Bacteria In Milk Research Articles

Colchicine can keep the viability of bacteria in mastitic milk by preventing leukocyte phagocytosis in dairy cow and goat

Despite the occurrence of mastitis, no bacteria were detected in any of the milk samples after culture. This is partially because the neutrophils present in milk phagocytose bacteria during milk preservation. In this study, we investigated whether colchicine inhibited the decrease in viable bacteria in milk by suppressing phagocytosis during preservation. The number of viable bacteria decreased when cow milk was preserved for 5 h. However, the addition of 0.1 and 1% colchicine significantly increased the number of viable bacteria (p < 0.05). The percentage of culture-negative cow’s milk increased more than two-fold after 5 h compared to that at 0 h of preservation, however this percentage was significantly reduced by the addition of colchicine (p < 0.05). When goat milk with mastitis was incubated with bacteria (Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus), the percentage of phagocytosed neutrophils decreased significantly with the addition of colchicine (p < 0.05). These results indicate that colchicine suppressed the decrease in the number of viable bacteria by preventing neutrophil phagocytosis during milk preservation. These findings may help in the identification of mastitis-causing bacteria and the selection of antibiotics for the treatment of mastitis.

A novel K57-specific Klebsiella pneumoniae phage disinfects milk and inhibits biofilm formation

Klebsiella pneumoniae (K. pneumoniae), especially serotype K57, is a major pathogen in dairy bovine mastitis, causing significant economic losses and posing a public health risk through contaminated dairy products. In addition, K57 is highly virulent among serotypes infecting humans, leading to serious conditions such as pyogenic liver abscess. In this study, we isolated and identified a bacteriophage called vB_Kp_Z57 that targets K57 serotype K. pneumoniae isolates from human and bovine sources. The phage has a latent period of 4 min and can produce approximately 233 phages per infected bacterial cell. vB_Kp_Z57 is stable over a temperature range of 4 °C to 60 °C and a pH range of 5–11. Sequencing and assembly of the phage genome revealed DNA molecules consisting of 40,316 base pairs. After genome annotation with bioinformatics software, it was discovered that the phage genome encodes 48 proteins, with no detected lysogeny genes, toxin genes, or tRNA-related genes. vB_Kp_Z57 was classified as a member of genus Przondovirus, family Autographiviridae. The results of bacteriostatic experiments show that vB_Kp_Z57 has a good effect on inhibiting bacterial growth. Notably, vB_Kp_Z57 significantly inhibited the growth of its host bacteria in milk at refrigerated temperatures of 4 °C and room temperature. Biofilm inhibition experiments revealed that phage vB_Kp_Z57 significantly reduced OD595 values in all phage-treated groups, indicating its potential as an effective biocontrol agent against K. pneumoniae. Our findings show the promise of vB_Kp_Z57 as a novel and environmentally friendly solution to address the challenges associated with K. pneumoniae in dairy production.

Establishment of a multiplex qPCR method for sensitive detection of proteolytic psychrotrophic bacteria in raw milk

Initial microbiological species and quantity of raw milk significantly affect dairy product quality. In particular, some psychrotrophic bacteria in raw milk can produce heat-stable hydrolases that reduce the stability of dairy products during their shelf life. The purpose of this study was to establish a multiplex real-time fluorescence quantitative polymerase chain reaction (qPCR) rapid detection method for Pseudomonas fluorescens and Lactococcus lactis subsp. lactis, which generally produce protease in raw milk. The primers and probes with good specificity, universality and high sensitivity to the target bacteria were screened by ordinary PCR and qPCR experiments. The quantitative linear relationship and sensitivity of the method for detecting pure DNA and artificially contaminated simulated milk samples were verified. The results showed that the limit of detection (LOD) of this method for pure DNA could reach 3.16×10-5 ng/μL. The detection of artificially contaminated samples showed that the LOD for P. fluorescens and L. lactis subsp. lactis could reach 250 and 22 CFU/mL, respectively. The multiplex qPCR method established in this study has good specificity and high sensitivity, which can be used to rapidly detect psychrotrophic bacteria in raw milk. It provides an effective reference strategy for the dairy industry to ensure the microbiological quality of raw milk from the source.

