The Coming Wave of Infectious Disease Rapid Diagnostics

John G. Bartlett, MD


November 10, 2011

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Developments in Infectious Disease Diagnostics

Hi, I am John Bartlett from Johns Hopkins University School of Medicine and I am here at the 2011 meeting of the Infectious Disease Society of America (IDSA) in Boston, Massachusetts. I want to discuss the new developments in diagnostics for detecting pathogens in infectious diseases.

This topic is about to undergo a sea-change in terms of how we detect resistant bacteria -- the unusual bacteria that we encounter in medicine. If you go into a typical microbiology laboratory today, the technology is about the same as it was 160 years ago when Louis Pasteur described the technology and subsequently when Hans Gram described the Gram stain. It's incredibly antiquated, completely different from the chemistry laboratory in terms of its adoption of modern technology.

That is about to change. We are seeing a gradual evolution of new techniques to define the bacteriology of infectious disease. These techniques come in various sizes and from suppliers -- there are an awful lot of them out there.

Phase 1: Pathogen Detection

For this audience, molecular techniques are now available that can quite easily detect methicillin-resistant Staphylococcus aureus, methicillin-sensitive S aureus, Group B Streptococcus, Legionnaires' disease, tuberculosis, and influenza -- a whole variety of pathogens. However, if you look at the menu that I have just described, it lists organisms that should never be there. That makes their detection in a clinical specimen almost diagnostic of disease. For example, nobody in the audience is probably carrying influenza. If it is present it means you are probably infected. However, if you can detect pneumococcus in the sputum, this would be great technology, but it won't tell you who has pneumococcal disease because so many people are carriers.

It is going to take some advanced technology in order to do quantitation, but the test that simply detects an organism can do so within an hour. There are multiple suppliers and a number of different pathogens on the list. This is technology that will become available very extensively in the near future. It is out there now, and many of you may have access to it; however its use is going to multiply exponentially.

That's the first phase -- pathogen detection for organisms that should never be there.

Phase 2: Separate the Colonizers From the Pathogens

The next phase will use much more sophisticated machinery, such as the T5000, to detect all bacteria -- all microbes, viruses, and fungi -- and do it quantitatively so you can separate the colonizers from the pathogens. It will do this within 8 hours and in the future, in about 3 hours. This technology will be highly sophisticated and very precise. For example, when this machine was used to detect H1N1 pandemic flu in the year 2009, it basically said "this is a strain of influenza that I have never seen before," and that led to the identification of a potential pandemic. That is the utility of this new technology.

For the moment, we are still stuck with conventional methods, but the more we get into the molecular technology, the more we are going to see that a laboratory can turn around the results in an hour and give us information that will be very important in terms of clinical care.

What might hold it back are time and money. Who is going to pay for it, and how fast can it be developed to the point that it can be readily incorporated into laboratory technology? In several years, the microbiology laboratory is likely to look much more like the chemistry laboratory with more automated machinery than it has now.

An important limitation at the present time is sensitivity testing. If we know the mechanism of resistance and have a gene, we can identify the sensitivity. However, it's going to be a long time before we will be able to identify all of the mechanisms of resistance and use that technology to tell us with which antibiotics we should treat the patient.

Drug Store Diagnoses

Point-of-care testing is a much different framework for diagnostic technology. The point-of-care test that we use most is for HIV infection. It is easy, and can be read by anyone who can see a red line. This test has revolutionized the management of HIV infection in the developing world because a relatively untrained health provider can easily do the test, and receive results in an hour that are almost 100% sensitive and specific.

That technology has been expanded so that we can identify a number of different pathogens, such as Neisseria gonorrhea, syphilis, and Chlamydia trachomatis. In the future, we are going to see point-of-care testing that is available to the consumer. It will be readily available in pharmacies, like the influenza vaccine. The patient will actually come to us with a diagnosis, saying "I'm here to see you because I went to Wal-Mart and got this test and it said I had ____ (fill in the blank)." That will make it much easier for the consumer, and probably a lot easier for us to manage a large patient load.

Rapid techniques, on the basis of molecular technology or antigen antibody detection, are coming very rapidly. The only things that might slow them down are the cost and the speed of development. Many of these technologies are currently available, and many of you are using them. Expect a lot more, and expect them to come quite fast. Thank you.


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