MRSA, You May Have Met Your Match...
Author: Mariah Obear
May 19th, 2011

Figure 1 (From Wikipedia)

MRSA is the strand of Staphylococcus aureus that is resistant to methicillin and many types of penicillin (As seen in Figure 1). It is responsible for many infections and deaths primarily for patients in hospitals. The leading detection test for MRSA is Polymerse Chain Reaction (PCR), which takes time and accuracy to correctly diagnose the type of Staphylococcus aureus a person is infected with (Haamann). PCR is costly, inaccurate, and can take too long for a result.

For years now, researchers have been searching for a solution to this problem. Researchers at a company called MicroPhage believe they have found a better test than PCR, all around. The Food and Drug Administration recently announced that they approved a test that is able to diagnose MRSA much faster than the leading technique. This new test is called “KeyPath MRSA/MSSA Blood Culture Test”. It will allow for the identification between MRSA and MSSA bacteria in a timely manner, allowing doctors to administer the correct antibiotics to their patients before MRSA has the opportunity to spread. This development will reduce the error of treating MRSA with the wrong antibiotic and save several lives (Haamann).

Figure 2 (From Wikipedia)

Working in the medical field has always been an interest of mine so when I stumbled across advancement in treatment and prevention of a common bacteria, I was intrigued to read more. Staphylococcus aureus is the common cause for a variety of staph infections. The most common place today to become infected happens to be in hospitals because people typically have undergone surgery or have compromised immune systems. This makes it easy for the bacteria to enter the body and to infect the person.

Aspiring to be a nurse, I will be responsible for many patients. Because Staph is such a common infection in hospitals, it is very likely that I will come across it as a nurse. I think it is important to follow up on the current research and advancements in the medical field, because in a few years I will have to do many of these new techniques. With the approval from the FDA, it is likely that this new way to test for MRSA will become a normal test found in many hospitals.


Staphylococcus aureus
Staphylococcus aureus is the bacteria responsible for the common staph infection.
Figure 3 (From MicroPhage)
Methicillin-resistant Staphylococcus aureus or MRSA for short, is a type of Staphylococcus aureus that is primarily resistant to methicillin. It is tough to kill because over the past years many of the strands have become resistant to serveral antibiotics. Resistance to multiple antibiotics makes it extremely urgent to diagnose and begin treatment as soon as the infection is noticed so there is time to try different antibiotics on the bacterium. Many strains of bacteria have been able to develop resistance to the antibiotics doctors once used to kill them with. Due to the majority of the useful antibiotics already having been created, it is rare to discover one that is more effective than the exhisting antibiotic. This leaves doctors with limited resources to fight off antibiotic resistant bacteria (Tortora).
Figure 4 (From "Modric")

Hospital stays are a prime site of infection by MRSA because many people have weakened immune systems or have undergone surgery (Haamann). Surgery is the easiest pathway for MRSA to infect a person because it can easily enter the body through a wound. Once the bacteria enters a patient, the patient's body is usually too weak to fight off the bacteria, it is not long before the bacteria spreads and infects the patient. Signs that MRSA has infected a person are redness, swelling, and pain to touch; typically fluid from the site of infection and a fever are present as well (as seen in figures 3 and 4). MRSA develops and spreads extremely rapidly. "The most frequent infection sites are nose and throat followed by skin infections" (Haamann). It can go from a small sore into sepsis in a matter of days. MRSA can cause blood infections, cellulitis, infection of the heart valves, pneumonia, toxic shock syndrome and even death. It is important to catch MRSA at the beginning of the infection, and quickly administer drugs to fight it off because of how quickly it progresses.

The two main types of Staphylococcus aureus found in hospitals are MRSA and MSSA; largly different, MRSA is resistant to methicillin, while MSSA is not. It is imporant for doctors to test the difference between the two types in order to effectively kill off the strain they find. Unfortunately, a misdiagnosis between the two could reult in the patient recieving the wrong antibiotic and could result in death.(Haamann)

Figure 5
Research Behind The KeyPath MRSA/MSSA Blood Culture Test
In 2005, "MRSA was responsible for more than 94,000 infections and 18,650 deaths" (Haamann). Even though the number of deaths have slowly reduced in the past few years, it is still a battle which many hospitals have to fight daily. Due to the large number of deaths MRSA causes, researchers have been urgently searching for a faster, more effective way of identifying MRSA versus MSSA and antibiotics that will destroy it (Haamann).

