Owner-assisted recovery and early discharge after surgical treatment in dogs with brachycephalic obstructive airway syndrome.

OBJECTIVES: This study aims to describe a perioperative protocol for dogs recovered from anaesthesia with the owners and discharged from the hospital on the same day after surgical management of brachycephalic obstructive airway syndrome and to determine whether implementation of this protocol was associated with reduced incidence of complications compared with standard anaesthesia recovery and 24 hours hospitalisation. MATERIALS AND METHODS: Medical records of dogs that underwent brachycephalic obstructive airway surgery over two consecutive years (June 2017 to May 2019) were reviewed retrospectively. Signalment, clinical signs, diagnostic findings, surgical procedures and postoperative respiratory complications were recorded. Data were compared using the chi-squared or Fisher's exact tests. RESULTS: Sixty-three dogs met the inclusion criteria for the study. Forty-two dogs underwent owner-assisted recovery and 21 dogs standard recovery. No statistical difference was found between groups in age, breed, gender, severity of respiratory or gastrointestinal clinical signs and surgical techniques employed. The incidence of postoperative complications was higher in dogs that received standard recovery (28%) compared to dogs recovered with the owners (2%). None of the dogs recovered with the owners and discharged the same day required veterinary assistance after discharge from the hospital. CLINICAL SIGNIFICANCE: Corrective surgery for brachycephalic obstructive airway syndrome was associated with lower postoperative respiratory complications when dogs were discharged on the same day after recovery with the owners. Owner-assisted recovery and early discharge are possible and safe and may decrease the incidence of postoperative complications. However, other unmeasured factors may have contributed to the lower complication rate in dogs recovered with the owners during the course of this study.

Two modes of evolution shape bacterial strain diversity in the mammalian gut for thousands of generations.

How and at what pace bacteria evolve when colonizing healthy hosts remains unclear. Here, by monitoring evolution for more than six thousand generations in the mouse gut, we show that the successful colonization of an invader Escherichia coli depends on the diversity of the existing microbiota and the presence of a closely related strain. Following colonization, two modes of evolution were observed: one in which diversifying selection leads to long-term coexistence of ecotypes and a second in which directional selection propels selective sweeps. These modes can be quantitatively distinguished by the statistics of mutation trajectories. In our experiments, diversifying selection was marked by the emergence of metabolic mutations, and directional selection by acquisition of prophages, which bring their own benefits and costs. In both modes, we observed parallel evolution, with mutation accumulation rates comparable to those typically observed in vitro on similar time scales. Our results show how rapid ecotype formation and phage domestication can be in the mammalian gut.

Titanium mesh osteosynthesis for the treatment of severely comminuted maxillofacial fractures in four dogs.

INTRODUCTION: Major goals in maxillofacial fracture treatment include to restore the dental occlusion, stabilise the major skeletal supports, restore the contour of the face and achieve proper function and appearance of the face. Titanium is considered an optimal material for maxillofacial reconstruction due to its biocompatibility, high strength, minimal inflammatory reaction and minimal imaging artefact. OBJECTIVES: To describe the clinical details, surgical technique, pre- and postoperative imaging and short- and long-term follow-up of severely comminuted maxillofacial fractures treated with titanium mesh and titanium screws in dogs. MATERIALS AND METHODS: Retrospective short case series included four client-owned dogs with maxillofacial fractures. After appropriate medical stabilisation, preoperative CT examination of the head was obtained in all patients for evaluation of fracture configuration and surgical planning. The maxillofacial fractures were stabilised by titanium mesh osteosynthesis. Short- and long-term clinical and radiographic follow-ups were available for all dogs. RESULTS: Proper dental occlusion and reconstruction of the anatomic buttresses was achieved in all cases. All dogs recovered uneventfully from the surgery and no complications were recorded on the long-term follow-up up to 43 months. Occlusion was maintained in all dogs, as well as excellent cosmesis of the midface. CLINICAL SIGNIFICANCE: Titanium mesh osteosynthesis can achieve sufficient rigidity and lead to uncomplicated healing of severely comminuted maxillofacial fractures. This internal fixation method can be considered a valuable option to treat maxillofacial fractures in particular in cases of large bone defect and midface reconstruction.

Negative impact on the reproductive potential of blue jack mackerel Trachurus picturatus by Kudoa infection of the ovary.

Reproduction of Trachurus picturatus off the western Portuguese coast was studied over 1 yr. During histological analyses, the presence of Kudoa sp. was detected in advanced vitellogenic oocytes. Kudoa infections are known to cause economic loss through the induction of post-mortem liquefaction of fish muscles, but ovarian infection as reported in this study will seriously affect the reproductive potential of the species and thus impact fisheries productivity. Only females showed gonad infection which led to total degradation of advanced vitellogenic oocytes. No macroscopic, somatic or condition indices revealed differences between infected and uninfected females, rendering this infection event a concealed suppression of reproduction.

The use of methylene blue to assist with parotid sialadenectomy in dogs.

