Shigellocidal properties of three Nigerian medicinal plants: Ocimum gratissimum, Terminalia avicennoides, and Momordica balsamina.

The prevalence of multidrug-resistant shigellae is an important concern in the treatment of shigellosis in many developing countries, and other therapies, including herbal agents, may provide an important alternative to antimicrobial agents. In this study, three Nigerian medicinal plants: Ocimum gratissimum, Terminalia avicennoides, and Momordica balsamina were investigated for their activities against multidrug-resistant Shigella species isolated from patients with bacilliary dysentery in Lagos. Decoctions of O. gratissimum and concoctions of O. gratissimum and T. avicennoides at crude concentration of 3,000 micrograms/mL markedly inhibited the growth of all isolates tested. Zones of inhibition indicating susceptibilities of the organisms varied from 18.3 to 21.5 mm for Shigella dysenteriae, 15.3 to 16.3 mm for S. flexneri, 18.8 to 19.3 mm for S. sonnei, and 16.5 mm for S. boydii. Except S. flexneri, minimum inhibitory concentration and minimum bactericidal concentration revealed a higher shigellocidal property of O. gratissimum/T. avicennoides concoction than other extracts in S. dysenteriae (300-515.6 vs 337.5-1,312.5 micrograms/mL), S. sonnei (309.4-543.8 vs 403.1-1,312.5 micrograms/mL), and S. boydii (243.8-337.5 vs 253-1,312.5 micrograms/mL). O. gratissimum showed a greater shigellocidal effect against the S. flexneri isolates, while extracts of M. balsamina possessed low shigellocidal potential. The results suggest that aqueous extracts of O. gratissimum and T. avicennoides as decoctions and concoctions could be useful in the treatment of shigellosis and should be clinically evaluated specially in Nigerian region.

Epidemiology of shigellosis in Lagos, Nigeria: trends in antimicrobial resistance.

Antimicrobial susceptibility of Shigella spp. and Escherichia coli, isolated from diarrhoeal patients in Lagos, was studied from March 1999 to February 2000. Four hundred fifty-nine isolates were identified as shigellae (62) and E. coli (397). Shigella flexneri, S. dysenteriae, S. boydii, and S. sonnei accounted, respectively, for 51.6%, 17.7%, 17.7%, and 13% of the total number of shigellae isolated. Eleven cases of shigellosis occurred in the age group of 0-9 years, 22 cases in the age group of 10-19 years, and 29 cases in the age group of > or = 20 years. Of the 397 E. coli isolates, 11 were enteropathogenic E. coli (EPEC), and 7 of these strains were isolated with shigellae from stools of patients aged 0-9 year(s) (71.4%) and 10-19 years (28.6%). Over 70% of the Shigella isolates were resistant to two or more drugs, including ampicillin and tetracycline. Twenty-one distinct multidrug resistance patterns were observed in these isolates. During 1990-2000, resistance to ampicillin increased from 70% to 90%, co-trimoxazole from 77% to 85%, chloramphenicol from 71% to 77%, streptomycin from 71% to 79%, and nalidixic acid from 0% to 11.3%. Resistance to tetracycline decreased from 89% to 79% but with MIC50 and MIC90 values outside the susceptible range. While resistance to ciprofloxacin and ofloxacin remained nil with MIC50 and MIC90 values of 0.008 and 0.0016 microgram/mL respectively. The results of this study revealed the endemicity of shigellosis with S. flexneri as the predominant serogroup in Lagos. Children and young adults were at a higher risk of severe shigellosis. The results also suggest that ampicillin, tetracycline, co-trimoxazole, and streptomycin should not be used as the first-line drugs in the treatment of shigellosis. Nalidixic acid should still be selectively used for treatment, while ciprofloxacin and ofloxacin can be ideal alternatives.