Horizontal transmission of a multidrug-resistant IncN plasmid isolated from urban wastewater

Wastewater treatment plants (WWTPs) are considered reservoirs of antibiotic resistance genes (ARGs). Given that plasmid-mediated horizontal gene transfer plays a critical role in disseminating ARGs in the environment, it is important to inspect the transfer potential of transmissible plasmids to have a better understanding of whether these mobile ARGs can be hosted by opportunistic pathogens and should be included in One Health's considerations. In this study, we used a fluorescent-reporter-gene based exogenous isolation approach to capture extended-spectrum beta-lactamases encoding mobile determinants from sewer microbiome samples that enter an urban water system (UWS) in Denmark. After screening and sequencing, we isolated a ∼73 Kbp IncN plasmid (pDK_DARWIN) that harboured and expressed multiple ARGs. Using a dual fluorescent reporter gene system, we showed that this plasmid can transfer into resident urban water communities. We demonstrated the transfer of pDK_DARWIN to microbiome members of both the sewer (in the upstream UWS compartment) and wastewater treatment (in the downstream UWS compartment) microbiomes. Sequence similarity search across curated plasmid repositories revealed that pDK_DARWIN derives from an IncN backbone harboured by environmental and nosocomial Enterobacterial isolates. Furthermore, we searched for pDK_DARWIN sequence matches in UWS metagenomes from three countries, revealing that this plasmid can be detected in all of them, with a higher relative abundance in hospital sewers compared to residential sewers. Overall, this study demonstrates that this IncN plasmid is prevalent across Europe and an efficient vector capable of disseminating multiple ARGs in the urban water systems.

Flagellar interference with plasmid uptake in biofilms: a joint experimental and modeling study

Plasmid conjugation is a key facilitator of horizontal gene transfer (HGT), and plasmids encoding antibiotic resistance drive the increasing prevalence of antibiotic resistance. In natural, engineered, and clinical environments, bacteria often grow in protective biofilms. Therefore, a better understanding of plasmid transfer in biofilms is needed. Our aim was to investigate plasmid transfer in a biofilm-adapted wrinkly colony mutant of Xanthomonas retroflexus (XRw) with enhanced matrix production and reduced motility. We found that XRw biofilms had an increased uptake of the broad host-range IncP-1ϵ plasmid pKJK5 compared to the wild type (WT). Proteomics revealed fewer flagellar-associated proteins in XRw, suggesting that flagella were responsible for reducing plasmid uptake. This was confirmed by the higher plasmid uptake of non-flagellated fliM mutants of the X. retroflexus wrinkly mutant as well as the wild type. Moreover, testing several flagellar mutants of Pseudomonas putida suggested that the flagellar effect was more general. We identified seven mechanisms with the potential to explain the flagellar effect and simulated them in an individual-based model. Two mechanisms could thus be eliminated (increased distances between cells and increased lag times due to flagella). Another mechanism identified as viable in the modeling was eliminated by further experiments. The possibility of steric hindrance of pilus movement and binding by flagella, reducing the frequency of contact and thus plasmid uptake, proved viable, and the three other viable mechanisms had a reduced probability of plasmid transfer in common. Our findings highlight the important yet complex effects of flagella during bacterial conjugation in biofilms.IMPORTANCEBiofilms are the dominant form of microbial life and bacteria living in biofilms are markedly different from their planktonic counterparts, yet the impact of the biofilm lifestyle on horizontal gene transfer (HGT) is still poorly understood. Horizontal gene transfer by conjugative plasmids is a major driver in bacterial evolution and adaptation, as exemplified by the troubling spread of antibiotic resistance. To either limit or promote plasmid prevalence and dissemination, we need a better understanding of plasmid transfer between bacterial cells, especially in biofilms. Here, we identified a new factor impacting the transfer of plasmids, flagella, which are required for many types of bacterial motility. We show that their absence or altered activity can lead to enhanced plasmid uptake in two bacterial species, Xanthomonas retroflexus and Pseudomonas putida. Moreover, we demonstrate the utility of mathematical modeling to eliminate hypothetical mechanisms.

Insights into the circular: The cryptic plasmidome and its derived antibiotic resistome in the urban water systems

Plasmids have been a concern in the dissemination and evolution of antibiotic resistance in the environment. In this study, we investigated the total pool of plasmids (plasmidome) and its derived antibiotic resistance genes (ARGs) in different compartments of urban water systems (UWSs) in three European countries representing different antibiotic usage regimes. We applied a direct plasmidome approach using wet-lab methods to enrich circular DNA in the samples, followed by shotgun sequencing and in silico contig circularisation. We identified 9538 novel sequences in a total of 10,942 recovered circular plasmids. Of these, 66 were identified as conjugative, 1896 mobilisable and 8970 non-mobilisable plasmids. The UWSs' plasmidome was dominated by small plasmids (≤10 Kbp) representing a broad diversity of mobility (MOB) types and incompatibility (Inc) groups. A shared collection of plasmids from different countries was detected in all treatment compartments, and plasmids could be source-tracked in the UWSs. More than half of the ARGs-encoding plasmids carried mobility genes for mobilisation/conjugation. The richness and abundance of ARGs-encoding plasmids generally decreased with the flow, while we observed that non-mobilisable ARGs-harbouring plasmids maintained their abundance in the Spanish wastewater treatment plant. Overall, our work unravels that the UWS plasmidome is dominated by cryptic (i.e., non-mobilisable, non-typeable and previously unknown) plasmids. Considering that some of these plasmids carried ARGs, were prevalent across three countries and could persist throughout the UWSs compartments, these results should alarm and call for attention.

Interphylum dissemination of NDM-5-positive plasmids in hospital wastewater from Fuzhou, China: a single-centre, culture-independent, plasmid transmission study

BACKGROUND

The global spread of plasmid-borne carbapenem resistance is an ongoing public health challenge; however, the nature of such horizontal gene transfer events among complex bacterial communities remains poorly understood. We examined the in-situ transfer of the globally dominant New Delhi metallo-β-lactamase (NDM)-5-positive IncX3 plasmid (denoted pX3_NDM-5) in hospital wastewater to simulate a real-world, One Health antimicrobial resistance context.

