Menu

Auto Tag: Antibiotic resistance

September 22, 2019

Complete genome sequencing of Comamonas kerstersii 8943, a causative agent for peritonitis.

Because of poor differentiation among the members of genus Comamonas using phenotypic methods, human infections caused by C. kerstersii are sporadically reported in the literature. Here, we represent the first complete genome sequence of C. kerstersii 8943, which caused peritonitis in a patient with continuous ambulatory peritoneal dialysis (CAPD). The complete genome with no gaps was obtained using third-generation Pacific Biosciences (PacBio) RSII sequencing system with single-molecule real-time (SMRT) analysis. Protein-coding genes, rRNAs and tRNAs were predicted. Functional annotations of the genome using different databases revealed several genes related to pathogenicity including antibiotic resistance genes and prophages. Our work demonstrates that whole genome sequencing can enhance the resolution of clinical investigations and our data can be used as a reference genome during the rapid diagnosis of C. kerstersii infections in the future.

Read more
September 22, 2019

Characterization of Streptococcus pluranimalium from a cattle with mastitis by whole genome sequencing and functional validation.

Streptococcus pluranimalium is a new member of the Streptococcus genus isolated from multiple different animal hosts. It has been identified as a pathogen associated with subclinical mastitis, valvular endocarditis and septicaemia in animals. Moreover, this bacterium has emerged as a new pathogen for human infective endocarditis and brain abscess. However, the patho-biological properties of S. pluranimalium remain virtually unknown. The aim of this study was to determine the complete genome sequence of S. pluranimalium strain TH11417 isolated from a cattle with mastitis, and to characterize its antimicrobial resistance, virulence, and carbon catabolism.The genome of S. pluranimalium TH11417, determined by single-molecule real-time (SMRT) sequencing, consists of 2,065,522 base pair (bp) with a G?+?C content of 38.65%, 2,007 predicted coding sequence (CDS), 58 transfer RNA (tRNA) genes and five ribosome RNA (rRNA) operons. It contains a novel ISSpl1 element (a memeber of the IS3 family) and a ?11417.1 prophage that carries the mef(A), msr(D) and lnu(C) genes. Consistently, our antimicrobial susceptibility test confirmed that S. pluranimalium TH11417 was resistant to erythromycin and lincomycin. However, this strain did not show virulence in murine pneumonia (intranasal inoculation, 107 colony forming unit – CFU) and sepsis (intraperitoneal inoculation, 107 CFU) models. Additionally, this strain is able to grow with glucose, lactose or galactose as the sole carbon source, and possesses a lactose-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS).We reported the first whole genome sequence of S. pluranimalium isolated from a cattle with mastitis. It harbors a prophage carrying the mef(A), msr(D) and lnu(C) genes, and is avirulent in the murine infection model.

Read more
September 22, 2019

Comprehensive profiling of four base overhang ligation fidelity by T4 DNA Ligase and application to DNA assembly.

Synthetic biology relies on the manufacture of large and complex DNA constructs from libraries of genetic parts. Golden Gate and other Type IIS restriction enzyme-dependent DNA assembly methods enable rapid construction of genes and operons through one-pot, multifragment assembly, with the ordering of parts determined by the ligation of Watson-Crick base-paired overhangs. However, ligation of mismatched overhangs leads to erroneous assembly, and low-efficiency Watson Crick pairings can lead to truncated assemblies. Using sets of empirically vetted, high-accuracy junction pairs avoids this issue but limits the number of parts that can be joined in a single reaction. Here, we report the use of comprehensive end-joining ligation fidelity and bias data to predict high accuracy junction sets for Golden Gate assembly. The ligation profile accurately predicted junction fidelity in ten-fragment Golden Gate assembly reactions and enabled accurate and efficient assembly of a lac cassette from up to 24-fragments in a single reaction.

Read more
September 22, 2019

Excision-reintegration at a pneumococcal phase-variable restriction-modification locus drives within- and between-strain epigenetic differentiation and inhibits gene acquisition.

