Mastitis, inflammatory disease of mammary glands, can be caused by various microorganisms.
Many antimicrobial agents have been evaluated to combat the causative agents. Development of
resistance in pathogens against conventional antibiotics may be high; hence at present study in vitro
efficacy of a new fluoroquinolone antibiotic (marbofloxacin) against isolated pathogens from clinical
mastitis was examined. Milk samples (73) were taken from 28 dairy farms around Shiraz.
Staphylococcus aureus (24.1%), Escherichia coli (18.1%), Streptococcus dysgalactiae (9.3%),
Corynebacterium bovis (9.3%), Staphylococcus epidermidis (3.7%) and Pseudomonas aeruginosa
(3.7%) were identified among 54 bacterial isolates. Antibiotic sensitivity test (Kirby-Bauer method)
was carried out for marbofloxacin, enrofloxacin, gentamicin, penicillin and tetracycline. Minimum
inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of marbofloxacin
against sensitive bacteria were also determined. Results showed that we all isolated bacteria were
sensitive to marbofloxacin, sensitivities against other antibiotics varied from zero to 94.1%. The
values obtained as MIC and MBC of marbofloxacin against three bacterial isolates (Staphylococcus
aureus, Streptococcus agalactiae, and Staphylococcus epidermidis) were in the range of 0.2 to 1.56?
g/ml and 0.8 to 6.25?g/ml, respectively. Since the isolated bacteria showed adequate sensitivities to
fluroquinolones, it is concluded that marbofloxacin can successfully be used for treatment of affected
cows with clinical mastitis