Table 1. Formaldehyde fixation of Bacillus anthracis Ames–infected skin tissue from guinea pigs in study of inactivation of bacterial Tier 1 Select Agents*.

Fixation time, d, no. samples	Maximum tissue weight, g	Maximum tissue size, mm	Total CFU recovered/g	Sample inactivation†	Positive control
7, 3	2.04	20 × 30 × 3	6.15 × 107	+/+‡	+/+
14, 3	1.94	23 × 28 × 3	5.41 × 107	–/–	+/+
21, 3	2.55	28 × 28 × 3	4.86 × 107	–/–	+/+

*Infected skin tissues from 3 guinea pigs were fixed for 7, 14, or 21 d in 4% paraformaldehyde, rinsed for 30 min in phosphate-buffered saline, and then homogenized. The maximum tissue weight, size, and CFU recovered per group are listed. +/– indicates presence or absence of growth in broth/on plates.
†100% of sample tested.
‡Of 3 samples, 1 was positive for growth.