title: Premature Termination of MexR Leads to Overexpression of MexAB-OprM Efflux Pump in Pseudomonas aeruginosa in a Tertiary Referral Hospital in India.
abstract: OBJECTIVE
  The present study was undertaken to investigate the mutations that are present in mexR gene of multidrug resistant (MDR) isolates of Pseudomonas aeruginosa collected from a tertiary referral hospital of north east India.
  
  
  METHODS
  76 MDR clinical isolates of P. aeruginosa were obtained from the patients who were admitted to or attended the clinics of Silchar medical college and hospital. They were screened phenotypically for the presence of efflux pump activity by an inhibitor based method. Acquired resistance mechanisms were detected by multiplex PCR. Real time PCR was performed to study the expression of mexA gene of MexAB-OprM efflux pump in isolates with increase efflux pump activity. mexR gene of the isolates with overexpressed MexAB-OprM efflux pump was amplified, sequenced and analysed.
  
  
  RESULTS
  Out of 76 MDR isolates, 24 were found to exhibit efflux pump activity phenotypically against ciprofloxacin and meropenem. Acquired resistance mechanisms were absent in 11 of them and among those isolates, 8 of them overexpressed MexAB-OprM. All the 8 isolates possessed mutation in mexR gene. 11 transversions, 4 transitions, 2 deletion mutations and 2 insertion mutations were found in all the isolates. However, the most significant observation was the formation of a termination codon at 35th position which resulted in the termination of the polypeptide and leads to overexpression of the MexAB-OprM efflux pump.
  
  
  CONCLUSIONS
  This study highlighted emergence of a novel mutation which is probably associated with multi drug resistance. Therefore, further investigations and actions are needed to prevent or at least hold back the expansion and emergence of newer mutations in nosocomial pathogens which may compromise future treatment options.
authors: Department of Life Science & Bioinformatics, Assam University, Silchar, Assam, India.
authors: Debarati
authors: D
authors: Choudhury
authors: Anamika
authors: A
authors: Ghose
authors: Department of Microbiology, Assam University, Silchar, Assam, India.
authors: Anamika
authors: A
authors: Ghosh
authors: Department of Microbiology, Silchar Medical College and Hospital, Silchar, Assam, India.
authors: Debadatta
authors: D
authors: Dhar Chanda
authors: Department of Life Science & Bioinformatics, Assam University, Silchar, Assam, India.
authors: Anupam
authors: A
authors: Das Talukdar
authors: Department of Life Science & Bioinformatics, Assam University, Silchar, Assam, India.
authors: Manabendra
authors: M
authors: Dutta Choudhury
authors: Department of Microbiology, Assam University, Silchar, Assam, India.
authors: Deepjyoti
authors: D
authors: Paul
authors: Department of Microbiology, Assam University, Silchar, Assam, India.
authors: Anand Prakash
authors: AP
authors: Maurya
authors: Atanu
authors: A
authors: Chakravarty
authors: Department of Microbiology, Silchar Medical College and Hospital, Silchar, Assam, India.
authors: Atanu
authors: A
authors: Chakravorty
authors: Department of Microbiology, Assam University, Silchar, Assam, India.
authors: Amitabha
authors: A
authors: Bhattacharjee
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000737:chemistry; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D018388:Codon, Terminator; D018432:Drug Resistance, Multiple; D017353:Gene Deletion; D020869:Gene Expression Profiling; D006801:Humans; D007194:India; D026901:Membrane Transport Proteins / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D011552:Pseudomonas Infections / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D062606:Tertiary Care Centers
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D018388:Codon, Terminator; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; C118597:MexB protein, Pseudomonas aeruginosa; C423620:MexR protein, Pseudomonas aeruginosa; C402263:OprM protein, Pseudomonas aeruginosa; D012097:Repressor Proteins