Clindamycin

All the identified S. aureus isolates were subjected to an in vitro antimicrobial susceptibility test by employing the modified Kirby–Bauer disc diffusion method as recommended by Clinical and Laboratory Standard Institute (CLSI) guidelines [19 ]. The antimicrobial disks used were ampicillin (30 μg), cefoxitin (30 μg), chloramphenicol (30 μg), ciprofloxacin (25 μg), clindamycin (31 μg), cotrimoxazole (25 μg), erythromycin (26 μg), gentamycin (28 μg), linezolid (30 μg), oxacillin (10 μg), tetracycline (20 μg), and penicillin (10 μg) from HiMedia, India.

The antibiotic susceptibility tests of the isolated organisms were done using Mueller Hinton Agar (MHA) by the standard disk diffusion technique of the Kirby-Bauer method as recommended by CLSI [21 ]. The following antibiotics with specified concentrations were used: ampicillin (10 μg), ampicillin-sulbactam (10/10 μg), amoxycillin-clavulanic acid (20/10 μg), cefixime (5 μg), ceftazidime (30 μg), ceftriaxone (30 μg), cefepime (30 μg), cefoxitin (30 μg), piperacillin (100 μg), piperacillin-tazobactam (100/10 μg), cotrimoxazole (1.25/23.75 μg), gentamicin (10 μg), amikacin (30 μg), imipenem (10 μg), meropenem (10 μg), ciprofloxacin (5 μg), levofloxacin (5 μg), colistin sulfate (10 μg), erythromycin (15 μg), clindamycin (2 μg), vancomycin (30 μg), teicoplanin (30 μg), doxycycline (30 μg), and chloramphenicol (30 μg) from HiMedia Laboratories, India.

The swabs collected were directly inoculated in duplicate on blood agar, (Oxoid) Mac Conkey agar and Muller Hinton agar (Oxoid). The pairs of inoculated media were incubated aerobically at 37 °C for 24 h and then examined for bacteria growth according to standard protocol [14 ]. The positive culture growths were examined for colony characteristics, Gram-reaction and biochemical characteristics as described by Cheesbrough (2000) [14 ]. The biochemical characteristics tested were: (i) catalase, (ii) coagulase, (iii) oxidase, (iv) hemolysis, (v) sugar fermentation, (vi) indole production, (vii) citrate utilization, (viii) urease activity, (ix) triple sugar iron and (x) hydrogen sulphide production.
Purified bacterial isolates were subjected to drug susceptibility tests using the Kirby Bauer disc diffusion method [14 ]. Commercially available antibiotic discs that were used include: ciprofloxacin, norfloxacin, gentamycin, erythromycin, clindamycin, cephalexin, co-trimoxazole, tetracycline, cefoxitin, ampicillin, vancomycin and chloramphenicol (Hi Media Laboratories Pvt. Ltd, India). These antibiotics were chosen based on the type of microorganisms frequently isolated and their availability at University Teaching Hospital.

The antimicrobial susceptibility testing of MRSA was detected using
the modified Kirby-Bauer disk diffusion method according to the clinical
laboratory standard institute (CLSI) guidelines (CLSI 2013 ). The following antimicrobials were used in
their respective concentration: Ciprofloxacin (5 μg),
Trimethoprim-Sulfamethoxazole (1.25/23.75 μg), Erythromycin (15 μg), Clindamycin
(2 μg), and Amikacin (30 μg) (Hi-Media, India). These antimicrobials were selected
based on the local usage to treat MRSA and considering the recommended
antimicrobial agents for MRSA infections.

Antibiotic susceptibility testing was performed by the Kirby–Bauer disk-diffusion method on Mueller–Hinton agar supplemented with 5% sheep blood for the following antimicrobial agents: penicillin (10 U), ampicillin (10 µg), erythromycin (15 µg), clindamycin (2 µg), ofloxacin (5 µg), cefotaxime (30 µg), linezolid (30 µg), and vancomycin (30 µg) (HiMedia Laboratories, Mumbai). The inoculum for susceptibility testing and interpretation was performed as per the Clinical and Laboratory Standards Institute (CLSI) guidelines [14 ].

The antibacterial activity was evaluated by the double micro-dilution method for the determination of minimum inhibitory (MIC) and bactericidal concentration (MBC) against six clinical bacterial strains and two Candida strains isolated from pregnant women with symptoms of vaginal infections according to the standard CLSI procedure and previously described methods [47 ,48 ]. Two Gram-positive (S. aureus MRSA, Enterococcus sp.) and four Gram-negative strains (Escherichia coli, Proteus mirabilis, Proteus vulgaris and Pseudomonas aeruginosa) were used to determine the antibacterial activity. The testing of antifungal activities was determined on C. albicans strains. Two laboratory strains were obtained from the Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, and four clinical isolates were obtained from the Faculty of Medicine, Clinical Center of Vojvodina, Department of Obstetrics and Gynecology, isolated during regular gynecological examination in women. Their use was approved by the Ethics Committee of the Faculty of Medicine. Microtiter plates were incubated in a thermostat for 24 h at 37 °C, and MIC and MBC were determined. The disk-diffusion method was applied for bacterial susceptibility of standard antibiotics (Himedia, Einhausen, Germany): erythromycin, clindamycin, ciprofloxacin, gentamicin, ofloxacin, chloramphenicol and levofloxacin.