Amoxicillin clavulanic acid

Antimicrobial susceptibility testing (AST) of E. coli and K. pneumoniae isolates was performed by the Kirby Bauer disk diffusion method according to the CLSI guideline [19 ]. The antimicrobial disks used for testing were ampicillin (10 µg) [tested only for E. coli], Amoxicillin-clavulanic acid (20/10 µg), piperacillin-tazobactam (100/10 µg), cefazolin (30 µg), cefuroxime (30 µg). cefixime (5 µg), cefotaxime (30 µg), ceftazidime (30 µg), cefepime (30 µg), imipenem (10 µg), ciprofloxacin (5 µg), trimethoprim sulphamethoxazole (1.25/23.75 µg), nitrofurantoin (300 µg), and amikacin (30 µg). Amoxicillin-clavulanic acid, piperacillin-tazobactam, ceftazidime, ciprofloxacin, and imipenem disks were purchased from the manufacturer Mast (Mast group Ltd, Liverpool, UK) with the remainder from HiMedia (HiMedia, India). The minimum inhibitory concentration (MIC) of ciprofloxacin was determined by E-test (0.002-32 µg/mL) (HiMedia, India), and those isolates with MIC ≥ 32 µg/mL were further tested by agar dilution method following the procedures described by CLSI [20 ]. An isolate was defined to display multidrug resistance (MDR) if non-susceptible to ≥ 1 agent in ≥ 3 antimicrobial categories [21 (link)]. Escherichia coli ATCC 25922 was used for quality control.

Eight K. pneumoniae isolates were received from the Medical Microbiology laboratories of three hospitals in Armenia between January 2019 and August 2019. All isolates were recovered from various clinical specimens (urine, sputum, throat, blood, and stool) of hospitalized patients. The isolates were identified using a matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF-MS) as described previously (59 (link)).
All isolates were tested using a disk diffusion method for susceptibility to a panel of 11 antibiotics, including ampicillin (10 mg), piperacillin-tazobactam (30/6 mg), amoxicillin-clavulanic acid (20 and 10 mg, respectively), ceftazidime (10 mg), cefepime (30 mg), norfloxacin (10 mg), levofloxacin (5 mg), amikacin (30 mg), imipenem (10 mg), meropenem (10 mg), and chloramphenicol (30 mg) (Mast Group, Merseyside, United Kingdom) according to the European Committee on Antimicrobial Susceptibility Testing protocol (EUCAST v.6.0, 2017) (60 ). The antibiotics chosen were those most frequently used in clinical settings in Armenia. Isolates resistant to three or more antibiotic classes were considered multidrug resistant.

The identification and susceptibility profiles of these four and other E.coli isolates were reported previously (50 (link)); in brief, each isolate was tested against a panel of 10 antibiotics using the disk diffusion method. The antibiotics included were ampicillin (10 mg), piperacillin-tazobactam (30/6 mg), amoxicillin-clavulanic acid (20/10 mg), ceftazidime (10 mg), cefepime (30 mg), norfloxacin (10 mg), levofloxacin (5 mg), amikacin (30 mg), imipenem (10 mg), meropenem (10 mg), and chloramphenicol (30 mg) (Mast Group, Merseyside, UK) according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) protocol (52 ). Isolates were determined to be ESBL producing if they showed resistance to ceftazidime and cefepime.