METHODS

For this transmission study, we tagged pX3_NDM-5 with the green fluorescent protein gene, gfp, using a CRISPR-based method and transferred the plasmid to a donor Escherichia coli strain. Bacteria were extracted from a hospital wastewater treatment plant (Fujian Provincial Maternity and Children's Hospital, Fuzhou, China) as the bacterial recipient community. We mixed this recipient community with the E coli donor strain carrying the gfp-tagged plasmid, both with and without sodium hypochlorite (NaClO) as an environmental stressor, and conducted several culture-based and culture-independent conjugation assays. The conjugation events were observed microscopically and quantified by fluorescence-activated cell sorting. We analysed the taxonomic composition of the sorted transconjugal pool by 16S rRNA gene amplicon sequencing and assessed the stability of the plasmid in the isolated transconjugants and its ability to transfer back to E coli.

FINDINGS

We show that the plasmid pX3_NDM-5 has a broad host range and can transfer across various bacterial phyla, including between Gram-negative and Gram-positive bacteria. Although environmental stress with NaClO did not affect the overall plasmid transfer frequency, it reduced the breadth of the transconjugant pool. The taxonomic composition of the transconjugal pool was distinct from that of the recipient communities, and environmental stress modulated the permissiveness of some operational taxonomic units towards the acquisition of pX3_NDM-5. Notably, pX3_NDM-5 transconjugants included the Gram-positive pathogen Enterococcus faecalis, and the plasmid could subsequently be reconjugated back to E coli. These findings suggest that E faecalis could act as a natural shuttle vector for the wide dissemination of pX3_NDM-5 plasmids.

INTERPRETATION

Our culture-independent conjugation model simulates natural environmental conditions and challenges the established theory that Gram-negative and Gram-positive bacteria rarely exchange clinically important plasmids. The data show that plasmids disseminate more widely across genera and phyla than previously thought. These findings have substantial implications when considering the spread of antimicrobial resistance across One Health sectors.

FUNDING

The Laboratory of Lingnan Modern Agriculture Project, the National Natural Science Foundation of China, the Natural Science Foundation of Fujian Province of China, and the Outstanding Young Research Talents Program of Fujian Agriculture and Forestry University.

Cooperative antibiotic resistance facilitates horizontal gene transfer

The rise of β-lactam resistance among pathogenic bacteria, due to the horizontal transfer of plasmid-encoded β-lactamases, is a current global health crisis. Importantly, β-lactam hydrolyzation by β-lactamases, not only protects the producing cells but also sensitive neighboring cells cooperatively. Yet, how such cooperative traits affect plasmid transmission and maintenance is currently poorly understood. Here we experimentally show that KPC-2 β-lactamase expression and extracellular activity were higher when encoded on plasmids compared with the chromosome, resulting in the elevated rescue of sensitive non-producers. This facilitated efficient plasmid transfer to the rescued non-producers and expanded the potential plasmid recipient pool and the probability of plasmid transfer to new genotypes. Social conversion of non-producers by conjugation was efficient yet not absolute. Non-cooperative plasmids, not encoding KPC-2, were moderately more competitive than cooperative plasmids when β-lactam antibiotics were absent. However, in the presence of a β-lactam antibiotic, strains with non-cooperative plasmids were efficiently outcompeted. Moreover, plasmid-free non-producers were more competitive than non-producers imposed with the metabolic burden of a plasmid. Our results suggest that cooperative antibiotic resistance especially promotes the fitness of replicons that transfer horizontally such as conjugative plasmids.

Conjugative plasmids inhibit extracellular electron transfer in Geobacter sulfurreducens

Geobacter sulfurreducens is part of a specialized group of microbes with the unique ability to exchange electrons with insoluble materials, such as iron oxides and electrodes. Therefore, G. sulfurreducens plays an essential role in the biogeochemical iron cycle and microbial electrochemical systems. In G. sulfurreducens this ability is primarily dependent on electrically conductive nanowires that link internal electron flow from metabolism to solid electron acceptors in the extracellular environment. Here we show that when carrying conjugative plasmids, which are self-transmissible plasmids that are ubiquitous in environmental bacteria, G. sulfurreducens reduces insoluble iron oxides at much slower rates. This was the case for all three conjugative plasmids tested (pKJK5, RP4 and pB10). Growth with electron acceptors that do not require expression of nanowires was, on the other hand, unaffected. Furthermore, iron oxide reduction was also inhibited in Geobacter chapellei, but not in Shewanella oneidensis where electron export is nanowire-independent. As determined by transcriptomics, presence of pKJK5 reduces transcription of several genes that have been shown to be implicated in extracellular electron transfer in G. sulfurreducens, including pilA and omcE. These results suggest that conjugative plasmids can in fact be very disadvantageous for the bacterial host by imposing specific phenotypic changes, and that these plasmids may contribute to shaping the microbial composition in electrode-respiring biofilms in microbial electrochemical reactors.

Microbial Interactions in Electroactive Biofilms for Environmental Engineering Applications: A Role for Nonexoelectrogens

Microbial electrochemical systems have gained much attention over the past decade due to their potential for various environmental engineering applications ranging from energy production to wastewater treatment to bioproduction. At the heart of these systems lie exoelectrogens-microorganisms capable of exporting electrons generated during metabolism to external electron acceptors such as electrodes. The bacterial biofilm communities on these electrodes are dominated by exoelectrogens but are nonetheless extremely diverse. So far, within the field, the main focus has been on the electroactive bacteria. However, to broaden our understanding of these communities, it is crucial to clarify how the remaining inhabitants of electrode-respiring biofilms contribute to the overall function of the biofilm. Ultimately, such insights may enable improvement of microbial electrochemical systems by reshaping the community structure with naturally occurring beneficial strains.