Phase-variation of Type I restriction-modification systems can rapidly alter the sequence motifs they target, diversifying both the epigenetic patterns and endonuclease activity within clonally descended populations. Here, we characterize the Streptococcus pneumoniae SpnIV phase-variable Type I RMS, encoded by the translocating variable restriction (tvr) locus, to identify its target motifs, mechanism and regulation of phase variation, and effects on exchange of sequence through transformation. The specificity-determining hsdS genes were shuffled through a recombinase-mediated excision-reintegration mechanism involving circular intermediate molecules, guided by two types of direct repeat. The rate of rearrangements was limited by an attenuator and toxin-antitoxin system homologs that inhibited recombinase gene transcription. Target motifs for both the SpnIV, and multiple Type II, MTases were identified through methylation-sensitive sequencing of a panel of recombinase-null mutants. This demonstrated the species-wide diversity observed at the tvr locus can likely specify nine different methylation patterns. This will reduce sequence exchange in this diverse species, as the native form of the SpnIV RMS was demonstrated to inhibit the acquisition of genomic islands by transformation. Hence the tvr locus can drive variation in genome methylation both within and between strains, and limits the genomic plasticity of S. pneumoniae.

Read more
September 22, 2019

Antibiotic-resistant indicator bacteria in irrigation water: High prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli.

Irrigation water is a major source of fresh produce contamination with undesired microorganisms including antibiotic-resistant bacteria (ARB), and contaminated fresh produce can transfer ARB to the consumer especially when consumed raw. Nevertheless, no legal guidelines exist so far regulating quality of irrigation water with respect to ARB. We therefore examined irrigation water from major vegetable growing areas for occurrence of antibiotic-resistant indicator bacteria Escherichia coli and Enterococcus spp., including extended-spectrum ß-lactamase (ESBL)-producing E. coli and vancomycin-resistant Enterococcus spp. Occurrence of ARB strains was compared to total numbers of the respective species. We categorized water samples according to total numbers and found that categories with higher total E. coli or Enterococcus spp. numbers generally had an increased proportion of respective ARB-positive samples. We further detected high prevalence of ESBL-producing E. coli with eight positive samples of thirty-six (22%), while two presumptive vancomycin-resistant Enterococcus spp. were vancomycin-susceptible in confirmatory tests. In disk diffusion assays all ESBL-producing E. coli were multidrug-resistant (n = 21) and whole-genome sequencing of selected strains revealed a multitude of transmissible resistance genes (ARG), with blaCTX-M-1 (4 of 11) and blaCTX-M-15 (3 of 11) as the most frequent ESBL genes. Overall, the increased occurrence of indicator ARB with increased total indicator bacteria suggests that the latter might be a suitable estimate for presence of respective ARB strains. Finally, the high prevalence of ESBL-producing E. coli with transmissible ARG emphasizes the need to establish legal critical values and monitoring guidelines for ARB in irrigation water.

Read more
September 22, 2019

Genomic analysis of consecutive Acinetobacter baumannii strains from a single patient.

Acinetobacter baumannii is one of the most important nosocomial pathogens, and thus it is required to investigate how it disseminate in hospitals and infect patients. We performed whole genome sequencing for 24 A. baumannii strains isolated successively from the blood of a single patient to evaluate whether repeated infections were due to re-infection or relapse infection and to investigate within-host evolution. The whole genome of the first strain, BL1, was sequenced de novo using the PacBio RSII system. BL2-BL24, were sequenced with an Illumina Hiseq4000 and mapped to the genome sequences of BL1. We identified 42 single-nucleotide variations among the strains. The SNVs differentiated the strains into three groups, BL1, BL2-BL16, and BL17-BL24, indicating that the patient suffered from re-infections or co-infections by similar, but different strains. The results also showed that A. baumannii strains in each group were rather stable at the genomic level. Our study emphasizes the importance of intensive infection control.

Read more
September 22, 2019

Microevolution of Neisseria lactamica during nasopharyngeal colonisation induced by controlled human infection.

Neisseria lactamica is a harmless coloniser of the infant respiratory tract, and has a mutually-excluding relationship with the pathogen Neisseria meningitidis. Here we report controlled human infection with genomically-defined N. lactamica and subsequent bacterial microevolution during 26 weeks of colonisation. We find that most mutations that occur during nasopharyngeal carriage are transient indels within repetitive tracts of putative phase-variable loci associated with host-microbe interactions (pgl and lgt) and iron acquisition (fetA promotor and hpuA). Recurrent polymorphisms occurred in genes associated with energy metabolism (nuoN, rssA) and the CRISPR-associated cas1. A gene encoding a large hypothetical protein was often mutated in 27% of the subjects. In volunteers who were naturally co-colonised with meningococci, recombination altered allelic identity in N. lactamica to resemble meningococcal alleles, including loci associated with metabolism, outer membrane proteins and immune response activators. Our results suggest that phase variable genes are often mutated during carriage-associated microevolution.

