The bacteria most likely to infect hospital patients are beginning to display an ability to resist the antibiotic vancomycin, the last available line of defense in the human battle against such microbes. Many
Staphylococcus aureus strains have already developed resistance to commonly used antibiotics such as penicillin and methicillin, and for nearly two decades vancomycin has been the only certain way to thwart an
S. aureus infection. Now it seems that the microbe is adapting resistance to vancomycin, which may leave only experimental new antibiotics to stop a public health crisis.
Staphylococcus aureus
|
The new super-resilient strain of the bacterium was discovered in May 1996 at the Juntendo University hospital in Tokyo, where it had infected a 4-month-old boy recovering from heart surgery. Japanese health officials reported the finding in May 1997 and provided an isolate of the bacterium to the U.S. Centers for Disease Control and Prevention, which confirmed the resistance profile, reporting in the 11 July 1997 issue of
Morbidity and Mortality Weekly Report that the bacterium exhibited low-level resistance to vancomycin. "Clinically, it showed decreased susceptibility. . . . It was not completely resistant to vancomycin," explains Michael Edmond, a hospital epidemiologist at the Medical College of Virginia in Richmond. "That means that the clinical outcome will depend on the site of the infection. How effective the treatment is really depends on how much vancomycin can be introduced into that area. In this case . . . the child had a wound infection, which is a case where enough vancomycin can be used to eliminate the infection. An infection in a place like the cerebral spinal fluid would be particularly hard to treat."
S. aureus infections of the cerebral spinal fluid are not common, but the discovery of this new strain hints that strains that are fully resistant to vancomycin and that could not be effectively treated in any location are emerging. Their emergence could give rise to a situation similar to that before the advent of antibiotics--when S. aureus was an extremely deadly germ.
S. aureus is commonly found on the skin and can live harmlessly in the nasal passages and pudendum. But, when the bacteria overgrow, enter the bloodstream, or produce a toxin, they can cause skin pustules, toxic shock syndrome, blood stream infections, pneumonia, and death. Because it is so prevalent, S. aureus is also the most common cause of surgical-site infections in hospitals. This makes the development of a completely antibiotic-resistant strain particularly worrisome for public health workers. And, says Edmond, "If we can't control it in the hospitals, it could easily spread out into the community."
Antibiotic resistance rises from genetic changes in the bacterium that either make it impenetrable by the antibiotic or that allow it to produce a chemical that reacts with the antibiotic, rendering the antibiotic harmless. Once one bacterium has developed such a resistance, it can be passed on to other bacteria either by transformation (a form of genetic recombination resulting in an exchange of DNA between microbes) or through plasmids (specialized rings of DNA that travel from microbe to microbe). Plasmids have been known to carry the information for resistance to four different antibiotics at once.
Hospital personnel may also be contributing to the likelihood that resistant S. aureus strains will develop and flourish. "The problem is that vancomycin is commonly used in hospitals, and it may have been overused," Edmond says. If the antibiotic is used on an infection where only a few of the bacteria are resistant to it, all but the vancomycin-resistant strain will die, leaving that strain to grow and reproduce with little competition. S. aureus is also a hardy bacterium that can survive outside of the body for weeks and travel considerable distances through the air, making it very easy to spread the infection.
Edmond was one of many health professionals who predicted the advent of vancomycin-resistant S. aureus. The bacterium has been efficient in defeating other antibiotics. For example, it developed resistance to penicillin in 1947, just four years after drug companies had begun mass-producing the medicine. Other common bacteria, including enterococcus, a common parasite in the human gut, have already developed vancomycin-resistant strains, and it seemed only a matter of time before this resistance was passed on to S. aureus. In 1992, a British researcher observed such a transfer take place in the laboratory, but until this year, no vancomycin-resistant S. aureus had been observed in the wild.
The Japanese doctors who discovered the resistant strain vigorously treated the infection with vancomycin, the antibiotic ampicillin/sulbactum, and arbekacin, an aminoglycoside approved for use against methicillin-resistant S. aureus in Japan but not in the United States. The organism tested negative for the genes responsible for vancomycin resistance in enterococci; the mechanism by which this strain was able to withstand vancomycin is still under investigation.
