Circulating foamy macrophages and other features of bacillus Calmette-Guérin challenge in Golden Syrian hamsters

Golden Syrian Hamsters are utilized as rodent research models for various bacterial diseases. They are highly susceptible to leptospirosis, making hamsters the most common model for testing and maintaining virulence of laboratory Leptospira strains as well as for bacterin vaccine efficiency testing. Hamsters are also used for modeling features of Bacillus Calmette-Guérin (BCG) and tuberculosis, as they consistently develop granulomas, differing from other BCG animal models. Circulating foamy macrophages have recently been identified in the blood of the hamsters following Leptospira challenge but not in controls. It has been unknown whether this phenomenon is specific to Leptospira/hamster interactions, or whether hamsters will produce circulating foamy macrophages in response to other bacterial infections. In this study, we established that hamsters develop circulating foamy macrophages when challenged intraperitoneally with BCG or Leptospira. In addition to circulating foamy macrophages, hamsters infected with BCG had widespread granuloma formation in major organs and injection sites which also contained resident foamy macrophages, as well as mineralized bodies, sometimes containing acid fast bacteria.