Fosfomycin for Non-Urinary Tract Infections: a systematic review.

Introduction: Although fosfomycin is currently approved for treating urinary tract infections, it is increasingly being used as salvage therapy for various infectious syndromes outside the urinary tract. This systematic review evaluates clinical and microbiological cure rates in patients with bacterial infections not restricted to the urinary tract where fosfomycin was used off-label. Materials and Methods: Articles from two databases (Pubmed and Scopus) were reviewed. The dosage, route, and duration of fosfomycin therapy along with the details of adjunctive antimicrobial agents were noted. The final outcomes captured were clinical or microbiological cures. Results: A total of 649 articles, not including duplicates, were selected for the title and abstract screening. After title and abstract screening, 102 articles were kept for full-text screening. Of the 102 articles, 23 studies (n=1227 patients) were kept in the final analysis. Of the 1227 patients, 301 (25%) received fosfomycin as monotherapy, and the remaining 926 75%) received fosfomycin in combination with at least one other antimicrobial agent. Most of the patients received intravenous fosfomycin (n=1046, 85%). Staphylococcus spp and Enterobacteriaceae were the most common organisms. The pooled clinical and microbiological cure rates were 75% and 84%, respectively. Conclusion: Fosfomycin has moderate clinical success in patients with non-urinary tract infections, especially when used with other antimicrobials. Due to the paucity of randomized controlled trials, fosfomycin's use should be limited to situations where no alternatives are supported by better clinical evidence.

Role of tigecycline in the treatment of urinary tract infections: a systematic review of published case reports.

Introduction: The emergence of multi-drug resistance has forced clinicians to occasionally use drugs that are not approved to treat urinary tract infections (UTIs). This systematic review aimed to evaluate the utility of tigecycline in patients with UTIs. Methodology: A systematic review of case studies was used to retrieve articles between 1.1.1999 to 1.1.2021 from two databases, PubMed and Embase. The title-abstract screening was done for 198 articles, out of which 69 articles were included for full-text screening. A total of 18 articles with 27 cases were included for final analysis. Results: Of the 27 cases, there were 13 cases with complicated UTI and five had catheter-associated UTI. The most common organisms were Klebsiella pneumoniae (n=11), Acinetobacter baumannii (n=9), and Escherichia coli (n=6). Tigecycline was used as monotherapy in 19 patients and as a combination therapy in 8 patients. The median duration of tigecycline was 13 (10-15) days. A favourable clinical or microbiological response at varying intervals was seen in 24/27 (88.9%). Within three months of a favourable response, recurrence of symptoms was seen in four patients. Conclusion: In a small analysis of published case reports, tigecycline appeared to be a relatively effective treatment in patients with UTIs, caused by multidrug-resistant organisms. Where tigecycline is the only susceptible drug, it can be used for treatment. Further research, such as randomized controlled trials, is needed to fully assess the drug's efficacy in this context.

Optineurin links Hace1-dependent Rac ubiquitylation to integrin-mediated mechanotransduction to control bacterial invasion and cell division.

Extracellular matrix (ECM) elasticity is perceived by cells via focal adhesion structures, which transduce mechanical cues into chemical signalling to conform cell behavior. Although the contribution of ECM compliance to the control of cell migration or division is extensively studied, little is reported regarding infectious processes. We study this phenomenon with the extraintestinal Escherichia coli pathogen UTI89. We show that UTI89 takes advantage, via its CNF1 toxin, of integrin mechanoactivation to trigger its invasion into cells. We identify the HACE1 E3 ligase-interacting protein Optineurin (OPTN) as a protein regulated by ECM stiffness. Functional analysis establishes a role of OPTN in bacterial invasion and integrin mechanical coupling and for stimulation of HACE1 E3 ligase activity towards the Rac1 GTPase. Consistent with a role of OPTN in cell mechanics, OPTN knockdown cells display defective integrin-mediated traction force buildup, associated with limited cellular invasion by UTI89. Nevertheless, OPTN knockdown cells display strong mechanochemical adhesion signalling, enhanced Rac1 activation and increased cyclin D1 translation, together with enhanced cell proliferation independent of ECM stiffness. Together, our data ascribe a new function to OPTN in mechanobiology.

A nutrient relay sustains subtropical ocean productivity.

