Ceftriaxone

According to the Clinical and Laboratory Standards Institute (CLSI) 2017 guidelines (9), a disk diffusion assay was performed on the isolated E. coli colonies. The antibiotic discs contained nalidixic acid (30 µg), ampicillin (10 µg), tetracycline (30 µg), cotrimoxazole (25 µg), chloramphenicol (30 µg), ceftriaxone (30 µg), ce xime (5 µg), cefotaxime (30 µg), ceftizoxime (30 µg), cefoxitin (30 µg), ceftazidime (30 µg), azithromycin (15 µg), cipro oxacin (5 µg), gentamicin (10 µg) and imipenem (10 µg) (Mast Diagnostics, United Kingdom).

The antimicrobial susceptibility of the all isolated bacteria was determined in vitro, utilizing the disc diffusion method in accordance with the CLSI criteria [7] . The tested antibiotics included ceftriaxone, cefotaxime, amoxicillin, cefepime, tazocin, ceftazidime, ciprofloxacin, gentamicin and colistin (MAST Diagnostics, Merseyside, UK). Susceptibility testing for meropenem and/or imipenem was performed according to the CLSI reference by using E-test method (Liofilchem, Italy). Carbapenem-resistant isolates were selected using the CLSI M100-S standard (27th edition) definition, i.e., not susceptible (intermediate or resistant, minimum inhibitory concentrations (MICs) of ≥2 µg/ml) to meropenem and/or imipenem, as defined by the current [12] (link).

In concordance with the Clinical and Laboratory Standards Institute; CLSI. 2018 [16], antimicrobial susceptibility testing was done on the Mueller-Hinton agar plates (Merck Co., Germany) by disk agar diffusion (DD) method against 16 following antimicrobials: levo oxacin (LEV; 5 µg); ceftazidime (CAZ; 30 µg), cefotaxime (CTX; 30 µg ), cefepime (FEP; 30 µg), ertapenem (ETP; 10 µg), amikacin (AK; 30 µg), meropenem (MER; 10 µg), ceftriaxone (CRO; 30 μg), ampicillin/sulbactam (SAM; 10/10 µg), cefoperazone (CFP; 75 µg), imipenem (IPM; 10 µg), nitrofurantoin (NIT;300 µg), gentamicin (GM; 10 µg), cipro oxacin (CIP; 5 µg), tetracycline (TET; 30 µg), and trimethoprim-sulfamethoxazole (SXT; 5 µg) (MAST Diagnostics, Merseyside, UK). The MDR and possible XDR/PDR strains were recognized according to the guidelines suggested by the European Center for Disease Control and Prevention (ECDC) (17) . E. coli ATCC 25922 was used as a quality control (QC) organism. Also, colistin susceptibility assay was performed for carbapenems-resistance isolates by broth microdilution method according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. The E. coli NCTC 13846 (a colistin resistant strain) was used as QC in colistin minimum inhibitory concentration (MIC) determination.

The antimicrobial susceptibility of the isolated bacteria was determined in vitro, utilizing the disc diffusion method in accordance with the CLSI criteria (Clinical and Laboratory Standards Institute (CLSI) 2018). The tested antibiotics included ceftriaxone, cefotaxime, amoxicillin, cefepime, tazocin, ceftazidime, ciprofloxacin, gentamicin, and colistin (MAST Diagnostics, Merseyside, UK). Susceptibility testing for meropenem and/or imipenem was performed according to the CLSI reference by using E test method (Liofilchem, Italy). Carbapenem-resistant isolates were selected using the CLSI M100-S standard (27th edition) definition, i.e., not susceptible (intermediate or resistant, minimum inhibitory concentrations (MICs) of ≥ 2 μg/ml) to meropenem and/or imipenem, as defined by the current (Miller et al. 2017) (link).