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Alejandra Andrea Latorre - One of the best experts on this subject based on the ideXlab platform.

  • Molecular diversity of Staphylococcus aureus and the role of Milking Equipment adherences or biofilm as a source for bulk tank milk contamination.
    Journal of dairy science, 2020
    Co-Authors: P.a. Pacha, M.a. Munoz, Gerardo González-rocha, Mario Quezada-aguiluz, Alejandro Aguayo-reyes, Helia Bello-toledo, I. San Martín, Alejandra Andrea Latorre
    Abstract:

    ABSTRACT Staphylococcus aureus is one of the most frequent pathogens causing intramammary infections in dairy herds. Consequently, virulence factors, pathobiology, and epidemiology of Staphylococcus aureus strains have been widely assessed through the years. Nevertheless, not much has been described about the epidemiology of Staph. aureus strains from bulk tank milk (BTM) and adherences on Milking Equipment (AMES), even when these strains may play a role in the quality of milk that is intended for human consumption. The objective of this study was to assess the strain diversity of 166 Staph. aureus isolates collected from 3 consecutive BTM samples, and from AMES in contact with milk from 23 Chilean dairy farms. Isolates were analyzed and typed using pulsed-field gel electrophoresis. Diversity of strains, both within and among farms, was assessed using Simpson's index of diversity (SID). On farms where Staph. aureus was isolated from both AMES and BTM (n = 8), pulsotypes were further analyzed to evaluate the role of AMES as a potential source of Staph. aureus strains in BTM. Among all Staph. aureus analyzed by pulsed-field gel electrophoresis, a total of 42 pulsotypes (19 main pulsotypes and 23 subtypes) were identified. Among dairy farms, strain diversity was highly heterogeneous (SID = 0.99). Within dairy farms, Staph. aureus strain diversity was variable (SID = 0 to 1), and 18 dairy operations (81.8%) had one pulsotype that was shared between at least 2 successive BTM samples. In those farms where Staph. aureus was isolated in both AMES and BTM (n = 8), 7 (87.5%) showed a clonal distribution of Staph. aureus strains between these 2 types of samples. The overlapping of certain Staph. aureus strains among dairy farms may point out common sources of Staph. aureus among otherwise epidemiologically unrelated farms. Indistinguishable Staph. aureus strains between AMES and BTM across dairy farms suggest that Staph. aureus–containing AMES may represent a source for BTM contamination, thus affecting milk quality. Our study highlights the role of viable Staph. aureus in AMES as a source for BTM contamination on dairy farms, and also describes the overlapping and presence of specific BTM and AMES pulsotypes among farms.

  • Short communication: Virulence profiles of Staphylococcus aureus isolated from bulk tank milk and adherences on Milking Equipment on Chilean dairy farms.
    Journal of dairy science, 2020
    Co-Authors: P.a. Pacha, M.a. Munoz, E. Paredes-osses, Alejandra Andrea Latorre
    Abstract:

    ABSTRACT Staphylococcus aureus is an important intramammary pathogen for dairy cows that also is remarkably important for public health. Multiple virulence factors can be involved simultaneously during the pathogenesis of a staphylococcal disease, including adhesion proteins, extracellular enzymes, and toxins. The main objective of this study was to assess virulence factors that are associated with cow intramammary infection (IMI) and of human health concern among Staph. aureus isolates obtained from bulk tank milk (BTM) and adherences on Milking Equipment surfaces. A total of 166 Staph. aureus isolates from 23 dairy farms were characterized according to their virulence profiles. For virulence factors of importance in IMI, the presence of the virulence markers thermonuclease (nuc) and coagulase (coa) and virulence genes such as fibronectin (fnbA) and intercellular adhesion (icaA, icaD) were assessed. For virulence factors of public health concern, presence of antimicrobial resistance (mecA and mecC) and enterotoxin (sea and seb) genes were analyzed. Among all Staph. aureus isolates, 5 virulence profiles were found; the profile nuc(+) coa(+) fnbA(+) icaA(+) icaD(+) mecA(−) mecC(−) sea(−) seb(−) was the most frequently observed (21 out of 23 dairy farms). No differences were found between the virulence profile frequencies of Staph. aureus from BTM and adherences on Milking Equipment surfaces. The virulence profiles most frequently observed included genes involved in the adherence and biofilm-forming ability of Staph. aureus, which could represent a potential advantage for the bacterium during the early stages of IMI colonization and for persistence on surfaces. Our results indicate a greater frequency of virulence factors of importance for IMI pathogenesis than virulence factors of public health concern, consistent with the dairy origin of isolates. The mecA, mecC, and seb genes were not observed among Staph. aureus isolates analyzed in this study. However, the sea gene was detected in 3 Staph. aureus isolated from BTM, thus posing a potential public health threat. Our results emphasize the importance of understanding the epidemiology and dynamics of Staph. aureus on dairy farms as a tool for the improvement of udder health and milk safety.