An easily modifiable conjugative plasmid for studying horizontal gene transfer

Horizontal gene transfer is an important mechanism in bacterial evolution and can occur at striking frequencies when mediated by mobile genetic elements. Conjugative plasmids are mobile genetic elements that are main drivers of horizontal transfer and a major facilitator in the spread of antibiotic resistance genes. However, conjugative plasmid models that readily can be genetically modified with the aim to study horizontal transfer are not currently available. The aim of this study was to develop a conjugative plasmid model where the insertion of gene cassettes such as reporter genes (e.g., fluorescent proteins) or antibiotic resistance genes would be efficient and convenient. Here, we introduced a single attTn7 site into the conjugative broad-host-range IncP-1 plasmid pKJK5 in a non-disruptive manner. Furthermore, a version with lower transfer rate and a non-conjugative version of pKJK5-attTn7 were also constructed. The advantage of having the attTn7 sites is that genes of interest can be introduced in a single step with very high success rate using the Tn7 transposition system. In addition, larger genetic fragments can be inserted. To illustrate the efficacy of the constructed pKJK5 plasmids, they were complemented with sfGFP (a gene encoding superfolder green fluorescent protein) in addition to seven different β-lactamase genes representing the four known classes of β-lactamases.

Biofilms can act as plasmid reserves in the absence of plasmid specific selection

Plasmids facilitate rapid bacterial adaptation by shuttling a wide variety of beneficial traits across microbial communities. However, under non-selective conditions, maintaining a plasmid can be costly to the host cell. Nonetheless, plasmids are ubiquitous in nature where bacteria adopt their dominant mode of life - biofilms. Here, we demonstrate that biofilms can act as spatiotemporal reserves for plasmids, allowing them to persist even under non-selective conditions. However, under these conditions, spatial stratification of plasmid-carrying cells may promote the dispersal of cells without plasmids, and biofilms may thus act as plasmid sinks.

Lead Drives Complex Dynamics of a Conjugative Plasmid in a Bacterial Community

Plasmids carrying metal resistance genes (MRGs) have been suggested to be key ecological players in the adaptation of metal-impacted microbial communities, making them promising drivers of bio-remediation processes. However, the impact of metals on plasmid-mediated spread of MRGs through selection, plasmid loss, and transfer is far from being fully understood. In the present study, we used two-member bacterial communities to test the impact of lead on the dispersal of the IncP plasmid pKJK5 from a Pseudomonas putida KT2440 plasmid donor and two distinct recipients, Variovorax paradoxus B4 or Delftia acidovorans SPH-1 after 4 and 10 days of mating. Two versions of the plasmid were used, carrying or not carrying the lead resistance pbrTRABCD operon, to assess the importance of fitness benefit and conjugative potential for the dispersal of the plasmid. The spread dynamics of metal resistance conveyed by the conjugative plasmid were dependent on the recipient and the lead concentration: For V. paradoxus, the pbr operon did not facilitate neither lead resistance nor variation in plasmid spread. The growth gain brought by the pbr operon to D. acidovorans SPH-1 and P. putida KT2440 at 1 mM Pb enhanced the spread of the plasmid. At 1.5 mM Pb after 4 days, the proteomics results revealed an oxidative stress response and an increased abundance of pKJK5-encoded conjugation and partitioning proteins, which most likely increased the transfer of the control plasmid to D. acidovorans SPH-1 and ensured plasmid maintenance. As a consequence, we observed an increased spread of pKJK5-gfp. Conversely, the pbr operon reduced the oxidative stress response and impeded the rise of conjugation- and partitioning-associated proteins, which slowed down the spread of the pbr carrying plasmid. Ultimately, when a fitness gain was recorded in the recipient strain, the spread of MRG-carrying plasmids was facilitated through positive selection at an intermediate metal concentration, while a high lead concentration induced oxidative stress with positive impacts on proteins encoding plasmid conjugation and partitioning.

Circulating miR-141 and miR-375 are associated with treatment outcome in metastatic castration resistant prostate cancer

Metastatic castration resistant prostate cancer (mCRPC) is associated with high mortality, where monitoring of disease activity is still a major clinical challenge. The role of microRNAs (miRs) has been widely investigated in prostate cancer with both diagnostic and prognostic potential. The aim of this study was to investigate the relationship between circulating miRs and treatment outcome in mCRPC patients. The relative expression of five miRs (miR-93-5p, -125b-1-5p, -141-3p, -221-3p, and miR-375-3p) was investigated in plasma samples from 84 mCRPC patients; 40 patients were treated with docetaxel (DOC cohort) and 44 patients with abiraterone (ABI cohort). Blood was sampled at baseline before treatment start and at radiological progression. The plasma levels of four miRs; miR-93-5p, -141-3p, -221-3p, and miR-375-3p decreased significantly after treatment initiation in patients receiving docetaxel, and for miR-141-3p and miR-375-3p the level increased again at the time of radiological progression. In the patients treated with abiraterone, the plasma level of miR-221-3p likewise decreased significantly after the first treatment cycle. High baseline levels of both miR-141-3p and miR-375-3p were significantly associated with a shorter time to radiological progression in both cohorts. Additionally, high baseline levels of miR-141-3p and miR-221-3p were significantly associated with a shorter overall survival (OS) in the ABI cohort, while high levels of miR-141-3p and miR-375-3p were significantly associated with shorter OS in the DOC cohort. Plasma levels of miR-141-3p and miR-375-3p may predict time to progression in mCRPC patients treated with docetaxel or abiraterone. The clinical impact of these findings is dependent on validation in larger cohorts.

Interspecies interactions reduce selection for a biofilm-optimized variant in a four-species biofilm model

Multispecies biofilms are structured and spatially defined communities, where interspecies interactions impact assembly and functionality. Here, we compared the spatial organization and growth of bacterial cells in differently composed biofilm communities over time to determine links between interspecies interactions and selection for biofilm phenotypes of individual species. An established model community consisting of Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus was used. It was found that interspecies interactions led to varying levels of selection for a new colony phenotype of X. retroflexus, depending on the presence/absence of other species. When M. oxydans was absent, X. retroflexus was not able to establish in the top layers of the biofilm, which led to selection for a hyper-matrix forming phenotype of X. retroflexus that successfully established in the biofilm top layers. No such phenotypic X. retroflexus variants were identified in the presence of M. oxydans. These findings indicate that interspecies interactions may lead to favourable localization of individual species in a multispecies biofilm and thereby reduce selection for competitive phenotypes.

