Klebsiella pneumoniae is an important opportunistic pathogen in humans and animals. Recently, K. pneumoniae KpC4 was identified as a causative agent of bacterial top rot in maize, which has been observed in many areas of Yunnan province, China. KpC4 is potentially dangerous to humans and livestock due to its cross-kingdom infection ability. Our study revealed the disease cycle of maize bacterial top rot caused by KpC4 and the ecological adaptability and host range of KpC4. We found same pathogenicity in maize between KpC4, the environmental strains E1, E4 (K1 serotype), E5, and the clinical strain K. pneumoniae 138 (Kp138). Alternative hosts of K. pneumoniae include not only humans and animals but also a variety of plants (such as maize, banana and sorghum). One of the survival strategies of K. pneumoniae is ecological adaptability, which is an essential factor for KpC4 to be able to cause bacterial top rot in maize. K. pneumoniae, for example, could survive in large numbers (2.34 ± 0.22 × 103 cfu/g) not only in the maize leaves (2.34 ± 0.22 × 103 cfu/g) under natural light, but persist in dried maize plant debris (1.51 × 104 cfu/g) for at least 6 months. K. pneumoniae strains from different sources can generally induce infection in susceptible hosts. Thus, this study revealed the ecological basis of KpC4 cross-kingdom infections, laying the foundation for the study of the mechanisms underlying cross-kingdom infections involving this type of human/animal opportunistic pathogen.
Keywords: Etiology; Klebsiella pneumoniae; KpC4; Maize bacterial top rot; Yunnan.
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