In January 2014, the transmission and infection rates for health care-acquired methicillin-resistant Staphylococcus aureus (MRSA) – a difficult-to-treat bacterial infection that had become a significant cause of illness, and occasionally death, in health care settings – were continuing to decrease throughout U.S. medical facilities, including those of the Department of Veterans Affairs (VA) and military health care systems.
Among VA medical centers, the decline was due largely to the organization’s MRSA Prevention Initiative, launched in 2007, a program that placed a MRSA prevention coordinator at each medical center, screened every VA patient for MRSA, imposed strict protective and hygienic protocols for health care workers, and promoted individual responsibility for infection control.
“[Clostridium] diff is now the the most frequently diagnosed health care-associated infection,” said Dr. Dale Gerding, a research physician at Chicago’s Hines VA Medical Center (VAMC) and a professor in the Department of Medicine of Loyola University Chicago Stritch School of Medicine.
But just as MRSA was declining, infection rates for another drug-resistant health care-acquired infection (HAI) were on the rise throughout the United States: Clostridium difficile, a cytotoxic bacterium of the gut and a major cause of diarrhea and colitis among infected patients. According to the U.S. Centers for Disease Control and Prevention (CDC), hospitalizations for the organism commonly referred to as C. diff have tripled over the last decade, and the diarrhea caused by its toxins (enterotoxins A and B) now kills about 14,000 Americans annually.
Neither the military nor veteran health care systems have been shielded from these increases; studies have shown that C. diff has surged among both active duty and veteran populations. The dramatic rate of increase can be explained by several factors that make it unique among HAIs. First, its onset coincides with the emergence of a particularly virulent and antibiotic-resistant strain (known among epidemiologists as the NAP1/ BI/027 strain) around 2001.
“C. diff is now the the most frequently diagnosed health care-associated infection,” said Dr. Dale Gerding, a research physician at Chicago’s Hines VA Medical Center (VAMC) and a professor in the Department of Medicine of Loyola University Chicago Stritch School of Medicine. “Certainly this new epidemic strain, and the much more severe, and more readily transmitted, disease in hospitals is probably behind that. Plus, there have been a lot of efforts to target MRSA in hospitals with processes to screen for carriage and isolate patients. So it may be that we’ve made some progress on MRSA but we’re struggling with C. diff.”
The epidemic strain of C. diff is both more difficult to control than many other pathogenic microrganisms, and more likely to recur in a patient, because of how it reproduces. As Deputy Assistant Secretary of Defense for Health Services Policy and Oversight Dr. Warren Lockette pointed out: “Clostridia are spore-producing bacteria like anthrax is. They have very interesting physiology. These spores can live in the environment for a long period of time. And that may be how people get repetitively colonized with them.” About 25 to 30 percent of patients who are infected with C. diff, said Gerding, will become infected at least once more. Nearly all surface sanitation methods used in the health care setting, except for diluted bleach, are ineffective in killing the organism’s spores.
Based on photomicrographic data, this illustration depicts the ultrastructural morphology exhibited by a single Gram-positive Clostridium difficile bacillus. Clostridium difficile is a spore-forming, anaerobic bacillus that produces two exotoxins: toxin A and toxin B. It is a common cause of antibiotic-associated diarrhea (AAD). It accounts for 15 to 25 percent of all episodes of AAD. Over the past several years nationwide, states have reported increased rates of C. difficile infection, noting more severe disease and an associated increase in mortality. C. difficile infection remains a disease mostly associated with health care (at least 80 percent). Patients most at risk remain the elderly, especially those using antibiotics. CDC image by Jennifer Hulsey
Another singular characteristic of C. diff is that it appears to be present, at least part of the time, in a healthy human gut. For reasons that are not fully understood – but which are the subject of numerous investigations – the presence of other bacteria in what’s knows as the “microbiome” of the intestine keeps C. diff in check; it’s only when it proliferates more rapidly than its neighbors that C. diff becomes pathogenic. For this reason, most C. diff infections are connected with medical care – in particular, treatment with broad-spectrum antibiotics that kill off other enteric bacteria – and infection risk generally increases with age. More than 90 percent of U.S. C. diff deaths happen to people 65 or older.
It is this last characteristic, said Gerding, that makes C. diff – while not more prevalent among military or veteran hospitals – a riskier disease overall for the veteran population. “The immune system probably does wane as you get older,” he said, “And this potentially could be a factor that makes older people more susceptible to C. diff, because part of the protection against the disease is antibodies that circulate in the blood against the toxins that C. diff makes.”
The Battle Plan
The fight against C. diff is no different, essentially, than the fight against other HAIs; the most obvious requirement is strict adherence to existing patient safety and quality control protocols, to keep C. diff spores away from patients and reduce the likelihood of infection.
In addition, said Lockette, the idiosyncrasies of the C. diff organism make it even more crucial for physicians to be careful with antibiotics. “We need to focus on making sure we reduce the non-judicious or indiscriminate use of antibiotics,” he said, “because I think there is general consensus that indiscreet use of antibiotics, or overuse of antibiotics, has led to C. difficile bacteria becoming resistant to the agents we normally use to treat them.”