Tejal S. Brahmbhatt

Neutrophil depletion causes a fatal defect in murine pulmonary Staphylococcus aureus clearance

BACKGROUND Staphylococcus aureus is the most common cause of healthcare-associated pneumonia. Despite the significant morbidity and mortality associated with the disease, animal models of S. aureus pneumonia are rare. MATERIALS AND METHODS We examined the pathogenicity of four different strains of S. aureus (both methicillin-sensitive and -resistant as well as Panton-Valentine leukocidin-positive and -negative) in four strains of immunocompetent inbred and outbred mice (FVB/N, C57Bl/6, BALB/c, ND4; n = 148). The immunological basis for the development of murine S. aureus pneumonia was then determined by selectively depleting neutrophils, lymphocytes, or pulmonary macrophages prior to the onset of infection. An additional cohort of animals was rendered immunosuppressed by induction of abdominal sepsis via cecal ligation and puncture 2, 4, or 7 d prior to the onset of pneumonia. RESULTS Nearly all immunocompetent mice survived, regardless of which strain of S. aureus was used or which strain of mouse was infected. Among animals with immune depletion or prior immunosuppression, survival was decreased only following neutrophil depletion (26% versus 90% alive at 7 d, P < 0.0001). Compared to immunocompetent animals, neutrophil-depleted mice with S. aureus pneumonia had delayed pulmonary bacterial clearance at 16 and 40 h but had no difference in levels of bacteremia. Neutrophil-depleted mice also had elevated levels of pulmonary monocyte chemotactic protein-1 (822 pg/mL versus 150 pg/mL, P < 0.05). In contrast, pulmonary histological appearance was similar in both groups as was dry/wet lung weight. CONCLUSIONS These results suggest that neutrophils play a critical role in the host response to S. aureus pneumonia, and the survival differences observed in neutrophil-depleted mice are associated with alterations in bacterial clearance and pulmonary cytokine response.

Agonistic Monoclonal Antibody Against CD40 Receptor Decreases Lymphocyte Apoptosis and Improves Survival in Sepsis

Sepsis causes a marked apoptosis-induced depletion of lymphocytes. The degree of lymphocyte apoptosis during sepsis strongly correlates with survival. CD40, a member of the TNFR family, is expressed on APCs and has potent antiapoptotic activity. In this study we determined whether an agonistic Ab against CD40 could protect lymphocytes from sepsis-induced apoptosis. Secondly, we examined potential antiapoptotic mechanisms of the putative protection. Lastly, we aimed to determine whether anti-CD40 treatment could improve survival in sepsis. CD1 mice were made septic by the cecal ligation and puncture method and treated postoperatively with anti-CD40 Ab. Treatment with anti-CD40 completely abrogated sepsis-induced splenic B cell death and, surprisingly, decreased splenic and thymic T cell death as well (p < 0.001). To investigate the mechanism of protection of anti-CD40 therapy on T cells, CD40 receptor expression was examined. As anticipated, the CD40 receptor was constitutively expressed on B cells, but, unexpectedly, splenic and thymic T cells were found to express CD40 receptor during sepsis. Furthermore, CD4+CD8− T cells were the predominant subtype of T cells expressing CD40 receptor during sepsis. Additionally, the antiapoptotic protein Bcl-xL was found to be markedly increased in splenic B and T cells as well as in thymic T cells after treatment with anti-CD40 Ab (p < 0.0025). Lastly, mice that were made septic in a double injury model of sepsis had improved survival after treatment with anti-CD40 as compared with controls (p = 0.05). In conclusion, anti-CD40 treatment increases Bcl-xL, provides nearly complete protection against sepsis-induced lymphocyte apoptosis, and improves survival in sepsis.

Lymphocyte Phenotyping to Distinguish Septic from Nonseptic Critical Illness

BACKGROUND Clinical signs and symptoms of sepsis are nonspecific and often indistinguishable from those of nonseptic critical illness. This ambiguity frequently delays the diagnosis of sepsis until culture results can confirm the presence or absence of an infectious organism. Lymphocyte phenotyping can be conducted rapidly and may provide information on the presence of infection before culture results are available. In this study, we hypothesized that lymphocyte phenotype can distinguish between septic and nonseptic critical illness. STUDY DESIGN C57Bl/6 mice were subjected to either P aeruginosa pneumonia or lipopolysaccharide-induced acute lung injury (ALI). Animals were sacrificed 24 hours postinjury and splenic lymphocytes were harvested. Additionally, 13 patients in a surgical ICU were enrolled in the study. Whole blood was obtained and lymphocytes were isolated by density gradient centrifugation. Lymphocyte phenotype was identified through flow cytometry after labeling lymphocytes for CD3, CD4, CD8, CD20, CD40, CD69, and CD86 with fluorochrome-conjugated antibodies. RESULTS CD69 expression on B cells and CD8+ splenocytes from septic mice was significantly increased compared with acute lung injury mice (p < 0.001 and p < 0.05, respectively). Similarly, CD4+ and CD8+ lymphocytes from septic patients had a two- to threefold increase in the expression of CD69 compared with nonseptic critically ill patients (p < 0.05). CONCLUSIONS These data indicated that CD69 expression on lymphocytes may be useful in distinguishing between septic and nonseptic critical illness. Continued investigation into the expression of CD69 during sepsis is warranted.

Trauma and BMI Mortality

Purpose of ReviewObesity has been recognized as an impactful comorbid condition. It has been demonstrated to be an independent risk factor for morbidity and mortality following trauma.Recent FindingsMultiple studies and reviews have strongly suggested obesity to be associated with increased risk for post-injury morbidity and mortality. As obesity is associated with a pro-inflammatory state, it has been suggested to negatively affect the respiratory, cardiovascular, coagulation, and renal systems and the ability and manner in which an obese patient heals.SummaryAs obesity continues to rise at alarming rates in the USA, this population of patients requires special consideration and continued research is underway to delineate relationships between obesity, trauma, and outcomes in an effort to improve overall care.

A comparison of alcohol positive and alcohol negative trauma patients requiring an emergency laparotomy

Background: The effect of alcohol exposure on patients undergoing a laparotomy for trauma is unknown. The purpose of this study was to compare outcomes of morbidity and mortality between alcohol positive and alcohol negative trauma patients who required emergent laparotomies using the National Trauma Data Bank (NTDB). Methods: A retrospective database analysis was performed using 28,354 NTDB incident trauma cases, from 2007 through 2012, who had been tested for alcohol and who required abdominal operations (using ICD‐9‐CM procedure codes) within 24 h of presentation. Variables used: age, gender, admission year, alcohol presence, ISS, GCS, injury type & mechanism, discharge status, hospital LOS, ICU stay, ventilator use, and hospital complications. Results: In adjusted analyses, there were no statistically significant differences between the alcohol positive and alcohol negative cohorts when evaluating in‐hospital mortality (OR, 0.93; 95% CI: 0.84–1.03), likelihood of earlier hospital discharge (HR, 1.02; 95% CI: 0.99–1.05), and the all‐inclusive category of in‐hospital complications (OR, 1.04; 95% CI: 0.97–1.12). Conclusions: After adjusting for age, gender, admission year, ISS, GCS, and injury mechanism, there were no major differences between the alcohol positive and alcohol negative cohorts when it came to in‐hospital mortality, likelihood of earlier hospital discharge, and most of the in‐hospital complications measured among adult trauma patients requiring emergency laparotomies.