Extracellular DNA enhances biofilm integrity and mechanical properties of mucoid Pseudomonas aeruginosa.

Pseudomonas aeruginosa is one of the most common biofilm-forming pathogens responsible for lung infections of individuals with cystic fibrosis (CF). P. aeruginosa becomes tolerant to antimicrobials in the biofilm state and is difficult to treat. Production of extracellular polymeric substances (EPS), such as alginate and extracellular DNA (eDNA), can allow adherence to abiotic and biotic surfaces, antimicrobial evasion, and resilience to environmental pressures. Alginate-producing mucoid variants of P. aeruginosa are frequently isolated from CF airway samples and are associated with worsening patient outcomes. While eDNA is a major structural component of nonmucoid P. aeruginosa biofilms, the potential role of eDNA in mucoid biofilms is unclear. Here, we investigate how eDNA contributes to clinical mucoid biofilm physiology and integrity. We predicted that eDNA plays a structural and mechanical role in mucoid biofilms. To test this, we quantified biofilm eDNA in mucoid biofilms and used microscopy and rheology to visualize eDNA and detect changes in biofilm structure and mechanics upon DNaseI treatment. We showed that biofilm eDNA abundance is diverse across clinical mucoid strains and observed a temporal increase in foci of eDNA within intact mucoid biofilms. Increased cell dispersal and reduced biomass were also observed following DNaseI treatment of mucoid biofilms. Degradation of eDNA also impacted the mechanical integrity of mucoid biofilms by increasing the stiffness and decreasing the cohesion of the biofilm. These findings advance our understanding of clinical mucoid P. aeruginosa biofilms and facilitate the development of new approaches to target biofilms by exploiting the functions of EPS components. IMPORTANCE Understanding the role of eDNA in mucoid Pseudomonas aeruginosa biofilms will lead to therapeutic strategies that combat the biophysical and structural function of EPS for the eradication of bacteria in mucoid biofilms during chronic infections. This knowledge can be used to further identify unknown matrix component interactions within pathogenic biofilm-forming clinical isolates.

Evaluation of Rodent Diet Stability when Stored in Conditions that Diverge from Guide Parameters.

An essential aspect of animal resource programs is the storage and provision of food for a variety of species. Environmental parameters for feed storage conditions (temperature less than 70 °F; relative humidity less than 50%) are recommended in the Guide for the Care and Use of Laboratory Animals, along with aspects of nutrition such as palatability, vermin-control measures, diet quality, and integrity of feed bags. After receiving a suggestion for improvement for environmental conditions in 2 feed storage locations during an AAALAC accreditation visit, we hypothesized that the packaging of contemporary rodent feed could sustain wider environmental variations in temperature and humidity without adverse impact on integrity and palatability. This study evaluated representative feed storage sites across campus buildings to capture the variation in environmental conditions that are inherent to large and diverse animal care programs. Each test storage location held 2 identical bags of feed (same type, lot, and expiration date) that were stored from June to September of 2021; some aspects of the project were repeated during summer 2022 with a similar rodent feed. Baseline nutrients were analyzed from feed samples collected at time 0 (control) and again after 1 and 3mo of storage. The overall nutritional values measured in feed at the end of the study were not significantly different from control values, regardless of test site and variation in environmental parameters. Retinol (as a measure of Vitamin A) was the only component that decreased significantly; however, final retinol levels were consistently above those necessary for appropriate nutrition for mice. Our animal care program stakeholders were briefed on the outcomes of this study with the intent to verify at future AAALAC site visits that our storage conditions are adequate for maintaining the nutritional quality of packaged rodent feed.

Assessment of the role of FGF15 in mediating the metabolic outcomes of murine Vertical Sleeve Gastrectomy (VSG).

