Morphological and Bactericidal Effects of Amikacin, Meropenem and Imipenem on Pseudomonas aeruginosa

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. Objectives: 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. Materials and 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.

[1]  A. Japoni,et al.  Antibiotic Susceptibility Patterns and Molecular Epidemiology of Metallo-β-Lactamase Producing Pseudomonas Aeruginosa Strains Isolated From Burn Patients , 2014, Iranian Red Crescent medical journal.

[2]  S. Farajnia,et al.  Antimicrobial Resistance Patterns and Prevalence of blaPER-1 and blaVEB-1 Genes Among ESBL-producing Pseudomonas aeruginosa Isolates in West of Iran , 2014, Jundishapur journal of microbiology.

[3]  J. Faghri,et al.  Morphological and Bactericidal Effects of Different Antibiotics on Helicobacter pylori , 2014, Jundishapur journal of microbiology.

[4]  A. Bakhrouf,et al.  Evidence of the adaptive response in Pseudomonas aeruginosa to 14 years of incubation in seawater , 2012, Annals of Microbiology.

[5]  Juming Tang,et al.  Using of infrared spectroscopy to study the survival and injury of Escherichia coli O157:H7, Campylobacter jejuni and Pseudomonas aeruginosa under cold stress in low nutrient media. , 2011, Food microbiology.

[6]  J. Oliver,et al.  Recent findings on the viable but nonculturable state in pathogenic bacteria. , 2010, FEMS microbiology reviews.

[7]  V. Mizrahi,et al.  Resuscitation-promoting factors as lytic enzymes for bacterial growth and signaling. , 2010, FEMS immunology and medical microbiology.

[8]  A. P. Fonseca,et al.  Effect of antibiotic‐induced morphological changes on surface properties, motility and adhesion of nosocomial Pseudomonas aeruginosa strains under different physiological states , 2007, Journal of applied microbiology.

[9]  J. Oliver.  The viable but nonculturable state in bacteria. , 2005, Journal of microbiology.

[10]  K. Gin,et al.  Monitoring of active but non-culturable bacterial cells by flow cytometry. , 2005, Biotechnology and bioengineering.

[11]  N. Rowan.  VIABLE BUT NON-CULTURABLE FORMS OF FOOD AND WATERBORNE BACTERIA: QUO VADIS? , 2004 .

[12]  T. Nyström.  Nonculturable bacteria: programmed survival forms or cells at death's door? , 2003, BioEssays : news and reviews in molecular, cellular and developmental biology.

[13]  M. Allegrini,et al.  Morphologic variations in bacteria under stress conditions: near-field optical studies. , 2006, Scanning.

[14]  V. Besnard,et al.  EVIDENCE OF VIABLE BUT NON-CULTURABLE STATE IN LISTERIA MONOCYTOGENES BY DIRECT VIABLE COUNT AND CTC-DAPI DOUBLE STAINING , 2000 .

[15]  C. Signoretto,et al.  mRNA Detection by Reverse Transcription-PCR for Monitoring Viability over Time in an Enterococcus faecalis Viable but Nonculturable Population Maintained in a Laboratory Microcosm , 2000, Applied and Environmental Microbiology.

[16]  M. Bally,et al.  RpoS-dependent stress tolerance in Pseudomonas aeruginosa. , 1999, Microbiology.

[17]  D. Weichart,et al.  Nonculturability: adaptation or debilitation? , 1998 .