Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
Departamento de Ciências Biológicas, Universidade do Estado de Minas Gerais, Carangola, MG, Brazil.
Microb Pathog. 2023 Oct;183:106304. doi: 10.1016/j.micpath.2023.106304. Epub 2023 Aug 9.
Invertebrates can provide a valuable alternative to traditional vertebrate animal models for studying bacterial and fungal infections. This study aimed to establish the larvae of the coleoptera Tenebrio molitor (mealworm) as an in vivo model for evaluating virulence and horizontal gene transfer between Staphylococcus spp. After identifying the best conditions for rearing T. molitor, larvae were infected with different Staphylococcus species, resulting in dose-dependent killing curves. All species tested killed the insects at higher doses, with S. nepalensis and S. aureus being the most and least virulent, respectively. However, only S. nepalensis was able to kill more than 50% of larvae 72 h post-infection at a low amount of 10 CFU. Staphylococcus infection also stimulated an increase in the concentration of hemocytes present in the hemolymph, which was proportional to the virulence. To investigate T. molitor's suitability as an in vivo model for plasmid transfer studies, we used S. aureus strains as donor and recipient of a plasmid containing the gentamicin resistance gene aac(6')-aph(2″). By inoculating larvae with non-lethal doses of each, we observed conjugation, and obtained transconjugant colonies with a frequency of 1.6 × 10 per donor cell. This study demonstrates the potential of T. molitor larvae as a reliable and cost-effective model for analyzing the virulence of Staphylococcus and, for the first time, an optimal environment for the plasmid transfer between S. aureus carrying antimicrobial resistance genes.
无脊椎动物可以为研究细菌和真菌感染提供一种有价值的替代传统脊椎动物动物模型。本研究旨在建立鞘翅目幼虫（黄粉虫）作为评估葡萄球菌属之间毒力和水平基因转移的体内模型。在确定了最佳的黄粉虫饲养条件后，幼虫被不同的葡萄球菌物种感染，导致剂量依赖性的杀伤曲线。所有测试的物种在更高的剂量下杀死昆虫，其中尼泊尔葡萄球菌和金黄色葡萄球菌的毒力最强和最弱。然而，只有尼泊尔葡萄球菌能够在低剂量 10 CFU 时在 72 小时后杀死超过 50%的幼虫。葡萄球菌感染还刺激了存在于血淋巴中的血球细胞浓度的增加，这与毒力成正比。为了研究黄粉虫幼虫作为体内模型进行质粒转移研究的适宜性，我们使用金黄色葡萄球菌菌株作为携带庆大霉素抗性基因 aac(6')-aph(2″)的质粒的供体和受体。通过接种幼虫非致死剂量的供体和受体，我们观察到了接合，并以每供体细胞 1.6×10 的频率获得了转导子菌落。本研究表明，黄粉虫幼虫作为分析葡萄球菌毒力的可靠且具有成本效益的模型具有潜力，并且首次为携带抗菌药物抗性基因的金黄色葡萄球菌之间的质粒转移提供了最佳环境。
