Intracellular and membrane-damaging activities of methyl gallate isolated from Terminalia chebula against multidrug-resistant Shigella spp.
Shigella spp. (Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei) cause bacillary dysentery (shigellosis), which is characterized by bloody mucous diarrhoea. Although a variety of antibiotics have been effective for treatment of shigellosis, options are becoming limited due to globally emerging drug resistance. In the present study, in vitro antibacterial activity of methyl gallate (MG) isolated from Terminalia chebula was determined by performing MIC, minimal bactericidal concentration (MBC) and time-kill kinetic studies. Bacterial membrane-damaging activity of MG was determined by membrane perturbation and transmission electron microscopy (TEM). Cellular drug accumulation, cell infection and assessment of intracellular activities of MG and reference antibiotics were performed using HeLa cell cultures. The bactericidal activity of MG against multidrug-resistant (MDR) Shigella spp. in comparison with other commonly used drugs including fluoroquinolone was demonstrated here. TEM findings in the present study revealed that MG caused the total disintegration of inner and outer membranes, and leakage of the cytoplasmic contents of S. dysenteriae. The level of accumulation of MG and tetracycline in HeLa cells incubated for 24  h was relatively higher than that of ciprofloxacin and nalidixic acid (ratio of intracellular concentration/extracellular concentration of antibiotic for MG and tetracycline>ciprofloxacin and nalidixic acid). The viable number of intracellular S. dysenteriae was decreased in a time-dependent manner in the presence of MG (4 × MBC) and reduced to zero within 20  h. The significant intracellular activities of MG suggested that it could potentially be used as an effective antibacterial agent for the treatment of severe infections caused by MDR Shigella spp.
Department of Biochemistry, University of Calcutta, 35 Ballygunge, Circular Road, Kolkata 700019, India.
Saurabh
S
Acharyya
Department of Biochemistry, University of Calcutta, 35 Ballygunge, Circular Road, Kolkata 700019, India.
Prodipta
P
Sarkar
National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme-XM, Beliaghata, Kolkata 700010, India.
Dhira R
DR
Saha
Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700009, India.
Amarendra
A
Patra
National Institute of Cholera and Enteric Diseases, P-33 CIT Road, Scheme-XM, Beliaghata, Kolkata 700010, India.
T
T
Ramamurthy
Department of Biochemistry, University of Calcutta, 35 Ballygunge, Circular Road, Kolkata 700019, India.
Prasanta K
PK
Bag
D000900:Anti-Bacterial Agents / Q000302:isolation & purification / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects*; D003593:Cytoplasm / Q000187:drug effects*; D004847:Epithelial Cells / Q000382:microbiology; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D046529:Microscopy, Electron, Transmission; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D012760:Shigella / Q000187:drug effects*; D029766:Terminalia / Q000737:chemistry*; D013997:Time Factors
D000900:Anti-Bacterial Agents; D010936:Plant Extracts; C052082:methyl gallate; D005707:Gallic Acid