Characterization and Identification of Pantoea calida from Contaminated Soil and Its Biocontrol by Streptomyces coeruleorubidus

The genus Pantoea is Gram-negative bacteria, distributed in contaminated soil but the increased numbers of Pantoea species were isolated from human bodies, indicating that these species are opportunistic pathogen and cause nosocomial infections. This research aimed to isolate, characterize, and biocontrol of Pantoea species, isolated and collected from soil. During searching for phosphate-degrading bacteria, isolate MO11 was obtained from soil samples and grow well on a medium containing tricalcium phosphate. It was identified according to morphology, physiology, and molecular methods. The antimicrobial susceptibility patterns to antibiotics were determined and the antibiotic resistance pattern reflects its clinical importance. It showed high resistance to Amoxicillin, Amikacin, and Gentamicin while it was sensitive to Imepinem and Meropenem. The isolate was identified as Pantoea calida with 97% and as P. agglomerans with 95% similarity level. Therefore, it is the first time to isolate this bacterium from the soil in Saudi Arabia. Streptomyces coeruleorubidus MM5 was previously isolated from contaminated soil and it was identified using molecular methods. It showed good inhibitory activity against Pantoea calida using the cross streak method, Agar plug diffusion method, and Agar well diffusion methods. Further, the active agent was extracted by ethyl acetate solvent from the extracellular filtrate and it showed excellent antibacterial activity against Pantoea cells which showed resistance to the routinely used antibiotics. In conclusion, although multidrug-resistant Pantoea cells pose a serious threat worldwide and the appropriate antibiotic must be prescribed after determining the sensitivity test, Streptomyces species have played a critical role as biocontrol agents.