Study Discovers Invisible Transmission of Common Hospital-Associated Infection

Clostridium difficile infection, commonly referred to as C. diff, leads to symptoms such as diarrhea, abdominal pain, and fever, and is fatal in approximately 6% of cases in the U.S. It is one of the most prevalent and highly contagious hospital-acquired infections, yet previous studies indicated that direct patient-to-patient transmission occurred infrequently. New research, however, has revealed that C. diff spreads more than three times as often as initially thought. Published in JAMA Network Open, the study also highlights that C. diff can silently spread from surface to surface and remain undetected for weeks before infecting a patient. These findings could prompt more stringent preventive strategies to curb the hidden transmission of the disease.

Researchers at University of Utah Health (Salt Lake City, UT, USA) took a novel approach by tracking C. diff across the hospital environment, rather than just focusing on patient-to-patient transmission. The team sampled C. diff from nearly 200 patients in two intensive care units (ICUs), as well as collecting thousands of samples from hospital room surfaces and healthcare providers' hands. Using whole genome DNA sequencing, the researchers were able to trace the movement of the bacteria with high precision. By examining the genetic differences between bacterial samples, the team could track C. diff’s movement throughout the healthcare setting. They were even able to determine whether two samples originated from the same patient or came from an external source. The study found that C. diff was present in 10% of ICU patient stays, either on the patient's body or in their immediate surroundings. In most of these instances, the bacteria were genetically identical to those found in another patient or in another patient’s room, indicating that the infection likely spread from one patient to another.

By tracking various bacterial strains on patients, healthcare workers’ hands, and surfaces in the environment, the researchers uncovered instances of potential transmission that might have gone unnoticed with traditional methods. Importantly, they found that in over half of the cases, the two patients involved were never even in the hospital at the same time—sometimes separated by weeks. This paradox can be explained by the remarkable resilience of C. diff; the bacteria can survive outside the body for long periods, resisting common antibacterial measures like alcohol-based sanitizers. Bacteria from one patient could be inadvertently transferred to surfaces in a different room, where they could remain viable until another patient encounters them, without detection. While not all strains of C. diff cause disease, and most of the bacteria observed in the study were harmless, the researchers note that the spread of non-disease-causing strains could point to undetected transmission of harmful C. diff strains. They hope their findings will encourage more robust precautions to prevent C. diff spread in hospitals. Wearing personal protective equipment such as gloves and gowns, alongside rigorous hand hygiene, is vital for reducing transmission risks.

“There's a lot going on under the hood that we're just not seeing,” said Michael Rubin, MD, PhD, epidemiologist and infectious diseases specialist in the Spencer Fox Eccles School of Medicine at the University of Utah and senior author on the study. “And if we ignore that, then we’re potentially putting patients at unnecessary risk. What I'm hoping we get from this paper is that health care providers put a greater emphasis on infection prevention measures and adhere to them as much as they possibly can. Those are the measures that can help interrupt this type of invisible transmission.”