Paenibacillus larvae is the etiological agent of American Foulbrood (AFB), a highly contagious brood disease of honey bees (Apis mellifera). AFB requires mandatory reporting to the veterinary authority in many countries and until now four genotypes, P. larvae ERIC I-IV, have been identified. We isolated a new genotype, ERIC V, from a Spanish honey sample. After a detailed phenotypic comparison with the reference strains of the ERIC I-IV genotypes, including spore morphology, non-ribosomal peptide (NRP) profiling, and in vivo infections of A. mellifera larvae, we established a genomic DNA Macrorestriction Fragment Pattern Analysis (MRFPA) scheme for future epidemiologic discrimination. Whole genome comparison of the reference strains and the new ERIC V genotype (DSM 106052) revealed that the respective virulence gene inventories of the five genotypes corresponded with the time needed to kill 100 % of the infected bee larvae (LT₁₀₀) in in vivo infection assays. The rarely isolated P. larvae genotypes ERIC II I-V with a fast-killing phenotype (LT₁₀₀ 3 days) harbor genes with high homology to virulence factors of other insect pathogens. These virulence genes are absent in the epidemiologically prevalent genotypes ERIC I (LT₁₀₀ 12 days) and ERIC II (LT₁₀₀ 7 days), which exhibit slower killing phenotypes. Since killing-retardation is known to reduce the success of hygienic cleaning by nurse bees, the identified absence of virulence factors might explain the epidemiological prevalences of ERIC genotypes. The discovery of the P. larvae ERIC V isolate suggests that more unknown ERIC genotypes exist in bee colonies. Since inactivation or loss of a few genes can transform a fast-killing phenotype into a more dangerous slow-killing phenotype, these rarely isolated genotypes may represent a hidden reservoir for future AFB outbreaks.

Paenibacillus幼虫是美国Foulbrood（AFB）的病原体，AFB是蜜蜂（Apis mellifera）的一种高度传染性高的繁殖疾病。AFB要求在许多国家/地区向兽医部门进行强制报告，到目前为止，已经鉴定出四种基因型，即幼虫ERIC I-IV。我们从西班牙蜂蜜样本中分离出一种新基因型ERICV。与ERIC I-IV基因型的参考菌株进行了详细的表型比较后，包括孢子形态，非核糖体肽（NRP）谱图和A. mellifera的体内感染幼虫，我们建立了基因组DNA宏限制性片段模式分析（MRFPA）方案，用于将来的流行病学鉴别。参照株和新的ERIC V基因型可（DSM 106052）的全基因组比较，可知：5种基因型的相应的毒力基因库存与杀死被感染的幼蜂的100％所需要的时间对应（LT ₁₀₀中）在体内感染分析。具有快速杀灭表型（LT ₁₀₀ 3天）的极少分离到的幼虫疟原虫基因型ERIC II IV具有与其他昆虫病原体的毒力因子高度同源的基因。这些毒力基因在流行病学上普遍存在的基因型ERIC I（LT ₁₀₀ 12天）和ERIC II（LT₁₀₀ 7天），表现出较慢的杀伤表型。由于已知杀害延迟会降低护士蜂进行卫生清洁的成功率，因此确定的无毒力因子可能可以解释ERIC基因型的流行病学流行程度。幼虫ERIC V分离株的发现表明蜂群中存在更多未知的ERIC基因型。由于一些基因的失活或丢失可以将快速杀死的表型转变为更危险的缓慢杀死的表型，因此这些很少分离的基因型可能代表了未来AFB爆发的隐性库。