Comparison of two amoxicillin/clavulanic acid-resistant profiles employing two types of assay disks: A pilot study in 50 isolates from a tertiary care hospital in India

Background: During a period from January to March 2005, there was a sudden 3.85-fold increase in isolates with in vitro resistance to amoxicillin/clavulanic acid at Sant Parmanand Hospital, a private tertiary care hospital in Delhi, India, without an increase in treatment failures.Objective: This pilot study was designed to assess whether 2 different brands (one exclusively used during the last quarter of 2004, one exclusively used during the first quarter of 2005) of antibiotic disks used at the hospital were related to the reported change in resistance pattern.Methods: During April 2005, 50 consecutive hospital isolates, 45 gram negative and 5 gram positive, were tested in parallel, employing 2 brands of amoxicillin/clavulanic acid disks: HiMedia disks (HiMedia Laboratories, Mumbai, India) and BBLTM Sensi-DiscTM Antimicrobial Susceptibility Test Discs (BD Diagnostic Systems, Sparks, Maryland).Results: Of 50 consecutive hospital isolates tested with the HiMedia disks, 40 were resistant and 10 were susceptible. Of those tested with the BBL disks, 10 were resistant and 40 were susceptible. The susceptibility profiles observed were significantly different (P<0.001).Conclusion: In this study, significantly different susceptibility results were found when 2 different brands of antibiotic disks were used to test the amoxicillin/clavulanic susceptibility of 50 consecutive isolates in this private hospital in India.