title: Morphological and Bactericidal Effects of Amikacin, Meropenem and Imipenem on Pseudomonas aeruginosa.
abstract: BACKGROUND
  Pseudomonas aeruginosa might be converted to coccoid bacteria under antibiotic stress. Bacterial conversion would increase resistance to antibiotics due to changes in cell wall crosslink or decreased metabolic activity. Morphology of P. aeruginosa under stress conditions (presence of antibiotics) can be changed to elongated bacilli, U shape and finally coccoid bacteria. Results of several researches showed that coccoid bacteria are one of the most important aspects of drug resistance. It would be the major reason for treatment failure.
  
  
  OBJECTIVE
  The aim of this study was to determine in vitro morphological and bactericidal effects of amikacin, meropenem and imipenem on P. aeruginosa isolated from clinical specimens.
  
  
  METHODS
  Eight P. aeruginosa isolates obtained from clinical samples of burned patients and standard strain ATCC 27853 were used in this study. Isolates were identified by biochemical tests and confirmed by PCR method using ITS specific primer. Minimum inhibitory concentrations (MICs) of three antibiotics were determined by E-test method. Bacteria were exposed to antibiotics at different concentrations. Bacterial morphology in different days was examined by specific microscope and viability of isolates was examined by flow cytometry.
  
  
  RESULTS
  All used antibiotics at sub MIC concentration had capability to induce coccoid bacteria. The highest rate of induced coccoid bacteria was 98.2% after 8 days, with contribution of imipenem and meropenem at 2 μg/mL concentration. Amikacin at 4 μg/mL concentration induced lower rate of coccoid bacteria (55.05%). Amikacin had a strong bactericidal effect on coccoid bacteria at 8 μg/mL concentration. Imipenem and meropenem showed very weak bactericidal effect on coccoid bacteria.
  
  
  CONCLUSIONS
  Induction of coccoid form of P. aeruginosa may be one of the important reasons for antibiotic treatment failure; therefore, prescribed dose of antibiotics should be carefully managed to prevent increasing antibiotic resistance and coccoid bacteria induction.
authors: Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Mohsen
authors: M
authors: Moghoofei
authors: Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Hossein
authors: H
authors: Fazeli
authors: Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Farkhondeh
authors: F
authors: Poursina
authors: Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Bahram
authors: B
authors: Nasr Esfahani
authors: Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Sharareh
authors: S
authors: Moghim
authors: Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Hamid
authors: H
authors: Vaez
authors: Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Shima
authors: S
authors: Hadifar
authors: Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran.
authors: Hajieh
authors: H
authors: Ghasemian Safaei
keywords: Coccoid Bacteria; Drug Resistance; Pseudomonas aeruginosa