Adulteration in dairy products presents food safety challenges, driven by economic factors. Processing may change specific biomarkers, thus affecting their effectiveness in detection. In this study, proteomics and metabolomics approaches were to investigate the detection of bovine milk (BM) constituents adulteration in pasteurized mare milk (PMM) and mare milk powder (MMP). Several bovine proteins and metabolites were identified, with their abundances in PMM and MMP increasing upon addition of BM. Proteins like osteopontin (OPN) and serotransferrin (TF) detected adulteration down to 1 % in PMM, whereas these proteins in MMP were utilized to identify 10 % adulteration. Biotin and N6-Me-adenosine were effective in detecting adulteration in PMM as low as 10 % and 1 % respectively, while in MMP, their detection limits extend down to 0.1 %. These findings offer insights for authenticating mare milk products and underscore the influence of processing methods on biomarker levels, stressing the need to consider these effects in milk product authentication.
Milk and dairy products are excellent sources of mineral elements, including Ca, P, Mg, Na, K and Zn. The purpose of this study was to determine the effect of non-thermal (homogenization) and thermal (heat treatment) treatments on the distribution of mineral elements in 4 milk fractions: fat, casein, whey protein, and aqueous phase. The study results revealed that the distribution of mineral elements (such as Mg and Fe) in fat fractions is extremely low, while significant mineral elements such as Ca, Zn, Fe, and Cu are mostly dispersed in casein fractions. For non-treated goat milk, Mo is the only element identified in the whey protein fraction, while K and Na are mostly found in the aqueous phase. Mineral element concentrations in fat (K, Zn, etc.) and casein fraction (Fe, Mo, etc.) increased dramatically after homogenization. Homogenization greatly decreased the concentration of mineral elements in the whey protein fraction (Ca, Na, etc.) and aqueous phase (Fe, Cu, etc.). After heat treatment, the element content in the fat fraction and casein fraction increased greatly when compared with raw milk, such as Cu and Mg in the fat fraction, Na and Cu in the whey protein fraction, the concentration of components such as Mg and Na in casein fraction increased considerably. On the other hand, after homogenization, Zn in the aqueous phase decreased substantially, whereas Fe increased significantly. Therefore, both homogenization and heat treatment have an effect on the mineral element distribution in goat milk fractions.
The distribution of mineral elements in milk is crucial for their absorption and utilization, however, there has been limited attention given to the status of mineral elements in goat milk. In this study, goat milk was collected at 4 lactation periods (1-3, 90, 150, 240 d) and separated into 4 fractions (fat, casein, whey, and aqueous phase). The concentrations of Mg, Ca, Na, K, Zn, Fe, Cu, Mn, Co, Ni, Mo, and Cr in 4 fractions were analyzed using an inductively coupled plasma emission spectrometer. Our findings reveal that Ca, Zn, Fe, Cu, Mn, and Cr exhibit the highest levels in casein, while Mo demonstrates the highest content in whey. Additionally, Mg, Na, K, and Ni display the highest concentrations in the aqueous phase. Specifically, the contents of Ca, Cu and Fe in casein decrease from 1-3 to 150 d of lactation but increase from 150 to 240 d of lactation. Furthermore, the content of Mg in the aqueous phase decreases from 1-3 to 90 d of lactation but increases from 90 to 240 d of lactation. The content of Na and K in the aqueous phase decreases from 1-3 to 150 d of lactation. Notably, the content of Mo in whey increases from 1-3 to 150 d of lactation and decreases from 150 to 240 d. Our research contributes to the advancement of understanding the bioavailability of mineral elements in goat milk.
