Amoxicillin clavulanate

Isolate identification and phenotypic susceptibility testing were performed according to standard procedures at each pathology service. At Dorevitch Pathology, the MSU submitted for laboratory testing was cultured on CHROMID CPS Elite (CPSE) agar incubated overnight at 35°C–37°C in air (bioMérieux). Identification of isolates was confirmed using MALDI-TOF MS on the VITEK MS platform (bioMérieux). Susceptibility testing was performed according to CLSI guidelines using disc diffusion against ampicillin, amoxicillin/clavulanate, cefazolin, ceftriaxone, ciprofloxacin, trimethoprim and nitrofurantoin (Bio-Rad) and supplementary susceptibility testing to fosfomycin, meropenem, ertapenem and gentamicin was performed in the event of E. coli ceftriaxone non-susceptibility.¹¹ Where susceptibility testing was not performed for Staphylococcus saprophyticus, we assumed trimethoprim susceptibility.^{12 (link)} We focused on E. coli for genomic characterization as it is the most frequently isolated bacterium in urine.

Screening for ESBL-E was performed by inoculating rectal swabs on selective medium supplemented with ceftazidime (bioMérieux, Marcy l’Etoile, France). After 24 h at 37 °C, the species were identified by MALDI-TOF (Matrix-Assisted Laser Desorption/Ionisation, time-of-flight mass spectrometry) analysis. Antibiotic susceptibility was tested using the standard agar diffusion method on Mueller-Hinton agar (Bio-Rad, Marnes-la-Coquette, France) according to CA-SFM 2012 guidelines. The following antibiotics (bioRad) were tested: amoxicillin, amoxicillin-clavulanate, ticarcillin, piperacillin, piperacillin-tazobactam, cefalotine, cefoxitine, moxalactam, cefotaxime, ceftazidime, aztreonam, cefepime, imipenem, ertapenem, meropenem, gentamicin, tobramycin, netilmicin amikacin, nalidixic acid, ofloxacin, ciprofloxacin and sulfamethoxazole. The double-disk synergy method was used to confirm ESBL production [25 (link)]. All ESBL-E − producing isolates were stored at −80 °C.

Urine analysis and strain identification were performed by conventional methods. Antimicrobial susceptibility study was determined using the standard disk diffusion method on Mueller Agar-Hinton (Oxoid) according to Clinical Laboratory Guidelines and Institute Standards [18 ]. Tested antibiotics (Bio-Rad) were as follows: amoxicillin-clavulanate, (10 μg) (AMX); amoxicillin, (20 μg/10 μg) (AMC); cefotaxime, (30 μg) (CTX); ceftazidime, (30 μg) (CAZ); cefoxitin (30 μg) (FOX); amikacin (30 μg) (AN); ciprofloxacin (10 μg) (CIP); nalidixic acid (10 μg) (NA); gentamicin (10 μg) (GEN); netilmicin (30 μg) (NET); tobramycin (10 μg) (NN); fosfomycine (10 μg) (FFL); trimethoprim + sulfamide (10 μg) (SXT); imipenem (10 μg) (IPM); and colistin (10 μg) (CL). The diameters of the zones of inhibition were interpreted according to the recommendations of the CLSI [18 ]. All strains isolated were screened for extended-spectrum β-lactamase (ESBL) production by the double-disk synergy test [19 (link)].