Lincomycin

The pattern of antimicrobial resistance was studied using the simple disk diffusion technique. The Mueller–Hinton agar (Merck, Germany) medium was used for this purpose. Antibiotic resistance of the MRSA strains against 18 commonly used antibiotics was determined using the instructions provided by the Clinical and Laboratory Standards Institute guidelines (18 ). Susceptibility of MRSA isolates was tested against ampicillin (10 µg/disk), gentamycin (10 µg/disk), lincomycin (2 µg/disk), cephalothin (30 µg/disk), imipenem (30 µg/disk), tetracycline (30 µg/disk), vancomycin (5 µg/disk), ciprofloxacin (5 µg/disk), norfloxacin (30 µg/disk), cotrimoxazole (30 µg/disk), clindamycin (2 µg/disk), trimethoprim-sulfamethoxazole (25 μg/disk), penicillin (10 µg/disk), oxacillin (1 µg/disk), erythromycin (15 µg/disk), azithromycin (15 µg/disk), ceftriaxone (30 µg/disk) and cefixime (5 µg/disk) antibiotic agents (Oxoid, UK). The plates containing the discs were allowed to stand for at least 30 minutes before incubation at 35°C for 24 hours. The diameter of the zone of inhibition produced by each antibiotic disc was measured and interpreted using the CLSI zone diameter interpretative standards (18 ). Staphylococcus aureus ATCC 25923 and Escherichia coli (E. coli) ATCC 25922 were used as quality control organisms in antimicrobial susceptibility determination.

The antimicrobial susceptibility of the 76 E. faecalis isolates was tested by broth microdilution using 13 antimicrobials. Susceptibility to vancomycin (0.25–128 mg l⁻¹), linezolid (0.25–128 mg l⁻¹), penicillin (0.25–128 mg l⁻¹), ampicillin (0.125–64 mg l⁻¹), gentamicin (2–1024 mg l⁻¹), streptomycin (4–2,048 mg l⁻¹), kanamycin (4–2,048 mg l⁻¹), tetracycline (0.25–128 mg l⁻¹), tigecycline (0.03–2 mg l⁻¹), erythromycin (0.125–64 mg l⁻¹), lincomycin (0.5-256 mg l⁻¹), ciprofloxacin (0.125-64 mg l⁻¹), and chloramphenicol (0.25–128 mg l⁻¹) (Oxoid, UK) was determined. E. faecalis ATCC 29212 was used as a quality control strain.
Susceptibility tests were performed according to recommendations by the Clinical and Laboratory Standards Institute (CLSI, 2015a ). MICs (minimal inhibitory concentrations) were evaluated based on the interpretative criteria of CLSI (CLSI, 2015c ) supplement VET01S for vancomycin, penicillin, ampicillin, erythromycin, tetracycline, doxycycline, and chloramphenicol for Enterococcus spp.; CLSI (CLSI, 2015b ) document M100-S25 for ciprofloxacin for Enterococcus spp.; and Comité de l´antibiogramme de la Société Française de Microbiologie (CA-SFM) (CA-SFM, 2015 ) for lincomycin and all aminoglycosides for Streptococcus spp.

The following 8 antibiotic agents of 5 different groups; macrolides, fluoroquinolones, tetracyclines, lincosamide, and pleuromutilins were used for the susceptibility tests: tylvalosin (Pharmgate Animal Health Canada, Inc), tilmicosin (ELANCO, Geneva), tylosin (ELANCO, USA), enrofloxacin (INVESA, Spain), doxycycline (Oxoid, UK), chlortetracycline (Oxoid, UK), lincomycin (Oxoid, UK), and tiamulin (Sandoz GmbH, Basel, Switzerland).