Interspecies interactions reduce selection for a biofilm optimized variant in a four-species biofilm model

Multispecies biofilms are structured and spatially defined communities, where interspecies interactions impact assembly and functionality. Here we compared the spatial organization and growth of bacterial cells in differently composed biofilm communities over time to determine links between interspecies interactions and selection for biofilm phenotypes of individual species. An established model community consisting of Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus was used. It was found that interspecies interactions led to varying levels of selection for a new colony phenotype of X. retroflexus, depending on the presence/absence of other species. When M. oxydans was absent, X. retroflexus was not able to establish in the top layers of the biofilm, which led to selection for a hyper-matrix forming phenotype of X. retroflexus that successfully established in the biofilm top layers. No such phenotypic X. retroflexus variants were identified in the presence of M. oxydans. These findings indicate that interspecies interactions may lead to favourable localization of individual species in a multispecies biofilm and thereby reduce selection for competitive phenotypes. This article is protected by copyright. All rights reserved.

Priority of Early Colonizers but No Effect on Cohabitants in a Synergistic Biofilm Community

The arrival order of different species to a habitat can strongly impact community assembly and succession dynamics, thus influencing functionality. In this study, we asked how prior colonization of one community member would influence the assembly of a synergistic multispecies biofilm community grown in vitro. We expected that the prior arrival would confer an advantage, in particular for good biofilm formers. Yet, we did not know if the cohabitants would be impaired or benefit from the pre-colonization of one member, depending on its ability to form biofilm. We used a consortium consisting of four soil bacteria; Stenotrophomonas rhizophila, Xanthomonas retroflexus, Microbacterium oxydans and Paenibacillus amylolyticus. This consortium has been shown to act synergistically when grown together, thus increasing biofilm production. The results showed that the two good biofilm formers gained a fitness advantage (increase in abundance) when allowed prior colonization on an abiotic surface before the arrival of their cohabitants. Interestingly, the significantly higher number of the pre-colonized biofilm formers did not affect the resulting composition in the subsequent biofilm after 24 h.

Fate of CMY-2-Encoding Plasmids Introduced into the Human Fecal Microbiota by Exogenous Escherichia coli

The gut is a hot spot for transfer of antibiotic resistance genes from ingested exogenous bacteria to the indigenous microbiota. The objective of this study was to determine the fate of two nearly identical blaCMY-2-harboring plasmids introduced into the human fecal microbiota by two Escherichia coli strains isolated from a human and from poultry meat. The chromosome and the CMY-2-encoding plasmid of both strains were labeled with distinct fluorescent markers (mCherry and green fluorescent protein [GFP]), allowing fluorescence-activated cell sorting (FACS)-based tracking of the strain and the resident bacteria that have acquired its plasmid. Each strain was introduced into an established in vitro gut model (CoMiniGut) inoculated with individual feces from ten healthy volunteers. Fecal samples collected 2, 6, and 24 h after strain inoculation were analyzed by FACS and plate counts. Although the human strain survived better than the poultry meat strain, both strains transferred their plasmids to the fecal microbiota at concentrations as low as 102 CFU/ml. Strain survival and plasmid transfer varied significantly depending on inoculum concentration and individual fecal microbiota. Identification of transconjugants by 16S rRNA gene sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) revealed that the plasmids were predominantly acquired by Enterobacteriaceae species, such as E. coli and Hafnia alvei Our experimental data demonstrate that exogenous E. coli of human or animal origin can readily transfer CMY-2-encoding IncI1 plasmids to the human fecal microbiota. Small amounts of the exogenous strain are sufficient to ensure plasmid transfer if the strain is able to survive the gastric environment.

Cerebrospinal fluid biomarkers for predicting development of multiple sclerosis in acute optic neuritis: a population-based prospective cohort study

Background

Long-term outcome in multiple sclerosis (MS) depends on early treatment. In patients with acute optic neuritis (ON), an early inflammatory event, we investigated markers in cerebrospinal fluid (CSF), which may predict a diagnosis of MS.

Methods

Forty patients with acute ON were recruited in a prospective population-based cohort with median 29 months (range 19–41) of follow-up. Paired CSF and serum samples were taken within 14 days (range 2–38), prior to treatment. Prospectively, 16/40 patients were by a uniform algorithm diagnosed with MS (MS-ON) and 24 patients continued to manifest isolated ON (ION) during follow-up. Levels of cytokines and neurofilament light chain (NF-L) were measured at the onset of acute ON and compared to healthy controls (HC). Significance levels were corrected for multiple comparisons (“q”). The predictive value of biomarkers was determined with multivariable prediction models using nomograms.

Results

CSF TNF-α, IL-10, and CXCL13 levels were increased in MS-ON compared to those in ION patients (q = 0.021, 0.004, and 0.0006, respectively). MS-ON patients had increased CSF pleocytosis, IgG indices, and oligoclonal bands (OCBs) compared to ION (q = 0.0007, q = 0.0058, and q = 0.0021, respectively). CSF levels of IL-10, TNF-a, IL-17A, and CXCL13 in MS-ON patients correlated with leukocyte counts (r > 0.69 and p < 0.002) and IgG index (r > 0.55, p < 0.037). CSF NF-L levels were increased in ON patients compared to those in HC (q = 0.0077). In MS-ON, a progressive increase in NF-L levels was observed at 7 to 14 days after disease onset (r = 0.73, p < 0.0065). Receiver-operating characteristic (ROC) curves for two multivariable prediction models were generated, with IL-10, CXCL13, and NF-L in one (“candidate”) and IgG index, OCB, and leukocytes in another (“routine”). Area under the curve was 0.89 [95% CI 0.77–1] and 0.86 [0.74–0.98], respectively. Predictions of the risk of MS diagnosis were illustrated by two nomograms.

Conclusions

CSF TNF-α, IL-10, CXCL13, and NF-L levels were associated with the development of MS, suggesting that the inflammatory and neurodegenerative processes occurred early. Based on subsequent diagnosis, we observed a high predictive value of routine and candidate biomarkers in CSF for the development of MS in acute ON. The nomogram predictions may be useful in the diagnostic work-up of MS.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1440-5) contains supplementary material, which is available to authorized users.

