American Foulbrood in the Czech Republic: ERIC II Genotype of Paenibacillus Larvae Is Prevalent.

Jana Biová,Marek Petřivalský,Jan Brus,Jaroslav Bzdil,Elena Carra,Silvie Dostálková,Jiří Danihlík

doi:10.3389/fvets.2021.698976

Abstract

American foulbrood (AFB) is a dangerous disease of honeybees (Apis mellifera) caused by the spore-forming bacterium Paenibacillus larvae. According to the ERIC (enterobacterial repetitive intergenic consensus) classification, five genotypes are distinguished, i.e., I, II, III, IV, and V, which differ in their virulence and prevalence in colonies. In the Czech Republic, AFB prevalence is monitored by the State Veterinary Administration; however, the occurrence of specific P. larvae genotypes within the country remains unknown. In this study, our aim was to genotype field P. larvae strains collected in the Czech Republic according to the ERIC classification. In total, 102 field isolates from colonies with AFB clinical symptoms were collected from various locations in the Czech Republic, and the PCR genotypization was performed using ERIC primers. We confirmed the presence of both ERIC I and II genotypes, while ERIC III, IV, and V were not detected. The majority of samples (n = 82, 80.4%) were identified as ERIC II, while the ERIC I genotype was confirmed only in 20 samples (19.6%). In contrast to other European countries, the ERIC II genotype is predominant in Czech honeybee colonies. The ERIC I genotype was mostly detected in border regions close to Poland, Slovakia, and Austria.

Highlights

American foulbrood (AFB) is defined as a dangerous contagious bacterial disease of honeybee (Apis mellifera) brood [1, 2]
Field isolates were collected from different regions of the Czech Republic and covered almost all regions with active outbreaks of AFB
Detailed information about the occurrence of P. larvae strains in Czech Republic has been missing; we aimed to perform the genotypization of P. larvae strains with the enterobacterial repetitive intergenic consensus (ERIC) primers generally used for P. larvae classification [8]

Summary

Introduction

American foulbrood (AFB) is defined as a dangerous contagious bacterial disease of honeybee (Apis mellifera) brood [1, 2]. AFB is caused by the spore-forming bacterium Paenibacillus larvae [1, 3]. The disease affects the bee larvae during the early developmental stages, whereas adult bees only transmit the infectious spores of P. larvae. When bee larvae consume food sources contaminated by P. larvae endospores, these spores germinate in the larval intestine. The youngest larvae (12–36 h after egg hatching) represent the most sensitive stage to the spores [1] when even a very low dose of spores (median lethal dose, LD50 ∼9 bacteria per larvae) is lethal in “in vitro” conditions [6]. The dead larvae degrade into typical brown, sticky, and partly fluid “jelly,” which is the primary clinical symptom for AFB diagnosis [4]

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