Résumé
Antibiotic resistance is an important problem in antibiotic treatment of infections, particularly in hospitals. Tomatidine is a plant secondary metabolite with antimicrobial and antifungal effects. This study examined the possible synergistic effect tomatidine with several antibiotics against standard and clinical strains of Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli. After determining the minimum inhibitory concentrations [MICs] of antibiotics and tomatidine against the bacterial isolates using broth microdilution method, the synergistic effect between tomatidine and antibiotics was evaluated by checkerboard method and calculation of FIC indices. Tomatidine alone did not show any antimicrobial effect. However, it had synergistic effect with gentamicin and cefepime against standard and clinical isolates of S. aureus and P. aeruginosa, respectively. It also had synergistic effect with ampicillin and ciprofloxacin only against standard strains of E. faecalis and P. aeruginosa, respectively. In conclusion, tomatidine could be considered as a potential antibiotic potentiator for gentamicin, cefepime and ciprofloxacin, and ampicillin against Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus faecalis infections, respectively. However, the toxicological and pharmacological properties of tomatidine for use as a therapeutic agent remain to be determined
Résumé
Disk diffusion test is the usual applicable method for assessing the antimicrobial susceptibility pattern in most institutions and hospitals. The aim of this study was to determine the reliability of resistant-reported results of disk diffusion test for 6 routinely used antibiotics against Gram-positive microorganisms of nosocomial origin, using E-test method. Over a 1-year period, clinical specimens [e.g. blood, tracheal secretions, wound secretions, urine, etc.] were obtained from hospitalized patients with defined nosocomial infection and were cultured. Isolated Gram-positive bacteria underwent disk diffusion test for cephalothin, oxacillin, clindamycin, ciprofloxacin, vancomycin, teicoplanin [only for Enterococci], and meropenem antibiotics. E-test method was performed for all isolates resistant or intermediately sensitive to the disks of any mentioned antibiotics. Data showed compatible results of disk diffusion test with the results of E-test method for cephalothin, oxacillin, ciprofloxacin, vancomycin, and teicoplanin. None of ciprofloxacin- and vancomycin-resistant isolates in disk diffusion test showed sensitivity in E-test method. Significant differences between the results of disk diffusion and E-test methods were observed for clindamycin and meropenem against S.aureus [p = 0.01 and 0.04, respectively] and Enterococcus spp [p = 0.03 and 0.02, respectively]. In order to increase the reliability of antimicrobial susceptibility results, it is recommended to perform E-test for nosocomial Gram-positive microorganisms that show antibiotic resistance by disk diffusion test and it is more important for clindamycin and meropenem