Nosocomial infections after severe trauma are associated with lower apolipoproteins B and AII

The microbiological profile of isolates recovered from ICU patients with traumatic brain injuries at a tertiary care center, Southern Region, Saudi Arabia

INTRODUCTION

Traumatic head injury THI is a Neurosurgical condition in which brain function is interrupted as a result of blunt (motor vehicle accidents MVA, falls, and assaults) or penetrating trauma. Nearly half of all injuries are caused by head trauma. Head traumas are a leading cause of death and organ loss in young people, where this population accounts for the vast majority of TBI patients.

METHODOLOGY

This retrospective cohort study was conducted at Asir Central Hospital, KSA with data from 2015 to 2019. Records of bacterial cultures and outcomes such as length of stay in the hospital were analyzed. In addition, treatment outcomes were also analyzed.

RESULTS

A total of 300 ICU patient samples (69 patients) were included. Patients' ages ranged from 13 to 87 years with a mean age of 32.4 ± 17.5 years old. The most frequently reported diagnosis was RTA (71 %), followed by SDH (11.6 %), The most isolated organisms from the recovered samples were Klebsiella pneumoniae (27 %), followed by Pseudomonas aeruginosa (14.7 %). Regarding susceptibility, Tigecycline was the most sensitive (44 %), followed by Gentamicin (43.3 %). A total of 36 (52.2 %) patients stayed for less than one month, 24 (34.8 %) stayed for 1-3 months, and 7 (10.1 %) stayed for 3-6 months. The mortality rate in our study population was (40.6 %) as 28 patients died.

CONCLUSION

The prevalence of pathogens in TBI needs to be determined in different institutions for the establishment of effective empiric antibiotic treatment following infections in traumatic brain injuries. This will ultimately help to improve treatment outcomes. In neurosurgical patients undergoing cranial procedures after trauma, a hospital-standardized antibiotic policy is effective in achieving low rates of bacterial infections especially MDR infections.

Evaluation of the Risk Factors of Nosocomial Pneumonia and the Prevalence of Antibiotic Resistance in Trauma Patients in Need of Immediate Intervention

Background: Pneumonia is the most common nosocomial infection reported worldwide in intensive care units. This study aimed to evaluate the risk factors of nosocomial pneumonia and the frequency of antibiotic resistance in trauma patients who need immediate intervention. Patients and Methods: This prospective cohort study was conducted in Shahid Rajaei Trauma Hospital in Shiraz between 2020 and 2021. All the trauma patients who needed immediate intervention (levels 1 and 2 based on the Canadian Emergency Department Triage and Acuity Scale) and had no symptoms of infection were included. Patients who were discharged or died before 48 hours were excluded. Results: The results demonstrated that major trauma (Injury Severity Score [ISS] ≥16), intubation, and use of invasive mechanical ventilation increase nosocomial pneumonia and death rate. The most common causes of nosocomial infections were Acinetobacter baumannii (23%) and coagulase-negative staphylococcus (18.5%). The highest levels of antibiotic resistance were related to cefoxitin, erythromycin, ciprofloxacin, and trimethoprim-sulfamethoxazole. Conclusions: Major trauma, intubation, and invasive mechanical ventilation were the effective factors in the development of nosocomial pneumonia. Continuous monitoring for mentioned risk factors and strict surveillance of antibiotic prescription can decrease the prevalence of nosocomial infections and subsequent deaths.

Characterization of the plasma proteome of nonhuman primates during Ebola virus disease or melioidosis: a host response comparison

Background

In-depth examination of the plasma proteomic response to infection with a wide variety of pathogens can assist in the development of new diagnostic paradigms, while providing insight into the interdependent pathogenic processes which encompass a host’s immunological and physiological responses. Ebola virus (EBOV) causes a highly lethal infection termed Ebola virus disease (EVD) in primates and humans. The Gram negative non-spore forming bacillus Burkholderia pseudomallei (Bp) causes melioidosis in primates and humans, characterized by severe pneumonia with high mortality. We sought to examine the host response to infection with these two bio-threat pathogens using established animal models to provide information on the feasibility of pre-symptomatic diagnosis, since the induction of host molecular signaling networks can occur before clinical presentation and pathogen detection.