Vertical sleeve gastrectomy (VSG) is the best current therapy for remission of obesity and its co-morbidities. It is understood to alter the enterohepatic circulation of bile acids in vivo. Fibroblast growth factor 19 (FGF19) in human and its murine orthologue Fgf15 plays a pivotal role in this bile acid driven enterohepatic signaling. The present study evaluated the metabolic outcomes of VSG in Fgf15 deficient mice. 6-8 weeks old male wildtype mice (WT) and Fgf15 deficient mice (KO) were fed a high fat diet (HFD) for 8 weeks. At 8th week of diet, both WT and KO mice were randomly distributed to VSG or sham surgery. Post-surgery, mice were observed for 8 weeks while fed a HFD and then euthanized to collect tissues for experimental analysis. Fgf15 deficient (KO) mice lost weight post VSG, but glucose tolerance in KO mice did not improve post VSG compared to WT mice. Enteroids derived from WT and KO mice proliferated with bile acid exposure in vitro. Post VSG both WT and KO mice had similarly altered bile acid enterohepatic flux, however Fgf15 deficient mice post VSG had increased hepatic accumulation of free and esterified cholesterol leading to lipotoxicity related ER stress, inflammasome activation, and increased Fgf21 expression. Intact Fgf15 mediated enterohepatic bile acid signaling, but not changes in bile acid flux, appear to be important for the metabolic improvements post-murine bariatric surgery. These novel data introduce a potential point of distinction between bile acids acting as ligands compared to their canonical downstream signaling pathways.

The Relationship between Aerobic Test Performance and Injuries in Police Recruits.

Lower levels of fitness are associated with an increased risk of injury in police recruits. The aim of this study was to determine the relationships between initial aerobic performance assessments and injury risk during police recruit training. Retrospective data from 219 police recruits undergoing training program at a state police training academy, including 20-m Multistage Fitness Test (MSFT) and 30-15 Intermittent Fitness Test (IFT) scores and injury data, were collected. Spearman's correlation analysis revealed a significant negative correlation between levels of fitness (MSFT rs = - 0.292, p < 0.001: 30-15 IFT rs=-0.315, p < 0.001) and rates of injury. Furthermore, a Pearson's correlation showed a strong correlation between MSFT and the 30-15 IFT scores (r = 0.877, p < 0.001). Police recruits with lower fitness were at a higher risk of injury than those with higher fitness over the duration of a recruit training program. These findings indicate that aerobic performance assessments may be used by law enforcement agencies to estimate the relative risks of injury among cadets.

Quantification of Induced Hypothermia from Aseptic Scrub Applications during Rodent Surgery Preparation.

Laboratory mice (Mus musculus) are prone to develop hypothermia during anesthesia for surgery, thus potentially impeding anesthetic recovery, wound healing, and future health. The core body temperatures of isoflurane-anesthetized mice are influenced by the choice of supplemental heat sources; however, the contribution of various surgical scrubs on the body temperatures of mice under gas anesthesia has not been assessed. We sought to quantify the effect of using alcohol (70% isopropyl alcohol [IPA]) compared with saline to rinse away surgical scrub on the progression of hypothermia in anesthetized mice (n = 47). IPA, room-temperature saline, or warmed saline (37 °C) was combined with povidone-iodine and then assessed for effects on core (rectal) and surface (infrared) temperatures. Agents were applied to a 2×2-cm shaved abdominal area of mice maintained on a water-recirculating blanket (at 38 °C) under isoflurane anesthesia (1.5% to 2.0% at 0.6 L/min) for 30 min. Although all scrub regimens significantly decreased body temperature at the time of application, treatments that included povidone-iodine led to the coldest core temperatures, which persisted while mice were anesthetized. Compared with room-temperature saline and when combined with povidone-iodine, warming of saline did not ameliorate heat loss. IPA alone demonstrated the most dramatic cooling of both surface and core readings at application but generated an unanticipated warming (rebound) phase during which body temperatures equilibrated with those of controls within minutes of application. Although alcohol is inappropriate as a stand-alone agent for surgical skin preparation, IPA is a viable alternative to saline-based rinses in this context, and its use should be encouraged within institutional guidance for rodent surgical procedures without concern for prolonged hypothermia in mice.

