The results of determining the potency of the antibiotic susceptibility discs prepared in the laboratory

Abstract

Background: Improper use of antibiotics increases bacterial resistance, prolongs treatment time, and increases economic costs. The disc diffusion method is widely used for antibiotic susceptibility testing. Antibiotic susceptibility disks of one manufacturer (Bioanalyse) are registered in our country’s diagnostic registration. Aim: Evaluating the potency of antibiotic susceptibility discs prepared in the laboratory. Materials and Methods: The potency of antibiotic susceptibility discs prepared in the laboratory was tested according to EUCAST and CLSI guidelines and compared to the manufacturer’s disc potency. Statistical analysis was performed using IBM SPSS 26.0 software, and the mean value (M) and standard deviation (SD) of quantitative variables were calculated. Results: The potency of antibiotic susceptibility discs prepared in the laboratory using four paper types was evaluated and compared with discs from two manufacturers. When testing the potency of all antibiotic susceptibility disks according to EUCAST and CLSI guidelines, the zone of inhibition was within the range of reference values. When comparing the potency of cefazolin 30 μg susceptibility discs with discs of two manufacturers, D1 discs showed statistically significant differences with M1 discs (p=0.009), and D1 discs (p=0.0001), and D3 discs (p=0.005) with M2 discs. Compared to the manufacturer’s 10 μg gentamicin discs, all laboratory discs showed statistical differences with M1 discs (p=0.0001) and D1 (p=0.002), D2 (p=0.01), and D3 (p=0.0001) discs showed statistical differences with M2 discs. For ciprofloxacin 5 μg discs, the potency of the D3 disc (p=0.0001) was statistically different in comparison to the M1 disc, D2 (p=0.003) and D4 (p=0.0001) disc was statistically different compared to the M2 disc potency. All vancomycin 30 μg susceptibility discs showed statistical differences compared to M1 and M2 discs (p<0.01). Conclusion: It was determined that the D4 disc, which produced a close range of inhibition, could be used in practice, as the activity of the antibiotic discs produced in the laboratory showed a minimal statistically significant difference in quantitative parameters compared to the manufacturer’s disc.