Methods

Herein we report the quantitative proteomic analysis of plasma collected at various times of disease progression from 10 EBOV-infected and 5 Bp-infected nonhuman primates (NHP). Our strategy employed high resolution LC–MS/MS and a peptide-tagging approach for relative protein quantitation. In each infection type, for all proteins with > 1.3 fold abundance change at any post-infection time point, a direct comparison was made with levels obtained from plasma collected daily from 5 naïve rhesus macaques, to determine the fold changes that were significant, and establish the natural variability of abundance for endogenous plasma proteins.

Results

A total of 41 plasma proteins displayed significant alterations in abundance during EBOV infection, and 28 proteins had altered levels during Bp infection, when compared to naïve NHPs. Many major acute phase proteins quantitated displayed similar fold-changes between the two infection types but exhibited different temporal dynamics. Proteins related to the clotting cascade, immune signaling and complement system exhibited significant differential abundance during infection with EBOV or Bp, indicating a specificity of the response.

Conclusions

These results advance our understanding of the global plasma proteomic response to EBOV and Bp infection in relevant primate models for human disease and provide insight into potential innate immune response differences between viral and bacterial infections.

Electronic supplementary material

The online version of this article (10.1186/s12014-019-9227-3) contains supplementary material, which is available to authorized users.

Cloning and characterization of an insect apolipoprotein (apolipophorin-II/I) involved in the host immune response of Antheraea pernyi

Apolipoproteins are protein components of lipoprotein particles, and are increasingly recognized to be functioning in the innate immune systems of both insects and mammals. Mammalian apolipoprotein B (apoB) is associated with a diverse range of innate immune defenses including suppression of bacterial pathogenesis, virus toxicity neutralization, and inhibition of cytokine releases from immune cells. However, little is known about apoB homologous insect apolipophorin-II/I (apoLp-II/I) in controlling of specific pathogen-host encounters such as microbial infections. In the present study, we describe cDNA cloning and characterization of an apoLp-II/I from Chinese oak silk worm, Antheraea pernyi. The apoLp-II/I cDNA is 10237bp in length, which possesses an open reading frame encoding 3305 amino acids. A consensus cleavage site RGRR presenting from Arg⁷¹⁰ to Arg⁷¹³ implies posttranslational cleavage of this protein. Ap-apoLp-II/I shares high sequence identities with apoLp-II/I in lepidoptera and other insects. In addition, considerable similarities also exist between Ap-apoLp-II/I and human apoB, which basically positioned in first 1000 residues of the amino termini. Tissue distribution and time-course expression results demonstrate that Ap-apoLp-II/I transcripts were detected predominantly in the fat body, less in epidermis and rarely in midgut, while the synthetic apoLp-II/I protein was abundant in hemocytes and plasma instead of the fatbody. Expression of Ap-apoLp-II/I was stimulated in response to bacterial challenge. In addition, our preliminary studies established a novel role for Ap-apoLp-II/I in regulating prophenoloxidase activation system. Taken together, apoLp-II/I may play an essential role in innate responses of Antheraea pernyi.

An FcγRIIa polymorphism with decreased C-reactive protein binding is associated with sepsis and decreased monocyte HLA-DR expression in trauma patients

BACKGROUND

A dysregulated immune response leading to sepsis is the most frequent cause of late posttraumatic deaths. We have found a novel anti-inflammatory pathway that is initiated by the acute phase protein, C-reactive protein (CRP), interacting with Fcγ receptor (FcγR) on monocytes. This pathway is protective in animal models of endotoxin shock. We hypothesized that genetic polymorphisms in the FcγR might contribute to monocyte responses and susceptibility to infectious complications after severe trauma.

METHODS

We conducted an observational study on a prospectively identified cohort of adult patients with convenience enrollment admitted after severe trauma. We enrolled 66 patients and collected blood samples at enrollment and again at 48 hours and 72 hours. Patients were followed through their hospital stay, and any septic events before 14 days were recorded. Cytokine and CRP levels were determined in the plasma from all three blood draws. In addition, DNA was extracted from blood and analyzed for the 131 H/R FcγRIIa polymorphism that strongly affects the binding of IgG and CRP to this receptor.

RESULTS

Elevated levels of interleukin 8 (IL-8), IL-6, IL-10, monocyte chemotactic protein 1, and CRP were associated with reduced time to posttraumatic sepsis in Cox regression analysis. Expression of monocyte human leukocyte antigen DR less than 45% on patient monocytes was also associated with sepsis (hazard ratio, 3.15; 95% confidence interval, 1.45-6.93). Genetic analysis found that individuals with the polymorphism of the FcγRIIa receptor that binds CRP poorly were also more likely to have decreased monocyte human leukocyte antigen DR and posttraumatic sepsis. In vitro studies showed that CRP could attenuate monocyte deactivation in volunteers with the polymorphism of the FcγRIIa receptor that binds CRP.

