Ciprofloxacin

Ciprofloxacin antimicrobial susceptibility testing discs are employed for testing the sensitivity of bacterial isolates to ciprofloxacin by the standard Bauer-Kirby disc diffusion method. This technique is a qualitative method to determine if bacteria are inhibited from growing around a disc containing an antimicrobial agent on a solid culture medium under standardized conditions. Each disc is a 6.0 mm diameter filter paper disc with “CIP 05” printed at the centre on both sides. During testing, the disc is placed on an agar surface that has already been inoculated with the test bacterium. Once the disc comes into contact with the moist agar, ciprofloxacin begins to diffuse outward from the disc.

The diffusion process produces a concentration gradient within the agar. The antimicrobial concentration is highest close to the disc and progressively decreases as the distance from the disc increases. Bacterial growth is inhibited in the area where the concentration remains effective against the test organism. Following incubation, this inhibition can appear as a clear zone or ring around the disc. The resulting zone can then be assessed according to the applicable standardized interpretation criteria. The disk diffusion procedure is performed using Mueller-Hinton Agar (MHA). This medium is among the most frequently used for routine susceptibility testing as it gives good reproducibility, it allows adequate growth of most bacterial pathogens and its level of inhibitors related to sulfonamides, trimethoprim and tetracyclines is low.

Antimicrobial susceptibility testing by the Kirby-Bauer method helps determine whether a bacterial isolate is susceptible or resistant to antimicrobial compounds. This information is valuable for clinical labs when considering antimicrobial agents for treatment of a bacterial infection. The use of standardized methods helps ensure that test conditions are uniform and results are interpretable. The Bauer-Kirby method evolved from earlier studies of antimicrobial susceptibility testing and was later standardized by means of reference procedures. Standardized procedures for disk systems have been published by the WHO and FDA, and the Clinical Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) have published extensive guidance for antimicrobial susceptibility testing.

Proper handling of sensitivity disks is important to the continued performance of the test. On receipt the disks should be stored immediately at recommended temperature. Preparation of medium, inoculum and incubation as per the prescribed procedure. Proper test conditions are critical for reliable and reproducible observations in disk diffusion testing.