Microbial surveys in Estonian dairies

Evaluation of the Potential of Biofilm Formation of Bifidobacterium longum subsp. infantis and Lactobacillus reuteri as Competitive Biocontrol Agents Against Pathogenic and Food Spoilage Bacteria

This study proposes to exploit the in vivo metabolism of two probiotics (Bifidobacterium longum subsp. infantis and Lactobacillus reuteri) which, upon adhesion on a solid surface, form a biofilm able to control the growth of pathogenic and food spoilage bacteria. The results showed that pathogenic cell loads were always lower in presence of biofilm (6.5-7 log CFU/cm2) compared to those observed in its absence. For Escherichia coli O157:H7, a significant decrease (>1-2 logarithmic cycles) was recorded; for Listeria monocytogenes, Staphylococcus aureus, and Salmonella enterica, cell load reductions ranged from 0.5 to 1.5 logarithmic cycles. When tested as active packaging, the biofilm was successfully formed on polypropylene, polyvinyl chloride, greaseproof paper, polyethylene and ceramic; the sessile cellular load ranged from 5.77 log CFU/cm2 (grease-proof paper) to 6.94 log CFU/cm2 (polyethylene, PE). To test the potential for controlling the growth of spoilage microorganisms in food, soft cheeses were produced, inoculated with L. monocytogenes and Pseudomonas fluorescens, wrapped in PE pellicles with pre-formed biofim, packed both in air and under vacuum, and stored at 4 and 15 °C: an effective effect of biofilms in slowing the decay of the microbiological quality was recorded.

Milk Hygiene in Rural Southwestern Uganda: Prevalence of Mastitis and Antimicrobial Resistance Profiles of Bacterial Contaminants of Milk and Milk Products

Mastitis and antimicrobial resistance are a big challenge to the dairy industry in sub-Saharan Africa. A study was conducted in Kashongi and Keshunga subcounties of Kiruhura District (in Uganda) where the government and private sector have deliberate programs to improve production efficiency, quality, and safety of milk and its products. The study aimed to determine the prevalence of mastitis, its common causative agents, antimicrobial sensitivity of mastitis causing organisms, and contaminants of processed milk products: yoghurt and ghee. Seventy-one milk, fourteen yoghurt, and three ghee samples were collected from nine farms. Of the 71 cows tested, 54 (76.1%) had mastitis. The mastitis cases from Keshunga were 32 (59.3%) and Kashongi contributed 22 (40.7%) of the cases. The common mastitis causative agents were Staphylococcus spp. (30.8%), Streptococcus spp. (12.3%), Corynebacterium spp.(15.4%), and E. coli (7.7%). Some of the isolates were resistant to tetracycline and penicillin. Prevalent contaminants of yoghurt were Staphylococcus spp. (8.3%), Streptococcus spp. (8.3%), Corynebacterium spp. (8.3%), and E. coli (8.3%), whereas all ghee contained Streptococcus spp. (100%). Prevalence of mastitis, antimicrobial resistance, and contamination of milk products are high in the study area. Targeted programs to prevent and control mastitis as well as antibiotic resistance are recommended.

The testing of sanitizers efficacy to enterococci adhered on glass surfaces

The aim of this work was to test the ability of 6 strains of enterococci to adhere on glass surfaces in environment with different content of milk residues and then to evaluate efficacy of 2 commercial sanitizers (alkaline and acidic) used in milk production. Tested enterococci were isolated from milk, dairy products and from rinse water after sanitation milking machine. Suspension of enterococci (8 log CFU.ml-1) was prepared in phosphate buffered saline (PBS), PBS with content 0.1% and 1% of skimmed reconstituted milk. Glass plates were immersed into bacterial suspension for 1 h at 37 °C. The number of enterococci adhered on glass surface in PBS achieved an average value 3.47 log CFU.mm-2, in PBS with 0.1% of milk 2.90 CFU.mm-2, in PBS with 1% of milk 2.63 CFU.mm-2. Differences between the tested files were not statistically significant (p >0.05). In the second part of work the glass plates with adhered enterococci were exposed to the effect of alkaline sanitizer (on basis of NaOH and NaClO), respectively acidic sanitizer (on basis of H3PO4). Sanitation solutions were prepared and tested according to manufacturer recommendations (concentration 0.25%, contact time 20 min, temperature   20 °C). Alkaline sanitation solution was 100% effective against all tested enterococci regardless to content of milk residues in environment. Acidic sanitation solution was 100% effective only against E. faecalisD (isolated from rinse water after sanitation). Average value of reduction of enterococci with acidic sanitation solution, which were on glass plates in environment PBS was 2.84 CFU.mm-2, in PBS with 0.1% of milk was 2.45 CFU.mm-2 and in PBS with 1% of milk was2.16 CFU.mm-2. It can be concluded, that increase of milk residues in environment decrease the adhesion of enterococci on glass surface, but also effectiveness of acidic sanitation solution.

