S. L. Baker
September 3, 2009
Clostridium difficile, usually known as simply C. difficile, is a bacterium that spreads by bacterial spores. And a new study raises the disturbing possibility that antibiotics taken by people who aren’t even ill from these bacteria can spur the germ into becoming a kind of bacterial spore spewing mega factory. So why is this concerning? It’s true that C. difficile can exist in the human body and never make you sick. But it can also cause serious illness and even be fatal — and incidences are of the infection are increasing. What’s more, strains of the bacteria are showing signs of becoming a serious drug-resistant superbug infection.
|C. difficile can cause illness when the germ grows out-of-control after a person takes antibiotics.|
C. difficile can cause illness when the germ grows out-of-control after a person takes antibiotics, especially fluoroquinolones, cephalosporins, clindamycin and penicillins. By killing off the normal body flora that should keep C. difficile in check, antibiotics can cause the bacteria to proliferate wildly and, when this happens, the bacteria produce toxins that attack the lining of the intestine. The result can be diarrhea, colitis and even death.
Although people who are elderly and already sick may succumb to C. difficile, just stopping antibiotics can help most people recover from the infection and taking probiotics can facilitate healing and restoring the body to normalcy, too. Ironically, however, in hopes of destroying the bacteria doctors often treat C. difficile with even more antibiotics, specifically heavy duty, side-effects heavy metronidazole (Flagyl) and vancomycin.
But these super powerful take-no-prisoners kind of antibiotics aren’t always able to zap C. difficile any more. According to the Mayo Clinic, an aggressive strain of the bacteria has emerged that produces far more deadly toxins than ever before. And this new strain has taken on characteristics of a superbug by showing resistance to antibiotics. Now research just published in the journal Infection and Immunity suggests that antibiotic treatment could be asymptomatically causing the transmission of huge numbers of C. difficile spores and contributing to the outbreaks that have recently been widely reported in hospitals and other environments.
Humans shed spores of this bacteria in their feces and these spores can survive dormant in the environment for long periods of time, under harsh conditions and in temperatures up to 70 degrees C. A new human host is infected when he or she happens to touch a surface contaminated with the spores and then touches and eats food or touches their lips.
Currently, healthcare professionals attempt to keep the threat of C. difficile under control by hand washing and by isolating patients who exhibit the symptoms of infection such as fever and diarrhea. But the new study suggests infection control in hospitals should include all patients receiving antibiotic treatment because these drugs could be causing even people with no symptoms of C. difficile infection to transmit large numbers of the bacteria’s spores.
[efoods]“C. difficile is a highly resistant and highly infectious pathogen and resistant to many front line antibiotics,” explained Dr Trevor Lawley, Wellcome Trust Sanger Institute researcher and lead author on the study, in a statement to the press. “Until now, animal studies have focused on the observable, acute symptoms of C. difficile. But, to understand how this highly infectious pathogen spreads, investigating the entire cycle of transmission is absolutely vital. We looked at mice carrying C. difficile and observed that they shed low levels of spores and, crucially, they did not infect other mice.”
The scientists treated mice with antibiotics and the balance of the microbial ecosystem inside the animals was thrown out of whack. Because C. difficile is now resistant to many antibiotics, the bacteria thrived, increased and dominated the microbiota of the mice — the same scenario that can happen in people.
The research team saw a dramatic rise in the levels of spores shed in the mice treated with antibiotics. The scientists have labeled the phenomenon a supershedder state which causes an increase in the transmission of C. difficile even in the absence of clinical symptoms. And the research raises the possibility that even after stopping antibiotics, the supershedder state could remain for some time.
“We treated mice with short and longer courses of antibiotics,” says Professor Gordon Dougan, Head of Pathogen Genetics at the Sanger Institute and senior author on the study. “After a short course most mice had dropped back to normal spore shedding levels around two weeks after cessation of the treatment. But after long term exposure to antibiotics some of the mice remained in their ‘supershedder’ state for weeks or even longer after treatment was stopped. We should consider that patients still pose a considerable transmission threat some weeks after treatment is terminated even if they have not exhibited signs of C. difficile disease.”
The scientists also found that there was a considerable threat from environmental contamination from even short-term housing of supershedder mice. That suggests that even a brief environmental contamination with these high levels of spores is a potential infection threat.
“C. difficile is a high-profile and rapidly emerging pathogen and is responsible for the death of a patient every hour in our hospitals — but its biology and transmission are so far poorly understood,” says Brendan Wren, Professor of Microbial Pathogenesis from the London School of Hygiene and Tropical Medicine’s Department of Infectious and Tropical Diseases. “At last we can monitor the transmission of this major pathogen using a tractable model system. This will be invaluable in determining the role of spore formation in transmission and how and why some C. difficile strains are more virulent and transmissible than others.”
The scientists also used their study to test disinfectants commonly used in hospitals to see if they really work at controlling C. difficile infection. Alcohol-based disinfectants were found to not work at all in preventing transmission. Instead, it took a 20 minute treatment with a strong spore-killing agent to reduce environmental C. difficile spore contamination enough to eliminate transmission of the germs. Bottom line: the standard methods used in hospitals to supposedly protect patients, visitors and healthcare personal from exposure to C. difficile are probably useless.
“This research has far reaching implications for treatment and infection control of a pathogen that is increasingly raising alarm among the global healthcare community,” Cambridge microbiologist Fiona Cooke stated in the media release. She explained that the research provides a better understanding of the interactions between C. difficile, the intestinal microbiota and the immune system of the host. “This opens up numerous opportunities including the development of new probiotic approaches, which could restore the balance of the intestinal microbiota and promote health,”she said.