Genetic and Functional Diversity Help Explain Pathogenic, Weakly Pathogenic, and Commensal Lifestyles in the Genus Xanthomonas.

The genus Xanthomonas has been primarily studied for pathogenic interactions with plants. However, besides host and tissue-specific pathogenic strains, this genus also comprises nonpathogenic strains isolated from a broad range of hosts, sometimes in association with pathogenic strains, and other environments, including rainwater. Based on their incapacity or limited capacity to cause symptoms on the host of isolation, nonpathogenic xanthomonads can be further characterized as commensal and weakly pathogenic. This study aimed to understand the diversity and evolution of nonpathogenic xanthomonads compared to their pathogenic counterparts based on their cooccurrence and phylogenetic relationship and to identify genomic traits that form the basis of a life history framework that groups xanthomonads by ecological strategies. We sequenced genomes of 83 strains spanning the genus phylogeny and identified eight novel species, indicating unexplored diversity. While some nonpathogenic species have experienced a recent loss of a type III secretion system, specifically the hrp2 cluster, we observed an apparent lack of association of the hrp2 cluster with lifestyles of diverse species. We performed association analysis on a large data set of 337 Xanthomonas strains to explain how xanthomonads may have established association with the plants across the continuum of lifestyles from commensals to weak pathogens to pathogens. Presence of distinct transcriptional regulators, distinct nutrient utilization and assimilation genes, transcriptional regulators, and chemotaxis genes may explain lifestyle-specific adaptations of xanthomonads.

A Brief Evaluation of a Copper Resistance Mobile Genetic Island in the Bacterial Leaf Spot Pathogen Xanthomonas euvesicatoria pv. perforans.

Due to the continuous use of copper containing bactericides without effective alternative bactericides, copper resistance has become more prevalent in plant pathogens, including Xanthomonas euvesicatoria pv. perforans (formerly Xanthomonas perforans), a predominant cause of bacterial leaf spot disease of tomato and pepper in the Southeastern United States. Previously, reports of copper resistance have been associated with a large conjugative plasmid. However, we have characterized a copper resistance genomic island located within the chromosome of multiple X. euvesicatoria pv. perforans strains. The island is distinct from a previously described chromosomally encoded copper resistance island in X. vesicatoria strain XVP26. Computational analysis revealed the genomic island to contain multiple genes associated with genetic mobility, including both phage-related genes and transposase. Among copper-tolerant strains of X. euvesicatoria pv. perforans isolated from Florida, the majority of strains were found to have the copper resistance chromosomally encoded rather than plasmid borne. Our results suggest that this copper resistance island may have two modes of horizontal gene transfer and that chromosomally encoded copper resistance genes may provide a fitness advantage over plasmid-borne resistance.

Xanthomonas infection and ozone stress distinctly influence the microbial community structure and interactions in the pepper phyllosphere.

While the physiological and transcriptional response of the host to biotic and abiotic stresses have been intensely studied, little is known about the resilience of associated microbiomes and their contribution towards tolerance or response to these stresses. We evaluated the impact of elevated tropospheric ozone (O3), individually and in combination with Xanthomonas perforans infection, under open-top chamber field conditions on overall disease outcome on resistant and susceptible pepper cultivars, and their associated microbiome structure, function, and interaction network across the growing season. Pathogen infection resulted in a distinct microbial community structure and functions on the susceptible cultivar, while concurrent O3 stress did not further alter the community structure, and function. However, O3 stress exacerbated the disease severity on resistant cultivar. This altered diseased severity was accompanied by enhanced heterogeneity in associated Xanthomonas population counts, although no significant shift in overall microbiota density, microbial community structure, and function was evident. Microbial co-occurrence networks under simultaneous O3 stress and pathogen challenge indicated a shift in the most influential taxa and a less connected network, which may reflect the altered stability of interactions among community members. Increased disease severity on resistant cultivar may be explained by such altered microbial co-occurrence network, indicating the altered microbiome-associated prophylactic shield against pathogens under elevated O3. Our findings demonstrate that microbial communities respond distinctly to individual and simultaneous stressors, in this case, O3 stress and pathogen infection, and can play a significant role in predicting how plant-pathogen interactions would change in the face of climate change.

Toward a consensus view in the management of acute facial injuries during the Covid-19 pandemic.

