Sažetak
Background: Increasing antibiotic resistance in Gram negative bacteria has led to the need for a faster and reliable method for determining antimicrobial susceptibility testing. In a resource poor setting like ours, it’s also important to look for methods that will be clinically and economically beneficial to the patient.
Aim: This study was aimed at evaluating the Epsilometer test (E-test) and conventional methods for determining antimicrobial susceptibility of isolates of Gram-negative enteric bacteria to ciprofloxacin and gentamicin.
Methods: Disc diffusion, E-test, broth dilution and agar dilution methods were performed on 54 bacterial isolates.
Results: Using the E-test, 88.9 % of bacterial isolates were resistant to ciprofloxacin, 92.6 % were resistant using broth microdilution, 96.3 % were resistant using agar dilution and 72.2 % were resistant using disc diffusion. Minimum Inhibitory Concentration (MIC50) of isolates for gentamicin showed significant difference for all the techniques (p < 0.05) while MIC90 for gentamicin and MIC50 and MIC90 for ciprofloxacin for all the techniques had no significant difference (p > 0.05). Both E-test and broth dilution methods showed high levels of agreement (p > 0.05), there were low levels of agreement between E-test and agar dilution method (p < 0.05), especially at MIC50.
Conclusion: The E-test can therefore be considered a reliable method to determine antimicrobial susceptibility testing and it gives results which are at least as accurate as those obtained by the broth dilution method.
Keywords: E-test, susceptibility, antibiotics, bacteria, infection
Résumé
Contexte: L’augmentation de la résistance aux antibiotiques dans les bactéries à Gram négatif a conduit à la nécessité d’une méthode plus rapide et fiable pour déterminer les tests de sensibilité des antimicrobiens. Dans un contexte de ressources pauvre comme le nôtre, il est également important de rechercher des méthodes qui seront cliniquement et économiquement bénéfiques pour le patient.
But: Cette étude visait à évaluer le test epsilomètre (E-test) et les méthodes classiques pour la détermination de la sensibilité des antimicrobiens des isolats de bactéries à Gram négatif entériques à la ciprofloxacine et la gentamicine.
Méthodes: La méthode de la diffusion sur disque, E-test, la dilution par bouillon et de la dilution par gélose a été effectuée sur 54 isolats bactériens.
Résultats: En utilisant le E-test, 88,9% des isolats bactériens étaient résistantes à la ciprofloxacine, 92,6% étaient résistants à l’aide de micro -dilution, 96,3% étaient résistants à l’aide de dilution par gélose et 72,2% étaient résistants à l’aide de diffusion sur disque. CMI50 des isolats pour la gentamicine a montré de différence significative pour toutes les techniques (p <0,05) tandis que CMI90 CMI50 pour la gentamicine et la ciprofloxacine et CMI90 pour toutes les techniques il n’y avait pas de différence significative (P> 0,05). Les deux méthodes de dilution E-test et le bouillon ont montré des niveaux élevés d’accord (p> 0,05), il y avait de faibles niveaux d’accord entre E-test et la méthode de dilution par gélose (p <0,05), en particulier à la CMI50.
Conclusion: Le E-test peut donc être considéré comme une méthode fiable pour déterminer les tests de sensibilité aux antimicrobiens et donne des résultats qui sont au moins aussi précis que ceux obtenus par la méthode de dilution par bouillon.
Correspondence: D. Olusoga Ogbolu, Department of Biomedical Sciences, College of Health Sciences, (Osogbo Campus), Ladoke Akintola University of Technology, Ogbomosho, Oyo State, Nigeria. E-mail: olusogadave@yahoo.com
Reference
National Institute of Allergy and Infectious
Diseases, NIAID. The problem of antibiotic
resistance. http://www.niaid.nih.gov/. 2004.
World Health Organization: Report on infectious disease. Overcoming antimicrobial resistance. Available at VRL: http://www.who.int/infectious-disease report/index. Html Accessed September 23, 2000.
Tan TY and Ng SY. Comparison of E-test, Vitek2 and agar dilution for susceptibility testing of colistin. Clin. Microbiol. Infect 2007; 13:541-544.
Baker CN, Stocker SA, Culver SH and Thorusberry CH. Comparison of the E-test to agar dilution, broth microdilution, and agar diffusion susceptibility testing techniques by using challenge set of bacteria. J. Clin. Microbiol 1991; 29(3):533-538.
Ewing WH. Edwards and Ewings identification of enterobacteriaceae. 4th ed. New York: Elsevier Science publishing 1986.
Barrow GI and Feltham RKA. Characters of Gram-negative bacteria. In: Cowan and Steel Manual for Identification of Medical Bacteria. 3rd edition, Cambridge University Press, 1993; 94-149.
Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. Seventeenth information supplement (M100-S17). Clinical and Laboratory Standards Institute, Wayne, PA 2007
Jerome RL, Anne Marie GA, Diederen MW, Jan AJ and Peter HJ. Comparative Evaluation of the Vitek 2, Disc diffusion, E-test, Broth microdilution, and Agar dilution susceptibility testing methods for Colistin in Clinical Isolates. J. Antimicrob. Chem. Ther 2007; 20 (3): 3726-3730.
Arroyo LA, Garcia-Curiel A, Pachon-Ibanez ME et al Llanos AC, Ruiz M, Pachon J, Aznar J. Reliability of the E test method for detection of colistin resistance in clinical isolates of Acinetobacter baumannii. J. Clin. Microbiol 2005; 43:903-905.
Nicodemo AC, Araujo MR, Ruiz SA and Gales AC. In-Vitro susceptibility of Stenotrophomonas maltophilia isolates: comparison of disc diffusion, E-test and agar dilution methods. J. Antimicrob. Chemother 2004; 53:604-608.
Jones RN, Erwin ME and Croco JL. Critical appraisal of E-test for the detection of fluoroquinolone resistance. Journal of Antimicrobial Chemotherapy 1996; 38: 21-25.
Di Bonaventura G, Ricci E, Loggia ND, Catamo G and Piccolomini R. Evaluation of the E test for antimicrobial susceptibility testing of Pseudomonas aeruginosa isolates from patients with long-term bladder catheterization. Journal of Clinical Microbiology 1998; 36: 824–826
Ani A, Malu A, Onah J, Queiroz D, Kirschner G and Rocha G. Antimicrobial susceptibility test of Helicobacter pylori isolated from Jos, Nigeria. Transactions of the Royal Society of Tropical Medicine and Hygiene 1998; Vol 93 (6): 659-661.
Galloway A, Wright J, Murphy O and Dickinson G. Sensitivity testing of Pseudomonas aeruginosa to ciprofloxacin: comparison of the modified Stokes’ method with MIC results obtained by the E-test .J Antimicrob Chemother 1999; 43: 314–315.