Isolation and evaluation of Pediococcus acidilactici YH-15 from cat milk: Potential probiotic effects and antimicrobial properties

The study aimed to screen for the possible presence of lactic acid bacteria (LAB) in cat milk in order to evaluate their probiotic properties. The isolates were characterized by biochemical identification, morphological tests and 16S rDNA sequencing. Afterward, gastrointestinal passage, in vitro safety and probiotic properties were evaluated. The results showed that the isolates had 10 strains of Pediococcus acidilactici permitted in the feed additive catalog. The high survival rate in the acid and bile salt resistance test reflected the good strain tolerance of the isolates to the simulated gastrointestinal conditions of the host in vitro. The mean inhibitory diameters of the 10 strains against chloramphenicol and tetracycline were 23.6 mm and 17.4 mm, respectively; none of the hemolytic tests showed α/β hemolytic ring. The bacteriostatic test showed that P. acidilactici YH-9, YH-14 and YH-15 had inhibitory effects on four common pathogenic bacteria, including Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Streptococcus. The adhesion test showed that P. acidilactici YH-15 had good adhesion to HT-29 cells. Based on these results, we concluded that P. acidilactici YH-15 extracted from cat milk has potential application as a clinical probiotic therapy and health care product.

The association between milk and dairy products intake and insomnia symptoms among Japanese adults in community-based cohort.

Objective: To examine the association between habitual intake of milk and dairy products and insomnia. Design: Cross-sectional study by using cohort study data among 60,633 participants (22,721 men and 37,912 women) aged 20-74 years in eastern Japan. The data of milk and dairy products intake, sleep status and other lifestyle habits were collected by self-administered questionnaires. The question about milk and dairy products included whole milk, low-fat milk, cheese, yogurt, and lactic acid bacteria beverages, and were assessed by frequency (< 1 time/week, 1-2 times/week, 3-6 times/ week, and ≥ 1 time/day). Sleep status was scored with the Athens Insomnia Scale. Results: Logistic regression analysis showed that adjusted odds ratio (OR) and 95% confidence interval (95% CI) for insomnia were statistically significantly lower for whole milk intake > 1 time/day compared to < 1 time/week in all (OR: 0.91; 95% CI: 0.86-0.96; P = 0.001). The similar results were shown for women (OR: 0.90; 95% CI: 0.85-0.97; P = 0.002), not for men. In contrast, the adjusted odds for insomnia were high in the group that had frequencies of 3-6 times/week of lactic acid bacteria beverages compared to <1 time/week (OR: 1.20, 95% CI: 1.11-1.29; P < 0.001 in all; OR: 1.36; 95% CI: 1.19-1.55; P < 0.001 in men; OR: 1.13; 95% CI: 1.03-1.24; P = 0.009 in women). Conclusions: This cross-sectional study of Japanese populations showed a tendency for no insomniacs to consume whole milk more frequently.

Identification and Characterization of Human Breast Milk and Infant Fecal Cultivable Lactobacilli Isolated in Bulgaria: A Pilot Study.