A culture-independent method for studying transfer of IncI1 plasmids from wild-type Escherichia coli in complex microbial communities

IncI1 plasmids play a central role in the transfer of antimicrobial resistance genes among Enterobacteriaceae in animals and humans. Knowledge on the dynamics of IncI1 plasmid transfer is limited, mainly due to lack of culture-independent methods that can quantify donor strain survival and plasmid transfer in complex microbial communities. The aim of this study was to develop a culture-independent method to study the dynamics of IncI1 plasmids transfer by fluorescence-activated cell sorting. We genetically modified three wild-type Escherichia coli of animal (n = 2) and human (n = 1) origin carrying bla_CMY-2 or bla_CTX-M-1 on two epidemic IncI1 plasmids (pST12 and pST7). Non-coding regions on the chromosome and on the IncI1 plasmid of each strain were tagged with mCherry (red) and GFPmut3 (green) fluorescent proteins, respectively, using lambda recombineering. A gene cassette expressing mCherry and lacI^q was inserted into the chromosome, whereas the plasmid was marked with a GFPmut3 cassette with LacI^q repressible promoter. Therefore, gfpmut3 was repressed in donor strains but expressed in recipient strains acquiring the plasmids. We demonstrated that genetic engineering of the strains did not affect the growth rate and plasmid transfer-ability in filter and broth matings. A proof-of-concept experiment using the CoMiniGut, an in vitro model of the colon, proved the validity of our method for studying the survival of wild-type E. coli and horizontal transfer of IncI1 plasmids under different pH and oxygen conditions. The dual-labeling method by fluorescent proteins is useful to determine persistence of exogenous E. coli and transfer dynamics of IncI1 plasmids in microbial communities.

Bacterial social interactions and the emergence of community-intrinsic properties

Bacterial communities are dominated and shaped by social interactions, which facilitate the emergence of properties observed only in the community setting. Such community-intrinsic properties impact not only the phenotypes of cells in a community, but also community composition and function, and are thus likely to affect a potential host. Studying community-intrinsic properties is, therefore, important for furthering our understanding of clinical, applied and environmental microbiology. Here, we provide recent examples of research investigating community-intrinsic properties, focusing mainly on community composition and interactions in multispecies biofilms. We hereby wish to emphasize the importance of studying social interactions in settings where community-intrinsic properties are likely to emerge.

A population-based prospective study of optic neuritis

BACKGROUND

Optic neuritis (ON) is often associated with multiple sclerosis (MS). Early diagnosis is critical to optimal patient management.

OBJECTIVE

To estimate the incidence of acute ON and the rates of conversion to MS and antibody-mediated ON.

METHOD

Population-based prospective study was performed in patients with ON from three ophthalmological departments and 44 practicing ophthalmologists from 2014 to 2016. Ophthalmological and neurological examination, magnetic resonance imaging (MRI), determination of aquaporin-4(AQP4)-IgG and myelin-oligodendrocyte glycoprotein (MOG)-IgG were investigated blindly.

RESULTS

In all, 63 patients were evaluated and 51 fulfilled the criteria for ON. All were Caucasian, with female:male ratio of 2.2:1 and a median age of 38 years (16-66); 44 (86%) had a single episode of ON (four bilateral), while 7/51 (14%) had recurrent ON. The overall age-specific incidence was 3.28 (2.44-4.31) per 100,000 person years, 2.02 for men and 4.57 for women. At follow-up, 20 patients met the diagnostic criteria for MS, MRI lesions disseminated in space and time in 17/20 patients. AQP4-IgG was detected in none, MOG-IgG was detected in two patients.

CONCLUSION

The prospective incidence of ON was estimated. MRI enabled a diagnosis of MS in a subgroup of patients. Antibody-mediated ON with specificity for MOG was detected in 4% of cases.

Type 3 Fimbriae Encoded on Plasmids Are Expressed from a Unique Promoter without Affecting Host Motility, Facilitating an Exceptional Phenotype That Enhances Conjugal Plasmid Transfer

Horizontal gene transfer (HGT), the transmission of genetic material to a recipient that is not the progeny of the donor, is fundamental in bacterial evolution. HGT is often mediated by mobile genetic elements such as conjugative plasmids, which may be in conflict with the chromosomal elements of the genome because they are independent replicons that may petition their own evolutionary strategy. Here we study differences between type 3 fimbriae encoded on wild type plasmids and in chromosomes. Using known and newly characterized plasmids we show that the expression of type 3 fimbriae encoded on plasmids is systematically different, as MrkH, a c-di-GMP dependent transcriptional activator is not needed for strong expression of the fimbriae. MrkH is required for expression of type 3 fimbriae of the Klebsiella pneumoniae chromosome, wherefrom the fimbriae operon (mrkABCDF) of plasmids is believed to have originated. We find that mrkABCDFs of plasmids are highly expressed via a unique promoter that differs from the original Klebsiella promoter resulting in fundamental behavioral consequences. Plasmid associated mrkABCDFs did not influence the swimming behavior of the host, that hereby acquired an exceptional phenotype being able to both actively swim (planktonic behavior) and express biofilm associated fimbriae (sessile behavior). We show that this exceptional phenotype enhances the conjugal transfer of the plasmid.

Presence of Pathogenic Bacteria and Viruses in the Daycare Environment

The number of children in daycare centers (DCCs) is rising. This increases exposure to microorganisms and infectious diseases. Little is known about which bacteria and viruses are present in the DCC environment and where they are located. In the study described in this article, the authors set out to determine the prevalence of pathogenic bacteria and viruses and to find the most contaminated fomites in DCCs. Fifteen locations in each DCC were sampled for bacteria, respiratory viruses, and gastrointestinal viruses. The locations were in the toilet, kitchen, and playroom areas and included nursery pillows, toys, and tables, among other things. Coliform bacteria were primarily found in the toilet and kitchen areas whereas nasopharyngeal bacteria were found mostly on toys and fabric surfaces in the playroom. Respiratory viruses were omnipresent in the DCC environment, especially on the toys.