Read more
September 22, 2019

The enterococcus cassette chromosome, a genomic variation enabler in enterococci.

Enterococcus faecium has a highly variable genome prone to recombination and horizontal gene transfer. Here, we have identified a novel genetic island with an insertion locus and mobilization genes similar to those of staphylococcus cassette chromosome elements SCCmec This novel element termed the enterococcus cassette chromosome (ECC) element was located in the 3′ region of rlmH and encoded large serine recombinases ccrAB similar to SCCmec Horizontal transfer of an ECC element termed ECC::cat containing a knock-in cat chloramphenicol resistance determinant occurred in the presence of a conjugative reppLG1 plasmid. We determined the ECC::cat insertion site in the 3′ region of rlmH in the E. faecium recipient by long-read sequencing. ECC::cat also mobilized by homologous recombination through sequence identity between flanking insertion sequence (IS) elements in ECC::cat and the conjugative plasmid. The ccrABEnt genes were found in 69 of 516 E. faecium genomes in GenBank. Full-length ECC elements were retrieved from 32 of these genomes. ECCs were flanked by attR and attL sites of approximately 50?bp. The attECC sequences were found by PCR and sequencing of circularized ECCs in three strains. The genes in ECCs contained an amalgam of common and rare E. faecium genes. Taken together, our data imply that ECC elements act as hot spots for genetic exchange and contribute to the large variation of accessory genes found in E. faeciumIMPORTANCEEnterococcus faecium is a bacterium found in a great variety of environments, ranging from the clinic as a nosocomial pathogen to natural habitats such as mammalian intestines, water, and soil. They are known to exchange genetic material through horizontal gene transfer and recombination, leading to great variability of accessory genes and aiding environmental adaptation. Identifying mobile genetic elements causing sequence variation is important to understand how genetic content variation occurs. Here, a novel genetic island, the enterococcus cassette chromosome, is shown to contain a wealth of genes, which may aid E. faecium in adapting to new environments. The transmission mechanism involves the only two conserved genes within ECC, ccrABEnt, large serine recombinases that insert ECC into the host genome similarly to SCC elements found in staphylococci. Copyright © 2018 Sivertsen et al.

Read more
September 22, 2019

Genomic surveillance of Enterococcus faecium reveals limited sharing of strains and resistance genes between livestock and humans in the United Kingdom.

Vancomycin-resistant Enterococcus faecium (VREfm) is a major cause of nosocomial infection and is categorized as high priority by the World Health Organization global priority list of antibiotic-resistant bacteria. In the past, livestock have been proposed as a putative reservoir for drug-resistant E. faecium strains that infect humans, and isolates of the same lineage have been found in both reservoirs. We undertook cross-sectional surveys to isolate E. faecium (including VREfm) from livestock farms, retail meat, and wastewater treatment plants in the United Kingdom. More than 600 isolates from these sources were sequenced, and their relatedness and antibiotic resistance genes were compared with genomes of almost 800 E. faecium isolates from patients with bloodstream infection in the United Kingdom and Ireland. E. faecium was isolated from 28/29 farms; none of these isolates were VREfm, suggesting a decrease in VREfm prevalence since the last UK livestock survey in 2003. However, VREfm was isolated from 1% to 2% of retail meat products and was ubiquitous in wastewater treatment plants. Phylogenetic comparison demonstrated that the majority of human and livestock-related isolates were genetically distinct, although pig isolates from three farms were more genetically related to human isolates from 2001 to 2004 (minimum of 50?single-nucleotide polymorphisms [SNPs]). Analysis of accessory (variable) genes added further evidence for distinct niche adaptation. An analysis of acquired antibiotic resistance genes and their variants revealed limited sharing between humans and livestock. Our findings indicate that the majority of E. faecium strains infecting patients are largely distinct from those from livestock in this setting, with limited sharing of strains and resistance genes.IMPORTANCE The rise in rates of human infection caused by vancomycin-resistant Enterococcus faecium (VREfm) strains between 1988 to the 2000s in Europe was suggested to be associated with acquisition from livestock. As a result, the European Union banned the use of the glycopeptide drug avoparcin as a growth promoter in livestock feed. While some studies reported a decrease in VREfm in livestock, others reported no reduction. Here, we report the first livestock VREfm prevalence survey in the UK since 2003 and the first large-scale study using whole-genome sequencing to investigate the relationship between E. faecium strains in livestock and humans. We found a low prevalence of VREfm in retail meat and limited evidence for recent sharing of strains between livestock and humans with bloodstream infection. There was evidence for limited sharing of genes encoding antibiotic resistance between these reservoirs, a finding which requires further research. Copyright © 2018 Gouliouris et al.