During the last few decades, the main focus of numerous studies has been on the human breast milk microbiota and its influence on the infant intestinal microbiota and overall health. The presence of lactic acid bacteria in breast milk affects both the quantitative and qualitative composition of the infant gut microbiota. The aim of this study was to assess the most frequently detected cultivable rod-shaped lactobacilli, specific for breast milk of healthy Bulgarian women and fecal samples of their infants over the first month of life, in 14 mother-infant tandem pairs. Additionally, we evaluated the strain diversity among the most common isolated species. A total of 68 Gram-positive and catalase-negative strains were subjected to identification using the MALDI-TOF technique. Predominant cultivable populations belonging to the rod-shaped lactic acid bacteria have been identified as Lacticaseibacillus rhamnosus, Limosilactobacillus fermentum, Lacticaseibacillus paracasei, and Limosilactobacillus reuteri. Also, we confirmed the presence of Lactiplantibacillus plantarum and Lactobacillus gasseri. Up to 26 isolates were selected as representatives and analyzed by 16S rRNA sequencing for strain identity confirmation and a phylogenetic tree based on 16S rRNA gene sequence was constructed. Comparative analysis by four RAPD primers revealed genetic differences between newly isolated predominant L. rhamnosus strains. This pilot study provides data for the current first report concerning the investigation of the characteristic cultivable lactobacilli isolated from human breast milk and infant feces in Bulgaria.

CHARACTERISTICS OF JUWET FRUIT YOGHURT WITH THE ADDITION OF SKIM MILK AND LACTIC ACID BACTERIA STARTER

In this study, the manufacture of juwet fruit yoghurt was studied with different treatments of adding skim milk and lactic acid bacteria starter. Yogurt is a processed milk product made through bacterial fermentation. Yogurt is known as a good source of protein, calcium, and probiotics, which can support digestive health and the immune system. Juwet fruit has a high antioxidant and vitamin C content so that juwet fruit has interesting potential to be made into yoghurt. Skim milk is used to utilize high lactose and protein so that the growth of lactic acid bacteria can grow optimally. Lactic acid bacteria are used for preservation, providing texture, and adding flavor to yoghurt drinks. The purpose of this study was to determine the addition of skim milk and lactic acid bacteria starter on the physicochemical, microbiological, and organoleptic characteristics of juwet yoghurt. This study used a Completely Randomized Design (CRD) factorial pattern consisting of two factors. Factor 1 addition of skim milk (5%, 7%, 9%). Factor 2 addition of starter (5%, 7%, 9%). Each treatment was repeated three times. The data obtained were analyzed using analysis of variance (ANOVA). If there is a significant difference between treatments, it is continued with the Duncan test (DMRT) and organoleptic test using the Scoring test with 25 trained panelists. The treatment of adding 9% skim milk and 9% starter was the best treatment that produced juwet yoghurt with a protein content of 2.1% ± 0.036, total titratable acid 2.1% ± 0.1, total soluble solids 22.7ºBrix ± 1.53, total lactic acid bacteria 10.5 log CFU/ml ± 0.023, pH 3.7 ± 0.058, antioxidants 34.0% ± 0.117, viscosity 6.8% ± 0.058, Vitamin C 5.8 ± 0.3, and organoleptic tests of color 2.88 (rather like), taste 3.24 (rather like), aroma 2.68 (rather like), texture 3.76 (like).

Membrane separation assisted colorimetric/fluorescent detection of β-galactosidase-positive bacteria in milk and milk powder based on the oxidase-like activity of CoOOH nanosheets

Species-specific enzymes provide a substantial boost to the precision and selectivity of identifying dairy products contaminated with foodborne pathogens, due to their specificity for target organisms. In this study, we developed cobalt oxyhydroxide nanosheets (CoOOH NSs) for a dual-mode biosensor capable of detecting β-galactosidase (β-Gal)-positive bacteria in milk and milk powder. The sensor exploits the oxidase-mimicking activity of CoOOH NSs, where β-Gal converts the substrate β-D-galactopyranoside to p-aminophenol, reducing CoOOH NSs to Co2+ and inhibiting the formation of the blue product from 3,3′,5,5′-tetramethylben-zidine. Sensitivity was enhanced through membrane filtration and β-Gal induction by isopropyl β-D-thiogalactoside. The assay achieved a detection limit of 5 cfu mL−1 and demonstrated recoveries (90.7 % to 103 %) and relative standard deviations <5.7 % in milk and milk powder samples. These findings underscore the potential of the sensor for detecting β-Gal-positive bacteria in dairy products.

Probiotic Lactobacillus rhamnosus species: considerations for female reproduction and offspring health.

