The microbiological quality of raw milk is of great significance for its impact on public health, for socio-economical and technological implications. The implementation of good hygienic practices by dairy farmers has leaded to a significant improvement of the microbiological quality of raw milk and a reduction in the level of pathogenic bacteria. Along with pathogens, a decrease of the Lactic Acid Bacteria (LAB) of interest in cheese-making has been observed. The biodiversity of the LAB involved in raw milk cheese production is considered a fundamental factor for features and quality of the products. LAB are also part of the indigenous microbiota of the teat canal so they are optimal candidates to design a probiotic product to prevent mastitis. The aims of the project are mainly three: 1) to evaluate the presence of LABs in raw milk of cow, goat and sheep, and to identify the farm management practices that can enhance their amount in milk; 2) to select an appropriate pool of LAB strains characterized by high resistance in the farm environment and by antibacterial activity against mastitis pathogens and food-borne bacteria; 3) to test the efficacy of the introduction of the selected LAB pool in dairy farm environment, in particular the effect in modulating raw milk microbiota composition and in preventing mastitis infections. The project will include three different trials: a field study, an in vitro study and an experimental trial. In the field study about 50 dairy farms (cattle or goat) will be involved, each farm will be visited twice (cold and hot season). A survey will be completed to collect information on housing, barn design, milking equipment and routine, milk cooling system. Samples of bulk tank milk, quarter forestripping milk, teat swaps, bedding materials will be collected. Animal and bedding cleanliness will be assessed using visual hygiene scores charts. The cleaning procedure of machine milking and tank milk temperature will be monitored. Microbiological analysis of milk and of other samples will be performed to evaluate Standard Plate Count, LAB counts and psycrotrophic bacteria; presence of pathogenic bacteria (Staphylococcus aureus, Listeria monocytogenes, Streptococcus agalactiae and other bacteria causing mastitis) will be investigated, bulk tank and quarter milk somatic cells will be counted. LAB strains isolated and identified will be tested by in vitro study for bacteriocins production; the activity of these antimicrobial proteins will be quantified against mastitis pathogens, using the minimum inhibitory concentration and the minimum bactericidal concentration test. The most active molecules will be characterized using ultra-performance liquid chromatography/high resolution-electrospray ionization mass spectrometry analysis. The most active and resistant LAB strains, able to grow under farm environment conditions, will be used to prepare a product that might be rich in bacteriocins and lactobacilli, to compete with bacteria living of the teat skin. The experimental trial will be conducted in some dairy cattle, goat and ovine farms to test the efficacy of the selected LAB. The choice of the substrate for inoculation (bedding or dipping solution..) will be evaluated through the results of the in vitro study. Bulk milk samples will be taken before the introduction of LAB in the farm and during the inoculation period, to verify the effect of the inoculated LABs on milk microbiota and mastitis incidence in the farms. The introduction of selected LAB strains in the farm would: 1) improve the biodiversity of milk microbiota, with positive effects on cheese-making and sensory of raw milk cheeses; 2) be useful to prevent mastitis and to control food-borne bacteria in raw milk and cheese. The utilization of these strains could decrease the use of antibiotic and consequently the potential problems caused by their use (residues in milk, influence on cheese-making procedures, increased antibiotic resistance).

Revisione Progetto SIR

POLIDORI, Paolo
2015-01-01

Abstract

The microbiological quality of raw milk is of great significance for its impact on public health, for socio-economical and technological implications. The implementation of good hygienic practices by dairy farmers has leaded to a significant improvement of the microbiological quality of raw milk and a reduction in the level of pathogenic bacteria. Along with pathogens, a decrease of the Lactic Acid Bacteria (LAB) of interest in cheese-making has been observed. The biodiversity of the LAB involved in raw milk cheese production is considered a fundamental factor for features and quality of the products. LAB are also part of the indigenous microbiota of the teat canal so they are optimal candidates to design a probiotic product to prevent mastitis. The aims of the project are mainly three: 1) to evaluate the presence of LABs in raw milk of cow, goat and sheep, and to identify the farm management practices that can enhance their amount in milk; 2) to select an appropriate pool of LAB strains characterized by high resistance in the farm environment and by antibacterial activity against mastitis pathogens and food-borne bacteria; 3) to test the efficacy of the introduction of the selected LAB pool in dairy farm environment, in particular the effect in modulating raw milk microbiota composition and in preventing mastitis infections. The project will include three different trials: a field study, an in vitro study and an experimental trial. In the field study about 50 dairy farms (cattle or goat) will be involved, each farm will be visited twice (cold and hot season). A survey will be completed to collect information on housing, barn design, milking equipment and routine, milk cooling system. Samples of bulk tank milk, quarter forestripping milk, teat swaps, bedding materials will be collected. Animal and bedding cleanliness will be assessed using visual hygiene scores charts. The cleaning procedure of machine milking and tank milk temperature will be monitored. Microbiological analysis of milk and of other samples will be performed to evaluate Standard Plate Count, LAB counts and psycrotrophic bacteria; presence of pathogenic bacteria (Staphylococcus aureus, Listeria monocytogenes, Streptococcus agalactiae and other bacteria causing mastitis) will be investigated, bulk tank and quarter milk somatic cells will be counted. LAB strains isolated and identified will be tested by in vitro study for bacteriocins production; the activity of these antimicrobial proteins will be quantified against mastitis pathogens, using the minimum inhibitory concentration and the minimum bactericidal concentration test. The most active molecules will be characterized using ultra-performance liquid chromatography/high resolution-electrospray ionization mass spectrometry analysis. The most active and resistant LAB strains, able to grow under farm environment conditions, will be used to prepare a product that might be rich in bacteriocins and lactobacilli, to compete with bacteria living of the teat skin. The experimental trial will be conducted in some dairy cattle, goat and ovine farms to test the efficacy of the selected LAB. The choice of the substrate for inoculation (bedding or dipping solution..) will be evaluated through the results of the in vitro study. Bulk milk samples will be taken before the introduction of LAB in the farm and during the inoculation period, to verify the effect of the inoculated LABs on milk microbiota and mastitis incidence in the farms. The introduction of selected LAB strains in the farm would: 1) improve the biodiversity of milk microbiota, with positive effects on cheese-making and sensory of raw milk cheeses; 2) be useful to prevent mastitis and to control food-borne bacteria in raw milk and cheese. The utilization of these strains could decrease the use of antibiotic and consequently the potential problems caused by their use (residues in milk, influence on cheese-making procedures, increased antibiotic resistance).
2015
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11581/373582
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