Ceftazidime clavulanate

Antimicrobial susceptibility testing (AST) was performed using Kirby-Bauer disc diffusion method on Muller-Hinton agar (BIOMARK^R Laboratories, India). Selected antimicrobial agents such as Ampicillin (10 µg), Amoxicillin-clavulanate (20/10 µg), Ciprofloxacin (5 µg), Tobramycin (10 µg), Gentamicin (10 µg), Cefixime (5 µg), Cefoxitin (30 µg), Cefuroxime (30 µg), Nitrofurantoin (300 µg), Rifampin (5 µg), Tetracycline (30 µg), Penicillin 10 units, Norfloxacin (10 µg), Vancomycin (30 µg), Trimethoprim-sulphamethoxzole (1.25/23.75 µg) (Abtek Biologicals Ltd, United Kingdom) and Cefotaxime (30 µg), Ceftazidime (30 µg), Cefotaxime-Clavulanate (30/10 µg), Ceftazidime-Clavulanate (30/10 µg) (HiMedia Laboratories Pvt Ltd India) were used for antimicrobial susceptibility test [19 ]. Zones of inhibition were measured after 16–18 h of incubation at 37 °C and classified as susceptible or resistant. Isolates intermediate between susceptible and resistant were considered as resistant [20 (link)]. Isolates resistant to three or more classes of antibiotics were considered as MDR [21 ].

Individual isolates were standardized to 0.5 McFarland using a SPECTROstar Nano^® UV–Vis spectrophotometer (BMG Labtech, Ortenberg, Germany). The standardized isolates were then streaked on Mueller–Hinton agar (MHA; Merck-Millipore, Darmstadt, Germany), and antibiotic disks were placed using the standard disk diffusion procedures. The antibiotic disks contained ceftazidime, cefotaxime (30 µg each; Mastdiscs AST, Liverpool, UK), ceftazidime–clavulanate, and cefotaxime–clavulanate (30 µg/10 µg each combination; HiMedia, Mumbai, India). After 16–18 h of incubation at 35 °C, an increase of at least 5 mm in zones of inhibition (ZOIs) between the standalone antibiotic disk and the disk with antibiotic plus clavulanate indicated ESBL production. K. pneumoniae ATCC^® 700603 and E. coli ATCC^® 25922 were used as controls.