High-throughput screening of multispecies biofilm formation and quantitative PCR-based assessment of individual species proportions, useful for exploring interspecific bacterial interactions

Multispecies biofilms are predominant in almost all natural environments, where myriads of resident microorganisms interact with each other in both synergistic and antagonistic manners. The interspecies interactions among different bacteria are, despite the ubiquity of these communities, still poorly understood. Here, we report a rapid, reproducible and sensitive approach for quantitative screening of biofilm formation by bacteria when cultivated as mono- and multispecies biofilms, based on the Nunc-TSP lid system and crystal violet staining. The relative proportion of the individual species in a four-species biofilm was assessed using quantitative PCR based on SYBR Green I fluorescence with specific primers. The results indicated strong synergistic interactions in a four-species biofilm model community with a more than 3-fold increase in biofilm formation and demonstrated the strong dominance of two strains, Xanthomonas retroflexus and Paenibacillus amylolyticus. The developed approach can be used as a standard procedure for evaluating interspecies interactions in defined microbial communities. This will be of significant value in the quantitative study of the microbial composition of multispecies biofilms both in natural environments and infectious diseases to increase our understanding of the mechanisms that underlie cooperation, competition and fitness of individual species in mixed-species biofilms.

VEGFA variants are associated with pre-school lung function, but not neonatal lung function

BACKGROUND

Vascular endothelial growth factor (VEGF) is implicated in airway remodelling and asthma development. We studied VEGFA gene variants and plasma levels and the development of lung function, bronchial hyperresponsiveness and asthma in childhood.

METHODS

We analysed 13 SNPs in the VEGFA gene in 411 children from the COPSAC2000 high-risk birth cohort. Asthma was diagnosed prospectively, and lung function measurements were obtained at birth and 6 years of age. Plasma VEGF levels were measured at 18 months of age. We used a Bonferroni adjusted significance level. Findings were replicated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort at age 8.

RESULTS

At age six, three SNPs from the same linkage block were associated with FEV1 (rs699947, P = 1.31E-05), independent of asthma, and there were suggestive associations between FEV1/FVC ratio and rs833052 and maximal mid-expiratory flow and rs6900017. Replication in the PIAMA cohort showed borderline association between FEV1 and rs699947 and significant meta-analysis result. SNPs upstream and nearby rs699947 were nominally associated with VEGF plasma levels. VEGF levels were not associated with asthmatic symptoms or lung function measures.

CONCLUSIONS AND CLINICAL RELEVANCE

VEGF gene variants are associated with lung function at school age, but not at birth, suggesting a role of VEGF in post-natal lung function development.

A spatiotemporal view of plasmid loss in biofilms and planktonic cultures

This Commentary by Madsen, Burmølle, and Sørensen discusses the article Non-invasive in situ monitoring and quantification of TOL plasmid segregational loss within Pseudomonas putida biofilms by Ma, Katzenmeyer, and Bryers. (2013. Biotechnol Bioeng. 110(11):2949-2958. DOI: 10.1002/bit.24953).

The interconnection between biofilm formation and horizontal gene transfer

Recent research has revealed that horizontal gene transfer and biofilm formation are connected processes. Although published research investigating this interconnectedness is still limited, we will review this subject in order to highlight the potential of these observations because of their believed importance in the understanding of the adaptation and subsequent evolution of social traits in bacteria. Here, we discuss current evidence for such interconnectedness centred on plasmids. Horizontal transfer rates are typically higher in biofilm communities compared with those in planktonic states. Biofilms, furthermore, promote plasmid stability and may enhance the host range of mobile genetic elements that are transferred horizontally. Plasmids, on the other hand, are very well suited to promote the evolution of social traits such as biofilm formation. This, essentially, transpires because plasmids are independent replicons that enhance their own success by promoting inter-bacterial interactions. They typically also carry genes that heighten their hosts' direct fitness. Furthermore, current research shows that the so-called mafia traits encoded on mobile genetic elements can enforce bacteria to maintain stable social interactions. It also indicates that horizontal gene transfer ultimately enhances the relatedness of bacteria carrying the mobile genetic elements of the same origin. The perspective of this review extends to an overall interconnectedness between horizontal gene transfer, mobile genetic elements and social evolution of bacteria.

Procalcitonin as a marker of postoperative complications

OBJECTIVE

Procalcitonin (PCT) is a 116 amino acid peptide that functions as a pro-hormone for calcitonin in the C cells of the thyroid gland. Large quantities of intact PCT are present in the blood of patients with sepsis, particularly when organ dysfunction occurs. PCT has been proposed as an early marker of postoperative complications. The aim of this study was to examine the diagnostic accuracy of PCT as a marker of postoperative complications by systematically reviewing the existing literature.

MATERIAL AND METHODS

The databases PubMed, Embase and the Cochrane Library were searched to find studies on the diagnostic accuracy of PCT in the postoperative phase. Primary studies were retrieved using specific inclusion and exclusion criteria.

RESULTS

A total of nine studies were included. These studies were heterogeneous regarding the spectrum of patients, complications, design and methodological quality according to QUADAS (quality assessment of studies of diagnostic accuracy). This could explain the marked variation in diagnostic accuracy. Considering all types of complications the sensitivity ranged from 37% to 100% and the specificity from 70% to 100%. On examining the infectious complications separately, it was found that the sensitivity ranged from 70% to 86% and the specificity from 45% to 98%.

CONCLUSIONS

Owing to a pronounced heterogeneity among the existing studies, the diagnostic accuracy of PCT as a marker for postoperative complications is not yet sufficiently clarified.

No association between hip geometry and four common polymorphisms associated with fracture: the Danish osteoporosis prevention study

Both osteoporosis and hip geometry are independently associated with fracture risk. There is a significant genetic contribution to the risk of osteoporosis, and evidence provided by twin studies has suggested that hip geometry may also in part be genetically programmed. Polymorphisms in a number of genes, including those coding for methylene-tetrahydrofolate reductase (MTHFR c.677C > T), the purinergic P2X(7) receptor (Glu496Ala and Ile568Asn), and the low-density lipoprotein receptor-related protein 5 (LRP5 exon 9 [c.266A > G]), have been associated with an increased fracture incidence and/or reduced bone mineral density (BMD). The aim of the present study was to test whether these polymorphisms influence hip structural geometry in perimenopausal women. The four polymorphisms were genotyped in 800 healthy recently perimenopausal women never using hormone replacement therapy. BMD of the femoral neck was measured using a Hologic QDR-2000 densitometer and femoral neck axis length, neck width, neck shaft angle, and femoral head diameter were measured from the screen images. Genotype frequencies were compatible with Hardy-Weinberg equilibrium. No significant differences between homozygotes for the minor allele and carriers of the common allele regarding parameters of hip geometry were demonstrated. According to the anthropometric characteristics of the subjects, only body height in the MTHFR TT genotype group was significantly different from the combined CT/CC genotype group (P < 0.05). The geometric dimensions of the proximal femur in perimenopausal women are not associated with the MTHFR c.677C > T, P2X(7) (Glu496Ala), P2X(7) (Ile568Asn), and LRP5 exon 9 (c.266A > G) polymorphisms.

