TABLE 1.

Results of diagnostic testing by thin smear, class-specific IFA serology, and amplification of three different gene targets by PCR^a for nine isolation-confirmed HME cases caused by E. chaffeensis

Patient no./isolate	Presence of morulaeb	IFA titerc				PCR target gene result
		First serum sample		Second serum sample		16S rRNA	VLPT (no. of repeats)	groESL operon
		IgM (days postonset)	IgG	IgM (days postonset)	IgG
1/Jax	−	16 (7)	256	32 (13)	1,024	+	+ (4)	+
2/St. Vincent	+	<16 (4)	<64	<16 (8)	<64	+	+ (3)	+
3/Osceola	+	16 (3)	<64	64 (9)	1,024	+	+ (4)	+
4/Wakulla	−	<16 (5)	512	256 (41)	2,048	+	+ (6)	+
5/Liberty	−	64 (3)	64	NTf	NT	+	+ (4)	+
6/West Paces	−	<16 (3)	<64	64 (51)	512	+d	+ (3)	NT
7/V5e	−	<16 (3)	<64	512 (43)	8,192	+	+ (4)	+
8/V6e	−	16 (3)	<64	512 (50)	2,048	+	+ (4)	+
9/V7e	−	<16 (4)	<64	128 (53)	256	+	+ (5)	+
No. positive/total (%)	2/9 (22.2)	4/9 (44.4)	3/9 (33.3)	7/8 (87.5)	7/8 (87.5)	9/9 (100)	9/9 (100)	8/8 (100)

^a16S rDNA was amplified by nested PCR, as required for patients 5 and 6. 

^bIntracytoplasmic aggregates of bacteria observed in peripheral blood smears. 

^cIFA titers for IgM of ≥16 and for IgG of ≥64 are considered evidence of current or past infection with E. chaffeensis. 

^dDetected by heminested assay. 

^eIsolates designated V5 to V7 were obtained at Vanderbilt University, although additional testing of whole blood and sera was conducted at CDC. 

^fNT, not tested.