Antibacterial Effect and Inflammatory Response in Relation to Antibiotic Treatment of Sepsis

Sepsis defines as life-threatening organ dysfunction caused by a dysregulated host response to infection. The importance of early administration of antibiotics in septic shock is undisputed, but the optimal antibiotic choice remains uncertain. Some national guidelines advocate single β-lactam antibiotic treatment while others recommend a combination of β-lactam and aminoglycoside. This thesis aimed to investigate the anti-bacterial properties and antibiotic-induced inflammatory responses of ß-lactam antibiotic compared with effects of the addition of an aminoglycoside in clinically relevant E. coli porcine intensive care sepsis/septic shock models. We also studied the host's antibacterial capacities in primary and secondary sepsis. In Paper I the addition of an aminoglycoside, in comparison with single β-lactam antibiotic treatment,  caused decreased bacterial growth in the liver and greater antibiotic-induced blood killing activity ex vivo. The results thereby constitute possible mechanisms to the previously reported improved survival in the most critically ill sepsis patients receiving the β-lactam/aminoglycoside combination. Also observed in this paper was that individual blood bactericidal capacity may have significant effects on antimicrobial outcome.   In Paper II we investigated endotoxin release in vivo after antibiotic treatment in comparison with no treatment. There were no differences, however, antibiotics did increase an inflammatory IL-6 response that was associated with leukocyte activation and pulmonary organ dysfunction. A secondary finding was that the addition of an aminoglycoside to a β-lactam induced trends towards less inflammation compared with β-lactam alone. Paper III compared how challenge with different pre-killed E. coli activates the inflammatory response, resulting in higher cytokine responses, more leucocyte activation and inflammatory capillary leakage after single β-lactam compared with live or heat-killed bacteria. The addition of an aminoglycoside lowered the β-lactam-induced responses. Paper IV demonstrated that animals with secondary sepsis exhibited an attenuated inflammatory response as expected; however, contrary to our hypothesis, the animals’ antibacterial capacities were intact and partly enhanced. We conclude that there are likely several beneficial effects of the addition of an aminoglycoside to a β-lactam therapy regimen in septic shock. Because host antibacterial capacities in secondary sepsis are enhanced, the need for bactericidal antibiotic combinations is not greater in secondary than in primary sepsis

Antibacterial Effect and Inflammatory Response in Relation to Antibiotic Treatment of Sepsis

Sepsis defines as life-threatening organ dysfunction caused by a dysregulated host response to infection. The importance of early administration of antibiotics in septic shock is undisputed, but the optimal antibiotic choice remains uncertain. Some national guidelines advocate single β-lactam antibiotic treatment while others recommend a combination of β-lactam and aminoglycoside. This thesis aimed to investigate the anti-bacterial properties and antibiotic-induced inflammatory responses of ß-lactam antibiotic compared with effects of the addition of an aminoglycoside in clinically relevant E. coli porcine intensive care sepsis/septic shock models. We also studied the host's antibacterial capacities in primary and secondary sepsis. In Paper I the addition of an aminoglycoside, in comparison with single β-lactam antibiotic treatment,  caused decreased bacterial growth in the liver and greater antibiotic-induced blood killing activity ex vivo. The results thereby constitute possible mechanisms to the previously reported improved survival in the most critically ill sepsis patients receiving the β-lactam/aminoglycoside combination. Also observed in this paper was that individual blood bactericidal capacity may have significant effects on antimicrobial outcome.   In Paper II we investigated endotoxin release in vivo after antibiotic treatment in comparison with no treatment. There were no differences, however, antibiotics did increase an inflammatory IL-6 response that was associated with leukocyte activation and pulmonary organ dysfunction. A secondary finding was that the addition of an aminoglycoside to a β-lactam induced trends towards less inflammation compared with β-lactam alone. Paper III compared how challenge with different pre-killed E. coli activates the inflammatory response, resulting in higher cytokine responses, more leucocyte activation and inflammatory capillary leakage after single β-lactam compared with live or heat-killed bacteria. The addition of an aminoglycoside lowered the β-lactam-induced responses. Paper IV demonstrated that animals with secondary sepsis exhibited an attenuated inflammatory response as expected; however, contrary to our hypothesis, the animals’ antibacterial capacities were intact and partly enhanced. We conclude that there are likely several beneficial effects of the addition of an aminoglycoside to a β-lactam therapy regimen in septic shock. Because host antibacterial capacities in secondary sepsis are enhanced, the need for bactericidal antibiotic combinations is not greater in secondary than in primary sepsis