The expansive gyres of the subtropical ocean account for a significant fraction of global organic carbon export from the upper ocean. In the gyre interior, vertical mixing and the heaving of nutrient-rich waters into the euphotic layer sustain local productivity, in turn depleting the layers below. However, the nutrient pathways by which these subeuphotic layers are themselves replenished remain unclear. Using a global, eddy-permitting simulation of ocean physics and biogeochemistry, we quantify nutrient resupply mechanisms along and across density surfaces, including the contribution of eddy-scale motions that are challenging to observe. We find that mesoscale eddies (10 to 100 km) flux nutrients from the shallow flanks of the gyre into the recirculating interior, through time-varying motions along density surfaces. The subeuphotic layers are ultimately replenished in approximately equal contributions by this mesoscale eddy transport and the remineralization of sinking particles. The mesoscale eddy resupply is most important in the lower thermocline for the whole subtropical region but is dominant at all depths within the gyre interior. Subtropical gyre productivity may therefore be sustained by a nutrient relay, where the lateral transport resupplies nutrients to the thermocline and allows vertical exchanges to maintain surface biological production and carbon export.

Cell response to substrate rigidity is regulated by active and passive cytoskeletal stress.

Morphogenesis, tumor formation, and wound healing are regulated by tissue rigidity. Focal adhesion behavior is locally regulated by stiffness; however, how cells globally adapt, detect, and respond to rigidity remains unknown. Here, we studied the interplay between the rheological properties of the cytoskeleton and matrix rigidity. We seeded fibroblasts onto flexible microfabricated pillar arrays with varying stiffness and simultaneously measured the cytoskeleton organization, traction forces, and cell-rigidity responses at both the adhesion and cell scale. Cells adopted a rigidity-dependent phenotype whereby the actin cytoskeleton polarized on stiff substrates but not on soft. We further showed a crucial role of active and passive cross-linkers in rigidity-sensing responses. By reducing myosin II activity or knocking down α-actinin, we found that both promoted cell polarization on soft substrates, whereas α-actinin overexpression prevented polarization on stiff substrates. Atomic force microscopy indentation experiments showed that this polarization response correlated with cell stiffness, whereby cell stiffness decreased when active or passive cross-linking was reduced and softer cells polarized on softer matrices. Theoretical modeling of the actin network as an active gel suggests that adaptation to matrix rigidity is controlled by internal mechanical properties of the cytoskeleton and puts forward a universal scaling between nematic order of the actin cytoskeleton and the substrate-to-cell elastic modulus ratio. Altogether, our study demonstrates the implication of cell-scale mechanosensing through the internal stress within the actomyosin cytoskeleton and its coupling with local rigidity sensing at focal adhesions in the regulation of cell shape changes and polarity.

Recovery of Tractions Exerted by Single Cells in Three-Dimensional Nonlinear Matrices.

Cell-generated tractions play an important role in various physiological and pathological processes such as stem-cell differentiation, cell migration, wound healing, and cancer metastasis. Traction force microscopy (TFM) is a technique for quantifying cellular tractions during cell-matrix interactions. Most applications of this technique have heretofore assumed that the matrix surrounding the cells is linear elastic and undergoes infinitesimal strains, but recent experiments have shown that the traction-induced strains can be large (e.g., more than 50%). In this paper, we propose a novel three-dimensional (3D) TFM approach that consistently accounts for both the geometric nonlinearity introduced by large strains in the matrix, and the material nonlinearity due to strain-stiffening of the matrix. In particular, we pose the TFM problem as a nonlinear inverse hyperelasticity problem in the stressed configuration of the matrix, with the objective of determining the cellular tractions that are consistent with the measured displacement field in the matrix. We formulate the inverse problem as a constrained minimization problem and develop an efficient adjoint-based minimization procedure to solve it. We first validate our approach using simulated data, and quantify its sensitivity to noise. We then employ the new approach to recover tractions exerted by NIH 3T3 cells fully encapsulated in hydrogel matrices of varying stiffness. We find that neglecting nonlinear effects can induce significant errors in traction reconstructions. We also find that cellular tractions roughly increase with gel stiffness, while the strain energy appears to saturate.

Cell shape and substrate stiffness drive actin-based cell polarity.

A general trait of living cells is their ability to exert contractile stresses on their surroundings and thus respond to substrate rigidity. At the cellular scale, this response affects cell shape, polarity, and ultimately migration. The regulation of cell shape together with rigidity sensing remains largely unknown. In this article we show that both substrate rigidity and cell shape contribute to drive actin organization and cell polarity. Increasing substrate rigidity affects bulk properties of the actin cytoskeleton by favoring long-lived actin stress fibers with increased nematic interactions, whereas cell shape imposes a local alignment of actin fibers at the cell periphery.

Coordination between Intra- and Extracellular Forces Regulates Focal Adhesion Dynamics.

