Paromomycin Reduces Vairimorpha (Nosema) ceranae Infection in Honey Bees but Perturbs Microbiome Levels and Midgut Cell Function

Abstract

Paromomycin is a naturally occurring aminoglycoside antibiotic that has effects on both prokaryotic and eukaryotic microbes. However, previous reports have indicated that it has little effect on microsporidia, including Vairimorpha (Nosema) ceranae, in cell culture models. V. ceranae is one of a number of microsporidia species that cause disease in honey bees and substantial efforts to find new treatment strategies for bees that are infected with these pathogens are ongoing. When testing compounds for potential activity against V. ceranae in whole organisms, we found that paromomycin reduces the infection intensity of this parasite. Critically, the necessary doses of paromomycin have high activity against the bacteria of the honey bee microbiome and cause evident stress in bees. Microsporidia have been shown to lack an essential binding site on the ribosome that is known to allow for maximal inhibition by paromomycin. Thus, it is possible that paromomycin impacts parasite levels through non-cell autonomous effects on microsporidia infection levels via effects on the microbiome or midgut cellular function. As paromomycin treatment could cause widespread honey bee health issues in agricultural settings, it does not represent an appropriate anti-microsporidia agent for use in the field.

Bleomycin reduces Vairimorpha (Nosema) ceranae infection in honey bees with some evident host toxicity

“…On day 6 post-infection, bees were treated with bleomycin at the indicated doses. Honey bee midguts were dissected at 4 days of drug feeding, and infection levels were assessed by spore counting and qPCR ( 13 ). We observed reductions in infection levels as assessed by spore counting and relative genome equivalents after bleomycin treatment at doses as low as 0.306 µg/mL ( Fig.…”

“…Thus, we looked at a number of transcriptional targets known to be upregulated by tissue damage in bees. First, we examined the expression of select shsp genes of the l(2)efl family, which have been identified as useful stress biomarker genes in honey bees ( 13 , 21 , 24 – 26 ). Using qPCR, we found that expression of 724367 and 410087 a was increased in the midguts of uninfected bees treated with bleomycin (at 25 µg/mL) relative to control bees after 2 days of feeding (Fig.…”

“…V. ceranae spores were obtained from infected individuals and serially passaged through bees as performed previously [see references ( 7 , 13 )] to provide spores for infection experiments. To isolate spores, midguts from infected or uninfected bees were individually crushed in 0.5 mL of H 2 O with a pestle, and the spore number was assessed by light microscopy.…”

“…DNA extraction was performed using a modified Smash and Grab DNA Miniprep protocol as described previously ( 13 ). The resulting DNA was used as a template for qPCR to determine the level of infection for Vairimorpha sp.…”

Chemical Identification of Secondary Metabolites from Rhizospheric Actinomycetes Using LC-MS Analysis: In Silico Antifungal Evaluation and Growth-Promoting Effects

“…Paromomycin is a naturally occurring aminoglycoside antibiotic, produced by Streptomyces rimosus sp. paromomycinus, that affects both prokaryotic and eukaryotic through the chelation with A-site of ribosome [18,19]. Valyldetoxinine and paromomycin hadn't ever been previously reported in A. humicola.…”