In Vitro Antimicrobial Activity of Stem Bark Extract of Azadirachta indica A. (JUSS) Against Antibiotic Resistant Salmonella enterica Serovar Typhi

Abstract

Typhoid fever treatment failure due to emergence of antibiotics resistant Salmonella enterica serovar Typhi has become a matter of concern to public health sector. This study was aimed at investigating the in vitro antimicrobial activity of stem bark extracts of Azadirachta indica A. (JUSS) against antibiotic resistant Salmonella enterica serovar Typhi isolates from stool samples of patients manifesting clinical features of typhoid fever. Fortyseven (47) isolates were identified as Salmonella sp. using conventional biochemical test, Microbact TM 12A/12E Gram-negative kits, and confirmed molecularly using ompC primers. Twelve (12) isolates out of the 47 were Salmonella enterica serovar Typhi identified serologically and confirmed molecularly using STY4220 primers. Antibiotics resistance profile of the Salmonella enterica serovar Typhi isolates showed that 12 (100%) were resistance to amoxicillin and amoxicillin/clavulanic acid, 9 (75%) resistance to tetracycline, cotrimoxazole and cefotaxime, 6 (50%) resistance to ceftriaxone, 3 (25%) resistance to nitrofurantoin, 2 (17%) resistance to chloramphenicol, 1 (8%) resistance to ofloxacin and ciprofloxacin; while 12 (100%) were sensitive to nalidixic acid and imipenem. Qualitative phytochemical and spectroscopic analysis of Azadirachta indica stem bark extracts revealed the presence of tannins, alkaloids, flavonoids, glycosides, saponins, phenolic and other organic compounds. At concentrations of 25-400 mg/ml, potency test of acetone and ethanolic bark extracts of the plant against the Salmonella enterica serovar Typhi isolates produced diameter zones of growth inhibition ranges from 18-35 mm and 15-31 mm respectively. The minimum inhibitory concentrations values of the extracts against the isolates also ranged from 50-100 mg/ml. It may be concluded from this results that the bark extracts of Azadirachta indica A. (JUSS) have good growth inhibitory effects against the antibiotics resistant Salmonella enterica serovar Typhi and can be developed further for chemotherapeutic application.