Activities of Macrolides in Combination with Vitamin D against Bacillus cereus Isolated from Soil of a Lanfill Site in Nsukka South East Nigeria

Background: The fast moving world of antibiotics resistance is now a big concern, since our antibiotics are in danger of extinction. This is a concern to us because; an empty ‘antibiotic pipeline’ leads to devastating future.

Aim: The aim of this study was to isolate Bacillus cereus from soil contaminated with various toxic and domestic wastes and investigate its sensitivity to macrolide antibiotics (erythromycin ERY and azithromycin AZM) in combination with vitamin D supplement.

Methodology: Five soil samples were collected from a landfill site and serially diluted up to 10ˉ6. B. cereus was isolated from the soil sample using Mannitol egg Yolk Polymyxin agar medium (MYP), a selective nutrient medium for B. cereus isolation. The sensitivity of B. cereus to erythromycin and azithromycin was screened in Mueller-Hinton agar (MHA) containing varying concentrations (5, 10, 20 mg/ml) of vitamin D. Agar without vitamin D (0.00mg/ml) served as the control. The activities of ERY and AZM in combination with vitamin D were determined by measuring the zones of inhibition.

Results: In vitro antibiotic susceptibility tests on our isolate showed maximum sensitivity to ERY and maximum resistance to AZM with 0.00 mg/ml (no combination) of vitamin D. Contrarily, ERY was found to be least active, with the zones of inhibitions decreasing from 28mm to 16mm, with increasing concentration of vitamin D. On the other hand, AZM achieved maximum sensitivity from 12mm to 25mm, with increasing concentration of vitamin D.

Conclusion: The activities appeared to be important but dose-dependent. So, the systematic use of Vitamin D in combination with macrolide antibiotics may be efficient in treating food and soil infections caused B. cereus. However, in vivo evaluation of these activities is needed.