Antibacterial Effect and Inflammatory Response in Relation to Antibiotic Treatment of Sepsis

Sepsis defines as life-threatening organ dysfunction caused by a dysregulated host response to infection. The importance of early administration of antibiotics in septic shock is undisputed, but the optimal antibiotic choice remains uncertain. Some national guidelines advocate single β-lactam antibiotic treatment while others recommend a combination of β-lactam and aminoglycoside. This thesis aimed to investigate the anti-bacterial properties and antibiotic-induced inflammatory responses of ß-lactam antibiotic compared with effects of the addition of an aminoglycoside in clinically relevant E. coli porcine intensive care sepsis/septic shock models. We also studied the host's antibacterial capacities in primary and secondary sepsis. In Paper I the addition of an aminoglycoside, in comparison with single β-lactam antibiotic treatment,  caused decreased bacterial growth in the liver and greater antibiotic-induced blood killing activity ex vivo. The results thereby constitute possible mechanisms to the previously reported improved survival in the most critically ill sepsis patients receiving the β-lactam/aminoglycoside combination. Also observed in this paper was that individual blood bactericidal capacity may have significant effects on antimicrobial outcome.   In Paper II we investigated endotoxin release in vivo after antibiotic treatment in comparison with no treatment. There were no differences, however, antibiotics did increase an inflammatory IL-6 response that was associated with leukocyte activation and pulmonary organ dysfunction. A secondary finding was that the addition of an aminoglycoside to a β-lactam induced trends towards less inflammation compared with β-lactam alone. Paper III compared how challenge with different pre-killed E. coli activates the inflammatory response, resulting in higher cytokine responses, more leucocyte activation and inflammatory capillary leakage after single β-lactam compared with live or heat-killed bacteria. The addition of an aminoglycoside lowered the β-lactam-induced responses. Paper IV demonstrated that animals with secondary sepsis exhibited an attenuated inflammatory response as expected; however, contrary to our hypothesis, the animals’ antibacterial capacities were intact and partly enhanced. We conclude that there are likely several beneficial effects of the addition of an aminoglycoside to a β-lactam therapy regimen in septic shock. Because host antibacterial capacities in secondary sepsis are enhanced, the need for bactericidal antibiotic combinations is not greater in secondary than in primary sepsis

Plasma hyaluronan, hyaluronidase activity and endogenous hyaluronidase inhibition in sepsis : an experimental and clinical cohort study

Background: Plasma hyaluronan concentrations are increased during sepsis but underlying mechanisms leading to high plasma hyaluronan concentration are poorly understood. In this study we evaluate the roles of plasma hyaluronan, effective plasma hyaluronidase (HYAL) activity and its endogenous plasma inhibition in clinical and experimental sepsis. We specifically hypothesized that plasma HYAL acts as endothelial glycocalyx shedding enzyme, sheddase. Methods: Plasma hyaluronan, effective HYAL activity and HYAL inhibition were measured in healthy volunteers (n = 20), in patients with septic shock (n = 17, day 1 and day 4), in patients with acute pancreatitis (n = 7, day 1 and day 4) and in anesthetized and mechanically ventilated pigs (n = 16). Sixteen pigs were allocated (unblinded, open label) into three groups: Sepsis-1 with infusion of live Escherichia coli (E. coli) 1 x 10(8) CFU/h of 12 h (n = 5), Sepsis-2 with infusion of E. coli 1 x 10(8) CFU/h of 6 h followed by 1 x 10(9) CFU/h of the remaining 6 h (n = 5) or Control with no E. coli infusion (n = 6). Results: In experimental E. coli porcine sepsis and in time controls, plasma hyaluronan increases with concomitant decrease in effective plasma HYAL activity and increase of endogenous HYAL inhibition. Plasma hyaluronan increased in patients with septic shock but not in acute pancreatitis. Effective plasma HYAL was lower in septic shock and acute pancreatitis as compared to healthy volunteers, while plasma HYAL inhibition was only increased in septic shock. Conclusion: Elevated plasma hyaluronan levels coincided with a concomitant decrease in effective plasma HYAL activity and increase of endogenous plasma HYAL inhibition both in experimental and clinical sepsis. In acute pancreatitis, effective plasma HYAL activity was decreased which was not associated with increased plasma hyaluronan concentrations or endogenous HYAL inhibition. The results suggest that plasma HYAL does not act as sheddase in sepsis or pancreatitis.Peer reviewe

