The Infectious Dose Shapes Vibrio cholerae Within-Host Dynamics

Determining the rates of bacterial migration, replication, and death during infection is important for understanding how infections progress. Separately measuring these rates is often difficult in systems where multiple processes happen simultaneously.

Bacterial translocation and microgap formation at a novel conical indexed implant abutment system for single crowns

Objectives A conometric concept was recently introduced in which conical implant abutments hold the matching crown copings by friction alone, eliminating the need for cement or screws. The aim of this in vitro study was to assess the presence of microgap formation and bacterial leakage at the Acuris conometric restorative interface of three different implant abutment systems. Material and methods A total of 75 Acuris samples of three implant-abutment systems (Ankylos, Astra Tech EV, Xive) were subjected to microbiological (n = 60) and scanning electron microscopic (SEM) investigation (n = 15). Bacterial migration into and out of the conical coupling system were analyzed in an anaerobic workstation for 48, 96, 144, and 192 h. Bacterial DNA quantification using qrt-PCR was performed at each time point. The precision of the conometric coupling and internal fit of cemented CAD/CAM crowns on corresponding Acuris TiN copings were determined by means of SEM. Results qrt-PCR results failed to demonstrate microbial leakage from or into the Acuris system. SEM analysis revealed minute punctate microgaps at the apical aspect of the conometric junction (2.04 to 2.64 µm), while mean cement gaps of 12 to 145 µm were observed at the crown-coping interface. Conclusions The prosthetic morse taper connection of all systems examined does not allow bacterial passage. Marginal integrity and internal luting gap between the ceramic crown and the coping remained within the clinically acceptable limits. Clinical relevance Conometrically seated single crowns provide sufficient sealing efficiency, relocating potential misfits from the crown-abutment interface to the crown-coping interface.

Next-Generation Sequencing Analysis of Root Canal Microbiota Associated with a Severe Endodontic-Periodontal Lesion

A patient with an unusual endo-periodontal lesion, without coronal decay or damage, likely caused by a deep periodontal lesion with subsequent endodontic bacterial migration, required medical care. Next-generation sequencing (NGS) was used to assess the endodontic microbiota in vestibular and palatal canals after tooth extraction, evidencing a predominant population (Fusobacterium nucleatum) in one endodontic canal, and a mixed bacterial population with six major populations almost equally distributed in the other endodontic canal (F. nucleatum, Porphyromonas gingivalis, P. endodontis, Parvimonas, Peptostreptococcus stomatis, Prevotella multiformis). These data could suggest different, separated ecologic niches in the same endodontic system, with potentially different pathogenicity levels, clinical manifestations and prognoses for every single canal of the same tooth.

Capillary bacterial migration on non-nutritive solid surfaces

Here we describe an additional type of bacterial migration in which bacterial cells migrate vertically across a non-nutritive solid surface carried by capillary forces. Unlike standard motility experiments, these were run on a glass slide inserted into a Falcon tube, partly immersed in a nutrient medium and partly exposed to air. Observations revealed that capillary forces initiated upward cell migration when biofilm was formed at the border between liquid and air. The movement was facilitated by the production of extracellular polymeric substances (EPS). This motility differs from earlier described swarming, twitching, gliding, sliding, or surfing, although these types of movements are not excluded. We therefore propose to call it “capillary movement of biofilm”. This phenomenon may be an ecologically important mode of bacterial motility on solid surfaces.

Anisotropic random walks reveal chemotaxis signaling output in run-reversing bacteria

The bias for a particular direction of rotation of the flagellar motor is a sensitive readout of chemotaxis signaling, which mediates bacterial migration towards favorable chemical environments. The rotational bias has not been characterized in Helicobacter pylori, which limits our understanding of the signaling dynamics. Here, we determined that H. pylori swim faster (slower) whenever their flagella rotate counterclockwise (clockwise) by analyzing their hydrodynamic interactions with bounding surfaces. The anisotropy in swimming speeds helped quantify the fraction of the time that the cells swam slower to report the first measurements of the bias. A stochastic model of run-reversals indicated that the anisotropy promotes faster spread compared to isotropic swimmers. The approach further revealed that the diffuse spread of H. pylori is likely limited at the physiological temperature due to increased reversal frequencies. Thus, anisotropic run-reversals make it feasible to study signal-response relations in the chemotaxis network in non-model bacterial species.Impact StatementAnisotropy in run and reversal swimming speeds promotes the spread of H. pylori and reveals temperature-dependent behavior of the flagellar switch.

Influence of pore geometry on motility and trapping of metal reducing bacteria

<p>Diverse processes such as bioremediation, biofertilization, and microbial drug delivery<br>rely on bacterial migration in porous media. However, how pore-scale confinement alters<br>bacterial motility is unknown due to the inherent heterogeneity in porous media. As a<br>result, models of migration are limited and often employ ad hoc assumptions.<br>We aim to determine the impact of pore confinement in the spreading dynamics of two<br>populations of motile metal reducing bacteria by directly visualizing individual <em>Acidovorax</em><br>and <em>Pelosinus</em> in an unconfined liquid medium and in a microfluidic chip containing regular<br>placed pillars. We observe that the length of runs of the two species differs from the<br>unconfined and confined medium. Results show that bacteria in the confined medium<br>display a systematic shorter jumps due to grain obstacles when compared to the open<br>porous medium. Close inspection of the trajectories reveals that cells are intermittently<br>and transiently trapped, which produces superdiffusive motion at early and subdiffusion<br>behavior at late times, as they navigate through the confined pore space. While in the open<br>medium, we observe a linearly increasing variance with respect to time for <em>Acidovorax</em>, and<br>for <em>Pelosinus</em> the variance increases at a much faster rate showing super diffusive behavior<br>at early times. At late times, the rate of growth in spreading increases for <em>Acidovorax</em> while<br>it reduces for <em>Pelosinus</em>. We finally discuss that the paradigm of run-and-tumble motility<br>is dramatically altered in the confined porous medium and its practical applications of<br>these effects on large-scale transport.</p>

Investigating the physical effects in bacterial therapies for avascular tumors

Tumor-targeting bacteria elicit anticancer effects by infiltrating hypoxic regions, releasing toxic agents and inducing immune responses. Although current research has largely focused on the influence of chemical and immunological aspects on the mechanisms of bacterial therapy, the impact of physical effects is still elusive. Here, we propose a mathematical model for the anti-tumor activity of bacteria in avascular tumors that takes into account the relevant chemo-mechanical effects. We consider a time-dependent administration of bacteria and analyze the impact of bacterial chemotaxis and killing rate. We show that active bacterial migration towards tumor hypoxic regions provides optimal infiltration and that high killing rates combined with high chemotactic values provide the smallest tumor volumes at the end of the treatment. We highlight the emergence of steady states in which a small population of bacteria is able to constrain tumor growth. Finally, we show that bacteria treatment works best in the case of tumors with high cellular proliferation and low oxygen consumption.