Identification and characterization of a novel metallo beta-lactamase, SZM-1, in Shenzhen Bay, South China

Metallo beta-Lactamases (MBLs) degrade most clinical beta-lactam antibiotics, especially Carbapenem, posing a huge threat to global health. Studies on environmental MBLs are important for risk assessment of the MBLs transmission among connected habitats, and between environment and human. Here, we described a novel metallo beta-Lactamases, named SZM-1 (Shenzhen metallo-beta-lactamase), from an Arenimonas metagenome-assembled genome recovered from the river sediment in the Shenzhen Bay area, south China. Phylogenetic analysis, primary sequence comparison, structural modeling suggested that the SZM-1 belongs to B1 MBL family, likely harboring a typical di-zinc catalytic center. Furthermore, the gene encoding the MBLs was cloned into Escherichia coli TOP10 for Carba NP test and antimicrobial susceptibility test. The results indicated that the SZM-1 had carbapenemase activity, and conferred the carrier to increased resistance toward carbapenems. Taken together, our results raise alarms about the emergence and spread of the SZM-1, and suggest further surveillance, especially in hospital settings and clinical isolates, to determine whether bla(SZM-1) is a mobilizable antibiotic resistance.