Pandrug-resistant Pseudomonas sp. expresses New Delhi metallo-β-lactamase-1 and consumes ampicillin as sole carbon source

Objectives: This study aims to investigate ampicillin catabolism in a pandrug-resistant strain, Pseudomonas sp. MR 02 of P. putida lineage.

Methods: The characterization of carbapenem resistance was done following the standard protocol. The broth macrodilution method was used to determine the MIC values of antimicrobial agents both in the presence and in the absence of phenylalanine-β-naphthylamide. High MIC values (>10 000 mg/L) of ampicillin led to speculation that it may serve as a growth substrate, and thus minimal medium was used to evaluate ampicillin as a nutrient. The growth of MR 02 was measured in minimal medium in the presence or absence of 0.4 mM EDTA, supplemented with ampicillin as sole carbon, nitrogen and energy source. RNA-seq was used to generate expression profiles of genes in ampicillin or glucose-grown cells. The bla_NDM-1 gene of MR 02 was cloned in the pHSG398 vector and expressed in Escherichia coli DH5α.

Results: Phenotypic analysis along with genome sequence data identifies Pseudomonas sp. MR 02 as a pandrug-resistant strain. Transcriptome data has revealed that bla_NDM-1 was among the top 50 differentially expressed genes in ampicillin grown cells compared to the glucose grown cells in the minimal medium. Heterologous expression of bla_NDM-1 gene in E. coli DH5α enabled its growth and subsistence on ampicillin as the sole source of carbon and energy.

Discussion: The ability of a pandrug-resistant Pseudomonas sp. MR 02 to consume ampicillin for growth has a huge implication in the bioremediation of β-lactam residues in the environment.