Women who have never smoked but who are regularly exposed to cigarette smoke at home or at work are almost twice as likely to develop coronary heart disease as women who are not exposed to tobacco smoke, according to a study in the 20 May 1997 issue of the journal
Circulation. This latest study is another black eye for the already embattled tobacco industry and new ammunition for individuals claiming that they have been unfairly harmed by so-called secondhand tobacco smoke.
New evidence. A recent report shows a strong link between secondhand smoke and coronary heart disease.
Over a dozen studies have been undertaken to assess the relationship between environmental tobacco smoke and coronary heart disease, but this is the strongest association yet observed. Other studies have found that nonsmokers exposed to environmental tobacco smoke increase their risk of coronary heart disease by 20-30%, although some studies have not been able to find any statistically significant excess risk associated with exposure to environmental tobacco smoke.
The authors of the latest study contend, however, that their research improves upon past efforts because they consider exposures to environmental tobacco smoke both at work and at home, while nearly all other studies have looked at exposures in only one location. Also, the authors adjusted for a broad range of risk factors for coronary heart disease, many of which could have confounded the results of past studies. Among these risk factors were age, alcohol intake, weight, hypertension, diabetes, cholesterol levels, menopausal status, use of post-menopausal hormones, use of oral contraceptives, exercise, saturated fat intake, vitamin E intake, aspirin intake, and parental history of myocardial infarction.
After adjusting for such factors, the authors found that, compared to women who reported no exposure to secondhand smoke, women occasionally exposed had a 58% greater chance of developing coronary heart disease, and women regularly exposed to smoke had a 91% greater chance of developing the disease. Ichiro Kawachi, an assistant professor of medicine at Harvard Medical School and the lead author of the study, called the results "startling."
Kawachi and colleagues at Harvard and at Brigham and Women's Hospital in Boston conducted the prospective study on a cohort of 32,046 women between the ages of 36 and 61 who were already participants in Harvard's Nurses' Health Study. In 1982, the women were asked about their exposure to secondhand tobacco smoke. The cohort was then followed until 1992 with study endpoints consisting of nonfatal myocardial infarction and fatal coronary heart disease.
A weakness of the study, concede the authors, was its reliance on the subjects to determine if they were regularly exposed, occasionally exposed, or not exposed to secondhand smoke. Also, this exposure evaluation was made only once at the beginning of the 10-year study period. The authors conclude that these circumstances would be likely to weaken the association between exposure to environmental tobacco smoke and heart disease. This is because smoking was banned from many hospitals during the study period, so nurses in the study group probably reported higher exposures at baseline than they would have toward the end of the study.
The results of the study may lend support to the claims of a group of flight attendants who brought suit in May against cigarette manufacturers for illnesses they attribute to years of exposure to environmental tobacco smoke in airplane cabins. The study could also strengthen the hand of 31 states' attorneys general who are trying to reach an out-of-court settlement with the tobacco companies for reimbursement of state Medicaid funds used to treat smokers. The proposed settlement between the attorneys general and cigarette manufacturers would give the tobacco industry limited protection against lawsuits such as that brought by the airline attendants. But it must first be approved by Congress and the president, who has voiced objection to the restraints that the deal places on the Food and Drug Administration to regulate tobacco as a drug in the future.
In 1993 Oregon passed a law--the first of its kind in the United States--that allows companies to keep secret the results of any voluntary environmental inspections as long as the firms promptly correct any violations of environmental laws and regulations turned up by these audits. As of May 1997, 21 other states had put similar "environmental audit" legislation on their books, and 13 more states are considering environmental privilege and immunity legislation. Some of these laws have also added provisions granting immunity from prosecution for environmental violations to companies that disclose environmental problems to regulators and promptly remedy them.