In these unprecedented times, OMFS surgeons are faced with dilemmas over the priority of treatment, safety of staff, safety of patients and the most appropriate use of available resources. Efforts should be made to provide the best evidence-based care, which will mean revisiting old techniques, and risk stratifying patients on a case by case basis. Recent experience from colleagues internationally has shown that even the wealthiest health care infrastructure is at best fragile. We hope this paper will add to the debate and hopefully provide a framework for decision making in OMFS trauma care during this difficult time.

Genome-resolved metagenomics to study co-occurrence patterns and intraspecific heterogeneity among plant pathogen metapopulations.

Assessment of pathogen diversity in agricultural fields is essential for informing management decisions and the development of resistant plant varieties. However, many population genomic studies have relied on culture-based approaches that do not provide quantitative assessment of pathogen populations at the field-level or the associated host microbiome. Here, we applied whole-genome shotgun sequencing of microbial DNA extracted directly from the washings of pooled leaf samples, collected from individual tomato and pepper fields in Alabama that displayed the classical symptoms of bacterial spot disease caused by Xanthomonas spp. Our results revealed that while the occurrence of both X. perforans and X. euvesicatoria within fields was limited, evidence of co-occurrence of up to three distinct X. perforans genotypes was obtained in 7 of 10 tomato fields sampled. These population dynamics were accompanied by the corresponding type 3 secreted effector repertoires associated with the co-occurring X. perforans genotypes, indicating that metapopulation structure within fields should be considered when assessing the adaptive potential of X. perforans. Finally, analysis of microbial community composition revealed that co-occurrence of the bacterial spot pathogens Pseudomonas cichorii and Xanthomonas spp. is common in Alabama fields and provided evidence for the non-random association of several other human and plant opportunists.

Changes in admission rates for spreading odontogenic infection resulting from changes in government policy about the dental schedule and remunerations.

The government changed the system of payment to general dental practitioners on 1 April 2005 from a fee/item to a banding system. The figures collected have shown that there has been a 62% increase in the number of patients who require admission for surgical treatment of spreading odontogenic infections compared with the 3-year period before this date.

Diver's harpoon gun: facial injury caused by an unusual weapon.

This unusual case of a facial injury caused by being shot with a diver's harpoon gun highlights the importance of good radiological assessment and careful planning before removal of the harpoon, and emphasises the need to control the barb.

Current trends and future perspectives in the surgical management of oral cancer.

Surgery remains the frontline treatment for oral cancer. Factors affecting the surgical management are related to the staging of the primary disease and the presence of regional or distant metastasis. Histopathological parameters such as tumour grade, depth and pattern of invasion are of paramount importance for the extent of the surgical treatment. Surgery of the neck is evolving to more selective treatments and the concept of sentinel lymph node biopsy is gradually been established in the management of the neck for early oral cancer. Reconstruction of the defect is mainly performed with free flaps. Further refinement in the flap selection and harvesting techniques will lead to free-style flap reconstruction, minimising the morbidity of the donor site and increasing the versatility of reconstruction at the recipient site.

Ultrasound-guided photodynamic therapy for deep seated pathologies: prospective study.

INTRODUCTION: Interstitial photodynamic therapy remains an attractive remedial option in minimally invasive surgery. Our aim in this prospective study was to evaluate the outcome following ultrasound-guided iPDT of deep-seated pathologies. Patients' reports on quality of life with clinical and radiological evaluation were the main end point parameters used to assess the outcome. MATERIALS AND METHODS: Sixty-eight patients were referred to the UCLH Head and Neck Centre for treatment of various deep-seated pathologies involving the head and neck region, upper and lower limbs. All patients underwent interstitial photodynamic therapy under general anaesthesia, using 0.15 mg/kg mTHPC as the photosensitising agent. Following treatment, patients were followed-up for a mean of 7 months. RESULTS: All three patients who presented with visual problems reported improvement after treatment. Also, 14/17 patients reported improvement of breathing. Improvement of swallowing was reported by 25/30 patients; while speaking improvement was evident in 16/22 patients and 33/40 reported reduction in the disfigurement caused by their pathology. All five patients with impeded limb function reported some degree of improvement. Clinical assessment showed that half of the patients had 'good response' to the treatment and a third reported 'moderate response' with two patients being free of disease. Radiological assessment comparing imaging 6-week post-PDT to the baseline showed stable pathology with no change in size in 13 patients, minimal response in 18 patients, moderate response in 23 patients and significant response in 11 patients. CONCLUSION: This study on 68 patients with deep-seated pathologies undergoing interstitial photodynamic therapy provided evidence that PDT can be the fourth modality in the management of tissue disease.