Lactobacillus rhamnosus is a type of bacteria known as a probiotic and is often used to support the health of the digestive system and vaginal flora. This type of bacteria has an important role, showing positive effects on female reproductive biology, particularly by maintaining the balance of microorganisms in the vagina, reducing the risk of infection, and strengthening the immune system to support maternal health during pregnancy. There are also studies showing that these probiotics prevent maternal obesity and gestational diabetes. Consuming probiotics containing Lactobacillus rhamnosus strains may support the intestinal health of breastfeeding mothers, but they may also contribute to the health of offspring. Therefore, this review focuses on the current available data for examining the effects of Lactobacillus rhamnosus strains on female reproductive biology and offspring health. A systematic search was conducted in the PubMed and Web of Science databases from inception to May 2024. The search strategy was performed using keywords and MeSH (Medical Subject Headings) terms. Inconsistent ratings were resolved through discussion. This review is strengthened by multiple aspects of the methodological approach. The systematic search strategy, conducted by two independent reviewers, enabled the identification and evaluation of all relevant literature. Although there is a limited number of studies with high heterogeneity, current literature highlights the important contribution of Lactobacillus rhamnosus probiotics in enhancing female reproductive health and fertility. Furthermore, the probiotic bacteria in breast milk may also support the intestinal health of newborn, strengthen the immune system, and protect them against diseases at later ages.

Antibacterial Mechanism of Garviecin LG34 Against S. Aureus and L. Monocytogenes and its Application in Milk Preservation

The objective of this study was to reveal the antibacterial mode of action of garviecin LG34 against S. aureus CICC 21600 and L. monocytogenes CICC 21633 and measure the inhibitions on these two foodborne pathogenic bacteria in milk. Antibacterial mechanism of garviecin LG34 was ascertained by its effect on the efflux of Potassium (K+) ions, extracellular electrical conductivity, UV-absorbing substances, potential across the membrane (ΔΨ), and cell permeability. The inhibition of garviecin LG34 against S. aureus CICC 21600 and L. monocytogenes CICC 21600 in milk was studied by viable counting method. Supplementation with 160 AU/ml of garviecin LG34 had a bactericidal effect on S. aureus CICC 21600 and L. monocytogenes CICC 21633. A total of 80, 160, and 320 AU/ml of garviecin LG34 resulted in the effusion of potassium ion and UV-absorbing substances, the leakage of cellular electrolytes, and the dissipation of electrical potential across the membrane of these two food-borne bacteria and showed a dose-dependent. Moreover, the increase in cell permeability of both strains was observed by flow cytometer after cells treated with 160 AU/ml of garviecin LG34. Garviecin LG34 significantly inhibited the growth of these two food-borne bacteria in milk, especially in skimmed milk. Garviecin LG34 could cause pore formation, intracellular materials release, and permeability increase of S. aureus CICC 21600 and L. monocytogenes CICC 21633, and could be applied to milk as bio-preservative.

Extracting and Characterizing Lactic Acid Bacteria from Human Milk

The greatest diet for babies is breast milk since it meets all of their nutritional needs and promotes healthy growth and development. Human milk contains thousands of different bacteria, the most prevalent ones being lactobacillus and Bifido bacterium. Since the use of probiotics is growing daily, it's important to comprehend their properties and health advantages. The combination of protein, fats, carbs, lipids, minerals, and vitamins found in breast milk helps to nourish an infant's body. Additionally, the bacteria in breast milk offer defense against infections. We will learn about lactic acid bacteria from this study so that we can commercially make probiotics from strains of these bacteria without utilizing lactose, as certain people are lactose intolerant and do not consume any lactose-containing products. The purpose of this article is to identify and isolate lactic acid bacteria while also discussing the advantages of probiotics for health. To understand the role lactic acid bacteria (LAB) from human milk play in the development and health of neonates, LAB must be extracted and identified. This study's objective was to identify, characterize, and segregate LAB strains from human milk samples obtained from nursing mothers in good health. The first isolation was carried out using selective medium, and then morphological, biochemical, and molecular characterization were performed. Through 16S rRNA gene sequencing, the isolates were identified. All things considered, the development of the neonatal gut microbiota and the overall health of infants depend on lactic acid bacteria (LAB). This review's objective is to gather the most recent data on the identification and isolation of LAB from human milk, with an emphasis on the techniques employed, the types of LAB discovered, and any potential health risks. Human milk is an essential source of beneficial bacteria, including several species of lactobacilli (LAB), due to its complex and dynamic nature. Our ability to isolate and accurately identify these germs has improved due to technological advancements in the molecular and microbiological sciences. This paper provides an extensive overview of the methods utilized to extract LAB from human milk, the genera and species that are commonly detected, and the implications of these findings for the nutrition and health of neonates.