Validation of the PHEEM instrument in a Danish hospital setting

The Postgraduate Hospital Educational Environment Measure (PHEEM) has been translated into Danish and then validated with good internal consistency by 342 Danish junior and senior hospital doctors. Four of the 40 items are culturally dependent in the Danish hospital setting. Factor analysis demonstrated that seven items are interconnected. This information can be used to shorten the instrument by perhaps another three items.

Positive impact of hormone replacement therapy on the fibrinolytic system: a long-term randomized controlled study in healthy postmenopausal women

BACKGROUND

The mechanisms by which postmenopausal hormone replacement therapy (HRT) may influence risk of cardiovascular disease are still unclear. Impaired fibrinolytic function is associated with an enhanced risk of cardiovascular disease and therefore the effect of HRT on fibrinolysis may be of importance.

OBJECTIVES

To investigate the prolonged effect of HRT on the fibrinolytic system and to determine whether two common polymorphisms in the plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) genes modulate this effect.

METHODS

Healthy postmenopausal women (n = 248) were randomized to HRT (n = 122) or no substitution (n = 126) 5 years prior to investigation.

RESULTS

Significantly higher values of t-PA activity and lower values of PAI-1 activity and PAI-1 antigen were found in the HRT group compared with the control group. This effect was independent of smoking and without influence from the two common polymorphisms PAI-1 -675(4G/5G) and t-PA intron8ins311. Furthermore, no difference between opposed estrogen (with norethisterone acetate as the gestagen component) and unopposed estrogen therapy was found. Both an intention-to-treat and a per-protocol analysis were performed and similar results were obtained.

CONCLUSIONS

Long-term treatment with HRT in healthy postmenopausal women was found to be associated with a beneficial fibrinolytic profile. This effect was found independent of smoking status, opposed and unopposed estrogen therapy had equal effect, and no influence of the two common polymorphisms PAI-1-675(4G/5G) and t-PA intron8ins311 was found. This effect of HRT on fibrinolytic capacity may be one of the beneficial effects of HRT in relation to cardiovascular diseases.

Effect of long-term hormone replacement therapy on tissue factor pathway inhibitor and thrombin activatable fibrinolysis inhibitor in healthy postmenopausal women: a randomized controlled study

It was recently reported from the Women's Health Initiative that healthy women using combined hormone replacement therapy (HRT) for 5 years have an increased cardiovascular risk. We hypothesize that the increased risk is confined to subgroups of atherosclerotic women. Such women may have higher arterial tissue factor expression and higher thrombin formation, and changes in tissue factor pathway coagulation inhibitor (TFPI) and thrombin activatable fibrinolysis inhibitor (TAFI) may be deleterious. Healthy postmenopausal women (n = 719) were randomized to hormone therapy [n = 357; opposed (n = 290) and unopposed (n = 67)] or no treatment (n = 362). Plasma TFPI and TAFI and the TFPI -287T/C and TAFI -438G/A polymorphisms were measured 5-6 years after randomization. Concentrations of TFPI were significantly lower in the hormone group than in the control group (P < 0.001) and in all genotypes of the TFPI polymorphism. Overall, concentrations of TAFI did not differ between the two groups but were reduced by hormone therapy in homozygotes for the rare TAFI -438 A allele (P < 0.05). The hormone effects on TFPI and TAFI were similar in smokers and non-smokers and in women using unopposed and opposed therapy. The observed decrease in TFPI may contribute to the increased cardiovascular risk associated with HRT.

Arthroscopic treatment of shoulder instability: current concepts and techniques

The incidence of glenohumeral joint instability is estimated to effect between 2 and 8% of the population. It represents at least one third of all shoulder related emergency room visits. When one considers the spectrum of shoulder instability, including transient subluxation, the true incidence of glenohumeral instability is probably grossly under-reported. Although any age group can be affected, shoulder instability is primarily a disease of the young. The occurrence of instability is inversely proportional to the age of the patient and the time of original injury. A patient who dislocates for the first time as a teen can expect a redislocation rate approaching 90% in his or her lifetime. Therefore, many authors recommend early surgical treatment to repair the lesion.

Association of a common allelic polymorphism (C677T) in the methylene tetrahydrofolate reductase gene with a reduced risk of osteoporotic fractures. A case control study in Danish postmenopausal women

Twin studies indicate a substantial genetic component in the development of osteoporosis. One of the latest studied candidate genes is the one coding for methylene tetrahydrofolate reductase (MTHFR) (C677T) in which a point mutation gives rise to a thermolabile variant of MTHFR. The aim of this study was to investigate the influence of this mutation on peripheral measures of bone density and on the odds ratios (OR) for hip and lower forearm fracture in a case control study of Danish postmenopausal women. A total of 74 women with lower forearm fracture, 41 women with hip fracture, and 207 age-matched controls were included. All had broadband ultrasound attenuation (BUA) and speed of sound (SOS) measured at the heel as well as bone mineral density (BMD) measured by dual X-ray absorptiometry at the distal forearm. The MTHFR (C677T) genotypes were determined using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Only 2 of 21 individuals with the TT genotype had sustained a fracture as opposed to 46 of 142 with the CT genotype and 67 of 159 with the CC genotype (P = 0.007). Using logistic regression, the following odds ratios were found when comparing the individuals homozygotic for the C-allele with those homozygotic for the T-allele: lower forearm fracture OR = 3.93 (1.25; 12.40, P = 0.02), hip fracture OR = 6.99 (l.35; 36.92, P = 0.02) and the fractures combined OR = 4.33 (1.73; 10.81, P = 0.002). In this study, the MTHFR (C677T) genotypes were not significantly associated with BMD at the lower forearm or with ultrasound parameters measured at the calcaneus. However, a significant increase in the odds ratio of fracture was found for the wild-type C-allele.

