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Resistance to penicillin of Staphylococcus aureus isolates from cows with high somatic cell counts in organic and conventional dairy herds in Denmark

Bennedsgaard, Torben Werner; Thamsborg, Stig Milan; Aarestrup, Frank Møller; Enevoldsen, Carsten; Vaarst, Mette and Christoffersen, Anna Bodil (2006) Resistance to penicillin of Staphylococcus aureus isolates from cows with high somatic cell counts in organic and conventional dairy herds in Denmark. Acta Veterinaria Scandinavica, 48 (24).

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Summary

Quarter milk samples from cows with high risk of intramammary infection were examined to determine the prevalence of Staphylococcus aureus (SA) and penicillin resistant SA (SAr) in conventional and organic dairy herds and herds converting to organic farming in a combined longitudinal and cross-sectional study. 20 conventional herds, 18 organic herds that converted before 1995, and 19 herds converting to organic farming in 1999 or 2000 were included in the study. Herds converting to organic farming were sampled three times one year apart; the other herds were sampled once. Risk of infection was estimated based on somatic cell count, milk production, breed, age and lactation stage. The high-risk cows represented about 49 % of the cows in the herds. The overall prevalence of SAr and SA among these cows was 4% (95% confidence interval: 2%-5%) and 29% (95% confidence interval: 24%-34%) respectively. The prevalence of penicillin resistance among SA infected cows was 12% (95% confidence interval: 6%-19%) when calculated from the first herd visits. No statistically significant differences were observed in the prevalence of SAr or the proportion of isolates resistant to penicillin between herd groups. The proportion of isolates resistant to penicillin was low compared to studies in other countries except Norway and Sweden. Based on the low prevalence of penicillin resistance of SA, penicillin should still be the first choice of antimicrobial agent for treatment of bovine intramammary infection in Denmark.


EPrint Type:Journal paper
Keywords:Antimicrobial resistance; Staphylococcus aureus; dairy cows; mastitis; somatic cell counts; organic farming
Subjects: Animal husbandry > Health and welfare
Research affiliation: Denmark > DARCOF II (2000-2005) > II. 5 Use of antimicrobials and occurrence of resistance in organic cattle herds
Deposited By: Bennedsgaard, Cand med vet Torben Werner
ID Code:4714
Deposited On:06 Apr 2005
Last Modified:19 Nov 2013 15:49
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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