Read more
September 22, 2019

Spread of the florfenicol resistance floR gene among clinical Klebsiella pneumoniae isolates in China.

Florfenicol is a derivative of chloramphenicol that is used only for the treatment of animal diseases. A key resistance gene for florfenicol, floR, can spread among bacteria of the same and different species or genera through horizontal gene transfer. To analyze the potential transmission of resistance genes between animal and human pathogens, we investigated floR in Klebsiella pneumoniae isolates from patient samples. floR in human pathogens may originate from animal pathogens and would reflect the risk to human health of using antimicrobial agents in animals.PCR was used to identify floR-positive strains. The floR genes were cloned, and the minimum inhibitory concentrations (MICs) were determined to assess the relative resistance levels of the genes and strains. Sequencing and comparative genomics methods were used to analyze floR gene-related sequence structure as well as the molecular mechanism of resistance dissemination.Of the strains evaluated, 20.42% (67/328) were resistant to florfenicol, and 86.96% (20/23) of the floR-positive strains demonstrated high resistance to florfenicol with MICs =512 µg/mL. Conjugation experiments showed that transferrable plasmids carried the floR gene in three isolates. Sequencing analysis of a plasmid approximately 125 kb in size (pKP18-125) indicated that the floR gene was flanked by multiple copies of mobile genetic elements. Comparative genomics analysis of a 9-kb transposon-like fragment of pKP18-125 showed that an approximately 2-kb sequence encoding lysR-floR-virD2 was conserved in the majority (79.01%, 83/105) of floR sequences collected from NCBI nucleotide database. Interestingly, the most similar sequence was a 7-kb fragment of plasmid pEC012 from an Escherichia coli strain isolated from a chicken.Identified on a transferable plasmid in the human pathogen K. pneumoniae, the floR gene may be disseminated through horizontal gene transfer from animal pathogens. Studies on the molecular mechanism of resistance gene dissemination in different bacterial species of animal origin could provide useful information for preventing or controlling the spread of resistance between animal and human pathogens.

Read more
September 22, 2019

Complete genome sequence of Bacillus velezensis ZY-1-1 reveals the genetic basis for its hemicellulosic/cellulosic substrate-inducible xylanase and cellulase activities.

Bacillus velezensis ZY-1-1 was isolated from the larval gut of the lignocellulose-rich diet-fed scarab beetle, Holotrichia parallela, and confirmed to possess extremely high xylanase (48153.8?±?412.1 U/L) and relatively moderate cellulase activity (610.1?±?8.2 U/L). Notably, these xylanase and cellulase activities were enhanced by xylan (1.4 and 5.8-fold, respectively) and cellulose (1.1 and 3.5-fold, respectively), which indicated the hemicellulosic/cellulosic substrate-inducible lignocellulolytic activities of this strain. The complete genome of B. velezensis ZY-1-1 comprises of 3,899,251 bp in a circular chromosome with a G?+?C content of 46.6%. Among the predicted 3688 protein-coding genes, 24 genes are involved in the degradation of lignocellulose and other polysaccharides, including 8, 7 and 2 critical genes for the degradation of xylan, cellulose and lignin, respectively. This genome-based analysis will facilitate our understanding of the mechanism underlying the biodegradation of lignocellulose and the biotechnological application of this novel lignocellulolytic bacteria or related enzymes.