CONCLUSION

Our findings suggest that a common genetic variation in the FcγRIIa receptor may contribute to infectious susceptibility in trauma patients. In vitro experiments suggest that this association is related to the inability of CRP to bind to this FcγRIIa receptor variant.

LEVEL OF EVIDENCE

Prognostic study, level III.

Serum Lipoproteins Are Critical for Pulmonary Innate Defense against Staphylococcus aureus Quorum Sensing

Hyperlipidemia has been extensively studied in the context of atherosclerosis, whereas the potential health consequences of the opposite extreme, hypolipidemia, remain largely uninvestigated. Circulating lipoproteins are essential carriers of insoluble lipid molecules and are increasingly recognized as innate immune effectors. Importantly, severe hypolipidemia, which may occur with trauma or critical illness, is clinically associated with bacterial pneumonia. To test the hypothesis that circulating lipoproteins are essential for optimal host innate defense in the lung, we used lipoprotein-deficient mice and a mouse model of Staphylococcus aureus pneumonia in which invasive infection requires virulence factor expression controlled by the accessory gene regulator (agr) operon. Activation of agr and subsequent virulence factor expression is inhibited by apolipoprotein B, the structural protein of low-density lipoprotein, which binds and sequesters the secreted agr-signaling peptide (AIP). In this article, we report that lipoprotein deficiency impairs early pulmonary innate defense against S. aureus quorum-sensing-dependent pathogenesis. Specifically, apolipoprotein B levels in the lung early postinfection are significantly reduced with lipoprotein deficiency, coinciding with impaired host control of S. aureus agr-signaling and increased agr-dependent morbidity (weight loss) and inflammation. Given that lipoproteins also inhibit LTA- and LPS-mediated inflammation, these results suggest that hypolipidemia may broadly impact posttrauma pneumonia susceptibility to both Gram-positive and -negative pathogens. Together with previous reports demonstrating that hyperlipidemia also impairs lung innate defense, these results suggest that maintenance of normal serum lipoprotein levels is necessary for optimal host innate defense in the lung.

Apolipoprotein B48, the Structural Component of Chylomicrons, Is Sufficient to Antagonize Staphylococcus aureus Quorum-Sensing

Serum lipoproteins (LP) are increasingly being recognized as dual purpose molecules that contribute to both cholesterol homeostasis and host innate defense. In fact, very low LP levels are associated with increased risk of bacterial infection in critically ill patients. In this respect, we reported that apolipoprotein B100 (apoB100), the 4536 amino acid structural protein of very low density lipoprotein (VLDL) produced by the liver, limits Staphylococcus aureus pathogenesis. S. aureus uses quorum-sensing (QS) via the accessory gene regulator (agr) operon and an autoinducing peptide (AIP) to coordinate expression of over 200 virulence genes. ApoB100 prevents agr activation by binding and sequestering secreted AIP. Importantly, human serum LP are produced not only by the liver, but are also produced by enterocytes, in the form of chylomicrons, during uptake of dietary lipids. In contrast to apoB100 in VLDL, human enterocytes use apoB48, the N-terminal 2152 amino acids (48%) of apoB100, as the structural component of chylomicrons. Interestingly, enteral feeding of critically ill patients has been associated with decreased risk of infectious complications, suggesting chylomicrons could contribute to host innate defense in critically ill patients when serum LP production by the liver is limited during the acute phase response. Therefore, we hypothesized that apoB48 would be sufficient to antagonize S. aureus QS. As expected, isolated apoB48-LP bound immobilized AIP and antagonized agr-signaling. ApoB48- and apoB100-LP inhibited agr activation with IC50s of 3.5 and 2.3 nM, respectively, demonstrating a conserved AIP binding site. Importantly, apoB48-LP antagonized QS, limited morbidity and promoted bacterial clearance in a mouse model of S. aureus infection. This work demonstrates that both naturally occurring forms of apolipoprotein B can antagonize S. aureus QS, and may suggest a previously unrecognized role for chylomicrons and enterocytes in host innate defense against S. aureus QS-mediated pathogenesis.