Emerging Pathogens


An in-depth look at the scientific community’s approach to pathogen identification & monitoring

Vol. 23 • Issue 5 • Page 12

Cover Story

Pathogens are defined as microorganisms that have harmful effects to humans. Every laboratory science student knows that. But what is an emerging pathogen? How does a laboratory determine what might be a potential pathogen next year? Like many areas of the clinical laboratory, it’s all about teamwork.

Emerging Pathogens Defined

An emerging pathogen is an outbreak of a known or previously unknown disease whose incidence has significantly increased. Decades of observation have given infectious ­disease professionals a substantial list of agents that cause disease in humans. This agent list is likely pinned to the bulletin board of every infectious disease (ID) professional in every city in the United States. Agents such as Mycobacterium tuberculosis, methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., Ehrlichia and approximately 60 others, are on the list. Some of the agents require that the health department be notified within four hours of diagnosis while others allow notification up to a week after diagnosis.

Monitoring Diseases

With their list of infectious agents in hand, ID professionals set up local databases to allow monitoring of what bacteria is being identified at their facility. This database and clinicians watch for trends in the diagnosis of pathogens. Two heads are better than one, King Solomon said, so local hospitals often have a committee that watches over current pathogens, antibiotic usage, numbers of patients in isolation, as well as any other marker the hospital has set up. One professional referred to this process as data mining or keeping an eye on data for relationships previously undiscovered.

Multi-drug resistant organisms, or MDROs, have become a problem for clinicians. The current MDROs being watched are:

  • methicillin-resistant Staphylococcus aureus (MRSA),
  • vancomycin-resistant Enterococcus spp. (VRE),
  • extended spectrum beta-lactamase (ESBL), and
  • carbapenem-resistant Enterobacteriaceae (CRE).

Pathogens such as these have led to committees within facilities that watch for unnecessary antibiotic usage and take steps to educate physicians, medical personnel, and the general public.

Teamwork Required

Teamwork is necessary for proper identification and eradication of pathogens. For example, in the last decade, Israel fought the battle to contain CRE and succeeded. They shared their findings with the world, which led to the Centers for Disease Control and Prevention (CDC) writing their 2006 “Guidelines for Management of Multidrug-Resistant Organisms in Healthcare Settings” now used in the U.S. Local healthcare facilities report to health departments, which report to the CDC, which report back to both the health departments and local facilities. This roundtable of information makes it possible for facilities to monitor their agent lists and set up their data mining software to keep an eye on what’s growing in the microbiology laboratory.

What’s growing in another part of the world may not be growing in the United States yet, but it might one day, which is why the CDC, health departments, and local ID personnel are vigilant in their watch to identify emerging pathogens. As well, not every city and county within the U.S. watch out for the same emerging pathogens. An example of this is CRE, not currently seen in the region of the United States where this article was written. But ID professionals are watching and monitoring and will be ready should that day come.

Better Detection

Identification of pathogens is improving as a result of better detection methods in use at the local laboratory level. Polymerase chain reaction (PCR) assays were once only seen at the reference laboratory level or higher, but with real-time assays more readily available, local healthcare facilities are now using increasing numbers of molecular detection methods.

What is of special interest to ID professionals are pathogens once seen only in animals or arthropods emerging into human pathogens. The National Institute of Allergy and Infectious Disease (NIAID) cites “changes in human demographics, behavior, land use and other factors” as contributing to the jump of pathogens from animals to humans. For example, there is an increase in the trade of exotic animals for pets and food that increases the exposure of humans to animal or arthropod carriers of various diseases.

Infectious disease professionals are also keeping watch for re-emerging pathogens. These old infectious disease enemies are reappearing because of natural genetic changes and adaptations. The NIAID reports that human behavior plays a role in the re-emergence of a disease. Humans, over the decades, have increased antibiotic use, or misused them entirely. Relaxation or decreased compliance with vaccination policies has led to increased cases of measles and pertussis. Some pathogens, such as anthrax and smallpox, are now being used as bioterrorism agents, which increases the threat to the civilian population.

The identification and monitoring of emerging and re-emerging pathogens is not done on one level. This process involves the laboratorian in the local microbiology laboratory, the healthcare facility’s ID personnel, county and state health departments all the way up to the CDC and perhaps even the World Health Organization. As the saying goes, “there is no I in TEAM.”


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About Author

Kim Ledingham, MT(AMT), MLT(ASCP)

Kim Ledingham is a medical technologist and freelance writer.

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