Tracking the metabolite footprint of four lactic acid bacteria in semiskimmed milk: A chemometric analysis

This study aimed to evaluate the strain‐specific fermentative behaviour and metabolite footprint of four Lactobacillus spp., in 48‐h fermented milks. Technological properties (net cell growth, pH and lactic acid production), exopolysaccharides (EPS), short‐chain fatty acids (SCFAs), α‐amino acids and peptides &lt;3 kDa were determined and evaluated by chemometrics. Inter‐strain differences were attributed to technological properties, SCFAs and D‐mannose/galactose/arabinose production. Three clusters (technological properties, EPS and SCFA production) were confirmed by Pearson's correlation and hierarchical clustering and principal component analysis explained 61% of LAB's differential fermentative behaviour. Post hoc chemometric analysis is useful to select LAB with better post‐ and paraprobiotic potential.

Foodborne bacteria in milk and milk products along the water buffalo milk chain in Bangladesh

Controlling foodborne pathogens in buffalo milk is crucial for ensuring food safety. This study estimated the prevalence of nine target genes representing seven critical foodborne bacteria in milk and milk products, and identified factors associated with their presence in buffalo milk chain nodes in Bangladesh. One hundred and forty-three milk samples from bulk tank milk (n = 34), middlemen (n = 37), milk collection centers (n = 37), and milk product shops (n = 35) were collected and analyzed using RT-PCR. Escherichia (E.) coli, represented through yccT genes, was the most prevalent throughout the milk chain (81–97%). Chi-squared tests were performed to identify the potential risk factors associated with the presence of foodborne bacteria encoded for different genes. At the middleman level, the prevalence of E. coli was associated with the Mymensingh, Noakhali, and Bhola districts (P = 0.01). The prevalence of Listeria monocytogenes, represented through inlA genes, and Yersinia (Y.) enterocolitica, represented through yst genes, were the highest at the farm level (65–79%). The prevalence of both bacteria in bulk milk was associated with the Noakhali and Bhola districts (P < 0.05). The prevalence of Y. enterocolitica in bulk milk was also associated with late autumn and spring (P = 0.01) and was higher in buffalo-cow mixed milk than in pure buffalo milk at the milk collection center level (P < 0.01). The gene stx2 encoding for Shiga toxin-producing (STEC) E. coli was detected in 74% of the milk products. At the middleman level, the prevalence of STEC E. coli was associated with the use of cloths or tissues when drying milk containers (P = 0.01). Salmonella enterica, represented through the presence of invA gene, was most commonly detected (14%) at the milk collection center. The use of plastic milk containers was associated with a higher prevalence of Staphylococcus aureus, represented through htrA genes, at milk product shops (P < 0.05). These results suggest that raw milk consumers in Bangladesh are at risk if they purchase and consume unpasteurized milk.

One-Year Monitoring of Prevalence and Diversity of Dairy Propionic Acid Bacteria in Raw Milk by Means of Culture-Dependent and Culture-Independent Methods.