Focal adhesions (FAs) are important mediators of cell-substrate interactions. One of their key functions is the transmission of forces between the intracellular acto-myosin network and the substrate. However, the relationships between cell traction forces, FA architecture, and molecular forces within FAs are poorly understood. Here, by combining Förster resonance energy transfer (FRET)-based molecular force biosensors with micropillar-based traction force sensors and high-resolution fluorescence microscopy, we simultaneously map molecular tension across vinculin, a key protein in FAs, and traction forces at FAs. Our results reveal strong spatiotemporal correlations between vinculin tension and cell traction forces at FAs throughout a wide range of substrate stiffnesses. Furthermore, we find that molecular tension within individual FAs follows a biphasic distribution from the proximal (toward the cell nucleus) to distal end (toward the cell edge). Using super-resolution imaging, we show that such a distribution relates to that of FA proteins. On the basis of our experimental data, we propose a model in which FA dynamics results from tension changes along the FAs.

Quantifying Tensile Force and ERK Phosphorylation on Actin Stress Fibers.

ERK associates with the actin cytoskeleton, and the actin-associated pool of ERK can be activated (phosphorylated in the activation loop) to induce specific cell responses. Increasing evidence has shown that mechanical conditions of cells significantly affect ERK activation. In particular, tension developed in the actin cytoskeleton has been implicated as a critical mechanism driving ERK signaling. However, a quantitative study of the relationship between actin tension and ERK phosphorylation is missing. In this chapter, we describe our novel methods to quantify tensile force and ERK phosphorylation on individual actin stress fibers. These methods have enabled us to show that ERK is activated on stress fibers in a tensile force-dependent manner.

Single cell rigidity sensing: A complex relationship between focal adhesion dynamics and large-scale actin cytoskeleton remodeling.

Many physiological and pathological processes involve tissue cells sensing the rigidity of their environment. In general, tissue cells have been shown to react to the stiffness of their environment by regulating their level of contractility, and in turn applying traction forces on their environment to probe it. This mechanosensitive process can direct early cell adhesion, cell migration and even cell differentiation. These processes require the integration of signals over time and multiple length scales. Multiple strategies have been developed to understand force- and rigidity-sensing mechanisms and much effort has been concentrated on the study of cell adhesion complexes, such as focal adhesions, and cell cytoskeletons. Here, we review the major biophysical methods used for measuring cell-traction forces as well as the mechanosensitive processes that drive cellular responses to matrix rigidity on 2-dimensional substrates.

Adaptive rheology and ordering of cell cytoskeleton govern matrix rigidity sensing.

Matrix rigidity sensing regulates a large variety of cellular processes and has important implications for tissue development and disease. However, how cells probe matrix rigidity, and hence respond to it, remains unclear. Here, we show that rigidity sensing and adaptation emerge naturally from actin cytoskeleton remodelling. Our in vitro experiments and theoretical modelling demonstrate a biphasic rheology of the actin cytoskeleton, which transitions from fluid on soft substrates to solid on stiffer ones. Furthermore, we find that increasing substrate stiffness correlates with the emergence of an orientational order in actin stress fibres, which exhibit an isotropic to nematic transition that we characterize quantitatively in the framework of active matter theory. These findings imply mechanisms mediated by a large-scale reinforcement of actin structures under stress, which could be the mechanical drivers of substrate stiffness-dependent cell shape changes and cell polarity.

Micropillar substrates: a tool for studying cell mechanobiology.

Increasing evidence has shown that mechanical cues from the environment play an important role in cell biology. Mechanotransduction or the study of how cells can sense these mechanical cues, and respond to them, is an active field of research. However, it is still not clear how cells sense and respond to mechanical cues. Thus, new tools are being rapidly developed to quantitatively study cell mechanobiology. Particularly, force measurement tools such as micropillar substrates have provided new insights into the underlying mechanisms of mechanosensing. In this chapter, we provide detailed protocol for fabrication, characterization, functionalization, and use of the micropillar substrates.

Actomyosin bundles serve as a tension sensor and a platform for ERK activation.

Tensile forces generated by stress fibers drive signal transduction events at focal adhesions. Here, we report that stress fibers per se act as a platform for tension-induced activation of biochemical signals. The MAP kinase, ERK is activated on stress fibers in a myosin II-dependent manner. In myosin II-inhibited cells, uniaxial stretching of cell adhesion substrates restores ERK activation on stress fibers. By quantifying myosin II- or mechanical stretch-mediated tensile forces in individual stress fibers, we show that ERK activation on stress fibers correlates positively with tensile forces acting on the fibers, indicating stress fibers as a tension sensor in ERK activation. Myosin II-dependent ERK activation is also observed on actomyosin bundles connecting E-cadherin clusters, thus suggesting that actomyosin bundles, in general, work as a platform for tension-dependent ERK activation.

