Variation in the propensity to release endotoxin after cefuroxime exposure in different gram-negative bacteria: uniform and dose-dependent reduction by the addition of tobramycin

Comparison of Microbial Sampling Sites and Donor-Related Factors on Corneal Graft Contamination

Grafts used for corneal donation should be sterile to avoid transplantation failure and secondary infection. However, there are no clear and globally accepted specifications from eye banks on microbial sampling sites. The objective of this study was to analyze microbial contamination of corneal grafts collected from different sampling sites. We found that the contamination rates and strain compositions significantly differed at different sampling sites. To clarify the effect of the microbial sampling site on corneal graft contamination, microbial sampling was conducted using 30 corneal grafts at the extraocular and intraocular sides of the graft in 2020 from the National Eye Bank of Taiwan. Microbial contamination significantly differed (p < 0.05) between the different sampling sites on the graft according to McNemar’s test. Although the two sampling sites showed the same specificity (33.33%), the sensitivity of sampling on the extraocular side (82.35%) was higher than that on the intraocular side (17.65%) of the graft. Donor-associated factors, including the cause of death, operating place, and cold compression, were analyzed using chi-square statistics, which revealed no significant differences in microbial contamination. Thus, our data provide evidence for the microbial sampling site of donated grafts and clear specifications for maintaining the quality of corneal grafts.

Mode of bacterial killing affects the inflammatory response and associated organ dysfunctions in a porcine E. coli intensive care sepsis model

Background

Sepsis is often treated with penicillin-binding protein 3 (PBP-3) acting β-lactam antibiotics, such as piperacillin-tazobactam, cefotaxime, and meropenem. They cause considerable bacterial structural changes and have in vitro been associated with an increased inflammatory response. In a clinically relevant large animal sepsis model, our primary aim was to investigate whether bacteria killed by a PBP-3-active antibiotic has a greater effect on the early inflammatory response and organ dysfunction compared with corresponding amounts of live or heat-killed bacteria. A secondary aim was to determine whether the addition of an aminoglycoside could mitigate the cefuroxime-induced response.

Method

Killed or live Escherichia coli were administrated as a 3-h infusion to 16 healthy pigs in a prospective, randomized controlled interventional experimental study. Cefuroxime was chosen as the PBP-3-active antibiotic and tobramycin represented the aminoglycosides. The animals were randomized to receive (I) bacteria killed by cefuroxime, (II) live bacteria, (III) bacteria killed by heat, or (IV) bacteria killed by the combination of cefuroxime and tobramycin. Plasma endotoxin, tumor necrosis factor alpha, interleukin-6, interleukin-10, leukocytes, and organ function were recorded at the start of the experiment and then hourly for 6 h.

Results

Differences in dynamics of concentration over time between the four treatment groups were found for the three cytokines (p < 0.001). Animals receiving cefuroxime-killed bacteria demonstrated higher responses than those receiving live (p < 0.05) or heat-killed bacteria (p < 0.01). The addition of tobramycin reduced the cefuroxime-induced responses (p < 0.001). The cytokine responses were associated with leucocyte activation that was further associated with pulmonary dysfunction and increases in lactate (p < 0.01).

Conclusions

In comparison with live or heat-killed bacteria, bacteria killed by a PBP-3-active antibiotic induced an increased inflammatory response that appears to be associated with deteriorated organ and cellular function. The addition of an aminoglycoside to the PBP-3-active antibiotic reduced that response.

Antibiotic treatment with one single dose of gentamicin at admittance in addition to a β-lactam antibiotic in the treatment of community-acquired bloodstream infection with sepsis

Background

Combination therapy in the treatment of sepsis, especially the value of combining a β-Lactam antibiotic with an aminoglycoside, has been discussed. This retrospective cohort study including patients with sepsis or septic shock aimed to investigate whether one single dose of gentamicin at admittance (SGA) added to β-Lactam antibiotic could result in a lower risk of mortality than β-Lactam monotherapy, without exposing the patient to the risk of nephrotoxicity.

