Occurrence of bla(NDM-1)-Positive Providencia spp. in a Pig Farm of China

Antibiotics have been extensively used to ensure the productivity of animals on intensive livestock farms. Accordingly, antimicrobial-resistant organisms, which can be transmitted to humans via the food chain, pose a threat to public health. The Enterobacterium antimicrobial resistance gene, bla(NDM-1), is a transmissible gene that has attracted widespread attention. Here, we aimed to investigate the prevalence of Enterobacteriaceae carrying bla(NDM-1) on an intensive pig farm. A total of 190 samples were collected from a pig farm in Hunan Province, China. Resistant isolates were selected using MacConkey agar with meropenem and PCR to screen for bla(NDM-1)-positive isolates. Positive strains were tested for conjugation, antimicrobial susceptibility, and whole-genome sequencing. Four bla(NDM-1)-positive Providencia strains were obtained, and multidrug resistance was observed in these strains. The structure carrying bla(NDM-1) did not conjugate to E. coli J53 after three repeated conjugation assays. This suggests that, in intensive farming, attention should be focused on animal health and welfare to reduce the frequency of antibiotic usage. Carbapenem-resistant Enterobacteriaceae in the breeding industry should be included in systematic monitoring programs, including animal, human, and environmental monitoring programs.