Even low levels of dairy propionic acid bacteria (dPAB) can cause cheese defects, resulting in severe economic losses for the producers of selected raw milk cheeses. Therefore, routine quality control of raw cheese milk for dPAB contamination is essential if propionic acid fermentation is undesired. Although knowledge of dPAB contamination of raw milk is important to understand cheese spoilage, long-term dPAB screening data are outdated, and studies taking into account different farm management parameters and their potential influence on dPAB levels are scarce. This study aims to provide insight into the dPAB levels of raw milk over time, to identify farm management factors that potentially influence dPAB levels, and to compare a cultural yeast extract lactate agar (YELA) and lithium glycerol agar (LGA) and a culture-independent method (qPCR) for dPAB quantification with respect to their applicability in routine quality control for the dairy industry. For this purpose, bulk tank milk from 25 dairy farms was screened for dPAB contamination over a one-year period. We were able to identify significant differences in the dPAB contamination levels in raw milk depending on selected farm-specific factors and observed relationships between the different types of milking systems and dPAB contamination levels in raw milk. When dPAB were quantified by cultivation on YELA, strong overgrowth of commensal microbiota impeded counting. Therefore, we conclude that quantification on LGA or by qPCR is preferable. Both methods, colony counting on LGA as well as quantification of dPAB using qPCR, have advantages for the application in (routine) quality control of raw milk, one being low-tech and inexpensive, the other being fast and highly specific, but the detection of (low level) dPAB contamination in raw milk remains a challenge.

Biodiversity and identification of spore-forming bacteria in raw milk from Korean dairy farm environment using the culturomics approach

Biodiversity and identification of spore-forming bacteria in raw milk from Korean dairy farm environment using the culturomics approach

Mastitis challenges in Serbian dairy farming: a study on somatic cell counts and pathogen distribution

Mastitis is pressing concern for dairy herds due to its economic impact and potential health risks. Somatic cell counts (SCC), reflecting udder health, plays a crucial role in mastitis diagnosis. Current research explores the distribution of SCC and its correlation with various mastitis-causing pathogens in dairy farms in Serbia. The study analyzed 194 individual cow milk samples and microbiological testing was conducted under aseptic conditions to isolate and identify mastitis pathogens. The microscopic reference method was employed for assessing SCC in the milk samples. Among mastitis-associated isolates, bacteria were present in 28.87 %, yeast in 12.38 %, while in 5.15 % of milk samples, both bacteria and yeast were present. The relationship between SCC in various sample types (negative, bacteria-positive, yeast-positive, and samples with both bacteria and yeast) was noted. Importantly, samples with both bacteria and yeast presence had the highest SCC. While SCC is a valuable tool for monitoring udder health and the effectiveness of mastitis control programs, its response to specific pathogens is complex and doesn’t allow differentiation between pathogen types easily. This research highlights the challenges in distinguishing pathogen types based solely on SCC.

Commensal bacteria in raw milk, the reservoirs for antibiotic resistance genes during cold chain transportation

The emergence and prevalence of antibiotic resistance genes (ARGs) in food pose a great threat to public health and have attracted globally attention. Shotgun metagenomics sequencing is widely used to characterize ARGs in the environment. However, the distribution, co-occurrence patterns, and host information of ARGs in raw milk to the cold chain transportation duration with shotgun metagenomics sequencing, are not fully understood in China. In this study, species annotation and ARG annotation were performed on 40 raw milk samples collected from Beijing (BJ), Hebei (HB), Inner Mongolia (NMG), Shanghai (SH), and Guangdong (GD) using shotgun sequencing based on the Illumina platform. A total of 4731 bacterial species were annotated, of which 37 were dominant (relative abundance >1%). And also, 259 ARGs were annotated, corresponding to 69 kinds of antibiotic resistance. The NMG samples, which had the lowest bacterial community richness and bacterial diversity, were annotated with the highest number of ARGs, revealing the potential risk of bacterial resistance in NMG samples. Spearman correlation analysis and network analysis were showed that the probable bacterial hosts of multiple highly abundant ARGs (MacB and VanRC) in samples from provinces except for the BJ samples were Pseudomonas and Serratia, rather than conventionally known foodborne pathogens. It is noteworthy that the relative abundance of Pseudomonas fluorescens conformed to the Allometricl function with the cold chain transportation duration, the finding that could provide a reference for assessing the freshness and the risk assessment of antibiotic resistance genes of raw milk. In addition, the dairy industry should be aware of the risk of ARGs transferring from highly abundant commensal bacteria. Raw milk for transportation by cold chain, higher abundance of Pseudomonas in some samples should be kept in mind, and the roles of ARGs carried by these bacteria should be further investigated.