Methods and findings

All patients with positive blood cultures were evaluated for participation (n = 1318). After retrospective medical chart review, a group of patients with community-acquired sepsis with positive blood cultures who received β-Lactam antibiotic with or without the addition of SGA (n = 399) were included for the analysis. Mean age was 74.6 yrs. (range 19–98) with 216 (54%) males. Sequential Organ Failure Assessment score (SOFA score) median was 3 (interquartile range [IQR] 2–5) and the median Charlson Comorbidity Index for the whole group was 2 (IQR 1–3). Sixty-seven (67) patients (17%) had septic shock. The 28-day mortality in the combination therapy group was 10% (20 of 197) and in the monotherapy group 22% (45 of 202), adjusted HR 3.5 (95% CI (1.9–6.2), p = < 0.001. No significant difference in incidence of acute kidney injury (AKI) was detected.

Conclusion

This retrospective observational study including patients with community-acquired sepsis or septic shock and positive blood cultures, who meet Sepsis-3 criteria, shows that the addition of one single dose of gentamicin to β-lactam treatment at admittance was associated with a decreased risk of mortality and was not associated with AKI. This antibiotic regime may be an alternative to broad-spectrum antibiotic treatment of community-acquired sepsis. Further prospective studies are warranted to confirm these results.

Extension of Pharmacokinetic/Pharmacodynamic Time-Kill Studies To Include Lipopolysaccharide/Endotoxin Release from Escherichia coli Exposed to Cefuroxime

The release of inflammatory bacterial products, such as lipopolysaccharide (LPS)/endotoxin, may be increased upon the administration of antibiotics. An improved quantitative understanding of endotoxin release and its relation to antibiotic exposure and bacterial growth/killing may be gained by an integrated analysis of these processes. The aim of this work was to establish a mathematical model that relates Escherichia coli growth/killing dynamics at various cefuroxime concentrations to endotoxin release in vitro.

The release of inflammatory bacterial products, such as lipopolysaccharide (LPS)/endotoxin, may be increased upon the administration of antibiotics. An improved quantitative understanding of endotoxin release and its relation to antibiotic exposure and bacterial growth/killing may be gained by an integrated analysis of these processes. The aim of this work was to establish a mathematical model that relates Escherichia coli growth/killing dynamics at various cefuroxime concentrations to endotoxin release in vitro. Fifty-two time-kill experiments informed bacterial and endotoxin time courses and included both static (0×, 0.5×, 1×, 2×, 10×, and 50× MIC) and dynamic (0×, 15×, and 30× MIC) cefuroxime concentrations. A model for the antibiotic-bacterium interaction was established, and antibiotic-induced bacterial killing followed a sigmoidal Emax relation to the cefuroxime concentration (MIC-specific 50% effective concentration [EC₅₀], maximum antibiotic-induced killing rate [E_max] = 3.26 h⁻¹ and γ = 3.37). Endotoxin release was assessed in relation to the bacterial processes of growth, antibiotic-induced bacterial killing, and natural bacterial death and found to be quantitatively related to bacterial growth (0.000292 endotoxin units [EU]/CFU) and antibiotic-induced bacterial killing (0.00636 EU/CFU). Increased release following the administration of a second cefuroxime dose was described by the formation and subsequent antibiotic-induced killing of filaments (0.295 EU/CFU). Release due to growth was instantaneous, while release due to antibiotic-induced killing was delayed (mean transit time of 7.63 h). To conclude, the in vitro release of endotoxin is related to bacterial growth and antibiotic-induced killing, with higher rates of release upon the killing of formed filaments. Endotoxin release over 24 h is lowest when antibiotic exposure rapidly eradicates bacteria, while increased release is predicted to occur when growth and antibiotic-induced killing occur simultaneously.

Dynamics of Endotoxin, Inflammatory Variables, and Organ Dysfunction After Treatment With Antibiotics in an Escherichia coli Porcine Intensive Care Sepsis Model

OBJECTIVES

To investigate the dynamics of antibiotic-induced endotoxin liberation and inflammatory response in vivo in a clinically relevant large animal intensive care sepsis model and whether the addition of an aminoglycoside to a β-lactam antibiotic affects these responses.

