The antibacterial and antibiofilm activity of Lactobacillus acidophilus isolated from vagina against methicillin-resistant Staphylococcus aureus

Background Bacterial infections caused by the genus Staphylococcus represent a grave threat to both humans and animals, and they are a major concern to health authorities. Over the past few decades, methicillin-resistant Staphylococcus aureus (MRSA) has been recognized as the principal nosocomial pathogen worldwide. Objective To investigate the antibacterial and antibiofilm activity of Lactobacillus acidophilus against locally isolated MRSA at different concentrations. Materials and methods MRSA isolates were tested against some antibiotics for testing antibiotic sensitivity. The antibacterial activity of L. acidophilus based on the minimal inhibitory concentration (MIC) of L. acidophilus that inhibits the visible growth of MRSA isolates was assessed using the microdilution method. Estimation of MIC of L. acidophilus was done. Biofilm quantification assay was then used for the determination of the antibiofilm activity of L. acidophilus. The MIC concentration was assessed by a microtiter reader. Results and conclusion The antibacterial activity was tested by agar diffusion method and broth microdilution method. The microdilution method was used to determine the MIC of L. acidophilus, whereas the antibiofilm activity was determined by using 96-well polystyrene microtiter plates. The results revealed that L. acidophilus has antibacterial activity in a concentration-dependent manner. The average diameter zone of inhibition observed against MRSA isolates ranged from 11 +/- 0.5 to 18 +/- 0.5 mm Moreover, at subinhibitory concentration, this extract developed an isolate-specific antibiofilm effect and presented highly significant (P < 0.05) variability in biofilm formation before and after addition of L. acidophilus. AA3 and AA12 isolates gave the lowest and highest antibiofilm activity, respectively. In conclusion, the supernatant of L. acidophilus is a promising alternative medication that can be used to treat the infection caused by MRSA.