Residents or Tourists: Is the Lactating Mammary Gland Colonized by Residential Microbiota?

The existence of the human milk microbiome has been widely recognized for almost two decades, with many studies examining its composition and relationship to maternal and infant health. However, the richness and viability of the human milk microbiota is surprisingly low. Given that the lactating mammary gland houses a warm and nutrient-rich environment and is in contact with the external environment, it may be expected that the lactating mammary gland would contain a high biomass microbiome. This discrepancy raises the question of whether the bacteria in milk come from true microbial colonization in the mammary gland ("residents") or are merely the result of constant influx from other bacterial sources ("tourists"). By drawing together data from animal, in vitro, and human studies, this review will examine the question of whether the lactating mammary gland is colonized by a residential microbiome.

Rapid Concentration and Detection of Bacteria in Milk Using a Microfluidic Surface Acoustic Wave Activated Nanosieve.

Rapid detection of microbes is a key feature for monitoring food quality. Unfortunately, current detection systems rely on labor-intensive and time-consuming lab-based processes that are not suitable for point-of-interest applications and typically require several days before results are available. Here, we demonstrate a microfluidic system capable of rapidly concentrating, fluorescent staining, and detecting bacteria in unprocessed complex biological media such as milk. This concentration is done using a surface acoustic wave-driven microfluidic device which operates based on the Bjerknes force, a force generated on one particle by another in its close proximity. We exploit this effect by exciting a tightly packed bed of 50 μm polystyrene microparticles temporarily with surface acoustic waves within a microfluidic device to capture and release bacterial cells on demand. The bacterial cells are fluorescently stained during capture and then detected using fluorescence microscopy upon release. This device offers a high capturing efficiency (>80%) and a 34 Colony Forming Units (CFU)/mL limit of detection, which is 1 order of magnitude below that of plate counting at 30 CFU per standard 100 μL plate (or 300 CFU/mL). This can be attained in just 1 h of processing at 10 μL/min. With this system, we demonstrate that bacterial detection from extremely low concentration samples down to the order of ∼10 CFU/mL is possible without requiring any additional external pre- or postprocessing.

Optimized Ultraviolet-C Processing Inactivates Pathogenic and Spoilage-Associated Bacteria while Preserving Bioactive Proteins, Vitamins, and Lipids in Human Milk.

Holder pasteurization (HoP) enhances donor human milk microbiological safety but damages many bioactive milk proteins. Though ultraviolet-C irradiation (UV-C) can enhance safety while better preserving some milk proteins, it has not been optimized for dose or effect on a larger array of bioactive proteins. We determined the minimal UV-C parameters that provide >5-log reductions of relevant bacteria in human milk and how these treatments affect an array of bioactive proteins, vitamin E, and lipid oxidation. Treatment at 6000 and 12 000 J/L of UV-C resulted in >5-log reductions of all vegetative bacteria and bacterial spores, respectively. Both dosages improved retention of immunoglobulin A (IgA), IgG, IgM, lactoferrin, cathepsin D, and elastase and activities of bile-salt-stimulated lipase and lysozyme compared with HoP. These UV-C doses caused minor reductions in α-tocopherol but not γ-tocopherol and no increases in lipid oxidation products. UV-C treatment is a promising approach for donor human milk processing.