DESIGN

Prospective, placebo-controlled interventional experimental study.

SETTING

University research unit.

SUBJECTS

Thirty-six healthy pigs administered Escherichia coli as a 3-hour infusion.

INTERVENTIONS

After 2 hours, during E. coli infusion, the animals were exposed to cefuroxime alone, the combination of cefuroxime and tobramycin, or saline.

MEASUREMENTS AND MAIN RESULTS

Plasma endotoxin, interleukin-6, tumor necrosis factor-α, leucocytes, and organ dysfunction were recorded for 4 hours after antibiotic treatment, and differences to the values before treatment were calculated. In vitro experiments were performed to ascertain whether endotoxin is released during antibiotic-induced bacterial killing of this E. coli strain. Despite differences between the treatment arms in vitro, no differences in plasma endotoxin were observed in vivo. Antibiotic-treated animals demonstrated a higher interleukin-6 response (p < 0.001), greater leucocyte activation (p < 0.001), and more pronounced deterioration in pulmonary static compliance (p < 0.01) over time than controls. Animals treated with the combination showed a trend toward less inflammation.

CONCLUSIONS

Treatment with antibiotics may elicit an increased inflammatory interleukin-6 response that is associated with leucocyte activation and pulmonary organ dysfunction. No observable differences were detected in plasma endotoxin concentrations. The reduction in cefuroxime-induced endotoxin release after the addition of an aminoglycoside in vitro could not be reproduced in this model.

Inflammatory, coagulatory and circulatory responses to logarithmic increases in the endotoxin dose in the anaesthetised pig

Although porcine intravenous endotoxin shock models are widely employed in experimental sepsis, endotoxin dose-effect studies are scarce. Our primary aim was to establish the dose response to increasing endotoxin doses in inflammatory, coagulatory and haemodynamic effect variables, as well as to determine the optimal time point for assessment in a pig model. A secondary aim was to study pathophysiological covariations between the different responses. Twenty anaesthetised piglets received endotoxin intravenously in doses of 0.063 ( n = 3), 0.25 ( n = 3), 1.0 ( n = 3), 4.0 ( n = 3), 8 ( n = 3) and 16 µg/kg/h ( n = 2). In addition, non-endotoxin piglets constituted a control group (n = 3). Physiological variables were registered and blood samples analysed for TNF-α, IL-6, leukocyte, platelet and haemoglobin concentrations hourly for 6 h. Increases in the endotoxin dose induced significant log—log cytokine responses as well as log—linear leukocyte and platelet responses. Significant log—linear responses were observed for circulatory parameters, plasma leakage, hypoperfusion and pulmonary compliance. Significant covariations in the responses were noted. In conclusion, there were log—log or log—linear responses to endotoxin suggesting a greater effect of a given dose at lower pre-existing endotoxin concentrations and lower doses of ≤ 1 µg/kg/h may be of advantage in experiments designed to study potential anti-endotoxin effects of experimental drugs or measures.

Early combination antibiotic therapy yields improved survival compared with monotherapy in septic shock: a propensity-matched analysis

BACKGROUND

Septic shock represents the major cause of infection-associated mortality in the intensive care unit. The possibility that combination antibiotic therapy of bacterial septic shock improves outcome is controversial. Current guidelines do not recommend combination therapy except for the express purpose of broadening coverage when resistant pathogens are a concern.

OBJECTIVE

To evaluate the therapeutic benefit of early combination therapy comprising at least two antibiotics of different mechanisms with in vitro activity for the isolated pathogen in patients with bacterial septic shock.

DESIGN

Retrospective, propensity matched, multicenter, cohort study.

SETTING

Intensive care units of 28 academic and community hospitals in three countries between 1996 and 2007.

SUBJECTS

A total of 4662 eligible cases of culture-positive, bacterial septic shock treated with combination or monotherapy from which 1223 propensity-matched pairs were generated.