INTRODUCTION: There is an important morbidity associated with parotidectomy. The most commonly reported permanent complication is facial nerve injury. Methylene blue staining has been used as an intra-operative tool to improve tissue visualisation and preserve facial nerve integrity. OBJECTIVES: To describe the functionality and feasibility of the use of methylene blue for parotidectomy in dogs. MATERIALS AND METHODS: Retrospective study included seven client-owned dogs that underwent parotidectomy after injection of methylene blue from 2016 to 2019 in a referral centre. Cross-sectional imaging was used to confirm parotid gland surgical disease and for staging purposes. All dogs underwent parotid resection and removal of the parotid duct after injection of methylene blue. Methylene blue was either administered via cannulation of the parotid duct or directly injected into the abnormal gland. RESULTS: In all cases, the gland stained dark blue within seconds without any evident leakage. Complete parotid gland resection and removal of the parotid duct was achieved successfully in all dogs with a mean surgical time of 97 minutes. Subjectively, the staining was useful to identify innervation outside the coloured gland and facilitated dissection. No complications, including facial nerve injury, were recorded. CLINICAL SIGNIFICANCE: Methylene blue staining for complete parotidectomy was feasible, rapid and easy in these dogs. It can be used as an indirect facial nerve identification technique, and can therefore facilitate dissection and possibly reduce the incidence of post-operative facial nerve paralysis.

Feasibility of the single-incision subxiphoid approach for video-assisted thoracoscopic surgery in dogs.

OBJECTIVES: To report early results of uniportal video-assisted thoracoscopic surgery in dogs using a single-incision subxiphoid approach. MATERIALS AND METHODS: Retrospective study of 10 client-owned dogs with: pyothorax (n=5), pericardial effusion (n=2), bilateral pneumothorax (n=1), retained surgical swab (n=1), cranial mediastinal mass (n=1). With the dog in dorsal recumbency a 3-4 cm incision was made over the xiphoid process. After resection of the xiphoid process, a tunnel was created towards the pleura and open access maintained with an Alexis™ wound retractor. The pleural cavity was explored with a 10 mm 30° or 5 mm 0° telescope and straight laparoscopic instruments. RESULTS: Median surgical time was 75 minutes. The SISA technique was performed successfully in five of 10 cases and allowed easy and adequate inspection of the intra-thoracic structures. One case was converted to lateral thoracotomy after laceration of the vena cava and one converted to median sternotomy because of adhesions. An additional port was placed in three cases to facilitate triangulation and surgical manipulation. No other intra-operative complications were encountered. CLINICAL SIGNIFICANCE: In this initial report of uniportal thoracic approach in dogs, this technique allowed excellent access and treatment of mediastinal structures. Further cases are required to assess its suitability for pulmonary surgery.

Trade-Offs of Escherichia coli Adaptation to an Intracellular Lifestyle in Macrophages.

The bacterium Escherichia coli exhibits remarkable genomic and phenotypic variation, with some pathogenic strains having evolved to survive and even replicate in the harsh intra-macrophage environment. The rate and effects of mutations that can cause pathoadaptation are key determinants of the pace at which E. coli can colonize such niches and become pathogenic. We used experimental evolution to determine the speed and evolutionary paths undertaken by a commensal strain of E. coli when adapting to intracellular life. We estimated the acquisition of pathoadaptive mutations at a rate of 10-6 per genome per generation, resulting in the fixation of more virulent strains in less than a hundred generations. Whole genome sequencing of independently evolved clones showed that the main targets of intracellular adaptation involved loss of function mutations in genes implicated in the assembly of the lipopolysaccharide core, iron metabolism and di- and tri-peptide transport, namely rfaI, fhuA and tppB, respectively. We found a substantial amount of antagonistic pleiotropy in evolved populations, as well as metabolic trade-offs, commonly found in intracellular bacteria with reduced genome sizes. Overall, the low levels of clonal interference detected indicate that the first steps of the transition of a commensal E. coli into intracellular pathogens are dominated by a few pathoadaptive mutations with very strong effects.

Rates of fitness decline and rebound suggest pervasive epistasis.

Unraveling the factors that determine the rate of adaptation is a major question in evolutionary biology. One key parameter is the effect of a new mutation on fitness, which invariably depends on the environment and genetic background. The fate of a mutation also depends on population size, which determines the amount of drift it will experience. Here, we manipulate both population size and genotype composition and follow adaptation of 23 distinct Escherichia coli genotypes. These have previously accumulated mutations under intense genetic drift and encompass a substantial fitness variation. A simple rule is uncovered: the net fitness change is negatively correlated with the fitness of the genotype in which new mutations appear--a signature of epistasis. We find that Fisher's geometrical model can account for the observed patterns of fitness change and infer the parameters of this model that best fit the data, using Approximate Bayesian Computation. We estimate a genomic mutation rate of 0.01 per generation for fitness altering mutations, albeit with a large confidence interval, a mean fitness effect of mutations of -0.01, and an effective number of traits nine in mutS(-) E. coli. This framework can be extended to confront a broader range of models with data and test different classes of fitness landscape models.

