Exaggerated Acute Lung Injury and Impaired Antibacterial Defenses During Staphylococcus aureus Infection in Rats with the Metabolic Syndrome

Rate and factors associated with surgical site infection following aseptic revision fixation of orthopaedic trauma injuries

PURPOSE

The primary aim of this study was to define the rate of infection following revision of fixation for aseptic failure. The secondary aims were to identify factors associated with an infection following revision and patient morbidity following deep infection.

METHODS

A retrospective study was undertaken to identify patients who underwent aseptic revision surgery during a 3-year period (2017-2019). Regression analysis was used to identify independent factors associated with SSI.

RESULTS

Eighty-six patients were identified that met the inclusion criteria, with a mean age of 53 (range 14-95) years and 48 (55.8%) were female. There were 15 (17%) patients with an SSI post revision surgery (n = 15/86). Ten percent (n = 9) of all revisions acquired a 'deep infection', which carried a high morbidity with a total of 23 operations, including initial revision, being undertaken for these patients as salvage procedures and three progressed to an amputation. Alcohol excess (odds ratio (OR) 1.61, 95% CI 1.01-6.36, p = 0.046) and chronic obstructive pulmonary disease (OR 11.1, 95% CI 1.00-133.3, p = 0.050) were independently associated with an increased risk of SSI.

CONCLUSION

Aseptic revision surgery had a high rate of SSI (17%) and deep infection (10%). All deep infections occurred in the lower limb with the majority of these seen in ankle fractures. Alcohol excess and COPD were independent risk factors associated with an SSI and patients with a history of these should be counselled accordingly.

LEVEL OF EVIDENCE

Retrospective Case Series, Level IV.

Can Neutrophils Prevent Nosocomial Pneumonia after Serious Injury?

Nosocomial pneumonia is a leading cause of critical illness and mortality among seriously injured trauma patients. However, the link between injury and the development of nosocomial pneumonia is still not well recognized. Our work strongly suggests that mitochondrial damage-associated molecular patterns (mtDAMPs), especially mitochondrial formyl peptides (mtFPs) released by tissue injury, play a significant role in developing nosocomial pneumonia after a serious injury. Polymorphonuclear leukocytes (neutrophils, PMN) migrate toward the injury site by detecting mtFPs through formyl peptide receptor 1 (FPR1) to fight/contain bacterial infection and clean up debris. Activation of FPR1 by mtFPs enables PMN to reach the injury site; however, at the same time it leads to homo- and heterologous desensitization/internalization of chemokine receptors. Thus, PMN are not responsive to secondary infections, including those from bacteria-infected lungs. This may enable a progression of bacterial growth in the lungs and nosocomial pneumonia. We propose that the intratracheal application of exogenously isolated PMN may prevent pneumonia coupled with a serious injury.

[Phagocytosis of alveolar macrophages is suppressed in a mouse model of lipopolysaccharide-induced acute lung injury]

OBJECTIVE

To investigate the changes in phagocytic function of alveolar macrophages (AMs) in mice with lipopolysaccharide (LPS)-induced acute lung injury (ALI) and explore the possible mechanism.

METHODS

Kunming mice were randomly divided into normal control group and ALI (induced by LPS instillation in the airway) model group. AMs were obtained from bronchoalveolar lavage fluid in both groups, and phagocytosis of the AMs was observed using flow cytometry and fluorescence microscopy. Western blotting and ELISA were used to detect the expression and secretion of IL-33 in the lung tissue of the mice. We also detected the secretion of IL-33 by an alveolar epithelial cell line MLE-12 in response to stimulation with different concentrations of LPS. The AMs from the normal control mice were treated with different concentrations of LPS and IL-33, and the changes in the phagocytic activity of the cells were observed.

RESULTS

Compared with those in normal control group, the percentage of AMs phagocytosing fluorescent microspheres was significantly decreased, and the expression of IL-33 in lung tissue and IL-33 level in the bronchoalveolar lavage fluid were significantly increased in ALI mice (P < 0.01). LPS (100-1000 ng/mL) obviously promoted the secretion of IL-33 in cultured MLE-12 cells (P < 0.01). Both LPS (10-500 ng/mL) and IL-33 (100 ng/mL) significantly inhibited the phagocytic activity of the AMs from normal control mice (P < 0.01).

