Antimicrobial Susceptibility Patterns of Environmental Streptococci Recovered from Bovine Milk Samples in the Maritime Provinces of Canada.
Determination of antimicrobial susceptibility of bovine mastitis pathogens is important for guiding antimicrobial treatment decisions and for the detection of emerging resistance. Environmental streptococci are ubiquitous in the farm environment and are a frequent cause of mastitis in dairy cows. The aim of the study was to determine patterns of antimicrobial susceptibility among species of environmental streptococci isolated from dairy cows in the Maritime Provinces of Canada. The collection consisted of 192 isolates identified in milk samples collected from 177 cows originating from 18 dairy herds. Results were aggregated into: (1)Streptococcus uberis(n= 70), (2)Streptococcus dysgalactiae(n= 28), (3) otherStreptococcispp. (n= 35), (4),Lactococcusspp. (n= 32), and (5)Enterococcusspp. (n= 27). Minimum inhibitory concentrations (MICs) were determined using the Sensititre microdilution system and mastitis plate format. Multilevel logistic regression models were used to analyze the data, with antimicrobial susceptibility as the outcome. The proportion of susceptibleS. uberisranged from 23% (for penicillin) to 99% (for penicillin/novobiocin), with a median of 82%. AllS. dysgalactiaewere susceptible to all antimicrobials except for penicillin (93% susceptible) and tetracycline (18% susceptible). The range of susceptibility for otherStreptococcusspp. was 43% (for tetracycline) to 100%, with a median percent susceptibility of 92%.Lactococcusspp. isolates displayed percent susceptibilities ranging from 0% (for penicillin) to 97% (for erythromycin), median 75%. For the antimicrobials tested, the minimum inhibitory concentrations were higher forEnterococcusspp. than for the other species. According to the multilevel models, there was a significant interaction between antimicrobial and bacterial species, indicating that susceptibility against a particular antimicrobial varied among the species of environmental streptococci and vice versa. Generally, susceptibility decreased with increasing within-herd average somatic cell count, isolates recovered in mid-lactation were more susceptible than isolates recovered in early lactation, and isolates recovered in samples collected post-clinical mastitis were more susceptible than isolates recovered from non-clinical lactating quarters. The results of this research support continued susceptibility of environmental streptococci to beta-lactam antimicrobials. A departure from the expected susceptibility to beta-lactams was the apparent reduced susceptibility ofS. uberisto penicillin.
Department of Health Management, University of Prince Edward Island , Charlottetown, PE , Canada.
Marguerite
M
Cameron
Department of Health Management, University of Prince Edward Island, Charlottetown, PE, Canada; Diagnostic Services, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, Canada.
Matthew
M
Saab
Department of Health Management, University of Prince Edward Island , Charlottetown, PE , Canada.
Luke
L
Heider
Department of Health Management, University of Prince Edward Island , Charlottetown, PE , Canada.
J Trenton
JT
McClure
Department of Pathology and Microbiology, University of Prince Edward Island , Charlottetown, PE , Canada.
Juan Carlos
JC
Rodriguez-Lecompte
Department of Health Management, University of Prince Edward Island , Charlottetown, PE , Canada.
Javier
J
Sanchez
Streptococcus dysgalactiae; Streptococcus uberis; antimicrobial susceptibility; bovine; environmental streptococci; intramammary infection
Res Vet Sci. 2011 Dec;91(3):349-57
20971488
Vet Q. 2007 Mar;29(1):18-31
17471788
J Vet Diagn Invest. 2009 Sep;21(5):698-701
19737768
Acta Vet Scand. 2013 Jul 18;55:53
23866930
J Dairy Sci. 2007 Nov;90(11):5089-96
17954749
J Vet Med B Infect Dis Vet Public Health. 2005 Apr;52(3):125-8
15876224
Vet Microbiol. 2008 Oct 15;131(3-4):348-57
18472369
J Dairy Sci. 2012 Mar;95(3):1283-300
22365211
J Dairy Sci. 2011 Mar;94(3):1616-26
21338829
Vet Microbiol. 2013 Jan 25;161(3-4):286-94
22964008
Epidemiol Infect. 2003 Apr;130(2):335-49
12729202
J Dairy Sci. 2005 Oct;88(10):3710-20
16162546
J Dairy Sci. 2012 Aug;95(8):4319-32
22818446
Appl Environ Microbiol. 2001 Jan;67(1):22-32
11133424
J Dairy Res. 2014 Nov;81(4):424-33
25230074
Curr Opin Microbiol. 2014 Jun;19:37-44
24997398
Vet Microbiol. 2014 Jul 16;171(3-4):374-81
24703745
J Clin Microbiol. 1996 May;34(5):1296-8
8727924
J Dairy Sci. 2007 Jan;90(1):262-73
17183094
Adv Drug Deliv Rev. 2001 Sep 1;50(3):245-59
11500230
J Dairy Sci. 2007 Jan;90(1):249-61
17183093
Vet Rec. 2005 Aug 27;157(9):245-50
16127133
Appl Environ Microbiol. 2010 Dec;76(24):7957-65
20952646
J Vet Diagn Invest. 2013 Sep;25(5):581-91
23907894
J Dairy Sci. 2002 Jan;85(1):132-8
11860105
J Dairy Sci. 2013;96(12):7538-49
24119795
BMC Vet Res. 2014 Jul 11;10:156
25015262
Int J Antimicrob Agents. 2015 Jul;46(1):13-20
26003836
J Dairy Sci. 2015 Jul;98(7):4521-34
25912858
J Dairy Sci. 2012 Dec;95(12):6957-62
22999286
Int J Antimicrob Agents. 2002 Mar;19(3):219-26
11932145
J Dairy Sci. 2006 Jul;89(7):2542-51
16772573
N Z Vet J. 2014 Mar;62(2):68-76
24215609
J Dairy Sci. 2014 Nov;97(11):6964-9
25242419
Vet Clin North Am Food Anim Pract. 2012 Jul;28(2):149-63
22664200
Acta Vet Scand. 2011 Jun 08;53:36
21649936
Vet Microbiol. 2009 Apr 14;136(1-2):142-9
19058930
J Dairy Sci. 2004 Aug;87(8):2393-400
15328260
J Dairy Sci. 2012 Mar;95(3):1209-21
22365205
Aust Vet J. 2015 Jul;93(7):227-33
26113347
J Dairy Sci. 2004 Aug;87(8):2433-41
15328265
Clin Microbiol Rev. 2013 Jul;26(3):547-603
23824373
J Dairy Sci. 2016 Mar;99(3):2118-30
26778315
Vet Microbiol. 2012 Nov 9;160(1-2):162-9
22677481
Antimicrob Agents Chemother. 2010 Mar;54(3):1140-5
20065061
J Dairy Sci. 2002 May;85(5):1111-8
12086045
J Dairy Sci. 2015 Sep;98(9):6216-25
26142865
Clin Microbiol Rev. 2002 Oct;15(4):647-79
12364374