Genetic recombination and molecular evolution.

Reduced rates of genetic recombination are often associated with reduced genetic variability and levels of adaptation. Several different evolutionary processes, collectively known as Hill-Robertson (HR) effects, have been proposed as causes of these correlates of recombination. Here, we use DNA sequence polymorphism and divergence data from the noncrossing over dot chromosome of Drosophila to discriminate between two of the major forms of HR effects: selective sweeps and background selection. This chromosome shows reduced levels of silent variability and reduced effectiveness of selection. We show that neither model fits the data on variability. We propose that, in large genomic regions with restricted recombination, HR effects among nonsynonymous mutations undermine the effective strength of selection, so that their background selection effects are weakened. This modified model fits the data on variability and also explains why variability in very large nonrecombining genomes is not completely wiped out. We also show that HR effects of this type can produce an individual selection advantage to recombination, as well as greatly reduce the mean fitness of nonrecombining genomes and genomic regions.

The evolution of a conjugative plasmid and its ability to increase bacterial fitness.

Conjugative plasmids are extra-chromosomal DNA elements that are capable of horizontal transmission and are found in many natural isolated bacteria. Although plasmids may carry beneficial genes to their bacterial host, they may also cause a fitness cost. In this work, we studied the evolution of the R1 plasmid and we found that, in spite of the R1 plasmid conferring an initial cost to its host, after 420 generations the cost disappeared in all five independent evolution experiments. In fact, in two of these five experiments evolved conjugative plasmids actually conferred a fitness advantage to their hosts. Furthermore, the relative fitness of the ancestral clone bearing one of the evolved plasmids is significantly higher than both the plasmid-free ancestral cells and the evolved cells carrying the evolved plasmid. Given that the R1 plasmid may spread among different species of enterobacteria, we wondered what the effect of the evolved plasmid would be inside Salmonella enterica cells. We found that the evolved plasmid is also able to dramatically increase the relative fitness of these cells. Our results suggest that even if general usage of antibiotics is halted, conjugative plasmids that have been selected with antibiotics in previous years can still persist among bacterial populations or even invade new strains.

The speed of Muller's ratchet with background selection, and the degeneration of Y chromosomes.

The rate of accumulation of deleterious mutations by Muller's ratchet is investigated in large asexual haploid populations, for a range of parameters with potential biological relevance. The rate of this process is studied by considering a very simple model in which mutations can have two types of effect: either strongly deleterious or mildly deleterious. It is shown that the rate of accumulation of mildly deleterious mutations can be greatly increased by the presence of strongly deleterious mutations, and that this can be predicted from the associated reduction in effective population size (the background selection effect). We also examine the rate of the ratchet when there are two classes of mutation of similar but unequal effects on fitness. The accuracy of analytical approximations for the rate of this process is analysed. Its possible role in causing the degeneration of Y and neo-Y chromosomes is discussed in the light of our present knowledge of deleterious mutation rates and selection coefficients.

The degeneration of asexual haploid populations and the speed of Muller's ratchet.

The accumulation of deleterious mutations due to the process known as Muller's ratchet can lead to the degeneration of nonrecombining populations. We present an analytical approximation for the rate at which this process is expected to occur in a haploid population. The approximation is based on a diffusion equation and is valid when N exp(-u/s) >> 1, where N is the population size, u is the rate at which deleterious mutations occur, and s is the effect of each mutation on fitness. Simulation results are presented to show that the approximation estimates the rate of the process better than previous approximations for values of mutation rates and selection coefficients that are compatible with the biological data. Under certain conditions, the ratchet can turn at a biologically significant rate when the deterministic equilibrium number of individuals free of mutations is substantially >100. The relevance of this process for the degeneration of Y or neo-Y chromosomes is discussed.

[Retrospective analysis of 80 cases of neonatal necrotizing enterocolitis]. / Análisis retrospectivo de 80 casos de enterocolitis necrotizante neonatal.

We present the cases of necrotizing enterocolitis (NEC) treated in our hospital between 1980 and 1994, in order to analyze the risk factors that appear in the disease. We elaborate treatment and follow-up protocols. Prematurity, low birth weight and perinatal stress have a significant influence in NEC. Hemodinamic inestability, bloody stools, abdominal distension with decrease gastric outlet, along with significant radiological evidence in 90 percent of the cases, should rise suspition of NEC. We find fundamental the prevention of the disease in premature newborns with risk factors. Mean gestational age was 33 weeks. Prematurity was found in 87.5 percent of the patients, with a mean birth weight of 1683 g. Symptoms appeared at the age of 14 days. 32 percent of the cases were operated, 13 cases (16%) presenting with pneumoperitoneum, and a Mortality rate 15 percent. We treated 15 patients with colonic stenosis by resection and end-to-end anastomosis, with 6 percent mortality global mortality rate for NEC has been 28 percent.