In vitro antibiotic susceptibility and biofilm production of Staphylococcus aureus isolates recovered from bovine intramammary infections that persisted or not following extended therapies with cephapirin, pirlimycin or ceftiofur

Table 1 Overview S. aureus isolates collected in three different field studies in which extended therapies were used for treatment of IMIs

	Extended therapy with
	Cephapirin	Pirlimycin	Ceftiofur
Total number of cases^a	29	40	17
Based on bacteriology
Cases in which S. aureus was eliminated	12	33	9
Cases in which S. aureus was isolated after therapy	17	7	8
Proportion of isolates that were eliminated (%)	41.3	82.5	52.9
Based on VNTR analysis
Isolates that were eliminated or that were distinct by VNTR before and after therapy	19	34	9
Isolates from persistent cases (same VNTR before and after therapy)	10	6	8
Proportion of isolates that were eliminated (%)	65.5	85.0	52.9
Number of isolates characterized in this study^b
Isolates from cured cases	12	23^c	9
Isolates from persistent cases (VNTR-confirmed)^c	10	6	8

^aCases are quarters infected with S. aureus. Isolates from cured cases are revealed when one S. aureus isolate is found before treatment but no S. aureus is detected after the end of treatment. Persistent cases are revealed when one S. aureus isolate is found before treatment and at least one S. aureus isolate is also found after the end of treatment.
^bCases that were not validated as persistent (possible new infections by a different S. aureus isolate) were excluded of the study. When multiple isolates were collected from the same cow (different quarters), only one isolate was selected for the study.
^cOnly the isolates collected before treatment were used for the rest of the study.

ISSN: 1297-9716