Short communication: Natural molecules for the control of Paenibacillus larvae, causal agent of American foulbrood in honey bees (Apis mellifera L.)

Pablo Giménez-Martínez,Noelia Cugnata,Daniela Arredondo,Karina Antunez,Sandra R Fuselli,Rosana De Castro,Rosa M Alonso-Salces

doi:10.5424/sjar/2019173-14740

Abstract

Aim of study: To evaluate the potential bactericidal activity of natural molecules against Paenibacillus larvae. Moreover, we investigated if molecules that exhibit antimicrobial activity were able to inhibit the proteolytic activity of the bacterium.Area of study: Isolates S1 and S2 were from Balcarce, Buenos Aires province, strain S3 from Rio Cuarto, Cordoba province, strain S4 from Concordia, Entre Rios province, strain S5 and S8 from Necochea, Buenos Aires, strain S6 and S7 from Mar del Plata, Buenos Aires, strain S9 from Modena, Italy and strain S10 from Emilia Reggio, Italy.Material and methods: Bacterial isolates identification was carried out by amplification of a specific 16S rRNA gene fragment of P. larvae using primers PL5 and PL4. Screening of the antimicrobial activity of thirteen molecules against four P. larvae isolates was conducted by the agar diffusion technique. The antimicrobial activity of selected molecules was evaluated by broth microdilution method.Main results: Menadione, lauric acid, monoglyceride of lauric acid and naringenin showed antimicrobial activity against ten P. larvae isolates. Menadione and lauric acid showed the strongest activities, with minimum inhibitory concentration mean values ranging 0.78-3.125 µg/mLand 25-50 µg/mL, respectively.Research highlights: Those concentrations are feasible to be applied at field level, and constitute promissory candidates to be evaluated using in vivo larval models.

Highlights

American foulbrood (AFB) is the most severe bacterial disease that affects honey bees, having a nearly cosmopolitan distribution (Genersch, 2010).AFB only kills infected honey bee larvae; it eventually leads to the collapse of the entire colony when left untreated
Screening of the antimicrobial activity of thirteen molecules against four P. larvae isolates was conducted by the agar diffusion technique
We evaluated the antimicrobial activity of different molecules against P. larvae

Summary

Introduction

American foulbrood (AFB) is the most severe bacterial disease that affects honey bees, having a nearly cosmopolitan distribution (Genersch, 2010). AFB only kills infected honey bee larvae; it eventually leads to the collapse of the entire colony when left untreated. AFB is considered to be very contagious; it is a notifiable disease in most countries (Djukic et al, 2014). Alonso-Salces, Daniela Arredondo, Karina Antúnez, et al. Is Paenibacillus larvae, a flagellated gram-positive bacterium, whose main characteristic is the formation of highly resistant endospores. Four P. larvae genotypes (Enterobacterial Repetitive Intergenic Consensus, ERIC I-IV) have been described, but only two are commonly detected under field conditions (ERIC I and II) (Genersch & Otten, 2003; Alippi et al, 2004)

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