Endotoxin tolerance variation over 24 h during porcine endotoxemia : association to changes in circulation and organ dysfunction

Endotoxin tolerance (ET), defined as reduced inflammatory responsiveness to endotoxin challenge following a first encounter with endotoxin, is an extensively studied phenomenon. Although reduced mortality and morbidity in the presence of ET has been demonstrated in animal studies, little is known about the temporal development of ET. Further, in acute respiratory distress syndrome ET correlates to the severity of the disease, suggesting a complicated relation between ET and organ dysfunction. Eighteen pigs were subjected to intensive care and a continuous endotoxin infusion for 24 h with the aim to study the time course of early ET and to relate ET to outcome in organ dysfunction. Three animals served as non-endotoxemic controls. Blood samples for cytokine analyses were taken and physiological variables registered every third hour. Production of TNF-α, IL-6, and IL-10 before and after endotoxin stimulation ex vivo was measured. The difference between cytokine values after and before ex vivo LPS stimulation (Δ-values) was calculated for all time points. ΔTNF-α was employed as the principal marker of ET and lower ΔTNF-α values were interpreted as higher levels of ET. During endotoxin infusion, there was suppression of ex vivo productions of TNF-α and IL-6 but not of IL-10 in comparison with that at 0 h. The ex vivo TNF-α values followed another time concentration curve than those in vivo. ΔTNF-α was at the lowest already at 6 h, followed by an increase during the ensuing hours. ΔTNF-α at 6 h correlated positively to blood pressure and systemic vascular resistance and negatively to cardiac index at 24 h. In this study a temporal variation of ET was demonstrated that did not follow changes in plasma TNF-α concentrations. Maximal ET occurred early in the course and the higher the ET, the more hyperdynamic the circulation 18 h later

The kinetics of SARS-CoV-2 viremia in COVID-19 patients receiving remdesivir

Detection of SARS-CoV-2 RNA in serum, viremia, has been linked to disease severity and outcome. The kinetics of viremia in patients receiving remdesivir has not been thoroughly studied and could help predict treatment response and outcome. We investigated the kinetics of SARS-CoV-2 viremia and factors associated with baseline viremia, viral clearance and 30-day mortality in patients receiving remdesivir. An observational study including 378 hospitalised patients (median age 67 years, 67% male) sampled with serum SARS-CoV-2 RT-PCR within +/- 24 h of initiation of remdesivir treatment. Baseline viremia was present in 206 (54%) patients with a median Ct value of 35.3 (IQR = 33.3-37.1). In patients with baseline viremia, the estimated probability of viral clearance was 72% by day 5. Ct values decreased significantly during remdesivir treatment for viremic patients, indicating an increase in viral load. In total, 44 patients (12%) died within 30 days, and mortality was significantly associated with viremia at baseline (OR = 2.45, p = 0.01) and lack of viral clearance by day 5 (OR = 4.8, p = < 0.01). Viral clearance was not associated with any individual risk factor. Viremia appears to be a prognostic marker before and during remedesivir treatment. The resolution of viremia was similar to patients not receiving remdesivir in other studies, and the decrease in Ct values during treatment questions the antiviral capacity of remdesivir in vivo. Prospective studies are warranted to confirm our findings

