Bacillus Cereus isolation and load from raw cow milk sold in Markets of Haramaya District, eastern Ethiopia

Ashebr Abraha,Sisay Alemu,Yimer Muktar,Teshome Bikila

doi:10.1186/s40550-017-0060-z

Ashebr Abraha, Sisay Alemu + Show 2 more

Open Access

https://doi.org/10.1186/s40550-017-0060-z

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Abstract

BackgroundBacillus cereus is a spore-forming bacterium that is widely distributed in the environment and can be detected in a variety of raw milk and milk products especially in vegetative form, which exposed directly in contact with the soil and produces toxins which caused food borne illness and considered as a significant public health hazard. A cross-sectional study was carried out to determine the prevalence and load of Bacillus cereus vegetative cells in raw bulk milk sold in market places at Bate, Haramaya and Aweday Towns, Eastern Ethiopia as well as to assess the in-vitro antimicrobial susceptibility of isolates. A total of 103 raw milk samples were collected and examined for the presence of Bacillus cereus by using Bacillus cereus selective agar media. The isolated presumptive colonies were further analyzed using standard microbiological methods to confirm the presence of Bacillus cereus. Spreading plate method was employed to count the bacteria from milk samples based on 10 fold serial dilutions. For antimicrobial susceptibility test, the disc diffusion test was employed using commercially available 10 antimicrobial discs.ResultsThe overall prevalence’s of Bacillus cereus in raw milk samples was 38.8%. Milk collected from Aweday market showed higher occurrence (46.9%) than from Bate (40%) and Haramaya town (31.7%). Analysis of bacterial count showed that, 60% of Bacillus cereus positive milk samples were with bacterial load above recommended limit (>105CFU/ml) for human consumption. However, there was no statistically significant difference (p > 0.05) on the occurrence of Bacillus cereus and bacterial load among different areas. Based on disc diffusion test, B. cereus isolates showed high resistance to Penicillin (100%), Ampicillin (100%), Amoxicillin (80%) and Cefoxitin (80%).ConclusionThe study indicated that milk samples from market areas were highly contaminated with Bacillus cereus, with potential risk for human consumption. This suggests the need for effective hygienic measures to be introduced during milk production and distribution to avoid public health hazards.

Highlights

Bacillus cereus is a spore-forming bacterium that is widely distributed in the environment and can be detected in a variety of raw milk and milk products especially in vegetative form, which exposed directly in contact with the soil and produces toxins which caused food borne illness and considered as a significant public health hazard
The objectives of the study were; to determine the occurrence of Bacillus cereus in raw bulk milk samples collected from market areas at Haramaya district; to evaluate Bacillus cereus load in raw milk samples and assess the susceptibility patterns of Bacillus cereus isolates to commercially available antimicrobials
Prevalence of Bacillus cereus The overall prevalence of Bacillus cereus in raw bulk milk was 38.8%, and the highest score was recorded from Aweday market followed by Bate and Haramaya town (Table 2)

Summary

Introduction

Bacillus cereus is a spore-forming bacterium that is widely distributed in the environment and can be detected in a variety of raw milk and milk products especially in vegetative form, which exposed directly in contact with the soil and produces toxins which caused food borne illness and considered as a significant public health hazard. Bacillus cereus is a facultative anaerobic, motile, grampositive, catalase positive, does not ferment mannitol, rod-shape, beta-hemolytic and spore-forming bacterium; that is widely distributed in the environment due to its ability to resist hostile conditions (Ceuppens et al 2013) and growth temperature ranging from 10 to 48 °C with optimal growth between 28 °C and 35 °C, pH values of 4.9 to 9.3 and water activities of 0.92 to 1.0 (OSPBH 2005) Another important trait of Bacillus cereus is their ability to grow at the storage temperature of milk (4–7 °C), which mainly determines the shelf life of pasteurized milk and derived milk products (TeGiffel et al 1995; Granum 2005). The unique nature of Bacillus cereus like heat resistance, endospore forming abilities, toxin production and psychrotrophic feature (ability to growing below 7 °C) gives ample scope for this organism to be a prime cause of public health hazard (Griffiths and Schraft 2002)

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