A major reason behind such legislation, says Christopher Rich, an attorney with the Oregon Department of Environmental Quality, is the growing complexity and volume of environmental regulations. "Because of this [regulatory] burden, the ability to find violations has increased significantly, and many would argue that it is almost physically impossible to comply with all the regulations on the books," he says. In response to this change, industries often undertake audits to ensure they are complying with current legislation. But such audits can be expensive and time-consuming. In addition, they create a so-called "paper trail" that would be available to the public. According to Jim Moore, a Seattle attorney who works with businesses, such audits "create a record that someone who is motivated out of political aspirations can use against a company." Laws that allow companies to keep this information privileged are an attempt to address such potential abuses of information, he says. This type of legislation is endorsed by business organizations such as the National Association of Manufacturers and the Colorado Association of Commerce & Industry, a major sponsor of the Colorado audit privilege law (the second such law in the United States), which is being used as a model for most subsequent audit privilege legislation.
The opposition to privilege and immunity laws, particularly by public interest groups, is enormous and heated. The laws' critics see them as a huge threat to public health and property. Ross Vincent is chairman of the Sierra Club's Environmental Quality Strategy Team and is responsible for coordinating the organization's opposition to audit privilege legislation, nationally and locally. Says Vincent, "Audit privilege laws threaten lives . . . by shielding environmental lawbreakers from prosecution. They also allow unscrupulous operators to conceal from the public, from prosecutors, and from the courts essential information about releases and exposures involving the huge universe of unregulated toxins. . . . They create an effective shield that will very likely encourage some polluters to report violations only selectively, thus committing criminal violations with fair confidence that they will not be caught. They remove some of the most important 'bottom line' incentives for investment in innovative technologies and practices, and for improved performance beyond mere compliance. And," he concludes, "they interfere with the ability of people harmed by unregulated pollution to recover damages from the responsible parties."
Thomas Lindley, an Oregon lawyer who was instrumental in writing that state's privilege legislation, argues that the laws don't really keep information secret from the public. For example, he notes, they don't protect information that must be reported to the EPA. But that fact doesn't reassure Mark Woodall, who heads the Sierra Club's task force opposing this legislation. "That's of little consequence to us," he says. "There's just a tremendous amount of information about any sort of organization that, [although] not required to be reported under our current system, is important for people to know."
Critics say that laws that grant immunity from prosecution can protect people who violate environmental laws and regulations. The EPA is opposed to the privilege and immunity laws for this reason. "We oppose them all," says Bertram Frey, deputy counsel for the EPA's Midwest region. "They block the search for truth," he says.
Moreover, Frey argues, such legislation can actually penalize companies that spend money to comply with environmental law and regulations. Companies that don't comply may have an economic advantage in states with such legislation because they potentially don't get penalized for failing to follow environmental regulations.
Instead of audit privilege laws, the EPA has a penalty mitigation policy that the agency says offers reduced penalties for companies that fix violations uncovered by voluntary audits. "We've gotten over 150 disclosures from over 400 facilities in the country," says Frey. "In the majority of the cases there has been no penalty. These are record-keeping violations." But they are not necessarily minor, Frey adds, because such reports involve toxic release inventories or information crucial to safe drinking water programs. "We think the EPA policy, offering significant mitigation, is very reasonable," says Woodall.
But in the opinion of Nancy Newkirk, a Washington lawyer who counsels businesses and tracks audit privilege legislation, the policy has weaknesses. "The [EPA] policy is quite good. But the Justice Department isn't bound by it [and] no other federal, state, or regulatory body is bound by it, so you can have a situation where a company does an audit, finds a problem, and gets treated as though the [EPA] found the problem," she says, which means the company may be punished. Newkirk says the EPA's opposition to audit privilege laws so far has consisted of testifying against such laws in state capitals and working to modify them. The agency has testified in Texas and Utah and is discussing legislation with Michigan. The EPA also opposed audit privilege legislation during debate in the last congress.
The EPA has another weapon against the laws, which to date it hasn't used: the agency can remove a state's authority to enforce federal environmental statutes. That would dry up federal environmental grants and also means that a state's businesses would have to deal with EPA regional headquarters for permits instead of state regulators, which can be far more time-consuming. In Colorado, Vincent is part of a group of environmental leaders who have petitioned the EPA to withdraw portions of Colorado's delegated authority under the Clean Water Act on the grounds that it prohibits the state from effectively enforcing the federal law and from operating a program approvable under federal law.