  • On-Farm Surfaces in Contact with Milk: The Role of Staphylococcus aureus-Containing Biofilms for Udder Health and Milk Quality
    Foodborne pathogens and disease, 2019
    Co-Authors: Alejandra Andrea Latorre, P.a. Pacha, Gerardo González-rocha, Iván San Martín, Mario Quezada-aguiluz, Alejandro Aguayo-reyes, Helia Bello-toledo, Ricardo Oliva, Alexis Estay, Julio Pugin
    Abstract:

    Staphylococcus aureus is a Gram-positive bacterium that causes intramammary infections and bulk tank milk (BTM) contamination in dairy operations around the world in spite of on-farm application of preventive measures. The study was conducted on a 30-cow dairy farm in the Nuble Region of Chile. For BTM culture and somatic cell count (SCC) analysis, three consecutive BTM samples were collected. Samples for bacterial culture (n = 16) were collected from macroscopic adherence on previously washed, sanitized, and dry Milking Equipment surfaces in direct contact with milk during Milking or cooling. A total of 48 S. aureus isolates from BTM, Milking Equipment, and cows' quarters with intramammary infections were analyzed by pulsed-field gel electrophoresis (PFGE). Selected Milking Equipment pieces were removed for biofilm visualization using scanning electron microscopy (SEM). S. aureus was isolated from all three BTM samples; the average SCC for the three BTM samples was 1,429,333 cells/mL. Fourteen of the 16 samples of Milking Equipment (87.5%) were culture positive for S. aureus. Biofilms were visualized by SEM in all four removed Milking Equipment pieces. Microorganisms observed by SEM in those biofilms were mainly coccus-shaped bacteria, and microbiological culture of these biofilms yielded viable S. aureus isolates in all samples. All pulsotypes observed among S. aureus isolates from BTM were indistinguishable from those in Milking Equipment surfaces. All PFGE pulsotypes observed among S. aureus isolates from biofilms on rubber liners were indistinguishable from isolates from intramammary infections in cows. Our findings suggest that Milking Equipment films may act as source of S. aureus contamination for BTM and cows during Milking, thus compromising the microbiological quality of milk used for manufacturing dairy products.

P.a. Pacha - One of the best experts on this subject based on the ideXlab platform.

  • Molecular diversity of Staphylococcus aureus and the role of Milking Equipment adherences or biofilm as a source for bulk tank milk contamination.
    Journal of dairy science, 2020
    Co-Authors: P.a. Pacha, M.a. Munoz, Gerardo González-rocha, Mario Quezada-aguiluz, Alejandro Aguayo-reyes, Helia Bello-toledo, I. San Martín, Alejandra Andrea Latorre
    Abstract:

    ABSTRACT Staphylococcus aureus is one of the most frequent pathogens causing intramammary infections in dairy herds. Consequently, virulence factors, pathobiology, and epidemiology of Staphylococcus aureus strains have been widely assessed through the years. Nevertheless, not much has been described about the epidemiology of Staph. aureus strains from bulk tank milk (BTM) and adherences on Milking Equipment (AMES), even when these strains may play a role in the quality of milk that is intended for human consumption. The objective of this study was to assess the strain diversity of 166 Staph. aureus isolates collected from 3 consecutive BTM samples, and from AMES in contact with milk from 23 Chilean dairy farms. Isolates were analyzed and typed using pulsed-field gel electrophoresis. Diversity of strains, both within and among farms, was assessed using Simpson's index of diversity (SID). On farms where Staph. aureus was isolated from both AMES and BTM (n = 8), pulsotypes were further analyzed to evaluate the role of AMES as a potential source of Staph. aureus strains in BTM. Among all Staph. aureus analyzed by pulsed-field gel electrophoresis, a total of 42 pulsotypes (19 main pulsotypes and 23 subtypes) were identified. Among dairy farms, strain diversity was highly heterogeneous (SID = 0.99). Within dairy farms, Staph. aureus strain diversity was variable (SID = 0 to 1), and 18 dairy operations (81.8%) had one pulsotype that was shared between at least 2 successive BTM samples. In those farms where Staph. aureus was isolated in both AMES and BTM (n = 8), 7 (87.5%) showed a clonal distribution of Staph. aureus strains between these 2 types of samples. The overlapping of certain Staph. aureus strains among dairy farms may point out common sources of Staph. aureus among otherwise epidemiologically unrelated farms. Indistinguishable Staph. aureus strains between AMES and BTM across dairy farms suggest that Staph. aureus–containing AMES may represent a source for BTM contamination, thus affecting milk quality. Our study highlights the role of viable Staph. aureus in AMES as a source for BTM contamination on dairy farms, and also describes the overlapping and presence of specific BTM and AMES pulsotypes among farms.

  • Short communication: Virulence profiles of Staphylococcus aureus isolated from bulk tank milk and adherences on Milking Equipment on Chilean dairy farms.
    Journal of dairy science, 2020
    Co-Authors: P.a. Pacha, M.a. Munoz, E. Paredes-osses, Alejandra Andrea Latorre
    Abstract:

    ABSTRACT Staphylococcus aureus is an important intramammary pathogen for dairy cows that also is remarkably important for public health. Multiple virulence factors can be involved simultaneously during the pathogenesis of a staphylococcal disease, including adhesion proteins, extracellular enzymes, and toxins. The main objective of this study was to assess virulence factors that are associated with cow intramammary infection (IMI) and of human health concern among Staph. aureus isolates obtained from bulk tank milk (BTM) and adherences on Milking Equipment surfaces. A total of 166 Staph. aureus isolates from 23 dairy farms were characterized according to their virulence profiles. For virulence factors of importance in IMI, the presence of the virulence markers thermonuclease (nuc) and coagulase (coa) and virulence genes such as fibronectin (fnbA) and intercellular adhesion (icaA, icaD) were assessed. For virulence factors of public health concern, presence of antimicrobial resistance (mecA and mecC) and enterotoxin (sea and seb) genes were analyzed. Among all Staph. aureus isolates, 5 virulence profiles were found; the profile nuc(+) coa(+) fnbA(+) icaA(+) icaD(+) mecA(−) mecC(−) sea(−) seb(−) was the most frequently observed (21 out of 23 dairy farms). No differences were found between the virulence profile frequencies of Staph. aureus from BTM and adherences on Milking Equipment surfaces. The virulence profiles most frequently observed included genes involved in the adherence and biofilm-forming ability of Staph. aureus, which could represent a potential advantage for the bacterium during the early stages of IMI colonization and for persistence on surfaces. Our results indicate a greater frequency of virulence factors of importance for IMI pathogenesis than virulence factors of public health concern, consistent with the dairy origin of isolates. The mecA, mecC, and seb genes were not observed among Staph. aureus isolates analyzed in this study. However, the sea gene was detected in 3 Staph. aureus isolated from BTM, thus posing a potential public health threat. Our results emphasize the importance of understanding the epidemiology and dynamics of Staph. aureus on dairy farms as a tool for the improvement of udder health and milk safety.

  • On-Farm Surfaces in Contact with Milk: The Role of Staphylococcus aureus-Containing Biofilms for Udder Health and Milk Quality
    Foodborne pathogens and disease, 2019
    Co-Authors: Alejandra Andrea Latorre, P.a. Pacha, Gerardo González-rocha, Iván San Martín, Mario Quezada-aguiluz, Alejandro Aguayo-reyes, Helia Bello-toledo, Ricardo Oliva, Alexis Estay, Julio Pugin
    Abstract:

