+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

DNA carryover in milk samples from routine milk recording used for PCR-based diagnosis of bovine Staphylococcus aureus mastitis



DNA carryover in milk samples from routine milk recording used for PCR-based diagnosis of bovine Staphylococcus aureus mastitis



Journal of Dairy Science 100(7): 5709-5716



Real-time PCR techniques are increasingly used to detect udder pathogens from milk samples collected non-aseptically at routine milk recording. The objectives of this study were (1) to estimate the statistical associations between cycle threshold (Ct) values for Staphylococcus aureus in non-aseptically collected composite samples taken at routine milk recording from cows milked consecutively with the same milking unit and milk meter; and (2) to formulate practical and plausible guidelines for understanding the diagnostic implications of PCR testing for Staph. aureus intramammary infection at routine milk recording. The study included 4 herds with conventional milking parlors and repeatedly low Ct-values for Staph. aureus (representing a high DNA load) in bulk tank milk. Composite milk samples were collected from all cows at all milking units during routine milk recording using the Tru-Test electronic milk meter (Tru-Test Group, Auckland, New Zealand) and analyzed using the PathoProof PCR (Thermo Fisher Scientific, Vantaa, Finland) assay. Milking clock times were retrieved at each milk meter to establish the milking order of the cows at each unit. A multinomial logistic regression was applied to estimate the association between Ct-values from cows milked consecutively with the same milking unit and milk meter. The following groups were selected based on Ct-values: (1) 0-31.3, (2) 31.4-33.9, (3) 34.0-37, (4) 37.1-39.9, and (5) 40 (negative result). The association between groups from cows milked consecutively with the same milking unit and milk meter was statistically significant. Approximately 60% of cows were in Ct group 5 if the antecedent cow was also in Ct group 5, but only 20% of cows were in Ct group 5 if the antecedent cow was in Ct group 1. The probability of cows being in Ct group 1 was not markedly influenced by the group of the antecedent cow. Statistical relationships in the intermediate range gave a plausible indication of a dose-response relationship. Carryover of bacterial DNA via the milking unit and milk meter is very likely to affect PCR results for Staph. aureus. Therefore, information about milking order must be considered in mastitis control efforts. We suggest a practical interpretation of PCR results: cows with a Ct-value <32 can be labeled "very likely to be infected with Staph. aureus," but cows with Ct-values of >37 and 32-37 can be labeled "very likely to be negative for Staph. aureus" and "uncertain Staph. aureus status," respectively.

Please choose payment method:






(PDF emailed within 0-6 h: $19.90)

Accession: 059622443

Download citation: RISBibTeXText

PMID: 28527807

DOI: 10.3168/jds.2016-12330


Related references

Detection of different Staphylococcus aureus strains in bovine milk from subclinical mastitis using PCR and routine techniques. Brazilian Journal of Microbiology 32(1): 27-31, January-March, 2001

Bovine milk proteome: quantitative changes in normal milk exosomes, milk fat globule membranes and whey proteomes resulting from Staphylococcus aureus mastitis. Journal of Proteomics 82: 141-154, 2013

Use of composite milk samples for diagnosis of Staphylococcus aureus mastitis in dairy cattle. Journal of the American Veterinary Medical Association 208(10): 1705-1708, 1996

Resistance situation and enterotoxin production capacity of Staphylococcus aureus strains from bovine mastitis milk samples. Schweizer Archiv für Tierheilkunde 141(6): 287-290, 1999

Resistance pattern and enterotoxin production of Staphylococcus aureus strains isolated from bovine mastitis milk samples. Schweizer Archiv fur Tierheilkunde 141(6): 287-290, 1999

Detection of virulence-associated genes in Staphylococcus aureus isolated from bovine clinical mastitis milk samples in Guangxi. Tropical Animal Health and Production 44(8): 1821-1826, 2012

Genetic diversity and antimicrobial susceptibility profiles among mastitis-causing Staphylococcus aureus isolated from bovine milk samples. American Journal of Veterinary Research 67(7): 1185-1191, 2006

Studies on antibiotics in ewe's milk. (a). Antibiotic levels in milk samples from ewes treated intramammarily with various mastitis preparations, (b). Inhibition of Staphylococcus aureus by ewe's milk containing various antibiotics. Refuah vet 25: 1, 57-69; 1-4, 1968

Bovine mastitis as the primary contamination source of milk and milk products with Staphylococcus aureus enterotoxins. Veterinarija ir Zootechnika (36): 21-26, 2006

Development and validation of a loop mediated isothermal amplification (LAMP) assay for the detection of Staphylococcus aureus in bovine mastitis milk samples. Molecular and Cellular Probes 30(5): 320-325, 2016

Occurrence of enterotoxin genes and macrorestriction analysis of Staphylococcus aureus isolated from bovine mastitis and bulk-tank milk samples in Italy. An epidemiological study. Italian Journal of Animal Science 3(1): 47-53, 2004

Distribution of superantigenic toxin genes in Staphylococcus aureus isolates from milk samples of bovine subclinical mastitis cases in two major diary production regions of China. Veterinary Microbiology 137(3-4): 276-281, 2009

Bovine mastitis: the diagnostic properties of a PCR-based assay to monitor the Staphylococcus aureus genotype B status of a herd, using bulk tank milk. Journal of Dairy Science 95(7): 3674-3682, 2012

Influence of milk, milk fractions and milk proteins on the growth and viability of mastitis-causing Staphylococcus aureus strain. Italian Journal of Animal Science 16(2): 321-328, 2017

The suitability of different methods for determining staphylococcus aureus from milk samples and staphylococcus aureus contamination of farm milk according to the results obtained. Meijeritieteellinen Aikakauskirja 37: 33-44, 1979