TABLE 1.

Fluoroquinolone susceptibility (MIC₉₀) of C. jejuni and C. coli cultured from commercial broiler chicken flocks at various ages^a

Farmb	Ciprofloxacin MIC90 (μg/ml) (no. of isolates)
	Flock 1				Flock 2
	3-5 wks		6-7 wks		3 wks		6 wks
	C. jejuni	C. coli	C. jejuni	C. coli	C. jejuni	C. coli	C. jejuni	C. coli
CF-1	NDc	ND	8 (24)	8 (2)	0.25 (30)	ND	2 (25)	2 (5)
CF-2	0.25 (30)	ND	0.5 (58)	0.5 (2)	16 (21)	16 (9)	16 (30)	ND
CF-3	ND	ND	4 (7)d	16 (2)d	0.125 (22)	8 (8)	16 (26)	16 (4)

^aC. jejuni (273 isolates) and C. coli (31 isolates) were cultured from the fresh cecal droppings of two consecutive flocks of commercial broiler chickens located on three geographically separated farms. Fluoroquinolone susceptibility was determined by agar dilution. All of the isolates from the same sampling exhibited the same MIC.

^bCampylobacter was cultured from most flocks when the birds were 3 and 6 weeks old; the exception was flock 1 on farm CF-2, from which Campylobacter was cultured when the birds were 5, 6, and 7 weeks old.

^cND, no bacteria detected by culturing.

^dThe birds were given sarafloxacin (20 ppm for 5 days) in their drinking water when they were 5 weeks old. Campylobacter isolates were cultured after this treatment.