Importantly, the carbapenem-resistant gene blaNDM-5 was detected in the IncX3 plasmid pTB203. In addition, seven virulence genes and one metal-resistance gene were also detected. The results of conjugation experiments and the transfer regions identification indicated that the blaNDM-5-harboring plasmid pTB203 could be transferred between E. coli strains.The results reflected the severe bacterial resistance in a poultry farm in Zhejiang province and increased our understanding of the presence and transmission of the blaNDM-5 gene.

Read more
April 21, 2020  |  

Comparative Genomic Analyses Reveal Core-Genome-Wide Genes Under Positive Selection and Major Regulatory Hubs in Outlier Strains of Pseudomonas aeruginosa.

Genomic information for outlier strains of Pseudomonas aeruginosa is exiguous when compared with classical strains. We sequenced and constructed the complete genome of an environmental strain CR1 of P. aeruginosa and performed the comparative genomic analysis. It clustered with the outlier group, hence we scaled up the analyses to understand the differences in environmental and clinical outlier strains. We identified eight new regions of genomic plasticity and a plasmid pCR1 with a VirB/D4 complex followed by trimeric auto-transporter that can induce virulence phenotype in the genome of strain CR1. Virulence genotype analysis revealed that strain CR1 lacked hemolytic phospholipase C and D, three genes for LPS biosynthesis and had reduced antibiotic resistance genes when compared with clinical strains. Genes belonging to proteases, bacterial exporters and DNA stabilization were found to be under strong positive selection, thus facilitating pathogenicity and survival of the outliers. The outliers had the complete operon for the production of vibrioferrin, a siderophore present in plant growth promoting bacteria. The competence to acquire multidrug resistance and new virulence factors makes these strains a potential threat. However, we identified major regulatory hubs that can be used as drug targets against both the classical and outlier groups.

Read more
April 21, 2020  |  

Genome plasticity favours double chromosomal Tn4401b-blaKPC-2 transposon insertion in the Pseudomonas aeruginosa ST235 clone.

Pseudomonas aeruginosa Sequence Type 235 is a clone that possesses an extraordinary ability to acquire mobile genetic elements and has been associated with the spread of resistance genes, including genes that encode for carbapenemases. Here, we aim to characterize the genetic platforms involved in resistance dissemination in blaKPC-2-positive P. aeruginosa ST235 in Colombia.In a prospective surveillance study of infections in adult patients attended in five ICUs in five distant cities in Colombia, 58 isolates of P. aeruginosa were recovered, of which, 27 (46.6%) were resistant to carbapenems. The molecular analysis showed that 6 (22.2%) and 4 (14.8%) isolates harboured the blaVIM and blaKPC-2 genes, respectively. The four blaKPC-2-positive isolates showed a similar PFGE pulsotype and belonged to ST235. Complete genome sequencing of a representative ST235 isolate shows a unique chromosomal contig of 7097.241?bp with eight different resistance genes identified and five transposons: a Tn6162-like with ant(2?)-Ia, two Tn402-like with ant(3?)-Ia and blaOXA-2 and two Tn4401b with blaKPC-2. All transposons were inserted into the genomic islands. Interestingly, the two Tn4401b copies harbouring blaKPC-2 were adjacently inserted into a new genomic island (PAGI-17) with traces of a replicative transposition process. This double insertion was probably driven by several structural changes within the chromosomal region containing PAGI-17 in the ST235 background.This is the first report of a double Tn4401b chromosomal insertion in P. aeruginosa, just within a new genomic island (PAGI-17). This finding indicates once again the great genomic plasticity of this microorganism.

Read more

Subscribe for blog updates:

Talk with an expert

If you have a question, need to check the status of an order, or are interested in purchasing an instrument, we're here to help.