Incidence of spore-forming bacteria in certain dairy products , with emphasis on factors affecting their germination
Abstract: The present study aimed to isolate and characterize strains of spore forming bacteria from traditional Egyptian dairy products. The study also examined the effect of nutrient factors on spores germination of spore forming bacteria isolated from Egyptian dairy products . An assessment of antibiotic response of spore forming isolates recovered from Egyptian dairy products has been also conducted. Results generated throughout this study can be summarized as follows:
Part One: Prevalence of spore-formers associated with milk and dairy products processing in Mansoura city.
• Ninety samples of traditional milk and dairy products were randomly collected from local markets in Mansoura city. These samples included 30 raw milk samples, 15 UHT milk samples, 15 skim milk powder samples, 15 Ras cheese samples and 15 Domiati cheese samples
• The total viable count of raw milk samples were ranged from 10.06 to 10.66 log cfu/ml. The total viable counts of Ras cheese and Domiati cheese varied from 8.78 to 9.35 and 9.28 to 9.65 log cfu/ml, respectively. The total viable count of skim milk powder was ranged from 4.00 to 4.87 log cfu/ml.
• Out of 388 suspected isolates, 87 isolates were identified as potential aerobic spore forming bacilli. These results could present contamination of milk and dairy product plants with aerobic spore forming bacteria that exist in raw milk may resist the effect of pasteurization and other processing factors until they reached to final products. Out of 87 potential spore forming isolates 5 isolates generally regarded as facultative anaerobes and could not hydrolyze starch (Group I), 37 isolates were also regarded as facultative anaerobes and could be able to complete starch hydrolysis, these isolates are considered to be a members of (Groups II), (Group III)includes strict aerobes and has not ability to hydrolyze starch representatives of 23isolates. However 22 isolates belong to as members of (group IV) that presents strict aerobes and has ability for starch hydrolysis.
• Confirmed group 1 isolates examined the capability of these spore forming isolates to ferment citrate, mannitol and maltose in addition examining the ability of these strains to reduce nitrate and gelatin hydrolysis.
• Confirmed group 2 isolates examined the capability of these spore forming isolates to ferment lactose, hydrolyze gelatin and casein, reduce nitrate to nitrite, form sporangium bulging and grow at 50°C.
• Confirmed group 3 isolates examined the capability of these spore forming isolates to hydrolyze gelatin and urea, form sporangium bulging and grow at both 37 °C and 50°C, in addition to oxidase production.
• Confirmed group 4 isolates examined the capability of these spore forming isolates to ferment rafinose and citrate, form sporangium bulging and grow at 50°C.
• API 50 CHB is specified for the characterization of Bacillus and related genera. Isolates were identified as B. cereus, B. subtilis, B. mycoides, B. pumilus, B. weihenstephanensis, B. thuringiensis, B. coagulans, B. sphaericus and B. licheniformis. The efficiency of API system for spore forming bacteria was approximately 80%. The API system could not was able to identify B. thuringiensis (4 isolates).
Publication year 2020
Organization Name
Country Egypt
Publisher Name: Mansoura University Faculty of Agriculture
Author(s) from ARC
Publication Type Master Thesis
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