Enhancing chloramphenicol and trimethoprim in vitro activity by Ocimum sanctum Linn. (Lamiaceae) leaf extract against Salmonella enterica serovar Typhi.
OBJECTIVE
To evaluate the antibacterial activity of Ocimum sanctum (O. sanctum) leaf extract, alone, and in combination with chloramphenicol (C) and trimethoprim (Tm) against Salmonella enterica serovar Typhi (S. typhi).


METHODS
The antibacterial activity of ethanolic extract of tulsi, O. sanctum, leaf (TLE; 500 μg) for 23 S. typhi isolates was determined following agar diffusion. The C (30 μg) and Tm (5 μg) activity alone and in combination with TLE (250 μg) was determined by disk diffusion. The zone diameter of inhibition (ZDI) for the agents was recorded, and growth inhibitory indices (GIIs) were calculated.


RESULTS
The S. typhi isolates (n=23), which were resistant to both C (ZDI 6 mm) and Tm (ZDI 6 mm), had TLE (500 μg) ZDIs 16-24 mm. The ZDIs of C and Tm were increased up to 15-21 mm and 17-23 mm, respectively, when TLE (250 μg) was added to the C and Tm discs. The GIIs ranged 0.789-1.235 and 0.894-1.352, due to combined activity against S. typhi isolates, of C and TLE and Tm and TLE, respectively.


CONCLUSIONS
The data suggest that TLE, in combination with C and Tm, had synergistic activity for S. typhi isolates, and hence O. sanctum is potential in combating S. typhi drug resistance, as well promising in the development of non-antibiotic drug for S. typhi infection.
Department of Microbiology, Bacteriology and Serology Unit, Calcutta School of Tropical Medicine, Kolkata, India. samtropmed@gmail.com
Shyamapada
S
Mandal
Manisha Deb
MD
Mandal
Nishith Kumar
NK
Pal
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002701:Chloramphenicol / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects; D004357:Drug Synergism; D006801:Humans; D031339:Ocimum / Q000737:chemistry*; D010936:Plant Extracts / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry; D012485:Salmonella typhi / Q000187:drug effects*; D014295:Trimethoprim / Q000494:pharmacology*; D014435:Typhoid Fever / Q000188:drug therapy
D000900:Anti-Bacterial Agents; D010936:Plant Extracts; D002701:Chloramphenicol; D014295:Trimethoprim