Infectious Diseases: Many Gains, Much To Do

Updated 12/5/2016

Great strides have been made in combating infectious diseases. However, past successes do not necessarily guarantee a bright future, especially in the face of emerging threats, according to speakers at the Infectious Diseases Society of America (IDSA) annual conference plenary symposium in New Orleans on October 26.

About 50 years ago, early success with antibiotics gave way to the realization that resistance had developed and the situation was getting worse. “We risk turning the clock back to a time when simple infections could kill. Modern medicine is at risk. Loss of effective medicine could make routine infections deadly. We need to act now or even drugs of last resort will soon be ineffective,” said Thomas Frieden, MD, MPH, director of the Centers for Disease Control and Prevention, in his talk.

Hospitals need to act as a community, not in isolation. “Even if you practice at the best facility in the world, you are, in many ways, at the mercy of the nursing home down the block, the healthcare provider across town, and the long-term acute care facility that sends patients to you. Patients move and bacteria move with them,” said Dr. Friesen.

Thinking outside of the box when it comes to infection control also applies to bacteria. The human microbiome is a repository of a vast number of bacteria, more of which are friendly rather than pathogenic. Antibiotic therapy that disrupts the human microbiome can lead to the dominance of the pathogens, however.

“Turning the tide on antimicrobial resistance involves finding resistant organisms faster and more completely in hospitals, nursing homes, the community, animals, and food; preventing infections more thoroughly through stewardship, system-wide infection control, vaccination, and improved treatment; stopping infections more quickly by surveillance and reporting, outbreak control, information sharing among hospitals, and improving laboratory capacity; and innovations in antibiotics, diagnosis, infection control, and vaccines,” said Dr. Frieden.

Antiretroviral therapy has also achieved success, but efforts must continue as the face of AIDS and infection with HIV changes. The incidence of HIV declined from 1995 to 2016, partly due to implementation of the President’s Emergency Plan for AIDS Relief (PEPFAR). As a result, life expectancy in sub-Saharan Africa has returned to its level prior to the HIV/AIDS epidemic, and treatment for pregnant women has increased to over 90%. The improved survival rate of infants has resulted in a doubling of the number of the 15-to-24 year olds in sub-Saharan Africa.

One new challenge is the disproportionate infection of new HIV infection in young women. “A 17-year-old is often quite taken by a college freshman 5 to 6 years older than them. Young men who don’t know they are HIV-positive infect 16- to 17-year-old young women who do not know they are HIV-positive and go on to infect their 20-year-old partner,” described Deborah Birx, MD, ambassador-at-large, State Department, in her talk.

PEPFAR has shifted its focus from the very young to people of various ages in target regions. In Kenya, for example, new infections were nearly the same in number among children and adults in 2000. By 2015, however, the numbers had shifted overwhelmingly to adults older than 35 years. Convincing this population, particularly young men, of the need for testing and care is paramount.

“We have had tremendous success after 20 years of antiretroviral therapy. Over 17 million people were on life-saving therapy in 2015. But our work is far from done. As we are here this week at this meeting, over 2000 children and over 19,200 adults will die from HIV; over 2800 babies will be infected with HIV; and over 37,000 adults will be affected with HIV, with over 7500 being young women,” said Dr. Birx.

The past and future influence of microorganisms on infectious disease and the future of medicine were addressed by David Relman, MD, Stanford University School of Medicine. “We like to think that we command this universe. We really don’t at all. This is a microbial planet,” he said.

The bacterial world that has been discovered through sequencing of DNA recovered directly from the environment, rather than tried-and-true culture techniques, has revealed a world very different from that perceived 50 years ago. “It’s not a world of gram-positive, gram-negative, acid-fast, fungi, and other microbes, the way textbooks have been organized and some still are,” said Dr. Relman in his talk.

A large chunk of bacterial life individually lacks the genetic wherewithal to live, yet, they do; many are found in the mouth, not just transiently. “We think that in their dependencies, they are supporting the growth of other microbes that are a clinical concern,” said Dr. Relman.

The microbial reality is that microbes seldom live alone. Rather, they live as members of a community—and this includes our gut. An analysis of genes recovered from 755 metagenomic samples from 100 healthy volunteers revealed that dozens of gene clusters that encode unknown products had proved present in over half of the people. In environments like this, the bacterial communities survive and thrive because of communication between the bacteria in the form of small molecules that shuttle between cells. Within the community, bacteria can produce compounds that they themselves do not use, but which benefit other members of the community and thus maintain the overall “health” of the community. This can have clinical implications. An example is the production of indole by antibiotic-resistant Escherichia coli, which allows more vulnerable bacteria in the population to survive the antibiotic stress.

Bacteria can offer lessons for clinical practice. Disturbance of a microbial ecosystem can have negative effects, as integration of environmental and host features can influence health management and disease classification. The maintenance of bacterial communities points the way to the therapeutic use of microbial compounds and “informed manipulation” of the microbiota.

DISCLOSURES

Thomas Frieden, Deborah Brix, David Relman: none

PRESENTATIONS

Special Opening Plenary Session: Infectious Diseases: Looking Back, Moving Forward

• Antibiotic Resistance & Where We Are Today: Thomas Frieden, MD, MPH, director, CDC
• 20 Years of Antiretroviral Therapy: Deborah L. Birx, MD, ambassador-at-large, State Department
• Microbes, Infectious Disease, and the Future of Medicine: David Relman, MD, Stanford University School of Medicine

Brian Hoyle, PhD, is a medical and science writer and editor from Halifax, Nova Scotia, Canada. He has been a full-time freelance writer/editor for over 15 years. Prior to that, he was a research microbiologist and lab manager of a provincial government water testing lab. He can be reached at hoyle@square-rainbow.com.