Quantification of Induced Hypothermia from Aseptic Scrub Applications during Rodent Surgery Preparation.

Laboratory mice (Mus musculus) are prone to develop hypothermia during anesthesia for surgery, thus potentially impedinganesthetic recovery, wound healing, and future health. The core body temperatures of isoflurane-anesthetized mice areinfluenced by the choice of supplemental heat sources; however, the contribution of various surgical scrubs on the bodytemperatures of mice under gas anesthesia has not been assessed. We sought to quantify the effect of using alcohol (70%isopropyl alcohol [IPA]) compared with saline to rinse away surgical scrub on the progression of hypothermia in anesthetizedmice (n = 47). IPA, room-temperature saline, or warmed saline (37 °C) was combined with povidone-iodine and thenassessed for effects on core (rectal) and surface (infrared) temperatures. Agents were applied to a 2×2-cm shaved abdominalarea of mice maintained on a water-recirculating blanket (at 38 °C) under isoflurane anesthesia (1.5% to 2.0% at 0.6 L/min)for 30 min. Although all scrub regimens significantly decreased body temperature at the time of application, treatments thatincluded povidone-iodine led to the coldest core temperatures, which persisted while mice were anesthetized. Comparedwith room-temperature saline and when combined with povidone-iodine, warming of saline did not ameliorate heat loss.IPA alone demonstrated the most dramatic cooling of both surface and core readings at application but generated an unanticipatedwarming (rebound) phase during which body temperatures equilibrated with those of controls within minutes ofapplication. Although alcohol is inappropriate as a stand-alone agent for surgical skin preparation, IPA is a viable alternativeto saline-based rinses in this context, and its use should be encouraged within institutional guidance for rodent surgicalprocedures without concern for prolonged hypothermia in mice.

Reproductive performance of mice in disposable and standard individually ventilated cages.

This study assessed the reproductive performance of mice housed in 2 types of individually ventilated caging systems. Breeding pairs from 48 female and 24 male mice of 3 established transgenic mouse breeding colonies were placed in either a standard or disposable ventilated caging system. For 3 breeding cycles, the number of pups born, pup survival rate to weaning, time interval between litters, and pup weights were monitored for each breeding pair. Disposable and standard cages were maintained in the same location during breeding. Environmental parameters included intracage temperature, humidity, and ammonia and carbon dioxide levels and room light intensity and sound. Overall, 776 offspring were produced. Breeding performance did not differ significantly between the 2 cage types. By 11 wk of age, the weights of pups from both cage types were equivalent. The intracage temperature was 1.1 °F warmer and light intensity at the site of the nest was 34 lx dimmer in disposable cages than in standard caging. The difference in lighting likely was due to nest location; the nests in the disposable cages were at the back of the cages and away from the anterior air supply, whereas in standard caging, nests were at the front of the cages, with the air supply at the rear. Under these husbandry conditions, mice housed in disposable caging systems have comparable breeding performance to those housed in standard individually ventilated cages.

Cardiac tissue Doppler and tissue velocity imaging in anesthetized New Zealand white rabbits.

New Zealand white rabbits are commonly used in cardiovascular research. Complete echocardiographic examination of the heart includes the evaluation of tissue Doppler (TDI) parameters, yet normal data are unavailable for rabbits. In addition, tissue velocity imaging (TV) is a potentially useful measure of myocardial function that has not yet been applied to rabbits. Anesthetized New Zealand white rabbits (n = 31) underwent echocardiography to establish the feasibility of performing TDI and TV and establishing corresponding reference values. Standard 2D, M-mode, and Doppler measurements were obtained in all rabbits and showed values comparable to previously published data. Interpretable TDI images were obtained in all 31 rabbits and TV in 24 of 31 rabbits. The values obtained were similar to those seen in healthy cats and are comparable to the values found in adult humans. TDI and TV can easily be added to standard echocardiographic evaluation in rabbits. The values from the current study, obtained in normal rabbits, can be used as reference values to improve characterization of cardiac disease in this species.