CONCLUSIONS

The phagocytic activity of AMs is weakened in ALI mice possibly due to direct LPS stimulation and the inhibitory effect of the alarmin IL-33 produced by LPS-stimulated alveolar epithelial cells.

Pathogens distribution and drug resistance in patients with acute cerebral infarction complicated with diabetes and nosocomial pulmonary infection

Background

This study aims to investigate the pathogen distribution and drug resistance in patients with acute cerebral infarction complicated with diabetes mellitus and nosocomial pulmonary infection.

Methods

From August 2015 to December 2017, 172 pathogenic bacterial strains from patients with acute cerebral infarction complicated with diabetes mellitus and nosocomial pulmonary infection in our hospital were identified, and the drug sensitivity was analyzed.

Results

Among these 172 strains of pathogenic bacteria, gram negative bacteria was the main cause of pulmonary infection in hospitalized patients with acute cerebral infarction, accounting for 75.6% of all pathogens. Furthermore, 80% of diabetic patients with cerebral infarction had lung infection induced by gram negative bacteria, which was significantly higher than that in non-diabetic patients (72.2%). Moreover, the drug resistance rate in the diabetic group (68.3%) was significantly higher than that in the non-diabetic group (54.3%). Gram positive bacteria accounted for 19.1% of all pathogenic bacteria. The infection rate of gram-positive bacteria in diabetic patients with cerebral infarction was 14.7%, which was lower than that in the non-diabetic group (22.6%). The drug-resistance rate was higher in the diabetic group (45.5%) than in the non-diabetic group (28.2%). Furthermore, the fungal infection rate in patients with lung infection in these two groups was 5.3 and 5.2%, respectively, and fungi presented with high sensitivity to commonly used antifungal agents.

Conclusion

In patients with acute cerebral infarction complicated with diabetes mellitus and nosocomial pulmonary infection, the majority of pathogens are multidrug-resistant gram negative bacilli. Pathogen culture should be conducted as soon as possible before using antibiotics, and antimicrobial agents should be reasonably used according to drug sensitivity test results.

Inhalable Levofloxacin Liposomes Complemented with Lysozyme for Treatment of Pulmonary Infection in Rats: Effective Antimicrobial and Antibiofilm Strategy

Treatment of bacterial infections becomes increasingly complicated due to increasing bacterial resistance and difficulty in developing new antimicrobial agents. Emphasis should be laid on improvising the existing treatment modalities. We studied the improved antimicrobial and antibiofilm activity of levofloxacin (LFX) and lysozyme (LYS) in microbiological studies. LFX at sub-minimum inhibitory concentration with LYS eradicated > 85% of preformed biofilm. LFX was actively loaded into the liposomes using pH gradient method and was spray-dried with LYS solution. Percent entrapment of LFX in liposome was > 80% and prolonged cumulative release of 85% LFX at the end of 12 h. In vitro lung deposition study and solid-state characterization for spray dried LFX liposome in combination with LYS (LFX liposome-LYS) was performed. Co-spray dried product had mass median aerodynamic diameter ranging < 5 μm. In pharmacodynamic study, Staphylococcus aureus infected rats were treated with LFX liposome-LYS. Lungs, bronchoalveolar lavage fluid (BALF), and nasal fluid were evaluated for microbial burden. Expression of cytokine levels in BALF and serum were also studied by ELISA. In addition, mRNA expression for lung inflammatory mediators and lung myeloperoxidase activity were carried out. Further, lungs and histological changes were observed grossly. Untreated infected rat lungs demonstrated higher mRNA expression for inflammatory markers, cytokine levels, and microbial load compared to vehicle control. Conversely, LFX liposome-LYS significantly abated these adverse repercussions. Histology findings were also in agreement of above. Acute toxicity study revealed safeness of LFX liposome-LYS. Our findings confirm LFX liposome-LYS exhibited prolonged, improved antibiofilm and antimicrobial efficacy in treating S. aureus infection.

Surgical site infection in overweight and obese Total Knee Arthroplasty patients

Purpose

This aim of this study was to evaluate the rate of surgical site infection (SSI) in patients undergoing Total Knee Arthroplasty (TKA), to improve our understanding of the associations between infection rate and obesity.

