TABLE 2.

Isolates susceptible, intermediate, or resistant as determined by caliper and Sirscan readings of zone diameters

Antibiotic(s)	Isolate(s)	NCCLS breakpoints (mm)	No. tested	SIc/SIsa	Rc/Rsb	SIc/Rsc	Rc/SIsd	Zone size(s) (mm) of Rc/SIs isolate(s)e	% of results that were very major errorsf
Amoxicillin-clavulanate	Staphylococcus sp.	≥20	127	102	19	1	5	20 (S), 20 (S), 20 (S), 21 (S), 22 (S)	3.9
	Gram-negative bacilli	14–17	87	73	14	0	0
Ampicillin	Gram-negative bacilli	14–16	209	87	122	0	0
Aztreonam	Gram-negative bacilli	16–21	241	219	18	0	4	16 (I), 17 (I), 17 (I), 17 (I)
Cefotaxime	Gram-negative bacilli	15–22	209	197	10	1	1	15 (I)
Cefuroxime sodium	Gram-negative bacilli	15–17	209	171	37	0	1	18 (S)	0.5
Cephalothin	Gram-negative bacilli	15–17	210	128	75	7	0
Ciprofloxacin	Gram-negative bacilli and Staphylococcus sp.	16–20	278	221	56	0	1	17 (I)
Clindamycin	Staphylococcus sp.	15–20	127	99	28	0	0
Erythromycin	Staphylococcus sp.	14–22	127	46	79	0	2	14 (I), 14 (I)
Gentamicin	Gram-negative bacilli and Staphylococcus sp.	13–14	364	326	35	1	2	14 (I), 14 (I)
Imipenem	Gram-negative bacilli	14–15	241	233	8	0	0
Mezlocillin	Pseudomonas sp.	≥16	28	18	10	0	0
	Other gram-negative bacilli	18–20	212	159	48	4	1	18 (I)
Nitrofurantoin	Gram-negative bacilli and Staphylococcus sp.	15–16	115	92	18	0	5	15 (I), 15 (I), 15 (I), 15 (I), 15 (I)
Norfloxacin	Gram-negative bacilli	18–20	87	1	86	0	0
Oxacillin	Coagulase-negative staphylococci	≥18	74	19	53	0	2	22 (S), 25 (S)	2.7
	S. aureus	11–12	53	38	15	0	0
Penicillin G	Staphylococcus sp.	28–29	127	115	12	0	0
Piperacillin	Pseudomonas sp.	≥18	28	26	1	0	1	19 (S)	3.6
	Other gram-negative bacilli	18–20	124	92	31	1	0
Trimethoprim-sulfamethoxazole	Gram-negative bacilli and Staphylococcus sp.	11–15	366	266	96	2	2	16 (S), 12 (I)	0.3
Vancomycin	Staphylococcus sp.	≥15	127	127	0	0	0

^aNumber of isolates susceptible or intermediate by both caliper and Sirscan. 

^bNumber of isolates resistant by both caliper and Sirscan. 

^cNumber of isolates susceptible or intermediate by caliper and resistant by Sirscan. 

^dNumber of isolates resistant by caliper and susceptible or intermediate by Sirscan. 

^eS, sensitive; I, intermediate; R, resistant. 

^f(Number of Rc/SIs isolates) − (number of intermediate isolates)/number of isolates tested × 100.