The milk fat globule membrane (MFGM) is a complex tri-layer membrane that wraps droplets of lipids in milk. In recent years, it has attracted widespread attention due to its excellent bioactive functions and nutritional value. MFGM contains a diverse array of bioactive lipids, including cholesterol, phospholipids, and sphingolipids, which play pivotal roles in mediating the bioactivity of the MFGM. We sequentially summarize the main lipid types in the MFGM in this comprehensive review and outline the characterization methods used to employ them. In this comprehensive review, we sequentially describe the types of major lipids found in the MFGM and outline the characterization methods employed to study them. Additionally, we compare the structural disparities among glycerophospholipids, sphingolipids, and gangliosides, while introducing the formation of lipid rafts facilitated by cholesterol. The focus of this review revolves around an extensive evaluation of the current research on lipid isolates from the MFGM, as well as products containing MFGM lipids, with respect to their impact on human health. Notably, we emphasize the clinical trials encompassing a large number of participants. The summarized bioactive functions of MFGM lipids encompass the regulation of human growth and development, influence on intestinal health, inhibition of cholesterol absorption, enhancement of exercise capacity, and anticancer effects. By offering a comprehensive overview, the aim of this review is to provide valuable insights into the diverse biologically active functions exhibited by lipids in the MFGM.
Food nutrition, function, sensory quality and safety became major concerns to the food industry. As a novel technology application in food industry, low temperature plasma was commonly used in the sterilization of heat sensitive materials and is now widely used. This review provides a detailed study of the latest advancements and applications of plasma technology in the food industry, especially the sterilization field; influencing factors and the latest research progress in recent years are outlined and upgraded. It explores the parameters that influence its efficiency and effectiveness in the sterilization process. Further research trends include optimizing plasma parameters for different food types, investigating the effects on nutritional quality and sensory attributes, understanding microbial inactivation mechanisms, and developing efficient and scalable plasma-based sterilization systems. Additionally, there is growing interest in assessing the overall quality and safety of processed foods and evaluating the environmental sustainability of plasma technology. The present paper highlights recent developments and provides new perspectives for the application of low temperature plasma in various areas, especially sterilization field of the food industry. Low temperature plasma holds great promise for the food industry's sterilization needs. Further research and technological advancements are required to fully harness its potential and ensure safe implementation across various food sectors.
Food Safety , Plasma Gases , Sterilization , Cold Temperature , Sterilization/methods , Food Quality
This study investigated the differences in proteins and metabolites from goat and bovine milk, and their mixtures, using data-independent-acquisition-based proteomics and metabolomics methods. In the skim milk, relative abundances of secretoglobin family 1D member (SCGB1D), polymeric immunoglobulin receptor, and glycosylation-dependent cell adhesion molecule 1 were increased, with an increase in the amount of 1-100 % bovine milk and served as markers at the 1 % adulteration level. In whey samples, ß-lactoglobulin and α-2-HS-glycoprotein could be used to detect adulteration at the 0.1 % adulteration level, and SCGB1D and zinc-alpha-2-glycoprotein at the 1 % level. The metabolites of uric acid and N-formylkynurenine could be used to detect bovine milk at adulteration levels as low as 1 % based on variable importance at a projection value of > 1.0 and P-value of < 0.05. Our findings suggest novel markers of SCGB1D, uric acid, and N-formylkynurenine that can help to facilitate assessments of goat milk authenticity.
The effects of ultrasound-assisted slightly acidic electrolyzed water thawing (UET), air thawing (AT), water thawing (WT) and microwave thawing (MT) on the quality, nutrients and microstructure were investigated. The UET treatment did not affect the lightness (L*) but reduced the redness (a*) and yellowness (b*) of the mutton. The UET treatment could better maintain the textural properties. The UET group had a higher immobilized water and lower free water, which was closer to the state of the control group. The UET treatment not only effectively inhibited the lipid oxidation but also reduced the loss of nutrients, especially minerals. The microstructure of the UET group was smoother and more complete, and the muscle fibers did not show significant breakage. In conclusion, UET treatment could better maintain the quality, nutrients and microstructure of thawed mutton. Therefore, UET could be regarded as a potential thawing method for application in the processing of meat products.
