Effect of single-dose carbapenem exposure on transcriptional expression of blaNDM-1and mexA in Pseudomonas aeruginosa.
The therapeutic option of a carbapenem antibiotic is compromised in Pseudomonas aeruginosa owing both to acquired and intrinsic resistance mechanisms. In recent years, New Delhi metallo-β-lactamase has been the focus as a predominant carbapenem resistance determinant. However, it is unclear which of the mechanisms might be adopted by a P. aeruginosa strain possessing both blaNDM-1and an overexpressed MexAB-OprM system during carbapenem therapy. This study investigated the interplay of both mechanisms in clinical isolates of P. aeruginosa when exposed to meropenem. Five strains were used: (i) strain overexpressing MexAB-OprM but with no blaNDM-1; (ii) strain harbouring blaNDM-1but expressing MexAB-OprM at basal level; (iii) strain possessing blaNDM-1and overexpressing MexAB-OprM; (iv) P. aeruginosa PAO1; and (v) P. aeruginosa K2733-PAO1 (ΔMexAB-OprMΔMexCD-OprJΔMexEF-OprNΔMexXY-OprM) into which blaNDM-1was cloned. Strains were incubated in Luria-Bertani broth with and without 1μg/mL meropenem. Total RNA was isolated at 45-min intervals and was immediately reverse transcribed to cDNA. This was repeated for 6h. Quantitative real-time PCR was performed for both resistance mechanisms. Meropenem exposure did not significantly elevate transcription of either the blaNDM-1or mexA gene. However, an interesting finding was that upon single-dose exposure to carbapenem, the efflux pump system played a major role in bacterial survival compared with NDM-1. This study gives an insight into the bacterial response to carbapenem antibiotic when two different resistance mechanisms coexist. This type of study would be helpful in designing future antimicrobials.
Department of Life Science & Bioinformatics, Assam University, Silchar, Assam, India.
Debarati
D
Choudhury
Department of Microbiology, Assam University, Silchar, Assam, India.
Deepjyoti
D
Paul
Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal, India.
Anindya Sundar
AS
Ghosh
Department of Life Science & Bioinformatics, Assam University, Silchar, Assam, India.
Anupam
A
Das Talukdar
Department of Life Science & Bioinformatics, Assam University, Silchar, Assam, India.
Manabendra
M
Dutta Choudhury
Department of Microbiology, Assam University, Silchar, Assam, India.
Anand Prakash
AP
Maurya
Department of Microbiology, Silchar Medical College and Hospital, Silchar, Assam, India.
Debadatta
D
Dhar Chanda
Department of Microbiology, Silchar Medical College and Hospital, Silchar, Assam, India.
Atanu
A
Chakravarty
Department of Microbiology, Assam University, Silchar, Assam, India. Electronic address: ab0404@gmail.com.
Amitabha
A
Bhattacharjee
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D015780:Carbapenems / Q000494:pharmacology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
D001425:Bacterial Outer Membrane Proteins; D015780:Carbapenems; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; D001618:beta-Lactamases; C552864:beta-lactamase NDM-1
Carbapenem; MexAB–OprM; Pseudomonas aeruginosa; bla(NDM-1)