MEASUREMENTS AND MAIN RESULTS

The primary outcome of study was 28-day mortality. Using a Cox proportional hazards model, combination therapy was associated with decreased 28-day mortality (444 of 1223 [36.3%] vs. 355 of 1223 [29.0%]; hazard ratio, 0.77; 95% confidence interval, 0.67-0.88; p = .0002). The beneficial impact of combination therapy applied to both Gram-positive and Gram-negative infections but was restricted to patients treated with beta-lactams in combination with aminoglycosides, fluoroquinolones, or macrolides/clindamycin. Combination therapy was also associated with significant reductions in intensive care unit (437 of 1223 [35.7%] vs. 352 of 1223 [28.8%]; odds ratio, 0.75; 95% confidence interval, 0.63-0.92; p = .0006) and hospital mortality (584 of 1223 [47.8%] vs. 457 of 1223 [37.4%]; odds ratio, 0.69; 95% confidence interval, 0.59-0.81; p < .0001). The use of combination therapy was associated with increased ventilator (median and [interquartile range], 10 [0-25] vs. 17 [0-26]; p = .008) and pressor/inotrope-free days (median and [interquartile range], 23 [0-28] vs. 25 [0-28]; p = .007) up to 30 days.

CONCLUSION

Early combination antibiotic therapy is associated with decreased mortality in septic shock. Prospective randomized trials are needed.

Propensity to release endotoxin after two repeated doses of cefuroxime in an in vitro kinetic model: higher release after the second dose

OBJECTIVES

To study endotoxin release from two strains of Escherichia coli after exposure to two repeated doses of cefuroxime in an in vitro kinetic model.

METHODS

Cefuroxime in concentrations simulating human pharmacokinetics was added to the bacterial solution with a repeated dose after 12 h. In another experiment, tobramycin was given concomitantly with the second dose of cefuroxime. Samples for viable counts and endotoxin analyses were drawn before the addition of antibiotics and at 2 and 4 h after each dose.

RESULTS

The propensity to release endotoxin, expressed as log10 endotoxin release (EU)/log10 killed bacteria, was higher after the second than after the first dose, 0.80+/-0.04 and 0.65+/-0.01, respectively, in the ATCC strain and 0.80+/-0.04 and 0.65+/-0.02, respectively, in the clinical strain (P<0.001). Endotoxin was released earlier after the second dose (P<0.001). Addition of tobramycin at the second dose reduced the endotoxin release in comparison with that of cefuroxime alone (P<0.001).

CONCLUSIONS

The propensity to liberate endotoxin is higher after the second dose of cefuroxime than after the first, resulting in a higher release of endotoxin than expected from bacterial count. The release after the second dose can be reduced by the addition of tobramycin.

Endotoxin neutralization and anti-inflammatory effects of tobramycin and ceftazidime in porcine endotoxin shock

Introduction

Antibiotics used for treatment of severe bacterial infections have been shown to exert effects on the inflammatory response in addition to their antibacterial effects. The aim of the present study was to investigate whether the biological effects of endotoxin in a porcine model could be neutralized by tobramycin, and whether tobramycin or ceftazidime was able to modulate the inflammatory response.

Method

Thirteen piglets were subjected to endotoxin infusion at an initial rate of 4 μg/kg per hour, which was reduced to 1 μg/kg per hour after 30 min. Before endotoxin infusion, the animals received saline (n = 4), ceftazidime (n = 5), or tobramycin (n = 4) at clinically relevant doses. Physiological parameters were measured and blood samples were taken hourly for 6 hours for analysis of tumour necrosis factor-α, IL-6 and endotoxin concentrations.

Results

All of the animals exhibited physiological signs of severe sepsis without major differences between the groups. Plasma endotoxin concentration was stable after 1 hour. There were no differences in endotoxin concentration or initial tumour necrosis factor-α and IL-6 concentrations between the groups. At 6 hours the IL-6 concentration was significantly lower in the ceftazidime group than in the saline group (P < 0.05), and in both the ceftazidime and the tobramycin groups there were significantly greater reductions from peak values (P < 0.05).

Conclusion

There was no neutralization of the biological effects of endotoxin in this porcine model. However, our data indicate a possible anti-inflammatory effect exerted by both ceftazidime and tobramycin, which manifested as a significantly greater reduction in IL-6 in comparison with the untreated group.