Research from the University of Houston has determined that a species of bacteria that has become resistant to many antibiotics might be tracking into homes on the soles of shoes. More than a third of randomly tested homes were contaminated with Clostridium difficile bacteria, and 40 percent of doorsteps were also infected with the bacteria. Depending upon the strain, C. difficile can cause intestinal infections, inflammation and severe diarrhea.

Study author M. Jahangir Alam, Ph.D., comments, “Shoes are contaminated from diverse sources, and we are regularly contaminating our doorsteps by shoes.”

The researchers tested three to five household items within 30 houses in Houston, Texas. They collected 127 environmental samples—from 63 shoe bottoms, 15 bathroom surface samples, 12 house floor dusts and 37 other household surfaces

They found that 41 of them harbored C. difficile and nearly 40 percent of the shoes were positive for the bacteria. They also found that a third of the bathroom surfaces harbored the bacteria, a third of house dust and 19 percent of other surfaces maintained the bacteria.

The cause of many intestinal disorders, this bacteria species has become increasingly resistant to antibiotics and many household cleaning products.