Development and Control of Bacterial Biofilms on Dairy Processing Membranes

Membrane fouling is a major operational problem that leads to reduced membrane performance and premature replacement of membranes. Bacterial biofilms developed on reverse osmosis membranes can cause severe flux declines during whey processing. Various types of biological, physical, and chemical factors regulate the formation of biofilms. Extracellular polymeric substances produced by constitutive microflora provide an effective barrier for the embedded cells. Cultural and microscopic techniques also revealed the presence of biofilms with attached bacterial cells on membrane surfaces. Presence of biofilms, despite regular cleaning processes, reflects ineffectiveness of cleaning agents. Cleaning efficiency depends upon factors such as pH of the cleaning agent, temperature, pressure, cleaning agent dose, optimum cleaning time, and cross-flow velocity during cleaning. Among different cleaning agents, surfactants help to prevent bacterial attachment to surfaces by reducing the surface tension of water and interfacial tension between the layers. Enzymes mixed with surfactants and chelating agents can be used to penetrate the biofilm matrix formed by microbes. Recent studies have shown the role of quorum-sensing-based cell-to-cell signaling, which provides communication within bacterial cells to form a mature biofilm, and also the role of applying quorum inhibitors to prevent biofilm formation. Major cleaning applications are also summarized in Table .

Determinants of water consumption in the dairy industry

This paper analyzes the correlations between selected technical, process and production factors, equipment profiles and water consumption statistics in four types of dairy plants. Dairy plants were surveyed both individually and in groups. Water consumption was most highly correlated (r > 0.868) with equipment profiles. The highest water consumption was observed in dairy plants operating milk powder departments. In those plants, organization and production factors could significantly reduce water consumption levels because in addition to milk powder, those plants also supplied eight other products. The indicators of water consumption per unit of the final product were correlated (at 0.820 > | r | > 0.663) with equipment profiles, the degree of process automation and employment. Variations in water consumption per unit of the final product were best explained in small plants supplying several products. The presented equations can be used to optimize water demand of various types of equipment and to determine the correlations with energy consumption for wastewater treatment. Our results can contribute to the development of water consumption models in dairy plants and the implementation of clean production standards.

Enterococci and their ability live out activity of sanitation detergents

We evaluated the effect of temperature decrease of sanitation solutions (35 °C) in condition of organic load (1% reconstituted powdered milk) and varying hardness of the water used for solution preparation (0 °, 15 °, 30 ° and 45 °) on the ability to randomly selected strains of enterococci survive exposure to acidic and alkaline sanitation solution (0.5% concentration, contact time 15 minutes) in model experiments. Increasing water hardness also increases the number surviving enterococci. Presence of organic loads and lower temperatures decreased the sanitation effect of the test solutions. The tested strains showed different tolerances to applied sanitation solutions. We found a weaker powerful of acid sanitation solution on base phosphoric acid after its application.https://doi.org/ 10.5219/166

Bacteria Staphylococcus spp. izolated from mastitis of sheep and their enterotoxigenic properties

In our study was followed occurrence of staphylococcal mastitis in herd of 350 sheep during one lactation season. We found, the bacteria S. schleiferi was identified in 88 from all 204 isolates. In high number were identified also S. caprae (33), S. chromogenes (21), S. aureus (19), S. epidermidis (17), respectively. Important was occurrence S. intermedius, S. simulans, S. xylosus a S. warneri, too. The Staphylococcuss spp. caused latent and subclinical forms of mastitis predominantly, showed into subacute mastitis (26.5%). Acute mastitis was determined in 7.8 %. Eight bacteria S. aureus, two S. chromogenes, and two S. epidermidis produced staphylococcal enterotoxins.