Phenotypic Variation of Tobramycin and Ofloxacin Resistance of Pseudomonas aeruginosa by Repeated Exhibition

Abstract

Pseudomonas aeruginosa has the ability to resist almost all available antibiotics by rapidly accumulating multiple resistance mechanisms and thus lead to a therapeutic impasse and higher mortality in infected patients.
 The objective of this study was to assess the phenotypic variation in resistance to tobramycin and ofloxacin from Pseudomonas aeruginosa by repeated exhibition after determination of the minimum inhibitory concentration.
 This is a prospective and descriptive study carried out in the Laboratory of Microbiology of Fundamental and Applied Biochemistry (Faculty of Sciences, Antananarivo) during the month of January 2020. The strains studied were the virulent wild strain of Pseudomonas aeruginosa PAO1 supplied by the Laboratory and two clinical strains of Pseudomonas aeruginosa from the Microbiology Laboratory of the Joseph Ravoahangy Andrianavalona University Hospital Center, Antananarivo.
 The strains of P. aeruginosa were cultured in the liquid culture medium (which is Luria Bertani, added with a buffer system of 3- (N-morpholino) propanesulfonic acid (LB-MOPS) which will stabilize the pH and a solid culture medium which is Columbia agar. Repeated exhibition to Tobramycin and Ofloxacin from these strains have been made. The MIC is determined by a visual evaluation of the turbidity of the various wells of the microplate.
 The MIC value of Pseudomonas aeruginosa with tobramycin and ofloxacin is very variable for the initial MIC until the 5th generation after repeated exhibition. More Pseudomonas aeruginosa is exposed to an antibiotic many times, the more it develops resistance to this antibiotic, even being sensitive at the start. That is to say, clinically, the dose prescribed for the antibiotic has been greatly exceeded if Pseudomonas aeruginosa is repeatedly exposed to the same antibiotic.