Forces driving epithelial wound healing.

A fundamental feature of multicellular organisms is their ability to self-repair wounds through the movement of epithelial cells into the damaged area. This collective cellular movement is commonly attributed to a combination of cell crawling and "purse-string" contraction of a supracellular actomyosin ring. Here we show by direct experimental measurement that these two mechanisms are insufficient to explain force patterns observed during wound closure. At early stages of the process, leading actin protrusions generate traction forces that point away from the wound, showing that wound closure is initially driven by cell crawling. At later stages, we observed unanticipated patterns of traction forces pointing towards the wound. Such patterns have strong force components that are both radial and tangential to the wound. We show that these force components arise from tensions transmitted by a heterogeneous actomyosin ring to the underlying substrate through focal adhesions. The structural and mechanical organization reported here provides cells with a mechanism to close the wound by cooperatively compressing the underlying substrate.

A localised soft tissue and bone enlargement in an infant mandible.

A 4-month-old infant was referred by a paediatrician for a rapidly growing swelling on the right side of the mandible of 1.5 months duration. His medical and family history was unremarkable. Palpation divulged a firm and tender enlargement with the overlying soft tissue showing no significant alteration in colour. CT scan revealed cortical irregularity involving the ramus on the right side along with right masseter muscle hypertrophy. Routine haematological investigation yielded values within normal limits except for a raised erythrocyte sedimentation rate. Histopathological examination of the tissue submitted following an open biopsy procedure showed reactive lamellar bone and trabeculae with fibrous marrow exhibiting inflammation. The final diagnosis of infantile cortical hyperostosis was clinched based on the clinicopathological correlation. A rare reactive bone dystrophy which could pose a certain diagnostic dilemma is addressed herewith.

Calcifying odontogenic cyst: a rare report of a nonneoplastic variant associated with cholesterol granuloma.

AIM: To report a case of a non-neoplastic variant of calcifying odontogenic cyst (COC) with the lining epithelium showing ameloblastomatous proliferation and capsule exhibiting features of a cholesterol granuloma. The importance of delineating this histologic variant from unicystic ameloblastoma and the formation of cholesterol granuloma in this variant is discussed. BACKGROUND: Calcifying odontogenic cyst is a developmental jaw cyst, which presents itself as both the neoplastic and the non-neoplastic forms. The ameloblastomatous variant of COC is often mistaken for unicystic ameloblastoma and treated aggressively. CASE REPORT: A 68-year-old female who presented with a cystic enlargement of the posterior mandible on the right side was suggestive of unicystic ameloblastoma based on radiography and initial biopsy report. Microscopic examination of the excision specimen, however, was fitting in favor of calcifying odontogenic cyst with ameloblastomatous proliferation. CONCLUSION: Identifying the non-neoplastic ameloblastomatous variant of COC from a cystic ameloblastoma is crucial as the treatment of the two lesions vary considerably. CLINICAL SIGNIFICANCE: This case emphasizes the need for thorough examination of the entire surgical specimen before arriving at an appropriate diagnosis.

Evidence of a large-scale mechanosensing mechanism for cellular adaptation to substrate stiffness.

Cell migration plays a major role in many fundamental biological processes, such as morphogenesis, tumor metastasis, and wound healing. As they anchor and pull on their surroundings, adhering cells actively probe the stiffness of their environment. Current understanding is that traction forces exerted by cells arise mainly at mechanotransduction sites, called focal adhesions, whose size seems to be correlated to the force exerted by cells on their underlying substrate, at least during their initial stages. In fact, our data show by direct measurements that the buildup of traction forces is faster for larger substrate stiffness, and that the stress measured at adhesion sites depends on substrate rigidity. Our results, backed by a phenomenological model based on active gel theory, suggest that rigidity-sensing is mediated by a large-scale mechanism originating in the cytoskeleton instead of a local one. We show that large-scale mechanosensing leads to an adaptative response of cell migration to stiffness gradients. In response to a step boundary in rigidity, we observe not only that cells migrate preferentially toward stiffer substrates, but also that this response is optimal in a narrow range of rigidities. Taken together, these findings lead to unique insights into the regulation of cell response to external mechanical cues and provide evidence for a cytoskeleton-based rigidity-sensing mechanism.