The objective of this study was to investigate the effect of lactation stage on the physical properties of milk fat globules (MFGs) and profiles of milk fatty acids (FAs) of milk from Laoshan dairy goats. Goat colostrum and milk samples were collected on days 1, 3, 30, 90, 150, and 240 postpartum. Milk fat content was found to significantly decrease during the first 90 d of lactation and increase thereafter as lactation progressed (P < 0.01). Average area particle size and volume particle size of MFGs showed trends similar to those of the milk fat content of goat milk with the extension of lactation, and the lowest levels were 2.39 µm and 3.97 µm on day 90, respectively (P < 0.01). The zeta-potential of MFGs significantly increased before 30 d of lactation, with a slight drop on day 90. It increased thereafter and tended to stabilize in the late stages of lactation (P < 0.01). The content of several saturated fatty acids (SFAs) (C10:0-C16:0) in early lactation, especially in colostrum, was lower than that in other stages of lactation (P < 0.05). Branched-chain fatty acids of the iso and anteiso series, including C13:0 anteiso, C15:0 anteiso, and C15:0 iso, were observed at high contents in mid-lactation goat milk (P < 0.01). As lactation progressed (3 d to 240 d), the content of SFAs significantly increased (P < 0.01), while the content of monounsaturated fatty acids and polyunsaturated fatty acids significantly decreased (P < 0.05). Furthermore, the content of C18:0 significantly increased during the first 30 d of lactation and decreased thereafter as lactation progressed (P < 0.01). Our results indicated that lactation stage has a pronounced effect on the physical properties of MFGs and the FA profiles of goat milk.
The composition and physical properties of milk fat affect the quality and sensory properties of dairy products. However, changes in the physical properties of milk fat globules (MFGs) and profiles of milk fatty acids (FAs) of goat milk throughout the lactation period remain unclear. In the current study, we found that milk fat content and particle size of goat MFG decreased significantly during 90 d of lactation and increased thereafter as lactation progressed. The content of saturated FAs significantly increased, while that of monounsaturated FAs and polyunsaturated FAs significantly decreased from colostrum to late-lactation milk. The characteristics of goat MFGs and milk FAs were affected by the lactation period, which may provide valuable insights into the utilization of MFGs from dairy goats.
Fatty Acids , Goats , Female , Animals , Milk , Lactation
The effects of air thawing (AT), water immersion thawing (WT), microwave thawing (MT) and ultrasound combined with slightly acidic electrolyzed water thawing (UST) on the myofibrillar protein (MP) properties (surface hydrophobicity, solubility, turbidity, particle size and zeta potential), protein oxidation (carbonyl content and sulfhydryl content) and structure (primary, secondary and tertiary) of frozen mutton were investigated in comparison with fresh mutton (FM). The solubility and turbidity results showed that the MP properties were significantly improved in the UST treatment. UST treatment could effectively reduce the MP aggregation and enhance the stability, which was similar to the FM. In addition, UST treatment could effectively inhibit protein oxidation during thawing as well. The primary structure of MP was not damaged by the thawing methods. UST treatment could reduce the damage to MP secondary and tertiary structure during the thawing process compared to other thawing methods. Overall, the UST treatment had a positive influence in maintaining the MP properties by inhibiting protein oxidation and protecting protein structure.
