Clindamycin

The antimicrobial susceptibility was performed by the disk diffusion method according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) [9 ]. Fifteen antimicrobial agents on Mueller-Hinton agar plates (Becton Dickinson, Franklin Lakes, NJ, USA) were tested: oxacillin, cefoxitin, gentamicin, erythromycin, clindamycin, tetracycline, chloramphenicol, ciprofloxacin, trimethoprim/sulfamethoxazole, fusidic acid, linezolid, rifampicin, tigecycline and vancomycin (Bio-Rad, Marnes la Coquette, France) and penicillin G (Oxoid, Basingstoke, England). The phenotype of resistance to macrolide-lincosamide-streptogramin B was tested and interpreted according to the EUCAST. vancomycin susceptibility was determined with E-test method (bioMerieux, Marcy-l’Etoile, France). Multidrug resistance (MDR) was defined as a resistance to three or more classes of antibiotics.

Susceptibility to cefoxitin, chloramphenicol, ciprofloxacin, clindamycin, fusidic acid, erythromycin, gentamicin, kanamycin, linezolid, mupirocin, quinupristin-dalfopristin, penicillin, rifampin, tetracycline, tobramycin and trimethoprim/sulfamethoxazole (BioRad, USA) was performed by disk diffusion method and to vancomycin and teicoplanic by Etest (bioMérieux, France) in accordance to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommendation (http://www.eucast.org). Multidrug resistance (MDR) was defined as resistance of MRSA to three or more district antimicrobial classes in addition to beta-lactams.

The MRSA isolates were tested for antibiotic susceptibility by disc diffusion test using the following discs: chloramphenicol (30 μg), ciprofloxacin (5 μg), clindamycin (2 μg), fusidic acid (10 μg), gentamycin (10 μg), erythromycin (15 μg), imipenem (10 μg), rifampicin (5 μg), tetracycline (30 μg), trimethoprim/sulfamethoxazole (1.25 + 23.75 μg) and vancomycin (30 μg) (BioRad, USA). The rates of susceptibility and resistance of isolated MRSA strains to the used antibiotic discs were detected.

Susceptibility to penicillin, cefoxitin, erythromycin, clindamycin, fusidic acid, gentamicin, ciprofloxacin, levofloxacin, rifampin, tetracycline and trimethoprim/sulfamethoxazole (BioRad, USA) was determined by the disk diffusion method and to vancomycin and teicoplanin by gradient E test (bioMérieux) in accordance with the EUCAST recommendation (http://www.eucast.org).

Fresh bacterial cultures were streaked in triplicate on base blood agar plates with 5% (v/v) horse blood and incubated at 30°C for 48 h. Blood agar plates were checked for β-haemolysis, α-haemolysis, or γ-haemolysis [35 (link)]. Susceptibility to antibiotics was determined by using the disk diffusion method on Muller Hinton agar (MHA) plates supplemented with 0.2% glucose and 0.4% yeast extract. The antibiotics used were ampicillin (AM; 10 μg), chloramphenicol (C; 30 μg), erythromycin (E; 15 μg), tetracycline (TE; 30 μg), clindamycin (CL; 2 μg), rifampicin (RA; 5 μg), and vancomycin (VAN; 30 μg) (Bio-Rad Laboratories, Hercules, CA, USA). MH plates were overlaid with soft MHA (containing 0.7% agar) inoculated at 0.5 McFarland with fresh bacterial culture. After 24 h of incubation at 37°C, the inhibition zone diameters around discs were measured, and the LAB isolates were categorized, according to the standard criteria [36 ], as resistant (R), intermediate resistant (I), or sensitive (S).