Methods

Data was reviewed for 839 primary TKA procedures performed at a National Arthroplasty Centre over one year (April 2007-March 2008). SSI data was collected at 30 days and one year post-operatively. Patients were grouped guided by the WHO classifications of obesity; normal (BMI < 25.0), overweight (BMI 25.00-29.99), obese class I (BMI 30.00-34.99), obese class II (BMI 35.00-39.99), obese class III (BMI ≥ 40.00). Statistical significance was assessed by Fisher's Exact Test.

Results

When grouped by BMI, 30.9% of patients were obese class I, 19.0% obese class II and 8.7% obese class III. Of the total cohort, 22 patients (2.6%) had superficial SSI and 13 (1.5%) had deep SSI. When comparing the obese class III cohort to all other cohorts (non-obese class III), the odds ratios for superficial SSI was 4.20 (95% CI [1.59, 11.09]; p = 0.009) and deep SSI was 6.97 (95% CI [2.22, 21.89]; p = 0.003). In the obese class III cohort, superficial SSI rate was higher in females (8.9%) than males (5.9%), yet deep SSI demonstrated the opposite, with a higher occurrence in males (11.8%) compared to females (5.4%).

Conclusion

This study suggests that obese class III TKA patients are at increased odds of superficial and deep SSI compared to other BMI cohorts. Interestingly, male obese class III patients demonstrated a higher rate of deep infection compared to their female counterparts. However, it must be noted that study findings are limited as confounders were unable to be accounted for in this retrospective study design.

Theoretical and Biological Evaluation of the Link between Low Exercise Capacity and Disease Risk

Large-scale epidemiological studies show that low exercise capacity is the highest risk factor for all-cause morbidity and mortality relative to other conditions including diabetes, hypertension, and obesity. This led us to formulate the energy transfer hypothesis (ETH): Variation in capacity for energy transfer is the central mechanistic determinant of the divide between disease and health. As a test of this hypothesis, we predicted that two-way selective breeding of genetically heterogeneous rats for low and high intrinsic treadmill running capacity (a surrogate for energy transfer) would also produce rats that differ for disease risks. The lines are termed low-capacity runners (LCRs) and high-capacity runners (HCRs) and, after 36 generations of selection, they differ by more than eightfold in running capacity. Consistent with the ETH, the LCRs score high for developing disease risks, including metabolic syndrome, neurodegeneration, cognitive impairment, fatty liver disease, susceptibility to cancer, and reduced longevity. The HCRs are resistant to the development of these disease risks. Here we synthesize ideas on nonequilibrium thermodynamics and evolution from Ilya Prigogine, Hans Krebs, and Peter Mitchell to formulate theoretic explanations for the ETH. First, at every moment in time, the atoms and molecules of organisms are reorganizing to pursue avenues for energy transfer. Second, this continuous organization is navigating in a constantly changing environment such that "strategies" are perpetually in flux and do not leave a simple footprint (evolution). Third, as a consequence, human populations demonstrate a wide variation in capacity for energy transfer that mirrors mechanistically the divide between disease and health.

Port d'Entrée for Respiratory Infections - Does the Influenza A Virus Pave the Way for Bacteria?

Bacterial and viral co-infections of the respiratory tract are life-threatening and present a global burden to the global community. Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus pyogenes are frequent colonizers of the upper respiratory tract. Imbalances through acquisition of seasonal viruses, e.g., Influenza A virus, can lead to bacterial dissemination to the lower respiratory tract, which in turn can result in severe pneumonia. In this review, we summarize the current knowledge about bacterial and viral co-infections of the respiratory tract and focus on potential experimental models suitable for mimicking this disease. Transmission of IAV and pneumonia is mainly modeled by mouse infection. Few studies utilizing ferrets, rats, guinea pigs, rabbits, and non-human primates are also available. The knowledge gained from these studies led to important discoveries and advances in understanding these infectious diseases. Nevertheless, mouse and other infection models have limitations, especially in translation of the discoveries to humans. Here, we suggest the use of human engineered lung tissue, human ex vivo lung tissue, and porcine models to study respiratory co-infections, which might contribute to a greater translation of the results to humans and improve both, animal and human health.