Letters to the Editor Effects of Shipping and Storage Conditions of Fecal Samples on Viability of

Johne’s disease is characterized by chronic granulomatous enteritis of ruminants caused by Mycobacterium paratuberculo-sis infection. Early diagnosis of infected animals is necessary to reduce contamination of the environment and to control dis-ease spread through feces (3, 6). About 75 % of positive ani-mals are either low or very low shedders (7, 8). Diagnostic samples for M. paratuberculosis identification are generally col-lected, shipped, and stored under various conditions that may influence the viability of M. paratuberculosis (2, 4, 5), thus changing the true status of the infected animal; in fact, the culture status especially of individual low or very low shedder animals could change from positive to negative. The aim of the present study was to mimic the most relevant conditions of shipment and storage of clinical samples ob-tained from naturally infected cattle and to study the effects of these conditions on the detection of M. paratuberculosis by standard bacteriological culture and real-time PCR. Fecal samples were collected from 11 cows confirmed to have Johne’s disease; samples were transported on ice and stored as described in Table 1. Fecal samples were tested for colony counts on Herrold’s egg yolk agar slant (three tubes each for three dilutions with mycobactin J and one without mycobactin J) (9) and by immunomagnetic bead capture of M. paratuber-culosis from feces and extraction of genomic DNA from cap-tured M. paratuberculosis, followed by PCR (1). Several of the first- and second-dilution tubes had an M. tuberculosis organism too-numerous-to-count status; thus, data analyses were restricted to dilution 3. The mean colony counts at week 16 were compared across treatments, using analysis of variance (ANOVA) (SPSS version 13.0 software for Windows; SPSS Inc., Chicago, IL). Pairwise comparisons of treatment means between treatment groups were performed with the Tukey correction for multiple comparisons. Results for each tube were dichotomized into positive or negative, based on the presence of at least one colony. Fisher’s exact test (intercoole