Entwistle Frances M, Coote Peter J
Biomedical Sciences Research Complex, School of Biology, The North Haugh, University of St Andrews, Fife, KY16 9ST, UK.
J Med Microbiol. 2018 Apr;67(4):585-597. doi: 10.1099/jmm.0.000696. Epub 2018 Feb 13.
To evaluate the suitability of Galleria mellonella larvae as an in vivo model and drug-screening tool for mycobacteria infections.
Larvae were infected using a range of inoculum sizes from a variety of rapid-growing mycobacteria, including strains of M. fortuitum, M. marinum and M. aurum. Larval survival, internal bacterial burden and the effects of amikacin, ciprofloxacin, ethambutol, isoniazid and rifampicin treatment on larval survival were measured over 144 h. The effects of these anti-mycobacterial drugs on phagocytosis and circulating haemocyte numbers were also examined using microscopy.
Larval survival decreased after infection with M. fortuitum and M. marinum in a dose-dependent manner, but remained unaffected by M. aurum. Heat-killed bacteria did not cause larval death. Where antibiotic monotherapy was efficacious, larval survival post-infection increased in a dose-dependent fashion. However, efficacy varied between different antibiotics and species of infecting mycobacteria and, apart from rifampicin, efficacy in vivo correlated poorly with the in vitro minimum inhibitory concentrations (MICs). Combinations of antibiotics led to higher survival of infected larvae than antibiotic monotherapy. Selected antibiotic treatments that enhanced larval survival reduced the overall internal burden of infecting mycobacteria, but did not eradicate the pathogens. Administration of amikacin or ethambutol to uninfected larvae induced an initial transient increase in the numbers of circulating haemocytes and reduced the phagocytic rate of haemocytes in larvae infected with M. marinum.
This report demonstrates the potential of employing a wax moth larvae model for studying fast-growing mycobacteria infections, and as a cheap, effective system for initial screening of novel treatments.
评估大蜡螟幼虫作为分枝杆菌感染的体内模型和药物筛选工具的适用性。
使用一系列接种量，从多种快速生长的分枝杆菌感染幼虫，包括偶然分枝杆菌、海分枝杆菌和金色分枝杆菌菌株。在144小时内测量幼虫存活率、体内细菌载量以及阿米卡星、环丙沙星、乙胺丁醇、异烟肼和利福平治疗对幼虫存活率的影响。还使用显微镜检查了这些抗分枝杆菌药物对吞噬作用和循环血细胞数量的影响。
感染偶然分枝杆菌和海分枝杆菌后，幼虫存活率呈剂量依赖性下降，但不受金色分枝杆菌影响。热灭活细菌未导致幼虫死亡。在抗生素单药治疗有效的情况下，感染后幼虫存活率呈剂量依赖性增加。然而，不同抗生素和感染分枝杆菌的种类之间疗效有所不同，除利福平外，体内疗效与体外最低抑菌浓度（MIC）的相关性较差。抗生素联合治疗导致感染幼虫的存活率高于抗生素单药治疗。选定的提高幼虫存活率的抗生素治疗降低了感染分枝杆菌的总体体内载量，但未根除病原体。给未感染的幼虫施用阿米卡星或乙胺丁醇会导致循环血细胞数量最初短暂增加，并降低感染海分枝杆菌的幼虫中血细胞的吞噬率。
本报告证明了使用蜡蛾幼虫模型研究快速生长的分枝杆菌感染的潜力，以及作为一种廉价、有效的新型治疗初步筛选系统的潜力。
