Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden
Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Appl Environ Microbiol. 2019 Jun 17;85(13). doi: 10.1128/AEM.00606-19. Print 2019 Jul 1.
, the causative agent of American foulbrood (AFB), is the primary bacterial pathogen affecting honeybees and beekeeping. The main methods for controlling AFB are incineration of diseased colonies or prophylactic antibiotic treatment (e.g., with tylosin), neither of which is fully satisfactory. The search for superior means for controlling AFB has led to an increased interest in the natural relationships between the honeybee-pathogenic and mutualistic microorganisms and, in particular, the antagonistic effects of honeybee-specific lactic acid bacteria (hbs-LAB) against These effects have been demonstrated only on individual larvae in controlled laboratory bioassays. Here we investigated whether supplemental administration of hbs-LAB had a similar beneficial effect on infection at colony level. We compared experimentally AFB-infected colonies treated with hbs-LAB supplements to untreated and tylosin-treated colonies and recorded AFB symptoms, bacterial spore levels, and two measures of colony health. To account for the complexity of a bee colony, we focused on (Bayesian) probabilities and magnitudes of effect sizes. Tylosin reduced AFB disease symptoms but also had a negative effect on colony strength. The tylosin treatment did not, however, affect spore levels and might therefore "mask" the potential for disease. hbs-LAB tended to reduce brood size in the short term but was unlikely to affect AFB symptoms or spores. These results do not contradict demonstrated antagonistic effects of hbs-LAB against at the individual bee level but rather suggest that supplementary administration of hbs-LAB may not be the most effective way to harness these beneficial effects at the colony level. The previously demonstrated antagonistic effects of honeybee-derived bacterial microbiota on the infectivity and pathogenicity of in laboratory bioassays have identified a possible new approach to AFB control. However, honeybee colonies are complex superorganisms where social immune defenses play a major role in resistance against disease at the colony level. Few studies have investigated the effect of beneficial microorganisms on bee diseases at the colony level. Effects observed at the individual bee level do not necessarily translate into similar effects at the colony level. This study partially fills this gap by showing that, unlike at the individual level, hbs-LAB supplements did not affect AFB symptoms at the colony level. The inference is that the mechanisms regulating the honeybee microbial dynamics within a colony are too strong to manipulate positively through supplemental feeding of live hbs-LAB and that new potential remedies identified through laboratory research have to be tested thoroughly , in colonies.
美洲幼虫腐臭病（AFB）的病原体是主要的细菌性病原，影响蜜蜂和养蜂业。控制 AFB 的主要方法是焚烧病群或预防性抗生素治疗（例如，使用泰乐菌素），但都不完全令人满意。寻找控制 AFB 的更好方法导致人们对蜜蜂 - 病原和共生微生物之间的自然关系产生了更大的兴趣，特别是对蜜蜂特异性乳酸菌（hbs-LAB）对 的拮抗作用产生了兴趣。这些作用仅在受控实验室生物测定中对单个幼虫进行了证明。在这里，我们研究了在群体水平上补充 hbs-LAB 是否对 感染具有类似的有益作用。我们比较了用 hbs-LAB 补充剂处理的 AFB 感染的蜂群与未处理和泰乐菌素处理的蜂群，并记录了 AFB 症状，细菌孢子水平和两个蜂群健康指标。为了说明蜜蜂群体的复杂性，我们重点关注（贝叶斯）概率和效应大小的幅度。泰乐菌素降低了 AFB 疾病症状，但也对蜂群强度产生了负面影响。但是，泰乐菌素处理并没有影响 孢子水平，因此可能“掩盖”了疾病的潜力。 hbs-LAB 在短期内可能会减少幼虫数量，但不太可能影响 AFB 症状或孢子。这些结果与在个体蜜蜂水平上证明的 hbs-LAB 对 的拮抗作用并不矛盾，而是表明在群体水平上补充 hbs-LAB 可能不是利用这些有益作用的最有效方法。先前在实验室生物测定中证明的蜜蜂源性细菌微生物群对 的感染力和致病性的拮抗作用已经确定了控制 AFB 的一种新方法。然而，蜜蜂群体是复杂的超级生物体，其中社会免疫防御在群体水平上抵抗疾病中起着重要作用。很少有研究调查有益微生物对蜜蜂疾病的影响在群体水平上。在个体蜜蜂水平上观察到的作用不一定转化为在群体水平上的类似作用。本研究通过表明，与个体水平不同，hbs-LAB 补充剂不会影响群体水平的 AFB 症状，部分填补了这一空白。这意味着调节蜂群内蜜蜂微生物动态的机制过于强大，无法通过补充喂养活的 hbs-LAB 进行积极操纵，并且通过实验室研究确定的新潜在疗法必须在蜂群中进行彻底测试。