Read more
September 22, 2019

Complete genome sequence of blaIMP-6-positive Metakosakonia sp. MRY16-398 isolate from the ascites of a diverticulitis patient.

A novel species of carbapenemase-producing Enterobacteriaceae (CPE) was isolated from a patient diagnosed with sigmoid colon diverticulitis. At first, laboratory testing suggested it was Klebsiella oxytoca or Pantoea sp.; however, a complete genome sequence of the isolate, MRY16-398, revealed that it could be novel species, most similar to [Kluyvera] intestini, of which taxonomic nomenclature is still under discussion. Orthologous conserved gene analysis among 42 related bacterial strains indicated that MRY16-398 was classified as the newly proposed genus Metakosakonia. Further, MRY16-398 was found to harbor the blaIMP-6 gene-positive class 1 integron (In722) in plasmid pMRY16-398_2 (IncN replicon, 47.4 kb in size). This finding implies that rare and opportunistic bacteria could be potential infectious agents. In conclusion, our results highlight the need for continuous monitoring for CPE even in nonpathogenic bacteria in the nosocomial environment.

Read more
September 22, 2019

Conjugative transfer of a novel Staphylococcal plasmid encoding the biocide resistance gene, qacA.

Staphylococcus aureus is the leading cause of skin and soft tissue infections (SSTI). Some S. aureus strains harbor plasmids that carry genes that affect resistance to biocides. Among these genes, qacA encodes the QacA Multidrug Efflux Pump that imparts decreased susceptibility to chlorhexidine, a biocide used ubiquitously in healthcare facilities. Furthermore, chlorhexidine has been considered as a S. aureus decolonization strategy in community settings. We previously conducted a chlorhexidine-based SSTI prevention trial among Ft. Benning Army trainees. Analysis of a clinical isolate (C02) from that trial identified a novel qacA-positive plasmid, pC02. Prior characterization of qacA-containing plasmids is limited and conjugative transfer of those plasmids has not been demonstrated. Given the implications of increased biocide resistance, herein we characterized pC02. In silico analysis identified genes typically associated with conjugative plasmids. Moreover, pC02 was efficiently transferred to numerous S. aureus strains and to Staphylococcus epidermidis. We screened additional qacA-positive S. aureus clinical isolates and pC02 was present in 27% of those strains; other unique qacA-harboring plasmids were also identified. Ten strains were subjected to whole genome sequencing. Sequence analysis combined with plasmid screening studies suggest that qacA-containing strains are transmitted among military personnel at Ft. Benning and that strains carrying qacA are associated with SSTIs within this population. The identification of a novel mechanism of qacA conjugative transfer among Staphylococcal strains suggests a possible future increase in the prevalence of antiseptic tolerant bacterial strains, and an increase in the rate of infections in settings where these agents are commonly used.

Read more
September 22, 2019

A mcr-1-carrying conjugative IncX4 plasmid in colistin-resistant Escherichia coli ST278 strain isolated from dairy cow feces in Shanghai, China.

Enterobacteriaceae, including Escherichia coli, has been shown to acquire the colistin resistance gene mcr-1. A strain of E. coli, EC11, which is resistant to colistin, polymyxin B and trimethoprim-sulfamethoxazole, was isolated in 2016 from the feces of a dairy cow in Shanghai, China. Strain EC11 identifies with sequence type ST278 and is susceptible to 19 frequently used antibiotics. Whole genome sequencing of strain EC11 showed that this strain contains a 31-kb resistance plasmid, pEC11b, which belongs to the IncX4 group. The mcr-1 gene was shown to be inserted into a 2.6-kb mcr-1-pap2 cassette of pEC11b. Plasmid pEC11b also contained putative conjugal transfer components, including an oriT-like region, relaxase, type IV coupling protein, and type IV secretion system. We were successful in transferring pEC11b to E. coli C600 with an average transconjugation efficiency of 4.6 × 10-5. Additionally, a MLST-based analysis comparing EC11 and other reported mcr-positive E. coli populations showed high genotypic diversity. The discovery of the E. coli strain EC11 with resistance to colistin in Shanghai emphasizes the importance of vigilance in detecting new threats like mcr genes to public health. Detection of mcr genes helps in tracking, slowing, and responding to the emergence of antibiotic resistance in Chinese livestock farming.

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.