Red Meat , Water , Water/chemistry , Proteins , Oxidation-Reduction , Hydrophobic and Hydrophilic Interactions
The composition and content of goat milk proteins are affected by many factors and have been extensively studied. However, variation in whey protein composition in goat milk throughout the lactation cycle has not been clarified. In the current study, 15 dairy goats were selected, and milk samples were collected at 1, 3, 30, 90, 150, and 240 d after delivery. Whey proteins were separated and digested and then identified using data-independent acquisition (DIA) and data-dependent acquisition proteomics approaches. Protein profiles identified using DIA were consistent with those of the data-dependent acquisition proteomics approach according to clustering and principal component analyses. Significant differences in the abundance of 238 proteins around the lactation cycle were identified using the DIA approach. Developmental changes of the whey proteome corresponding to lactation stage were revealed: plasminogen, α-2-macroglobulin, and fibronectin levels decreased from d 1 to 240, whereas polymeric immunoglobulin receptor, nucleobindin 2, fatty acid-binding protein 3, and lactoperoxidase increased from d 1 to 240. Protein-protein interaction analysis showed that fibronectin with a higher degree of connectivity is a central node. The findings are of great significance to better understanding the potential role of specific proteins and the mechanism of protein biosynthesis or intercellular transport in the mammary glands related to the physiological changes of dairy goats.
Fibronectins , Proteomics , Female , Animals , Whey Proteins/chemistry , Lactation/metabolism , Milk Proteins/analysis , Goats/metabolism
Mare milk(MM)production is lower than that of cow milk (CM), making it a premium product. Unfortunately, sellers adulterate MM with cheap CM to unscrupulously gain more profits. This study aimed to analyze MM adulteration with CM using proteomics and metabolomics. Using univariate and multivariate statistical analysis, the relative abundances of certain proteins of caseins and secretoglobin family 1D member were found to be higher with a higher CM admixture percentage. In addition, several metabolites, such as orotic and 4-aminonicotinic acids, increased in the mare-cow milk mixture with an increased CM percentage. Accordingly, these proteins and metabolites distinguished MM adulterated with CM at levels as low as 1 %.These findings can serve as the basis for clarifying the differences at the proteome and metabolome in milk from minor dairy animals and ensure milk authenticity.
Milk , Proteomics , Cattle , Animals , Female , Horses , Mass Spectrometry , Chromatography, Liquid , Metabolomics
The effects of air thawing, water thawing, slightly acidic electrolyzed water thawing, ultrasound-assisted water thawing (WUT) and ultrasound-assisted slightly acidic electrolyzed water thawing (EUT) on the myofibrillar protein conformation and gel quality of chicken breasts were investigated. In the EUT group, protein solubility was higher (52.43%) than other thawing groups, and particle size was 24.57% smaller than the control group. Gel of EUT and WUT groups had stronger elasticities than the control group. Gel whiteness level was not significantly different between the EUT and control group. Gel water holding capacity of the EUT group was 9.07% greater than the control group. Gel water distributions and mobilities of the EUT and WUT groups were closer to the control group. The gel of the EUT group had a compact and homogeneous network. In conclusion, EUT treatment effectively reduced conformation disruption and improved gel properties, which was conducive to producing gel products.
Chickens , Water , Animals , Muscle Proteins , Solubility , Protein Conformation
Casein micelles (CM) play an important role in milk secretion, stability, and processing. The composition and content of milk proteins are affected by physiological factors, which have been widely investigated. However, the variation in CM proteins in goat milk throughout the lactation cycle has yet to be fully clarified. In the current study, milk samples were collected at d 1, 3, 30, 90, 150, and 240 of lactation from 15 dairy goats. The size of CM was determined using laser light scattering, and CM proteins were separated, digested, and identified using data-independent acquisition (DIA) and data-dependent acquisition (DDA)-based proteomics approaches. According to clustering and principal component analysis, protein profiles identified using DIA were similar to those identified using the DDA approach. Significant differences in the abundance of 115 proteins during the lactation cycle were identified using the DIA approach. Developmental changes in the CM proteome corresponding to lactation stages were revealed: levels of lecithin cholesterol acyltransferase, folate receptor α, and prominin 2 increased from 1 to 240 d, whereas levels of growth/differentiation factor 8, peptidoglycan-recognition protein, and 45 kDa calcium-binding protein decreased in the same period. In addition, lipoprotein lipase, glycoprotein IIIb, and α-lactalbumin levels increased from 1 to 90 d and then decreased to 240 d, which is consistent with the change in CM size. Protein-protein interaction analysis showed that fibronectin, albumin, and apolipoprotein E interacted more with other proteins at the central node. These findings indicate that changes in the CM proteome during lactation could be related to requirements of newborn development, as well as mammary gland development, and may thus contribute to elucidating the physical and chemical properties of CM.
