Phenotypic identification of the resistance mechanism of Burkholderia gladiolii and Burkholderia plantarii bacteria and in vitro sensitivity to bactericides for agricultural use

Abstract

The bacteria Burkholderia glumae, Burkholderia gladiolii and Burkholderia plantarii are important in rice cultivation, for causing spotting and grain blight. The objective of this research was to phenotypically identify resistance mechanisms of B. gladiolii, B. plantarii and in vitro sensitivity to bactericides for agricultural use. Bacterial isolates of B. gladiolii and B. plantarii were provided by the Plant Microbiology Laboratory of the National Agrarian University, Nicaragua. The identification of the mechanism of resistance and sensitivity to bactericides for agricultural use was carried out by the Bauer-Kirby method (agar diffusion), the size of the inhibition halos was measured, the size and shape of the inhibition halos produced were observed by the synergy between the antibiotic disks. Six isolates with derepressed AmpC resistance mechanism were identified, of these, four were from B. gladiolii and two from B. plantarii; One multiresistant isolate with the presence of AmpC and five that did not show resistance mechanisms were identified. The Burkholderia gladiolii bacterial isolates (D4 and M4) were sensitive to oxolinic acid compared to the isolates (V5, D2I, V2, T5 and D3) and the B. plantarii isolates (T5II).  The M4 isolate of B. gladiolii was susceptible to oxolinic acid plus gentamicin, while the isolates of Burkholderia gladiolii (D4, D2I and D3) and the isolate of Burkholderia plantarii (T5II) were not very susceptible, unlike the bacterial isolates of B. gladiolii (T5 and V2) that did not show sensitivity to said commercial product. The 1.5 kg ha^-1 commercial dose of oxolinic acid inhibited the highest number of isolates compared to the 1 kg ha^-1 dose. The biologic product based on Bacillus subtillis and the formulated product streptomycin sulfate plus oxytetracycline had no inhibitory effect on Burkholderia gladiolii and Burkholderia plantarii isolates.