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.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 cytometryResults: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.

Distribution of the Strains of Multidrug-resistant, Extensively Drug-resistant, and Pandrug-resistant Pseudomonas aeruginosa Isolates from Burn Patients

“…The prevalence of colonization in healthy people is very low, but it is increased in hospitalized patients, especially those treated with broad-spectrum antibiotics. [ 3 7 ] Nowadays, nosocomial infections and subsequent antibiotic resistance are one of the serious problems at a global level, so that each year, a large number of patients involved with these infections and lose their lives. [ 1 8 ] P. aeruginosa is one of the most common bacteria in nosocomial infections, especially in burn units.…”

“…Burn patients, because of losing the skin barrier, are very vulnerable to infection. [ 7 9 ] It can be transmitted through the flora contamination be in touch with different surfaces in hospitals, such as equipment, disinfectant solutions, nurse's hands, and may spread among other patients. [ 10 11 ] The ability to use multiple mechanisms, including decreased outer membrane permeability, expression of efflux pump, produces antibiotic degradative enzymes, alginate production and transfer of resistance genes, the bacteria has enabled to show a high level of resistance to the most used antibiotics.…”

Evaluation of Biofilm Formation and Frequency of Multidrug-resistant and Extended Drug-resistant Strain in Pseudomonas aeruginosa Isolated from Burn Patients in Isfahan

“…Rapid acquisition of multidrug resistance (MDR) leads to high morbidity and mortality, especially in burn centers. [ 4 5 ] P. aeruginosa infections are mostly difficult-to-treat because of the low antibiotic sensitivity and the high rate of the emergence of antimicrobial resistance during the process of the treatment. [ 6 7 ] Accumulation of resistance after exposure to various antibiotics and cross-resistance among them may result in MDR, extended drug-resistant (XDR), and pan drug-resistant (PDR).…”

Pseudomonas aeruginosa: Diseases, Biofilm and Antibiotic Resistance

“…Furthermore, burn patients, due to the loss of skin barrier, showed high vulnerability to infections [23]. Novel therapeutic agents against the P. aeruginosa, improve the effectiveness of present antimicrobial agents and degrade biofilm in burn wounds, were needed [24], such bacterium is causing 75% of deaths in the burned patients, as it might be developing persistent biofilm related to infections, expressing many virulence factors, as well as mechanisms of antibiotic resistance.…”