Caseins , Micelles , Animals , Female , Caseins/chemistry , Goats/metabolism , Lactation , Milk Proteins/analysis , Proteome/metabolism , Proteomics
The effects of air thawing (AT), water thawing (WT), slightly acidic electrolyzed water (ET), ultrasound-assisted water thawing (WUT) and ultrasound-assisted slightly acidic electrolyzed water (EUT) on the quality and myofibrillar protein (MP) structure of chicken breasts were investigated. The results showed that WUT and EUT could significantly improve the thawing rate compared with AT, WT, and ET groups. The EUT group not only had lower thawing loss, but also their immobilized and free water contents were similar to fresh sample according to the low-field nuclear magnetic resonance (LF NMR) results. The EUT treatment had no adverse effect on the primary structure of the protein. The secondary and tertiary structures of MP were more stable in the EUT group according to Raman and fluorescence spectra. The muscle fibers microstructure from EUT group was neater and more compact compared with other thawing methods. Therefore, EUT treatment could be considered as a novel potential thawing method in the food industry.
Chickens , Water , Acids , Animals , Water/chemistry
The contribution of colostrum to passive immunity transfer and intestinal protection in newborn ruminants is well known; however, it is currently unclear how colostrum intake affects intestinal innate immunity. We investigated the effects of bovine colostrum intake on ileal morphology, expression of genes involved in intestinal innate immunity, and serum concentrations of inflammatory cytokines in newborn lambs. Twenty-seven newborn male Hu lambs were used, of which 18 were bottle-fed either bovine colostrum (C24h; n = 9) or bovine mature milk (M24h; n = 9) within the first 2 h after birth at an intake of approximately 8% of BW; the remaining nine lambs did not receive any feeding (N24h). Blood and ileal tissue samples were collected after the lambs were slaughtered at 24 h after birth. Ileal villus height and villus height-to-crypt depth ratio were significantly higher in C24h than those in N24h and M24h lambs (P < 0.01). Messenger RNA (mRNA) abundance of toll-like receptor (TLR)-2, TLR3, TLR4, TLR6, TLR7, TLR8 and tumour necrosis factor alpha in the ileum was lower in C24h than that in N24h lambs (P < 0.05). Moreover, C24h lambs had a lower TLR3 mRNA abundance (P < 0.01) and a trend of lower TLR6 (P = 0.06) and interleukin 1 beta (P = 0.08) expression compared with those in M24h lambs. We also observed strong positive correlations of tumour necrosis factor alpha expression with that of TLR2 (r = 0.71; P < 0.001), TLR4 (r = 0.88; P < 0.001) and TLR8 (r = 0.83; P < 0.001). Interestingly, the expression of barrier-related molecules, including mucin-13, lysozyme, claudin (CLDN)-1, CLDN2, CLDN4, CLDN7, CLDN12, occludin, zonula occluden-1 and junctional adhesion molecule-1, was consistently lower in C24h lambs than that in N24h and M24h lambs (P < 0.05). These results indicated that the beneficial roles of colostrum intake on intestinal protection in newborn lambs were associated with low TLR expression, which was reflected by improved intestinal development and reduced inflammatory response. Further studies using fluorescence in situ hybridisation and immunohistochemical methods are needed to further explore the mechanisms underlying the lower expression of intestinal barrier-related molecules due to colostrum feeding.
