TABLE 1.

Antimicrobial susceptibilities of serogroup C and meningococci of other serogroups or nongroupable meningococci from patients and carriers

Isolate group and antibiotic	MIC (μg/ml)			% Strainsa
	Range	50%	90%	S	I	R
Clinical isolates (n = 112)
Serogroup C (n = 72)
Penicillin	0.015–0.5	0.12	0.25	33.3	66.7	0.0
Ampicillin	0.03–0.5	0.25	0.5	5.6	94.4	0.0
Cefotaxime	≤0.0003–0.015	0.003	0.007	100.0	—b	—
Ceftriaxone	0.0003–0.0015	0.0007	0.0015	100.0	—	—
Rifampin	≤0.007–0.12	0.03	0.12	100.0	—	0.0
Ciprofloxacin	0.003–0.006	0.006	0.006	100.0	0.0	0.0
Sulfadiazine	25–>100	100	>100	0.0	—	100.0
Non-serogroup C (n = 40)
Penicillin	≤0.007–0.12	0.06	0.12	65.0	35.0	0.0
Ampicillin	0.015–0.5	0.12	0.25	40.0	60.0	0.0
Cefotaxime	≤0.0003–0.015	0.003	0.007	100.0	—	—
Ceftriaxone	0.0003–0.0015	0.0007	0.0015	100.0	—	—
Rifampin	≤0.007–0.12	0.03	0.12	100.0	—	0.0
Ciprofloxacin	0.003–0.006	0.006	0.006	100.0	0.0	0.0
Sulfadiazine	≤1–>100	25	100	15.0	—	85.0
Carrier isolates (n = 789)
Serogroup C (n = 89)
Penicillin	≤0.007–0.5	0.12	0.25	36.0	64.0	0.0
Ampicillin	0.03–1	0.25	0.5	13.5	86.5	0.0
Cefotaxime	0.0007–0.015	0.003	0.007	100.0	—	—
Ceftriaxone	0.00015–0.007	0.0015	0.0015	100.0	—	—
Rifampin	≤0.007–0.25	0.03	0.12	100.0	—	0.0
Ciprofloxacin	0.0015–0.006	0.006	0.006	100.0	0.0	0.0
Sulfadiazine	5–>100	>100	>100	4.5	—	95.5
Non-serogroup C (n = 700)
Penicillin	≤0.007–0.5	0.06	0.25	64.1	35.9	0.0
Ampicillin	≤0.007–1	0.12	0.5	37.1	62.9	0.0
Cefotaxime	≤0.0003–0.03	0.003	0.007	100.0	—	—
Ceftriaxone	≤0.00007–0.015	0.0007	0.0015	100.0	—	—
Rifampin	≤0.007–2	0.03	0.12	100.0	—	0.0
Ciprofloxacin	≤0.0003–0.012	0.006	0.006	100.0	0.0	0.0
Sulfadiazine	≤1–>100	100	>100	7.7	—	92.3

^aS, I, and R, susceptible, intermediate, and resistant, respectively. 

^b—, category not determined.