Antimicrobial Susceptibility of Udder Pathogens Isolated from Dairy Herds in the West Littoral Region of Uruguay

Table 2 In vitro susceptibility of 41 strains of Coagulase Negative Staphylococcus obtained from clinical and sub-clinical bovine mastitis cases from the West Littoral Region of Uruguay.

	MIC¹(μg/ml)				% Resistance
Antimicrobial Agent	MIC₅₀²	MIC₉₀³	Range	Breakpoint	VETMIC	Agar disk diffusion test
Penicillin	0.5	> 4	0.12–> 8	≥ 0.25	27.0	22.0 ⁵
Ampicillin	0.5	2	≤ 0.12–> 16	≤ 0.5	24.4	22.0 ⁵
Oxacillin	≤ 0.5	≤ 0.5	≤ 0.5–1	≥ 4	0.0	0.0
Cephalotin	≤ 4	≤ 4	≤ 4	≤ 32	0.0	0.0
Gentamicin	≤ 1	≤ 1	≤ 1–4	≥ 16	0.0	0.0
Erythromycin	≤ 0.5	≤ 0.5	≤ 0.5	≥ 8	0.0	0.0
Oxitetracycline	2	> 64	≤ 0.25–> 64	≥ 16	13.9	13.9 ⁶
Enrofloxacin	≤ 0.25	≤ 0.25	≤ 0.25–0.5	≥ 2	0.0	0.0
Neomycin	≤ 1	≤ 1	≤ 1–64	≥ 64	2.0	2.0
Clindamycin	≤ 1	≤ 1	≤ 1	≥ 4	0.0	....⁴....
Amoxicillin/Clavulanic acid	....⁴....	....⁴....	....⁴....	....⁴....	....⁴....	0.0
Trimethoprim/Sulfamethox.	0.25	0.5	< 0.06–8	≥ 4	7.3	0.0 ⁵

¹ Minimum inhibitory concentration. ² Lowest concentration inhibiting 50% of the isolated tested.
³ Lowest concentration inhibiting 90% of the isolated tested. ⁴ Test not performed.
⁵. No significant differences between methods. ⁷ Tetracycline disk were used to perform agar disks diffusion.

ISSN: 1751-0147