The debate over audit privilege legislation will soon move to Washington, DC. In June, senators Kay Bailey Hutchison (R-Texas) and Trent Lott (R-Mississippi) introduced federal audit privilege legislation. This is the second time around for such federal legislation; an earlier attempt, which appeared to protect willful criminal conduct by not specifically excluding it, died in the last congress.
Taking the lead among the countries of Latin America, the Mexican government on 16 July 1997 unveiled a program designed to phase out all uses of the pesticides DDT and chlordane within 10 years. Calling for an 80% reduction in the use of DDT over the next five years, cessation of additional uses by the year 2007, and elimination of the use of chlordane by December 1998, Mexico hopes its experience will provide a model for other Latin American and Caribbean countries attempting to reduce their own dependence on organochlorine pesticides.
The specific elements of the program as they relate to each chemical are contained in a North American Regional Action Plan (NARAP) for each chemical. The NARAPs were drafted by the Commission for Environmental Cooperation (CEC), a Montreal-based intergovernmental organization that is jointly administered by Carol Browner, administrator of the U.S. EPA; Julia Carabias, minister of the Environment, Natural Resources, and Fisheries of Mexico; and Christine Stewart, minister of Environment Canada. The CEC was created to coordinate the agenda of the North American Agreement on Environmental Cooperation, which serves as a complement to the environmental provisions established under the North American Free Trade Agreement.
Pesticide prohibition. Mexico has launched an ambitious program to phase out the use of the dangerous pesticides DDT and chlordane.
|
DDT, which has long been banned in both the United States and Canada, still finds limited use in Mexico as part of the country's arsenal in the war against the Anopheles mosquito, carrier of the Plasmodium parasite that causes malaria. Approximately 60% of the Mexican territory, representing an area inhabited by close to 45 million people, provides an environment suitable for malaria transmission. According to Cristina Cortinas de Nava, coordinator of the Union of Chemical Substances and Environmental Evaluation at the Mexican National Institute of Ecology in Mexico City, the NARAP for DDT will build upon the country's existing malaria control program--which has successfully reduced the annual incidence of the disease from 2.4 million cases in the 1940s and 1950s to approximately 5,000 cases today--while simultaneously reducing annual domestic DDT production and use from 25,000 tons to a production rate of approximately 600 tons. The use of DDT is presently restricted to selected government-authorized applications in dwellings.
Much of the success of Mexico's malaria control program (there have been no recorded deaths from malaria since 1982) is due to improvements in sanitation, increased disease surveillance, and integrated pest management schemes that focus pesticide applications on critical habitats and stages in the mosquito's life cycle. According to de Nava, the NARAP will use these proven strategies while conducting experimental pilot studies on alternatives to DDT. Such alternatives include biological control agents such as larval parasites and adult predators, microbial products such as Bacillus thuringiensis, and other less persistent pesticides such as pyrethroids. Additionally, the NARAP calls for increased community involvement in the malaria control program, increased enforcement against illegal uses of DDT, and restrictions on transborder movement of malaria-infected populations.
That Mexico has been able to successfully limit the spread of malaria while simultaneously reducing the use of DDT leaves de Nava hopeful about eliminating the pesticide's use altogether. "I'm very optimistic; the campaign has already made great strides," she said. "The problem is one of economics--alternatives can cost up to three times as much as DDT, and we need to be sure that the alternatives don't pose risks [that are greater than] those posed by DDT."
Use in Mexico of chlordane, which is banned from use in the United States and Canada, is limited to urban applications for the control of termites. Until recently, Mexico imported approximately 45 tons of chlordane annually from the United States (where it is legal to manufacture it). Under the NARAP for chlordane, however, Mexico intends to deplete its existing stocks and will no longer allow imports of the pesticide. Furthermore, Velsicol, the sole U.S. manufacturer of chlordane, announced in May of this year that it had voluntarily ceased production at all of its national and international facilities.
Under the NARAP for chlordane, a multi-phase regulatory program has been initiated that focuses primarily on the development of an integrated termite control strategy, prohibition of importation, environmental monitoring and risk assessment of chlordane-exposed individuals, monitoring of existing stocks, and cancellation of the existing registration for use in Mexico.
