The objective of this work was to identify isolated Staphylococcus species
and to investigate their sensitivity to some antibacterial drugs. The
material used for these investigations were Staphylococcus isolates
originating from milk samples. A total of 25 strains of Staphylococcus
isolates were examined, including 24 from milk samples from cows with
mastitis, and one strain was isolated from a milk sample from a cow following
treatment for mastitis. For primary identification, catalase and oxidase
tests were used, as well as the free coagulase test. Following the
preliminary tests, the isolated strains were identified using commercial
systems ID32 STAPH (bioM?rieux, France) and the BBL Crystal Gram-Positive ID
Kit (Becton Dickinson, USA) according to the enclosed instructions. The
Staphylococcus isolates were examined for sensitivity to the following:
oxacillin, penicillin, cefoxitin, gentamicin, erythromycin, chloramphenicol,
tetracycline, ciprofloxacin, sulfametoxazol/trimetoprim, and vacomycin using
the disk diffusion method and the broth microdilution method as recommended
by the Clinical and Laboratory Strandards Institute - CLSI(2003), and the
results were interpreted according to CLSI recommendations from 2008 and
2010. Antibiogram disks manufactured by Becton Dickinson (USA) were used, and
the broth microdilution method was applied using pure antibiotic substances
from different manufacturers: erythromycin, chloramphenicol, cefoxitin,
gentamicin, oxacillin, tetracycline (Sigma Aldrich, USA), sulfametoxazol
(Fluka, USA), penicillin (Calbiochem, Germany), vancomycin (Abbott
laboratories, USA), ciprofloxacin and trimetoprim (Zdravlje A.D., Serbia).
All 25 strains were catalase positive and oxidase negative. Of the 25
strains, 19 were coagulase positive and 6 were coagulase negative.With the
implementation of the disk diffusion method on 19 strains of S. aureus, 17
were established to be resistant to penicillin (89.5%), and 2 strains to
gentamicin (10.5%). The investigation of 3 strains of S. xylosus using the
disk diffusion method showed that one strain was resistant to tetracycline
(33.3%) and to oxacillin (33.3%), while another strain was found to be
resistant to penicillin (33.3%). The third strain of S. xylosus was sensitive
to all the examined antibiotics. Two strains of S. simulans and one strain of
S. haemolyticus were not found to be resistant to any of the examined
antibiotics using the disk diffusion method. The implementation of the broth
microdilution method yielded in 13 strains of S. aureus resistance to
penicillin (68.4%) with MIC values from 0.5 to 4 ?g/m, in 2 strains to
gentamicin (10.5%) with MIC values of 32 ?g/ml, and intermediary sensitivity
to chloramphenicol was established in 9 strains of S. aureus (47.4%) with MIC
values of 16 ?g/ml and to vancomycin in 1 strain of S. aureus (5.3%) with MIC
values of 4 ?g/ml.