    Staphylococcus aureus is a Gram-positive bacterium that causes intramammary infections and bulk tank milk (BTM) contamination in dairy operations around the world in spite of on-farm application of preventive measures. The study was conducted on a 30-cow dairy farm in the Nuble Region of Chile. For BTM culture and somatic cell count (SCC) analysis, three consecutive BTM samples were collected. Samples for bacterial culture (n = 16) were collected from macroscopic adherence on previously washed, sanitized, and dry Milking Equipment surfaces in direct contact with milk during Milking or cooling. A total of 48 S. aureus isolates from BTM, Milking Equipment, and cows' quarters with intramammary infections were analyzed by pulsed-field gel electrophoresis (PFGE). Selected Milking Equipment pieces were removed for biofilm visualization using scanning electron microscopy (SEM). S. aureus was isolated from all three BTM samples; the average SCC for the three BTM samples was 1,429,333 cells/mL. Fourteen of the 16 samples of Milking Equipment (87.5%) were culture positive for S. aureus. Biofilms were visualized by SEM in all four removed Milking Equipment pieces. Microorganisms observed by SEM in those biofilms were mainly coccus-shaped bacteria, and microbiological culture of these biofilms yielded viable S. aureus isolates in all samples. All pulsotypes observed among S. aureus isolates from BTM were indistinguishable from those in Milking Equipment surfaces. All PFGE pulsotypes observed among S. aureus isolates from biofilms on rubber liners were indistinguishable from isolates from intramammary infections in cows. Our findings suggest that Milking Equipment films may act as source of S. aureus contamination for BTM and cows during Milking, thus compromising the microbiological quality of milk used for manufacturing dairy products.

Ynte H. Schukken - One of the best experts on this subject based on the ideXlab platform.

  • Biofilm in Milking Equipment on a dairy farm as a potential source of bulk tank milk contamination with Listeria monocytogenes
    Journal of dairy science, 2010
    Co-Authors: Alejandra A. Latorre, J.s. Van Kessel, Jeffrey S. Karns, M.j. Zurakowski, Abani K. Pradhan, Kathryn J. Boor, Bhushan M. Jayarao, Beth A. Houser, C.s. Daugherty, Ynte H. Schukken
    Abstract:

    The objective of this study was to assess the presence of a Listeria monocytogenes-containing biofilm in Milking Equipment as a potential source of bulk tank milk contamination on a dairy farm where milk contamination had been previously documented. Samples were collected from Milking Equipment and Milking parlor premises on 4 occasions and analyzed for the presence of L. monocytogenes. Pulsed-field gel electrophoresis (PFGE) typing was conducted on L. monocytogenes isolates from the Milking Equipment, parlor and storage room floors, bulk tank milk, and in-line milk filters. Pieces from milk meters and rubber liners were obtained to visually assess the presence of a biofilm using scanning electron microscopy. A total of 6 (15%), 4 (25%), and 1 (6%) samples were culture-positive for L. monocytogenes in the first, second, and third sample collection, respectively. Two samples were L. monocytogenes hly PCR-positive but were culture-negative in the fourth sample collection. Combined AscI and ApaI restriction analysis yielded 6 PFGE types for 15 L. monocytogenes isolates obtained from Milking Equipment, parlor, bulk tank milk, and milk filters. A predominant and persistent PFGE type (PFGE type T) was observed among these L. monocytogenes isolates (9/15 isolates). Scanning electron microscopy of samples from the bottom cover of 2 milk meters showed the presence of individual and clusters of bacteria, mainly associated with surface scratches. The presence of a bacterial biofilm was observed on the bottom covers of the 2 milk meters. Prevention of the establishment of biofilms in Milking Equipment is a crucial step in fulfilling the requirement of safe, high-quality milk.

  • Molecular Ecology of Listeria monocytogenes: Evidence for a Reservoir in Milking Equipment on a Dairy Farm
    Applied and environmental microbiology, 2008
    Co-Authors: Alejandra A. Latorre, Jeffrey S. Karns, M.j. Zurakowski, Abani K. Pradhan, Kathryn J. Boor, Jo Ann S. Van Kessel, Ruth N. Zadoks, Ynte H. Schukken
    Abstract:

