In vitro Antagonistic Activity of Bifidobacterium breve Isolated from Breast-fed Infants Human Gastrointestinal Microflora against Two Clinical Strains of Staphylococcus aureus (MRSA and MSSA)

The antibacterial activity of Bifidobacterium breve against methicillin-resistant Staphylococcus aureus MRSA from human middle ear infection (otitis media) as well as methicillin-susceptible Staphylococcus aureus (MSSA) strain was tested in vitro. MRSAis a multidrug-resistant microorganism and the principal nosocomial pathogen worldwide. The Bifidobacterium breve (b1, b2, b3 and b4) strains which isolated from healthy human infants were employed. All the Bifidobacterium isolates mentioned above have been identified as novel probiotics with a greater ability to survive at low pH and high concentrations of bile salt in vitro, and with a growth rate of 3.5-4.5 and 5.5% in NaCl solution. The growth inhibitory effect produced by the antagonistic activity of the lactic acid bacteria on the MRSA and MSSA strains was tested on solid medium using agar spot test.

All bifidobacteria Cells (b1, b2 and b4) except (b3) showed high antibacterial activity after 24 h of their incubation anaerobically at 37°C with significance differences (P≤ 0.05). MRS media (control) showed no activity. No significant differences appeared between MRSA and MSSA strains with antagonistic activity of bifidobacterial cells against both of them. In contrast the antibacterial activity of lactic acid bacteria (LAB) under the current study was more potent than the activity of ofloxacin (positive control).