Common Variables That Influence Sepsis Mortality in Mice

Abstract

Sepsis is characterized by a dysregulated host immune response to infection, leading to organ dysfunction and a high risk of death. The cecal ligation and puncture (CLP) mouse model is commonly used to study sepsis, but animal mortality rates vary between different studies. Technical factors and animal characteristics may affect this model in unanticipated ways, and if unaccounted for, may lead to serious biases in study findings. We sought to evaluate whether mouse sex, age, weight, surgeon, season of experiments, and timing of antibiotic administration influenced mortality in the CLP model. Methods: We created a comprehensive dataset of C57BL/6J mice that had undergone CLP surgery within our lab during years 2015-2020 from published and unpublished studies. The primary outcome was defined as the time from sepsis induction to death or termination of study (14 days). The Log rank test and Cox regression models were used to analyze the dataset. The study included 119 mice, of which 43% were female, with an average age of 12.6 weeks, an average weight of 25.3 g. 38 (32%) of the animals died. Results: In the unadjusted analyses, experiments performed in the summer and higher weight predicted a higher risk of mortality. In the stratified Cox model by sex, summer season (adjusted hazard ratio [aHR]=5.61, p=0.004) and delayed antibiotic administration (aHR=1.46, p=0.029) were associated with mortality in males, whereas higher weight (aHR=1.52, p=0.005) significantly affected mortality in females. In addition, delayed antibiotic administration (HR=1.42, p=0.025) was associated with mortality in the nonsummer seasons, but not in the summer season. Discussion: In conclusion, some factors specific to sex and season have a significant influence on sepsis mortality in the CLP model. Consideration of these factors along with appropriate group matching or adjusted analysis is critical to minimize variability beyond the experimental conditions within a study.

Preclinical Mouse Models in Sepsis: Don’t Throw the Baby Out with the Bathwater [Response to Letter]

“…Although we agree that the CLP model may yield variable results according to these factors, the same can be said for many animal models, as well as clinical conditions among different study populations. Our study 1 essentially highlights biological and technical variables that influence sepsis mortality and does not construe a criticism of the CLP model, and this was not implied in our manuscript. Instead, our report 1 was intended to reveal some essential characteristics of animals and the laboratory environment that should be considered in the experimental design for sepsis studies.…”

“…Our study 1 essentially highlights biological and technical variables that influence sepsis mortality and does not construe a criticism of the CLP model, and this was not implied in our manuscript. Instead, our report 1 was intended to reveal some essential characteristics of animals and the laboratory environment that should be considered in the experimental design for sepsis studies. Our report 1 found that sepsis mortality rates were influenced by the timing of antibiotic administration, animal weight and the season (summer vs non-summer seasons), and this occurred differently in males vs females.…”

“…Instead, our report 1 was intended to reveal some essential characteristics of animals and the laboratory environment that should be considered in the experimental design for sepsis studies. Our report 1 found that sepsis mortality rates were influenced by the timing of antibiotic administration, animal weight and the season (summer vs non-summer seasons), and this occurred differently in males vs females. These effects are not unique to the CLP model.…”

Preclinical Model in Sepsis: Should We Abandon the CLP? [Letter]

“…We read with interest the study by Garcia et al, “Common Variables That Influence Sepsis Mortality in Mice”. 1 Based on their own experience, authors identified some factors specific to sex and season that significantly influence sepsis mortality in the CLP model, therefore questioning the status of this model as the gold standard in preclinical research on sepsis.…”

Sepsis sensitizes behavioural amphetamine responses while inducing inflammatory and neurotrophic vulnerability in the cecal ligation and puncture model

“…The sham-operated group received only 50-ml/kg saline immediately, and 12 h after surgery, and the volume of saline corresponded to antibiotic administration (Hubbard et al, 2005). The mortality rate of CLPinduced rats was around 30%, according to the literature (Garcia et al, 2023).…”