S

erratia marcescens. S. marcescens is a Gram negative organism which belongs to the family Enterobacteriaceae. It can be pathogenic, most often found as a UTI, though it does also pose problems for immunocompromised individuals, especially those in a hospital setting -- leading to nosocomial infections. To make matters worse, S. marcesens has a habit of being antibiotic resistant, making it a very hard organism to clear. One of its hallmarks is that most isolates produce a reddish pigment called prodigiosin (see below), which assists in identification of the pesky bug.

From a historical, and religious, point of view, S. marcesens has been theorized to be the culprit in Eucharistic miracles involving bleeding hosts. However I'm not aware of it being confirmed in any such cases, if there have been any cases recently (of which I am also not aware).

Serratia marcesens