    A longitudinal study aimed to detect Listeria monocytogenes on a New York State dairy farm was conducted between February 2004 and July 2007. Fecal samples were collected every 6 months from all lactating cows. Approximately 20 environmental samples were obtained every 3 months. Bulk tank milk samples and in-line milk filter samples were obtained weekly. Samples from Milking Equipment and the Milking parlor environment were obtained in May 2007. Fifty-one of 715 fecal samples (7.1%) and 22 of 303 environmental samples (7.3%) were positive for L. monocytogenes. A total of 73 of 108 in-line milk filter samples (67.6%) and 34 of 172 bulk tank milk samples (19.7%) were positive for L. monocytogenes. Listeria monocytogenes was isolated from 6 of 40 (15%) sampling sites in the Milking parlor and Milking Equipment. In-line milk filter samples had a greater proportion of L. monocytogenes than did bulk tank milk samples (P < 0.05) and samples from other sources (P < 0.05). The proportion of L. monocytogenes-positive samples was greater among bulk tank milk samples than among fecal or environmental samples (P < 0.05). Analysis of 60 isolates by pulsed-field gel electrophoresis (PFGE) yielded 23 PFGE types after digestion with AscI and ApaI endonucleases. Three PFGE types of L. monocytogenes were repeatedly found in longitudinally collected samples from bulk tank milk and in-line milk filters.

  • Comparison of Staphylococcus aureus Isolates from Bovine and Human Skin, Milking Equipment, and Bovine Milk by Phage Typing, Pulsed-Field Gel Electrophoresis, and Binary Typing
    Journal of clinical microbiology, 2002
    Co-Authors: Ruth N. Zadoks, Ynte H. Schukken, W. Van Leeuwen, D. Kreft, Lawrence K. Fox, Herman W. Barkema, A. Van Belkum
    Abstract:

    Staphylococcus aureus isolates (n = 225) from bovine teat skin, human skin, Milking Equipment, and bovine milk were fingerprinted by pulsed-field gel electrophoresis (PFGE). Strains were compared to assess the role of skin and Milking Equipment as sources of S. aureus mastitis. PFGE of SmaI-digested genomic DNA identified 24 main types and 17 subtypes among isolates from 43 herds and discriminated between isolates from bovine teat skin and milk. Earlier, phage typing (L. K. Fox, M. Gershmann, D. D. Hancock, and C. T. Hutton, Cornell Vet. 81:183-193, 1991) had failed to discriminate between isolates from skin and milk. Skin isolates from humans belonged to the same pulsotypes as skin isolates from cows. Milking Equipment harbored strains from skin as well as strains from milk. We conclude that S. aureus strains from skin and from milk can both be transmitted via the Milking machine, but that skin strains are not an important source of intramammary S. aureus infections in dairy cows. A subset of 142 isolates was characterized by binary typing with DNA probes developed for typing of human S. aureus. Typeability and overall concordance with epidemiological data were lower for binary typing than for PFGE while discriminatory powers were similar. Within several PFGE types, binary typing discriminated between main types and subtypes and between isolates from different herds or sources. Thus, binary typing is not suitable as replacement for PFGE but may be useful in combination with PFGE to refine strain differentiation.

M.a. Munoz - One of the best experts on this subject based on the ideXlab platform.

  • Molecular diversity of Staphylococcus aureus and the role of Milking Equipment adherences or biofilm as a source for bulk tank milk contamination.
    Journal of dairy science, 2020
    Co-Authors: P.a. Pacha, M.a. Munoz, Gerardo González-rocha, Mario Quezada-aguiluz, Alejandro Aguayo-reyes, Helia Bello-toledo, I. San Martín, Alejandra Andrea Latorre
    Abstract:

