Characterisation of a chromosomally-encoded extended-spectrum β-lactamase gene blaPER-3 in Aeromonas caviae of chicken origin

Evolution and Emergence of Antibiotic Resistance in Given Ecosystems: Possible Strategies for Addressing the Challenge of Antibiotic Resistance

Antibiotics were once considered the magic bullet for all human infections. However, their success was short-lived, and today, microorganisms have become resistant to almost all known antimicrobials. The most recent decade of the 20th and the beginning of the 21st century have witnessed the emergence and spread of antibiotic resistance (ABR) in different pathogenic microorganisms worldwide. Therefore, this narrative review examined the history of antibiotics and the ecological roles of antibiotics, and their resistance. The evolution of bacterial antibiotic resistance in different environments, including aquatic and terrestrial ecosystems, and modern tools used for the identification were addressed. Finally, the review addressed the ecotoxicological impact of antibiotic-resistant bacteria and public health concerns and concluded with possible strategies for addressing the ABR challenge. The information provided in this review will enhance our understanding of ABR and its implications for human, animal, and environmental health. Understanding the environmental dimension will also strengthen the need to prevent pollution as the factors influencing ABR in this setting are more than just antibiotics but involve others like heavy metals and biocides, usually not considered when studying ABR.

Molecular and Functional Characterization of a Novel Plasmid-Borne bla NDM-Like Gene, bla AFM-1, in a Clinical Strain of Aeromonas hydrophila

Purpose

An increasing frequency of antibiotic resistance has been observed in both clinical and environmental Aeromonas hydrophila isolates in recent years. However, there are still very few in-depth studies regarding the role of plasmids in the antibiotic resistance of A. hydrophila. Hence, we investigated the molecular and functional characterization of a multidrug-resistant plasmid encoding an NDM-like metallo-β-lactamase, AFM-1, in the clinical A. hydrophila isolate SS332.

Methods

The minimum inhibitory concentrations (MICs) of 24 antibiotics against A. hydrophila SS332 were measured by the agar dilution method. The genome of A. hydrophila SS332 was sequenced with PacBio and Illumina platforms. Six plasmid-borne antimicrobial resistance genes were chosen for cloning, including bla_AFM-1, bla_OXA-1, msr(E), mph(E), aac(6ʹ)-Ib10, and aph(3ʹ)-Ia. Phylogenetic analysis, amino acid sequence alignment, and comparative genomic analysis were performed to elucidate the active site requirements and genetic context of the bla_AFM-1 gene.

Results

A. hydrophila SS332 showed high levels of resistance to 15 antibiotics, especially those with MIC levels at or above 1024 μg/mL, including ampicillin, cefazolin, ceftriaxone, aztreonam, spectinomycin, and roxithromycin. Six plasmid-borne resistance genes from A. hydrophila were verified to be functional in E. coli DH5α. AFM-1 shared 86% amino acid identity with NDM-1 and showed resistance to ampicillin, cefazolin, cefoxitin, and ceftazidime. In addition, the bla_AFM-1 gene was associated with three different novel ISCR19-like elements, designated ISCR19-1, ISCR19-2 and ∆ISCR19-3, which may be involved in the acquisition and mobilization of the bla_AFM-1 gene.

Conclusion

Our investigation showed that plasmid-borne resistance genes can contribute to antibiotic resistance in A. hydrophila SS332. A novel bla_NDM-like gene, bla_AFM-1, was verified to be functional and associated with novel ISCR19-like elements. This fact indicated the risk of spread of bla_AFM-1 genes and ISCR19-like elements.