Colostrum , Tumor Necrosis Factor-alpha , Animals , Animals, Newborn , Cattle , Colostrum/metabolism , Female , Ileum/metabolism , Immunity, Innate , Male , Pregnancy , RNA, Messenger/metabolism , Sheep , Sheep, Domestic , Toll-Like Receptor 3/analysis , Toll-Like Receptor 3/metabolism , Toll-Like Receptor 4 , Toll-Like Receptor 6/analysis , Toll-Like Receptor 6/metabolism , Toll-Like Receptor 8/analysis , Toll-Like Receptor 8/metabolism , Tumor Necrosis Factor-alpha/metabolism
Biofilm formation is a serious threat in the meat industry, mainly since it aids food-borne pathogen survival. Biofilms are often difficult to eliminate, and it is essential to understand the best possible deployable measures to remove or inactivate biofilms. We systematically reviewed the published in vitro studies that investigated various methods for removing biofilms in red meat. Publicly available databases, including Google Scholar and PubMed, were queried for relevant studies. The search was restricted to articles published in the English language from 2010 to 2021. We mined a total of 394 studies, of which 12 articles were included in this review. In summary, the studies demonstrated the inhibitory effect of various methods, including the use of bacteriophages, dry heat, cold atmospheric pressure, ozone gas, oils, and acids, on red meat extract or red meat culture. This systematic review suggests that in addition to existing sanitation and antibiotic procedures, other methods, such as the use of phage cocktails and different oils as nanoparticles, yield positive outcomes and may be taken from the in vitro setting to industry with prior validation of the techniques.
Bacteriophages , Red Meat , Bacteria , Bacteriophages/physiology , Biofilms , Food Microbiology , Meat/microbiology , Oils
Casein micelles (CMs) contribute to the physicochemical properties and stability of milk. However, how the proteome of CMs changes following heat treatment has not been elucidated. Here, changes in the proteins of CMs in samples of Holstein, buffalo, yak, goat, and camel milk following heat treatment were investigated using a LC-MS/MS approach. According to the hierarchical clustering results, Holstein, yak, and buffalo milk samples had similar CMs protein components, followed by goat and camel milk samples. Changes in lipoprotein lipase and α-lactalbumin in CMs were dependent on the intensity of heat treatment and were similar among the studied species, whereas changes in κ-casein, lactoferrin, and apolipoprotein A-I differed among different types of milk. These results provide information on the distribution and variations of the proteomes of CMs following heat treatment, which will assist in the identification of proteins that are dissociated and attached to CMs from different dairy species during heat treatment.
Caseins , Micelles , Animals , Chromatography, Liquid , Hot Temperature , Milk/chemistry , Milk Proteins/analysis , Tandem Mass Spectrometry , Whey Proteins
Fresh Milk Bar (FMB), an emerging dairy retail franchise, is used to instantly produce and sell pasteurized milk and other dairy products in China. However, the quality and safety of pasteurized milk in FMB have received little attention. The objective of this study was to investigate the prevalence, antimicrobial resistance, and virulence genes of Escherichia coli, Staphylococcus aureus, and Streptococcus in 205 pasteurized milk samples collected from FMBs in China. Four (2.0%) isolates of E. coli, seven (3.4%) isolates of S. aureus, and three (1.5%) isolates of Streptococcus agalactiae were isolated and identified. The E. coli isolates were resistant to amikacin (100%), streptomycin (50%), and tetracycline (50%). Their detected resistance genes include aac(3)-III (75%), blaTEM (25%), aadA (25%), aac(3)-II (25%), catI (25%), and qnrB (25%). The S. aureus isolates were mainly resistant to penicillin G (71.4%), trimethoprim-sulfamethoxazole (71.4%), kanamycin (57.1%), gentamicin (57.1%), amikacin (57.1%), and clindamycin (57.1%). blaZ (42.9%), mecA (28.6%), ermB (14.3%), and ermC (14.3%) were detected as their resistance genes. The Streptococcus strains were mainly resistant to tetracycline (66.7%) and contained the resistance genes pbp2b (33.3%) and tetM (33.3%). The virulence genes eae and stx2 were only found in one E. coli strain (25%), sec was detected in two S. aureus strains (28.6%), and bca was detected in one S. agalactiae strain (33.3%). The results of this study indicate that bacteria with drug resistance and virulence genes isolated from the pasteurized milk of FMB are a potential risk to consumers' health.
