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To the Editor:

We read with interest the recent publication by Romero et al on detection of Mycobacterium avium subspecies paratuberculosis (MAP) in surgical tissue from Crohn's disease patients.1 Indeed, and possibly even more significant, was another recent earlier report by the same group on culture detection of viable MAP organisms from peripheral blood of 50% of their patients with Crohn's disease.2 The latter observation, if independently confirmed by other laboratories, would be important since a positive MAP culture from blood (as opposed to inflamed and ulcerated intestinal tissue) might be less prone to environmental contamination. In addition, detection of MAP in Crohn's disease may have even greater significance in its etiopathogenesis and offer potential for specific treatment. Now, especially with the recognition of HIV/AIDS and the rapid evolution of organ transplantation over the past 2 decades or so, a multitude of ubiquitous organisms have emerged as potentially serious infectious agents in these immune suppressed patients, including MAP. As a result, most credible clinical laboratories, particularly in modern university-teaching centers, have developed a great deal of experience and expertise in routine detection of MAP bacteremia.

For this present study, blood cultures were submitted from 22 consecutive patients with Crohn's disease for MAP using previous reported culture methods1,2 except that approximately 10 ml of whole blood were used for culture rather than 500 ul of re-suspended buffy coat.2 For all blood cultures, BACTEC MYCO/F Lytic blood culture bottles were used (Becton Dickinson Diagnostic Instrument Systems, Sparks, MD). All laboratory studies were done with laboratory staff unaware of the diagnosis of Crohn's disease.

Clinical features of Crohn's disease in the patient group are shown in Table 1. The results showed that 100% of these 22 Crohn's disease patients, evaluated consecutively, had negative MAP blood cultures. These results from a tertiary care referral center microbiology laboratory show that, in a population comparable to that previously published elsewhere,2 viable MAP organisms were not detected in blood cultures.

Table 1. Clinical Features of Crohn's Disease
Sex/Age DxYrsLocaleBehaviorMedsGranulomaResection
  1. a

    M, male; F, female; IC, ileocolonic; C, colonic; I, ileal; UGI, upper gastrointestinal; S, structuring P, penetrating; NSNP, non-stricturing, non-penetrating; Pr, Prednisone; IM, Imuran. Age at diagnosis in years and years followup data.

M/3523ICSPrYesYes
F/434CpPr/ImYesNo
M/2448IC/UGIpPr/ImYesYes
M/I818IC/UGIpPr/ImYesYes
F/215ICSPrYesYes
M/455CSNoneYesNo
F/3018IC/UGISPr/ImYesYes
M/3510CSPrYesNo
M/2617C/UGISPr/ImYesYes
M/2620ISPrYesYes
M/3318ICpNoneYesYes
M/184CNSNPPrYesYes
F/1915ICPPrYesYes
M/1626IPNoneYesYes
F/1321IC/UGIPPrYesYes
F/1124IC/UGISPrYesYes
F/3619IC/UGISPrYesYes
F/248ICNSNPPrYesNo
F/3229ISPr/ImYesYes
F/328ICPPrYesNo
F/282ICNSNPNoneYesNo
F/2115ICSPr/ImYesYes

The distinctly different MAP culture results in our patients compared to those published by the Florida group1,2 raise the issue of environmental contamination, possibly associated with additional steps required for buffy coat preparations. An alternative explanation, although most unlikely, might be that the investigators in these studies were evaluating biological materials from a unique Crohn's disease patient group related to a unique geographic area. Further studies in Crohn's disease from similar hospitals with access to expert clinical microbiological expertise are essential.

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