News for Germophobes
The controversy over the effects on human health of widespread use of antibiotics in livestock continues. At the end of 2011, the Food and Drug Administration (FDA) recommended the phasing out of this practice, beginning in April 2012, long used by farmers to promote faster growth in food-producing animals such as cattle, pigs, and poultry. Called “nontherapeutic antibiotics,” the drugs were often touted by livestock producers as a way to decrease illness in animals raised in overcrowded housing and stressed by truck hauls to the slaughterhouse. But the health benefits to the animal were never proved in scientific studies and factory farming was likely the biggest threat to the animals’ health. Many studies have furthermore found that nontherapeutic antibiotics have contributed to the rise of antibiotic resistance in microbes that infect humans.
FDA’s main target is the antibiotic class called cephalosprins. These drugs have become a backup line of defense in the treatment of human infections resistant to earlier generations of antibiotics, such as penicillins. Some microbiologists applaud the FDA’s step, but others feel it doesn’t go far enough because many of the recommendations to cut back on antibiotic use are voluntary. Successful strategies for reversing the tide of antibiotic resistance have been difficult to find. As long as we continue widespread use of antibiotics, expect widespread occurrence of antibiotic-resistant germs.
A Malaria Vaccine
The disease malaria is caused by a protozoan parasite with several different life cycle stages that occur inside mosquitoes and inside an infected person. Most parasites with complex life cycles have been difficult to prevent by inventing a vaccine against infection. Scientists have been trying to perfect a malaria vaccine for more than two decades with little success.
In late 2011, Ghana’s Kwame Nkrumah University finished studies on a new malaria vaccine that, although not perfect, reduces the risk of malaria by about 50 percent. The final phase of clinical testing of the vaccine was conducted in 6,000 children of sub-Saharan Africa, where malaria has always taken a high toll. The disease kills more than a million people each year, mostly children under age 5 in sub-Saharan Africa.
The Ongoing Listeria Outbreak
A food-borne outbreak associated with Listeria-contaminated cantaloupes continues to take lives. The outbreak began in mid-summer of 2011 when contaminated melons from a farm in upstate New York and another in Colorado were implicated by the U.S. Food and Drug Administration as the source of the pathogen Listeria monocytogenes. In a few months, more than 100 people were sickened from eating the melons and about two dozen people died.
Cantaloupes have been implicated in other food-borne outbreaks in the past. No one is sure why the melon is a higher risk for carrying food-borne pathogens than other fruits. Most fruits can carry germs on their skin because they pick up contamination from fertilizers or from animals that move through the growing fields before harvesting. Contamination can enter the edible portion of the fruit when it is sliced. But cantaloupes are rather porous compared with fruits such as apples. The pathogens might be able to penetrate the melon’s outer skin even without slicing open the fruit.
Listeria monocytogenes is one of the more prevalent food-borne pathogens worldwide. It is found almost everywhere in soil and yet little information has been gathered on how it survives in nature. The organism is known to inhabit the digestive tract of humans and many other animal species. Microbiologists also know this pathogen tolerates cold temperatures that slow down the growth of most other bacteria. This attribute of Listeria allows it to proliferate in refrigerated foods and explains why outbreaks occur from eating cheeses, deli meats, and fruit salads, even when these foods were properly refrigerated.
The disease listeriosis has symptoms similar to almost every other type of food-borne illness: nausea, vomiting, and diarrhea. But L. monocytogeneses also attacks the nervous system in serious infections. Like most pathogens, it presents a greater danger to people in the so-called “high-risk” health groups: pregnant women, the elderly, young children, people with chronic disease, and the immunocompromised.
Bacteria and Colon Cancer Linked?
In 2011, two research teams working independently concluded that certain bacteria of the large intestine can be linked to higher rates of colon cancer. Microbiologists have long known that bacteria of the genus Fusobacterium inhabit the human mouth and the human intestines and that of other animals. In the intestines, these bacteria ferment sugars and produce mainly butyric acid. Until now, that activity was the organism’s only claim to fame.
The recent studies indicate that Fusobacterium infiltrate intestinal tissue in patients with colon cancer. This finding led researchers to propose that Fusobacterium may be linked in some way to the events leading to cancer. But microbiologists do not know if Fusobacterium is part of the cancer’s cause or whether the bacteria simply find cancerous tissue easier to infect then healthy tissue.
Often the presence of a microbial species in the body gives a good indication of a disease. But Fusobacterium normally lives in the body and is part of a person’s normal flora. It is much more difficult to figure out if normal flora are causing disease or are taking advantage of conditions in the body due to a disease that has been caused by something else. For the moment, there is no reason to fear the bacteria living inside your intestines and vital to good health and nutrition.