According to Andrew Hamilton, scientific director of the CEC, Mexico will look to agencies within the United States and Canada for both technical expertise in implementing the NARAPs and assistance in obtaining funding. "Involvement by U.S. and Canadian agencies will help to strengthen proposals geared toward international lending agencies such as the World Bank," he said. "For example, the U.S. Agency for International Development [USAID] has had significant experience from its work in the tropics." The USAID can be of direct assistance to Mexico in terms of providing expertise in malaria control and they can also help by directly acting as co-sponsors for grant proposals to the World Bank.
Hamilton reaffirmed Mexico's commitment to eliminating its use of organochlorines, and stated that among the incentives for terminating the pesticides' use is a desire to take part in the international effort to reduce the migration of persistent chemicals to arctic environments. "The idea of a tropical country taking an active role in the Arctic won't go unnoticed," he said.
The Health of Nations
Since 1902, the Pan American Health Organization (PAHO), the world's oldest international agency, has been working to combat disease and improve living standards in the Americas and the Caribbean. Though wars, political schisms, language barriers, and mistrust have been formidable challenges to its mission, PAHO continues to unite diverse peoples against the common enemies of natural disaster and disease.
The task facing PAHO, which acts as the regional office of the World Health Organization (WHO), is a formidable one. In Latin America and the Caribbean, 130 million people do not have access to safe drinking water and 160 million lack permanent access to basic health services. Despite such obstacles, PAHO has made huge achievements in protecting public health, such as completely eradicating polio from the region. The last wild polio virus in the Americas was detected on 5 September 1991 in Peru.
Part of PAHO's success stems from its ability to adapt the resources of the most technologically advanced countries to the needs of the most isolated villages. For example, PAHO distributes relevant health information throughout the Americas via its World Wide Web site, located at http://www.paho.org/. The site is as expansive and diverse as the region it covers, with information on everything from which countries are experiencing measles outbreaks to what public health resources are available in Barbados to the infant mortality trends in Nicaragua.
The What's New link on the PAHO home page provides links to the most current information, which in turn is linked to other related material. For example, from the What's New page users can access the latest articles written for NutriInfo, PAHO's electronic food and nutrition magazine, and then follow the Back link on the NutriInfo page to access the PAHO Food and Nutrition Program home page. (Users should be aware that links labeled "Back" always lead to more general information.) Also available under the What's New link are the contents and abstracts of the most current issues of the Pan American Journal of Public Health and information on ordering the latest books and technical papers published by PAHO. Upcoming PAHO conferences, the status of certain diseases in the Americas, and PAHO press releases are also provided under the What's New link.
The majority of the public health information on the PAHO site is found through the Technical Information home page. The Technical Information page lists the seven major divisions of PAHO with links to pages covering each division's programs and projects. Information on how to obtain PAHO/WHO fellowships and how to subscribe to PAHO's AHEALTH listserv discussion group can also be found by following the Fellowships link and the Information Systems link on this page. The Disasters/Humanitarian Assistance link on the Technical Information page is connected to a list of materials to help nations prepare for and recover from natural disasters. Information is provided on how to contact relief coordinators, the contents of a WHO emergency health kit, how to order relief supply management software, PAHO's quarterly disaster newsletter, and a wide range of disaster training materials. An extensive disaster database available on the Web is also being planned. The Health Systems and Services Development division home page includes a link to the home page of BRIDGE, a newsletter on health research, and to directories of public health institutions throughout Latin America and the Caribbean.
The Country Health Profiles link on the PAHO home page takes users to a list of all the countries and colonies in the region that PAHO serves. Each item on this list is a link to a health summary for that territory, updated every four years, with statistics such as rate of population growth, the age and geographic distribution of the population, infant mortality, and life expectancy.
Under the Media Center link on the PAHO home page, users can click on the PAHO Speakers' Bureau link to get details on how to bring a PAHO public health expert to their communities to meet with local professional or community groups. There are also links to the first two issues of PAHO's new Perspectives on Health magazine. More information on PAHO's many print and electronic publications is available under the Publications link on the home page. As with the Web site itself, most of these publications are available in both English and Spanish.
Last Update: August 29, 1997