Microbial contamination and antimicrobial susceptibility pattern of bacterial isolates from sorghum and millet derived local beverage (Obushera) consumed in Mbarara City, Ugand

Abstract

The high consumption and unconventional manner in which locally derived sorghum and millet beverages (Obushera) are processed in Uganda prompted the need to establish microbial safety of the beverages. Microbial contamination and its variation with storage time and temperature, antibiotic susceptibility of pathogenic bacterial isolates, and nutritional content of Obushera (n = 96) were determined. Handling and hygiene practices of processors and vendors of Obushera (n = 28) were also determined. Among the four categories of Obushera found in Mbarara city, Ekitiribita had the highest total viable counts (TVC) with a median of 4.62 log CFU/ml, followed by Obwenkiga and Obutiire with a median of 4.31 and 4.25 log CFU/ml, respectively. Microbial contaminants isolated included: Providencia spp.7(7.3%), Coagulase-positive Staphylococci 23(24%), Pseudomonas spp.3(3.1%), Enterobacter cloacae 12 (12.5%), Enterobacter aerogens 3 (3.1%), Proteus vulgaris 15(15.6%), Klebsiella spp. 13(13.5%), Streptococcus spp. 7(7.3%), and Escherichia coli 11 (11.5%). Saccharomyces cerevisiae (65.6%), Candida spp. (28.1%), Mucor spp. and Aspergillus niger accounted for 52.1% contamination of all samples. The above microbial contaminants persisted with storage except Providencia spp., Proteus vulgaris, Mucor spp. and Aspergillus niger. Microbial and nutritional analyses showed a positive significant correlation between microbial counts and amino acid, carbohydrates, reducing sugar concentration and pH in Obushera (p-value < 0.05). All isolated strains of bacteria were resistant to more than one family of antibiotics used. The review of hygiene and handling practices revealed that they did not conform to good manufacturing practices neither did they meet the East African Standards of < 2 log10 CFU/ml TVC. Overall, this study revealed that Obushera consumed in Mbarara City, Uganda, is a high-risk beverage due to the high rate of microbial contamination and antibiotic resistance.