Pre-exposure to mechanical ventilation and endotoxemia increases Pseudomonas aeruginosa growth in lung tissue during experimental porcine pneumonia

Background: Immune system suppression during critical care contributes to the risk of acquired bacterial infections with Pseudomonas (P.) aeruginosa. Repeated exposure to endotoxin can attenuate systemic inflammatory cytokine responses. Mechanical ventilation affects the systemic inflammatory response to various stimuli. Aim: To study the effect of pre-exposure to mechanical ventilation with and without endotoxin-induced systemic inflammation on P. aeruginosa growth and wet-to-dry weight measurements on lung tissue and plasma and bronchoalveolar lavage levels of tumor necrosis factor alpha, interleukins 6 and 10. Methods: Two groups of pigs were exposed to mechanical ventilation for 24 hours before bacterial inoculation and six h of experimental pneumonia (total experimental time 30 h): A(30h+Etx) (n = 6, endotoxin 0.063 mu g x kg(-1) x h(-1)) and B-30h (n = 6, saline). A third group, C-6h (n = 8), started the experiment at the bacterial inoculation unexposed to endotoxin or mechanical ventilation (total experimental time 6 h). Bacterial inoculation was performed by tracheal instillation of 1x10(11) colony-forming units of P. aeruginosa. Bacterial cultures and wet-to-dry weight ratio analyses were done on lung tissue samples postmortem. Separate group comparisons were done between A(30h+Etx) vs.B-30h (Inflammation) and B-30h vs. C-6h (Ventilation Time) during the bacterial phase of 6 h. Results: P. aeruginosa growth was highest in A(30h+Etx), and lowest in C-6h (Inflammation and Ventilation Time both p<0.05). Lung wet-to-dry weight ratios were highest in A(30h+Etx) and lowest in B-30h (Inflammation p<0.01, Ventilation Time p<0.05). C-6h had the highest TNF-alpha levels in plasma (Ventilation Time p<0.01). No differences in bronchoalveolar lavage variables between the groups were observed. Conclusions: Mechanical ventilation and systemic inflammation before the onset of pneumonia increase the growth of P. aeruginosa in lung tissue. The attenuated growth of P. aeruginosa in the non-pre-exposed animals (C-6h) was associated with a higher systemic TNF-alpha production elicited from the bacterial challenge

Predicting cytokine kinetics during sepsis; a modelling framework from a porcine sepsis model with live Escherichia coli

Background: Describing the kinetics of cytokines involved as biomarkers of sepsis progression could help to optimise interventions in septic patients. This work aimed to quantitively characterise the cytokine kinetics upon exposure to live E. coli by developing an in silico model, and to explore predicted cytokine kinetics at different bacterial exposure scenarios. Methods: Data from published in vivo studies using a porcine sepsis model were analysed. A model describing the time courses of bacterial dynamics, endotoxin (ETX) release, and the kinetics of TNF and IL-6 was developed. The model structure was extended from a published model that quantifies the ETX-cytokines relationship. An external model evaluation was conducted by applying the model to literature data. Model simulations were performed to explore the sensitivity of the host response towards differences in the input rate of bacteria, while keeping the total bacterial burden constant. Results: The analysis included 645 observations from 30 animals. The blood bacterial count was well described by a one-compartment model with linear elimination. A scaling factor was estimated to quantify the ETX release by bacteria. The model successfully described the profiles of TNF, and IL-6 without a need to modify the ETXcytokines model structure. The kinetics of TNF, and IL-6 in the external datasets were well predicted. According to the simulations, the ETX tolerance development results in that low initial input rates of bacteria trigger the lowest cytokine release. Conclusion: The model quantitively described and predicted the cytokine kinetics triggered by E. coli exposure. The host response was found to be sensitive to the bacterial exposure rate given the same total bacterial burden