Citrobacter-induced colitis in mice with murine acquired immunodeficiency syndrome

Abstract

Over the period of a year, colitis was observed in 44 mice raised in a conventional nonspecific pathogen-free colony, 41 of these having concomitant retrovirus-induced murine acquired immunodeficiency syndrome (MAIDS). The lesions varied from bacterial colonization to hyperplasia of colonic mucosa to severe, often fatal, ulceration. Citrobacter rodentium was isolated from the colon and/or liver of 2 mice with colitis. When C57BL/6 mice with or without MAIDS were given graded doses of the bacterium, only those with MAIDS developed colitis, and C rodentium was reisolated from their livers. Thus, mice with MAIDS can develop severe disease following opportunistic infection with an environmental contaminant of the colony that is nonpathogenic for normal adult mice.

Figure 1

Colon from a B6 mouse with murine acquired immunodeficiency syndrome given 2.5 × 10² Citrobacter rodentium 17 days before necropsy. Mucosal hyperplasia is associated with growth of bacteria (indicated by an arrow), but there is minimal inflammatory response. HE; 100×.

Figure 2

Colonic crypt hyperplasia in Figure 1 mouse. HE; 1,000×.

Figure 3

Higher magnification of the section in Figure 1 showing extensive bacterial growth with minimal damage to epithelial cells. HE; 400×.

Figure 4

Longitudinal section of the colon from a B6 mouse with murine acquired immunodeficiency syndrome that died 11 days after receiving 2.5 × 10⁶ Citrobacter rodentium. The severe ulceration, edema, bacterial growth, and neutrophil infiltration illustrated affected most of the colon. HE; 100×.

Figure 5

Colon from a control B6 mouse given 2.5 × 10⁶ Citrobacter rodentium 17 days before necropsy; bacterial colonies and mucosal lesions are absent. HE; 100×.

Figure 6

Colon of the control mouse in Figure 5 showing normal crypts. HE; 1,000×.