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Characterization of NDM-1-Producing Carbapenemase in Proteus mirabilis among Broilers in China
Xiaolin Zhu1,2, Yaru Zhang1,3, Zhangqi Shen1
1College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
Abstract:
Carbapenem-resistant pathogens mediated by metallo-beta-lactamases (MBLs) have spread worldwide, where NDM-1 is a typical and key MBL. Here, we firstly discussed the distribution characterization of NDM-1, which produces multidrug-resistant Proteus mirabilis among broilers in China. From January to April 2019, 40 (18.1%, 40/221) blaNDM-1-carrying P. mirabilis strains were recovered from commercial broilers in slaughterhouse B in China. All the isolates were resistant to imipenem, meropenem and other β-lactams. These isolates belong to five clusters identified via pulsed field gel electrophoresis (PFGE). Further studies on twenty representative strains revealed that seven blaNDM-1 genes were located on plasmids with sizes of 104.5-138.9 kb. Notably, only three strains (PB72, PB96 and PB109) were successfully transferred to Escherichia coli J53, while the other four isolates were located in nontransferable plasmids. The rest were harbored in chromosomes. Ulteriorly, based on whole genome sequencing (WGS), these twenty isolates showed four typical phylogenetic clades according to single nucleotide polymorphisms (SNPs) of a core genome and presented four main genomic backbone profiles, in which type II/III strains shared a similar genetic context. All of the above is evidence of blaNDM-1 transmission and evolution in P. mirabilis, suggesting that the prevalence may be more diverse in broiler farms. Accordingly, as intestinal and environmental symbiotic pathogens, blaNDM-1-positive P. mirabilis will pose greater threats to the environment and public health.
Insights
Metallo-beta-lactamases (MBLs) like NDM-1 are spreading globally. This study found NDM-1 producing multidrug-resistant Proteus mirabilis in Chinese broilers, highlighting potential public health risks from these resistant bacteria.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Genomics
Background:
- Metallo-beta-lactamases (MBLs) are a significant cause of carbapenem resistance in pathogens worldwide.
- New Delhi metallo-beta-lactamase 1 (NDM-1) is a key MBL, contributing to the spread of multidrug resistance.
- The presence and characterization of NDM-1 in food-producing animals like broilers are crucial for understanding transmission dynamics.
Purpose of the Study:
- To investigate the distribution and characteristics of NDM-1 producing Proteus mirabilis in commercial broilers in China.
- To analyze the genetic elements (plasmids, chromosomes) carrying the blaNDM-1 gene.
- To understand the phylogenetic relationships and genomic backbone profiles of these resistant strains.
Main Methods:
- Isolation and identification of blaNDM-1 carrying Proteus mirabilis from broiler samples.
- Antimicrobial susceptibility testing against carbapenems and other beta-lactams.
- Pulsed field gel electrophoresis (PFGE) for strain typing.
- Plasmid analysis, conjugation experiments, and whole genome sequencing (WGS).
Main Results:
- Forty blaNDM-1 positive Proteus mirabilis strains (18.1%) were recovered from broilers, all resistant to carbapenems.
- Seven blaNDM-1 genes were located on plasmids (104.5-138.9 kb), with some transferable to E. coli.
- Whole genome sequencing revealed four distinct phylogenetic clades and genomic backbone profiles, indicating blaNDM-1 transmission and evolution.
Conclusions:
- The study confirms the presence and spread of NDM-1 producing Proteus mirabilis in Chinese broiler populations.
- The genetic diversity and plasmid-mediated or chromosomal location of blaNDM-1 highlight its adaptability and transmission potential.
- These findings underscore the potential threat of NDM-1 positive Proteus mirabilis to environmental and public health.
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