Fusidic acid

Standard antibiotic susceptibility testing by the disc diffusion test was performed for cefoxitin (30 μg), fusidic acid (10 μg), erythromycin (15 μg), clindamycin (2 μg), trimethoprim/sulphamethoxazole (25 μg), gentamicin (10 μg), norfloxacin (10 μg), ciprofloxacin (5 μg), rifampin (5 μg) and vancomycin (5 μg) (all antibiotic discs from Oxoid, Basingstoke, Hampshire, England), with a 0.5 McFarland bacterial suspension in 0.85 % NaCl on Mueller–Hinton agar (Oxoid). After 16–20 h of incubation at 36 °C, the zone diameters were measured and each isolate was evaluated according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints (http://www.eucast.org, accessed 2015-03-20).
Standard minimum inhibitory concentration (MIC) determination with the Etest (bioMérieux) was performed for vancomycin and teicoplanin on Mueller–Hinton agar (Oxoid) with a bacterial suspension adjusted to 0.5 McFarland in 0.85 % NaCl. The results were determined after 24 h of incubation at 36 °C, and, again, each isolate was evaluated according to EUCAST breakpoints.
Isolates resistant to ≥3 antibiotic groups tested were considered multidrug-resistant (MDR).

Antibiotic susceptibility was done by Kirby-Bauer disk diffusion method8 (link) against a panel of antibiotics which included cefoxitin (30µg), linezolid (30µg), rifampin (5µg), fusidic acid (10µg), fosfomycin (50µg), tigecycline (15µg), tetracycline (30µg), chloramphenicol (30µg), ciprofloxacin (5µg), gentamicin (10µg), clindamycin (2µg), erythromycin (15µg), and sulfamethoxazole/trimethoprim (25µg) (Oxoid, UK). S. aureus ATCC 25923 was used as quality control strain. Results were interpreted according to the Clinical and Laboratory Standard Institute (CLSI) guidelines 2015. Minimum inhibitory concentrations (MICs) were performed for vancomycin (Sigma-Aldrich) using agar dilution method.9 (link)

S. epidermidis isolates (n = 183) were obtained during various surgical procedures due to suspected or verified PJI at the University Hospitals of Örebro and Linköping from 1999 to 2015 and from 1993 to 2015, respectively. The finding of S. epidermidis in multiple tissue samples (≥2) was interpreted as a PJI in accordance with the proposed definition of PJI [3 (link), 4 (link)]. Isolates were collected from patients with infected hip (n = 126), knee (n = 41), shoulder (n = 12), or elbow (n = 4) joint prostheses, then identified to the species level according to routine laboratory procedures and confirmed by MALDI-TOF MS (MicroflexLT and Biotyper 3.1, Bruker Daltonics, Bremen, Germany).
Standard antibiotic susceptibility testing by disc diffusion test (DDT) and MIC determination was performed according to EUCAST guidelines. MIC was determined by Etest for tedizolid, linezolid (Liofilchem, Roseto degli Abruzzi, Italy), and vancomycin (BioMérieux, Marcy-l’Etoile, France). DDT was performed for cefoxitin (30 μg), fusidic acid (10 μg), erythromycin (15 μg), clindamycin (2 μg), trimethoprim/sulfamethoxazole (25 μg), gentamicin (10 μg), norfloxacin (10 μg), and rifampin (5 μg) (Oxoid, Basingstoke, Hampshire, England).

Antibiotic susceptibility testing (AST) of S. aureus isolates was performed by disc diffusion test according to EUCAST guidelines and the breakpoint table v.10.0 (2020)⁵⁹ . The antibiotics tested were penicillin (10 µg), trimethoprim-sulfamethoxazole (25 µg), cefoxitin (30 µg), fusidic acid (10 µg), clindamycin (2 µg), erythromycin (15 µg), linezolid (10 µg), tetracycline (30 µg), norfloxacin (10 µg), ciprofloxacin (5 µg), gentamicin (10 µg) and rifampicin (5 µg) (Oxoid, Basingstoke, UK).

The antibiotic susceptibility patterns of penicillin (P, 10 units), clindamycin (DA; 2 μg), chloramphenicol (C; 30 μg), gentamicin (CN; 10 μg), erythromycin (E; 15 μg), cefoxitin (FOX; 30 μg), sulfamethoxazole/trimethoprim (SXT; 1.25/23.75 μg), vancomycin (VA; 30 μg), rifampicin (RD; 5 μg), linezolid (LZD; 30 μg), mupirocin (MUP; 5 μg), ciprofloxacin (CIP; 5 μg), fusidic acid (FD; 10 μg) and novobiocin (NV; 5 μg) (Oxoid) were determined according to the antibiotic disk diffusion method [17 ]. The plates were incubated at 35°C for 24 hours. The zones of inhibition were determined whether the microorganism was susceptible, intermediately resistant, or resistant to each antibiotic.