Milk , Staphylococcus aureus , Animals , Anti-Bacterial Agents/pharmacology , Drug Resistance , Drug Resistance, Bacterial/genetics , Escherichia coli/genetics , Microbial Sensitivity Tests , Prevalence , Staphylococcus aureus/genetics , Virulence/genetics
Animal production and health are of significant economic importance, particularly regarding the world food supply. Animal and veterinary sciences have evolved immensely in the past six decades, particularly in genetics, nutrition, housing, management and health. To address major challenges such as those posed by climate change or metabolic disorders, it is of utmost importance to use state-of-the-art research tools. Proteomics and the other post-genomic tools (transcriptomics or metabolomics) are among them. Proteomics has experienced a considerable development over the last decades. This brought developments to different scientific fields. The use and adoption of proteomics tools in animal and veterinary sciences has some limitations (database availability or access to proteomics platforms and funding). As a result, proteomics' use by animal science researchers varies across the globe. In this viewpoint article, we focus on the developments of domestic animal proteomics over the last decade in different regions of the globe and how the researchers have coped with such challenges. In the second part of the article, we provide examples of funding, educational and laboratory establishment initiatives designed to foster the development of (animal-based) proteomics. International scientific collaboration is a definitive and key feature in the development and advancement of domestic animal proteomics. SIGNIFICANCE: Animal production and health are very important for food supply worldwide particularly as a source of proteinaceous foods. Animal and veterinary sciences have evolved immensely in the last decades. In order to address the major contemporary challenges facing animal and veterinary sciences, it is of utmost importance to use state-of-the-art research tools such as Proteomics and other Omics. Herein, we focus on the major developments in domestic animal proteomics worldwide during the last decade and how different regions of the world have used the technology in this specific research field. We address also major international efforts aiming to increase the research output in this area and highlight the importance of international cooperation to address specific problems inherent to domestic animal proteomics.
Animals, Domestic , Proteomics , Animals , Computational Biology , Metabolomics , Retrospective Studies
This study investigated the occurrence and resistance rates of Staphylococcus aureus strains isolated from raw milk in the dairy farms over two seasons (spring and autumn) and across four regions that included 11 provinces in China. In total, 750 raw milk samples from the 405 dairy farms were collected. Fifteen antimicrobial agents were tested for antimicrobial resistance via disk diffusion tests, and PCR tests were performed to identify drug resistance genes of S. aureus isolates. Out of 750 samples, 276 (36.8%) were positive for S. aureus, with 150 (41.1%) being positive in spring and 126 (32.7%) being positive in autumn. The occurrence rate of S. aureus in northeastern China (45%) was higher than that in western China (33%) and southern China (31.9%), respectively, and the rate significantly (p < 0.05) differed from those of western China and southern China. Of 276 isolates, 261 (94.6%) strains were resistant to more than 1 antimicrobial drug, and 193 (69.9%) strains were multidrug resistant. The blaZ (46.3%), dfrG (35.5%), and tetM (27.2%) genes were detected at a high frequency in the S. aureus strains. Our data revealed a variation (p < 0.05) in the resistance patterns in the different regions and across the two seasons. The occurrence and drug resistance rates of S. aureus isolated from raw milk obtained from dairy farms may still cause severe problems in China.
Anti-Bacterial Agents/pharmacology , Drug Resistance, Bacterial/genetics , Milk/microbiology , Staphylococcus aureus/drug effects , Staphylococcus aureus/genetics , Animals , Cattle , China/epidemiology , Disk Diffusion Antimicrobial Tests , Drug Resistance, Multiple, Bacterial/genetics , Farms , Female , Polymerase Chain Reaction , Residence Characteristics , Seasons
