title: Expression of efflux pump MexAB-OprM and OprD of Pseudomonas aeruginosa strains isolated from clinical samples using qRT-PCR.
abstract: BACKGROUND
  Pseudomonas aeruginosa is one of the most common nosocomial pathogens with high mortality rates. Organisms such as Pseudomonas aeruginosa have the ability to develop high level MDR (Multi drug resistance). The MexAB-OprM system is one of the largest multi-drug resistant efflux pumps with high levels of expression and the first finding of the RND (Resistance-nodulation-division) family in P. aeruginosa.
  
  
  OBJECTIVE
  For better understanding of the antibiotic resistance mechanism in P. aeruginosa, this study was conducted to determine the expression of the genes encoding these efflux pumps in 100 strains of P. aeruginosa isolated from patients admitted to various hospitals in Hamadan using quantitative Real-Time PCR (qRT-PCR).
  
  
  METHODS
  This study examined 100 strains of P. aeruginosa isolated from patients admitted to various hospitals in Hamadan. Then, 31 samples were selected based on collected specimen type and their antibiotic susceptibility pattern; i.e., the samples with reduced susceptibility to antibiotics, particularly carbapenems. Antibiotic disk diffusion method was performed for aminoglycoside, quinolone and carbapenem. Furthermore, MIC method was performed for ciprofloxacin, gentamicin and imipenem. Finally, qRT-PCR was used for determining the efflux pump genes expression.
  
  
  RESULTS
  Among eight selected antibiotics, the greatest resistance was to levofloxacin (61.2%, n = 19) and the lowest one to imipenem (9.6%, n = 3). All isolates (100%, n = 31) exhibited efflux pump MexAB-OprM genes but different expression was observed in different strains. The result of gene expression indicated that significant differences in expression of MexR (P value = 0.003), OprD (P value < 0.001), and MexB (P value = 0.026) genes. In addition, there was high level of MexR gene expression in bacteria that leads to reduced expression of MexA, MexB, and OprM. The OprD gene was presented in all strains but different expression has been observed.
  
  
  CONCLUSIONS
  Identifying the bacterial resistance mechanisms is very complicated. Although efflux pump MexAB-OprM plays an important role in antibiotic resistance in P. aeruginosa, because of acting the efflux pumps on antibiotics in a non-specific manner, it is elusive to consider or describe an antibiotic resistance based on the presence or absence of an efflux pump.
authors: 1)Brucellosis Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. 2)Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.mohammad.arabestani@gmail.com.
authors: Mohammad Reza
authors: MR
authors: Arabestani
authors: Brucellosis Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
authors: Mojtaba
authors: M
authors: Rajabpour
authors: Brucellosis Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
authors: Rasoul
authors: R
authors: Yousefi Mashouf
authors: 1)Brucellosis Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. 2)Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.
authors: Mohammad Yousef
authors: MY
authors: Alikhani
authors: Brucellosis Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
authors: Seyed Masoud
authors: SM
authors: Mousavi
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D003428:Cross Infection; D024901:Drug Resistance, Multiple, Bacterial; D015870:Gene Expression; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D018272:Porins / Q000235:genetics / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; C118597:MexB protein, Pseudomonas aeruginosa; C402263:OprM protein, Pseudomonas aeruginosa; D018272:Porins; C077157:OprD protein, Pseudomonas aeruginosa