Longitudinal temperature measurement can determine humane endpoints in BALB/c mouse models of ESKAPEE infection

Antimicrobial resistance (AMR) is a worldwide problem, which is driving more preclinical research to find new treatments and countermeasures for drug-resistant bacteria. However, translational models in the preclinical space have remained static for years. To improve animal use ethical considerations, we assessed novel methods to evaluate survival after lethal infection with ESKAPEE pathogens (<i>Enterococcus faecium, Staphylococcus aureus</i>, <i>Klebsiella pneumoniae</i>, <i>Acinetobacter baumannii</i>, <i>Pseudomonas aeruginosa</i>, <i>Enterobacter cloacae</i>, and <i>Escherichia coli</i>) in pulmonary models of infection. Consistent with published lung infection models often used for novel antimicrobial development, BALB/c mice were immunosuppressed with cyclophosphamide and inoculated intranasally with individual ESKAPEE pathogens or sterile saline. Observations were recorded at frequent intervals to determine predictive thresholds for humane endpoint decision-making. Internal temperature was measured via implanted IPTT300 microchips, and external temperature was measured using a non-contact, infrared thermometer. Additionally, clinical scores were evaluated based on animal appearance, behaviour, hydration status, respiration, and body weight. Internal temperature differences between survivors and non-survivors were statistically significant for <i>E. faecium, S. aureus</i>, <i>K. pneumoniae</i>, <i>A. baumannii</i>, <i>E. cloacae</i>, and <i>E. coli</i>, and external temperature differences were statistically significant for <i>S. aureus</i>, <i>K. pneumoniae</i>, <i>E. cloacae</i>, and <i>E. coli</i>. Internal temperature more precisely predicted mortality compared to external temperature, indicating that a threshold of 85ºF (29.4ºC) was 86.0% predictive of mortality and 98.7% predictive of survival. Based on our findings, we recommend future studies involving BALB/c mice ESKAPEE pathogen infection use temperature monitoring as a humane endpoint threshold.

抗菌药物耐药性（Antimicrobial Resistance, AMR）是全球性公共卫生难题，正推动大量临床前研究以发掘针对耐药菌的新型治疗方案与应对策略。然而临床前研究领域的转化模型多年来始终停滞不前。为优化实验动物使用的伦理规范，本研究针对肺部感染模型中ESKAPEE致病菌群（屎肠球菌Enterococcus faecium、金黄色葡萄球菌Staphylococcus aureus、肺炎克雷伯菌Klebsiella pneumoniae、鲍曼不动杆菌Acinetobacter baumannii、铜绿假单胞菌Pseudomonas aeruginosa、阴沟肠杆菌Enterobacter cloacae及大肠埃希菌Escherichia coli）的致死感染后存活情况，探索了新型评估方法。与常用于新型抗菌药物研发的已发表肺部感染模型一致，本研究采用环磷酰胺对BALB/c小鼠进行免疫抑制，随后经鼻接种单一ESKAPEE致病菌或无菌生理盐水。研究人员通过高频次记录观测数据，以确定人道终点决策的预测阈值。核心体温通过植入式IPTT300微芯片进行测量，体表体温则采用非接触式红外体温计检测。此外，临床评分基于动物外观、行为、机体水合状态、呼吸状态及体重进行评估。粪肠球菌、金黄色葡萄球菌、肺炎克雷伯菌、鲍曼不动杆菌、阴沟肠杆菌及大肠埃希菌感染组中，存活小鼠与非存活小鼠的核心体温差异均具有统计学显著性；而金黄色葡萄球菌、肺炎克雷伯菌、阴沟肠杆菌与大肠埃希菌感染组中，两组小鼠的体表体温差异亦具有统计学显著性。相较于体表体温，核心体温可更精准地预测小鼠死亡率：当核心体温阈值设定为85华氏度（29.4摄氏度）时，其预测死亡率的准确率达86.0%，预测存活率的准确率达98.7%。基于本研究结果，我们建议后续开展涉及BALB/c小鼠ESKAPEE致病菌肺部感染模型的研究时，可将体温监测作为人道终点阈值指标。