1Plant Protection Department, Faculty of Agriculture, Suez Canal University, Ismailia, Egypt
2Microbiology Department, Faculty Agriculture, Fayoum University, Fayoum, 63514, Egypt
Zoology Department, Faculty of Science, Fayoum University, Fayoum-63514, Egypt
*Corresponding author's E-mail: aaa11@fayoum.edu.eg
Results revealed that only two bacterial strains amongst five isolates were pathogenic, identified as Bacillus megaterium and Bacillus circulans. the lc50 of Bacillus megaterium were 9.9 × 105 and 2.9 × 106 while the lc50 of Bacillus circulans were 8.65 × 106 and 2.2 × 107 cfu/ml for forth and fifth larval instars of silkworm, respectively. Further, fourth larval instar was more sensitive than the fifth depending on the values of relative sensitivity between the two tested instars. Antimicrobial activity of antibiotics by disc diffusion method showed that all isolates were very sensitive against three antibiotics, (noroxin, tarivi d and Flumox).
Antibiotic, bacteria, pathogenicity, silkworm