    ABSTRACT Staphylococcus aureus is one of the most frequent pathogens causing intramammary infections in dairy herds. Consequently, virulence factors, pathobiology, and epidemiology of Staphylococcus aureus strains have been widely assessed through the years. Nevertheless, not much has been described about the epidemiology of Staph. aureus strains from bulk tank milk (BTM) and adherences on Milking Equipment (AMES), even when these strains may play a role in the quality of milk that is intended for human consumption. The objective of this study was to assess the strain diversity of 166 Staph. aureus isolates collected from 3 consecutive BTM samples, and from AMES in contact with milk from 23 Chilean dairy farms. Isolates were analyzed and typed using pulsed-field gel electrophoresis. Diversity of strains, both within and among farms, was assessed using Simpson's index of diversity (SID). On farms where Staph. aureus was isolated from both AMES and BTM (n = 8), pulsotypes were further analyzed to evaluate the role of AMES as a potential source of Staph. aureus strains in BTM. Among all Staph. aureus analyzed by pulsed-field gel electrophoresis, a total of 42 pulsotypes (19 main pulsotypes and 23 subtypes) were identified. Among dairy farms, strain diversity was highly heterogeneous (SID = 0.99). Within dairy farms, Staph. aureus strain diversity was variable (SID = 0 to 1), and 18 dairy operations (81.8%) had one pulsotype that was shared between at least 2 successive BTM samples. In those farms where Staph. aureus was isolated in both AMES and BTM (n = 8), 7 (87.5%) showed a clonal distribution of Staph. aureus strains between these 2 types of samples. The overlapping of certain Staph. aureus strains among dairy farms may point out common sources of Staph. aureus among otherwise epidemiologically unrelated farms. Indistinguishable Staph. aureus strains between AMES and BTM across dairy farms suggest that Staph. aureus–containing AMES may represent a source for BTM contamination, thus affecting milk quality. Our study highlights the role of viable Staph. aureus in AMES as a source for BTM contamination on dairy farms, and also describes the overlapping and presence of specific BTM and AMES pulsotypes among farms.

  • Short communication: Virulence profiles of Staphylococcus aureus isolated from bulk tank milk and adherences on Milking Equipment on Chilean dairy farms.
    Journal of dairy science, 2020
    Co-Authors: P.a. Pacha, M.a. Munoz, E. Paredes-osses, Alejandra Andrea Latorre
    Abstract:

    ABSTRACT Staphylococcus aureus is an important intramammary pathogen for dairy cows that also is remarkably important for public health. Multiple virulence factors can be involved simultaneously during the pathogenesis of a staphylococcal disease, including adhesion proteins, extracellular enzymes, and toxins. The main objective of this study was to assess virulence factors that are associated with cow intramammary infection (IMI) and of human health concern among Staph. aureus isolates obtained from bulk tank milk (BTM) and adherences on Milking Equipment surfaces. A total of 166 Staph. aureus isolates from 23 dairy farms were characterized according to their virulence profiles. For virulence factors of importance in IMI, the presence of the virulence markers thermonuclease (nuc) and coagulase (coa) and virulence genes such as fibronectin (fnbA) and intercellular adhesion (icaA, icaD) were assessed. For virulence factors of public health concern, presence of antimicrobial resistance (mecA and mecC) and enterotoxin (sea and seb) genes were analyzed. Among all Staph. aureus isolates, 5 virulence profiles were found; the profile nuc(+) coa(+) fnbA(+) icaA(+) icaD(+) mecA(−) mecC(−) sea(−) seb(−) was the most frequently observed (21 out of 23 dairy farms). No differences were found between the virulence profile frequencies of Staph. aureus from BTM and adherences on Milking Equipment surfaces. The virulence profiles most frequently observed included genes involved in the adherence and biofilm-forming ability of Staph. aureus, which could represent a potential advantage for the bacterium during the early stages of IMI colonization and for persistence on surfaces. Our results indicate a greater frequency of virulence factors of importance for IMI pathogenesis than virulence factors of public health concern, consistent with the dairy origin of isolates. The mecA, mecC, and seb genes were not observed among Staph. aureus isolates analyzed in this study. However, the sea gene was detected in 3 Staph. aureus isolated from BTM, thus posing a potential public health threat. Our results emphasize the importance of understanding the epidemiology and dynamics of Staph. aureus on dairy farms as a tool for the improvement of udder health and milk safety.

Gerardo González-rocha - One of the best experts on this subject based on the ideXlab platform.