[Evidence-based use of clinical biochemistry]

Evidence-based use of clinical biochemistry integrates into clinical decision-making the best research evidence with the clinical expertise of the physician and the expectations and concerns of the patient. The best research evidence for the clinical use of a biochemical test should be appraised in close collaboration between clinicians and specialists in clinical biochemistry, as familiarity with both the clinical problem and the analytical performance of the test is necessary. At present, it is difficult to ensure an evidence-based use of biochemical tests. More and methodologically better studies of the clinical value of biochemical tests are needed, and methods should be developed that make it possible to assess the results of such studies by systematic reviews and meta-analyses. Clinical biochemistry is an interdisciplinary specialty, and papers on the clinical value of biochemical tests are published in a vast number of journals of different clinical specialties as well as those of clinical biochemistry. It is thus almost impossible to keep abreast of the subject. The establishment of a system for literature surveillance focusing on methodologically sound studies of the clinical value of biochemical tests would be advantageous. Lastly, training and education on how to find and assess the existing evidence for the clinical use of biochemical tests are needed.

[Questions as evident key to knowledge: teaching medical students evidence-based medicine]

INTRODUCTION

In Denmark, as in other countries, there is an increasing focus on evidence-based medicine (EBM) as a necessary tool for using modern sources of information, but until now EBM training has not been incorporated in our undergraduate curriculum.

MATERIAL AND METHODS

This course is given in the ninth semester (out of 13) and the subject matter is clinical biochemistry. The course consists of seven (one-hour) lectures over three weeks. First, the EBM method is introduced, then the students split up into small groups, choose their own diagnostic problem, and carry out a structured search. The search leads to the choice of a scientific article, which is subsequently presented to and discussed by all the students. We asked about their opinion of the course by questionnaire.

RESULTS

The answers to the questionnaire confirmed that the students have improved their ability to read and assess scientific articles and to seek information, and it has stimulated them to understand concepts instead of memorising details.

DISCUSSION

Although the assessment of this course was positive, it can no doubt be improved and further developed. In our opinion the use of EBM should not be confined to one course. The medical students should be introduced to EBM at an early stage, thereby abling them to practice it throughout their training.

The joint capsule and joint laxity in dogs with hip dysplasia

Present knowledge of the complexity of joint diseases makes it difficult to investigate the causes and early pathogenesis of canine hip dysplasia. Clinical signs of canine hip dysplasia including joint laxity may be a result of primary or secondary alterations of the joint. We already know that joint laxity is related to effusive synovitis (ie, accumulation of synovial fluid) and to other primary collagenous diseases. Canine hip dysplasia may be a third collagenous disease associated with joint laxity. This paper summarizes some of the studies that investigated the relationship between joint laxity and a defect in collagen metabolism and the influence that alterations in transsynovial flow have on joint laxity.

Angiotensin converting enzyme inhibitor therapy and acute pancreatitis

Angiotensin converting enzyme (ACE) inhibitors are generally well tolerated. Worldwide, only few reports have been published associating pancreatitis with ACE inhibitor therapy. We report a case in whom there was no other likely explanation for the acute pancreatitis than enalapril therapy, which was temporally associated with the symptoms. Possible mechanisms underlying the induction of pancreatitis by ACE inhibitors are discussed. With the increasing use of ACE inhibitors, the incidence of rare adverse effects such as potentially lethal pancreatitis is likely to increase. Clinicians need to be aware of this association.

Serum concentrations of procollagen type III aminoterminal peptide in growing dogs with hip dysplasia

The aim of the present study was to investigate the use of procollagen type III aminoterminal peptide (PIIINP) measurements in serum as an indicator of progress of fibrosis of coxofemoral joint capsules in hip dysplasia in immature dogs. High serum concentrations of PIIINP may indicate ongoing fibrosis with enhanced synthesis and deposition of fibrillar type III collagen, or an alteration in degradation and elimination of circulating PIIINP (Hørslev-Petersen et al. 1988a). Therefore, high concentrations of PIIINP in serum was expected in dogs with hip dysplasia, which is a developmental condition with capsular fibrosis and osteoarthritis (Gay et al. 1986).

Inclination and anteversion of collum femoris in hip dysplasia and coxarthritis

Femoral neck angles were measured radiographically in 41 dogs examined for hip dysplasia. Steep femoral neck inclination was found to be a phenomenon of hip dysplasia and coxofemoral joint laxity. The altered biomechanics of a steep femoral neck inclination may be a factor in the pathogenesis of hip dysplasia and secondary osteoarthritis.

Procollagen type-III aminoterminal peptide in serum and synovial fluid of dogs with hip dysplasia and coxarthrosis

Hip dysplasia is an affection of the coxofemoral joint that progresses until stabilization is caused by fibrosis and osteoarthritic changes. This stabilization process can be examined by clinical and radiographic methods. The capability of evaluating the procollagen concentrations in liquids, such as serum and synovial fluid, has further offered the basis for an objective biochemical evaluation of the stabilization process. Our study was performed to evaluate whether determination of procollagen concentrations was suitable for the use in practice. The procollagen type-III aminoterminal peptide (P-III-NP) concentration was measured in serum and in synovial fluid from coxofemoral joints in 20 dogs. Dogs were grouped on the basis of evidence of dysplasia and osteoarthritic changes of the hip: (1) a control group of 6 dogs without clinical or radiographic signs of hip dysplasia, and (2) dysplastic group of 14 dogs, which was further grouped with respect to the coxofemoral joint laxity, as determined by the Ortolani test. Synovial fluid concentration of P-III-NP was significantly (P less than 0.05) higher in fluid from dysplastic joints than in fluid from normal joints. Serum concentrations of P-III-NP were significantly (P less than 0.05) higher in dogs in which results of the Ortolani test were positive.