Historically, staphylococci, pseudomonads, and Escherichia coli have been the nosocomial infection troika; nosocomial pneumonia, surgical wound infections, and vascular accessrelated bacteremia have caused the most illness and death in hospitalized patients; and intensive care units have been the epicenters of antibiotic resistance.
A warm spot can be noticed in the portion of your arm where there occurred the blood clot. You can also feel like having a burning sensation around the affected area and also at times you might feel like the area is warm when touched. In case of serious blood clots in arm, the area affected can turn red and inflamed.
In brief: Many things. Assuming you mean in the veins not the arteries. Blood clots in the arm arm divided into deep (more serious) and superficial. Deep vein thrombosis of the arm is most commonly seen in hospitalized patients that have certain kinds of long iv's in called picc lines. In a young person i often treat clot in the subclavian/axillary veins from venous tos. It can be caused by repetative motion injury.