Assessment of antibiotic resistance in Erwinia rhapontici, the causal agent of pink grain of cereals
Keywords:
bacterioses of grain crops, isolation of bacteria, selective media, phytosanitary requirements, plant quarantine, diagnosisAbstract
The opportunistic bacterium Erwinia rhapontici causes pink bacteriosis of wheat and rye grain, significantly reducing the quality of grain products and limiting grain export. Isolation of pure bacterial culture is necessary for effective diagnostics, required for disease prevention. Presence of E. rhapontici in infected plants as a part of bacterial complex, requires selective factors, such as antibiotics. Resistance of E. rhapontici strains VNIIKR-B-0065 from Sorbus aucuparia and VNIIKR-B-0102 from Triticum durum to various antibiotics was determined. When using disks with antibiotics, the lowest inhibition level of the bacterial growth was noted in the cases of tylosin and ampicillin, which makes them promising for the selective medium. Enrofloxacin, ceftazidime, amikacin, ciprofloxacin, meropenem, cefoperazone and tetracycline statistically significantly inhibited the growth of E. rhapontici. Meropenem and enrofloxacin suppressed the growth of the pathogen the most. In liquid medium with 2,3,5-triphenyltetrazolium chloride (standard indicator of the oxidation-reduction reaction), antibiotics promising for use in the selective nutrient medium were determined and their optimal concentrations that do not affect the growth of the target bacteria were established. These are ampicillin 0.1 mg/L, bacitracin 100 mg/L, vancomycin 0.1 mg/L, kasugamycin 25 mg/L, novobiocin 2.5 mg/L, penicillin G 3 mg/L, tetracycline 50 mg/L, and tylosin 50 mg/L. A quantitative difference in antibiotic resistance was noted between the two strains of E. rhapontici, which may be due to their specific genetic properties. The results obtained laid the foundation for the study of a large number of E. rhapontici isolates to develop the final composition of the selective medium.