  • Molecular diversity of Staphylococcus aureus and the role of Milking Equipment adherences or biofilm as a source for bulk tank milk contamination.
    Journal of dairy science, 2020
    Co-Authors: P.a. Pacha, M.a. Munoz, Gerardo González-rocha, Mario Quezada-aguiluz, Alejandro Aguayo-reyes, Helia Bello-toledo, I. San Martín, Alejandra Andrea Latorre
    Abstract:

    ABSTRACT Staphylococcus aureus is one of the most frequent pathogens causing intramammary infections in dairy herds. Consequently, virulence factors, pathobiology, and epidemiology of Staphylococcus aureus strains have been widely assessed through the years. Nevertheless, not much has been described about the epidemiology of Staph. aureus strains from bulk tank milk (BTM) and adherences on Milking Equipment (AMES), even when these strains may play a role in the quality of milk that is intended for human consumption. The objective of this study was to assess the strain diversity of 166 Staph. aureus isolates collected from 3 consecutive BTM samples, and from AMES in contact with milk from 23 Chilean dairy farms. Isolates were analyzed and typed using pulsed-field gel electrophoresis. Diversity of strains, both within and among farms, was assessed using Simpson's index of diversity (SID). On farms where Staph. aureus was isolated from both AMES and BTM (n = 8), pulsotypes were further analyzed to evaluate the role of AMES as a potential source of Staph. aureus strains in BTM. Among all Staph. aureus analyzed by pulsed-field gel electrophoresis, a total of 42 pulsotypes (19 main pulsotypes and 23 subtypes) were identified. Among dairy farms, strain diversity was highly heterogeneous (SID = 0.99). Within dairy farms, Staph. aureus strain diversity was variable (SID = 0 to 1), and 18 dairy operations (81.8%) had one pulsotype that was shared between at least 2 successive BTM samples. In those farms where Staph. aureus was isolated in both AMES and BTM (n = 8), 7 (87.5%) showed a clonal distribution of Staph. aureus strains between these 2 types of samples. The overlapping of certain Staph. aureus strains among dairy farms may point out common sources of Staph. aureus among otherwise epidemiologically unrelated farms. Indistinguishable Staph. aureus strains between AMES and BTM across dairy farms suggest that Staph. aureus–containing AMES may represent a source for BTM contamination, thus affecting milk quality. Our study highlights the role of viable Staph. aureus in AMES as a source for BTM contamination on dairy farms, and also describes the overlapping and presence of specific BTM and AMES pulsotypes among farms.

  • On-Farm Surfaces in Contact with Milk: The Role of Staphylococcus aureus-Containing Biofilms for Udder Health and Milk Quality
    Foodborne pathogens and disease, 2019
    Co-Authors: Alejandra Andrea Latorre, P.a. Pacha, Gerardo González-rocha, Iván San Martín, Mario Quezada-aguiluz, Alejandro Aguayo-reyes, Helia Bello-toledo, Ricardo Oliva, Alexis Estay, Julio Pugin
    Abstract:

    Staphylococcus aureus is a Gram-positive bacterium that causes intramammary infections and bulk tank milk (BTM) contamination in dairy operations around the world in spite of on-farm application of preventive measures. The study was conducted on a 30-cow dairy farm in the Nuble Region of Chile. For BTM culture and somatic cell count (SCC) analysis, three consecutive BTM samples were collected. Samples for bacterial culture (n = 16) were collected from macroscopic adherence on previously washed, sanitized, and dry Milking Equipment surfaces in direct contact with milk during Milking or cooling. A total of 48 S. aureus isolates from BTM, Milking Equipment, and cows' quarters with intramammary infections were analyzed by pulsed-field gel electrophoresis (PFGE). Selected Milking Equipment pieces were removed for biofilm visualization using scanning electron microscopy (SEM). S. aureus was isolated from all three BTM samples; the average SCC for the three BTM samples was 1,429,333 cells/mL. Fourteen of the 16 samples of Milking Equipment (87.5%) were culture positive for S. aureus. Biofilms were visualized by SEM in all four removed Milking Equipment pieces. Microorganisms observed by SEM in those biofilms were mainly coccus-shaped bacteria, and microbiological culture of these biofilms yielded viable S. aureus isolates in all samples. All pulsotypes observed among S. aureus isolates from BTM were indistinguishable from those in Milking Equipment surfaces. All PFGE pulsotypes observed among S. aureus isolates from biofilms on rubber liners were indistinguishable from isolates from intramammary infections in cows. Our findings suggest that Milking Equipment films may act as source of S. aureus contamination for BTM and cows during Milking, thus compromising the microbiological quality of milk used for manufacturing dairy products.