The idea of the "KeyPath MRSA/MSSA blood culture test" came about by researchers working for MicroPhage. The process was based off the understanding that "Bacteriophages have the potential to quickly identify pathogens and their drug sensitivity" (Roehr). Researches found that bacteriophages worked extremely well as "vectors" for the bacteria found in the patient. By placing the bacteria into the bacteriophage, they were able tell what drugs would successfully kill the bacterium, and what drugs that particular bacterium would be resistant to (Roehr).

Researchers from MicroPhage developed and ran tests based off this concept; their results were astounding. After reviewing blood samples from 1,116 patient's blood, gathered from four main hospitals, the researchers found that the test was able to correctly identify MRSA 98.9% of the time and MSSA 99.4% of the time. Not only were the tests extremely accurate, but they were completed in around five and a half hours (Roehr).

Before the KeyPath MRSA/MSSA blood test was created, doctors had to wait several days for the return of lab tests. A polymerase chain reaction test was used to inform doctors of the drugs that would not work on the type of bacteria they were testing (as seen in figure 5). The PCR test is costly, has about a 10% failure rate, and simply is not fast enough (Roehr).
Figure 6 (From MicroPhage)

Upon the approval of the KeyPath MRSA/MSSA blood test, doctors are now able to identify the type of Staphylococcus aureus present in their patient’s body with a blood sample. "Aside from blood culture equipment, the test does not require any specific instruments to get results, which makes it useful in any laboratory" (FDA). The results of the test can be read several days before the PCR's test results. In addition to a faster identification, the test tells doctors what type of antibiotic will work on the cultured bacteria as opposed the types that will not work. This allows for doctors to quickly administer drugs that will kill the bacteria and avoids the risk that the type of antibiotic they administer might not be effective on that bacterium (Roehr). "This not only saves time in diagnosing potentially life-threatening infections but also allows health care professionals to optimize treatment and start appropriate contact precautions to prevent the spread of the organism" (Nordiqvist).

Figure 7 (From MicroPhage)

How The Test Works

The test was created in a way so people could quickly learn the techniques and easily preform the tests.
To perform the test, a small amount of blood is added to two different test tubes, one for identifying Staphylococcus aureus and the other for susceptibility (antibiotic) testing. "Each section has bacteriophages and reagents used for identification" (Roehr). After incubation, one simply adds a drop to each "detection well" and reads the results from the test (as seen in figure 7).

The Food and Drug Administration (FDA) approved the use of the KeyPath MRSA/MSSA blood culture test on May 6,2011. After the approval from the FDA, the developers of the KeyPath MRSA/MSSA blood culture test reported that the largest accomplishment in their product was that it is “Simple to perform and without the need for expensive equipment… making high value diagnostics accessible to all institutions, large and small” (

Literature Cited:

1) Antimicrob, J. "KeyPath™ MRSA/MSSA Blood Culture Test." MicroPhage, Inc. - Accelerated Bacterial Diagnostics and Antimicrobial Susceptibility Tests. Microphage, May 2011. Web. 5 May 2011.

2) Haamann, Frank, Madeleine Dulon, and Albert Nienhaus. "MRSA as an occupational disease: a case series." International Archives of Occupational & Environmental Health 84.3 (2011): 259-266. Academic Search Premier. EBSCO. Web. 19 May 2011.

3) "FDA Clears First Test to Quickly Diagnose and Distinguish MRSA and MSSA." U S Food and Drug Administration Home Page. FDA, 6 May 2011. Web. 19 May 2011.

4) Modric, John. "MRSA Staph Infection Pictures |" Current Health Articles. Health Hype. Web. 5 May 2011.

5) Nordqvist, Christian. "FDA Clears First Test." Medical News Today. 9 May 2011. Web. 12 May 2011.

6) Roehr, Bob. "5-Hour Diagnostic Test for MRSA." Medscape. 28 Oct. 2008. Web. 5 May 2011.

7) Tortora, Gerard J., Berdell R. Funcke, and Christine L. Case. “Ch 11, The Prokaryoke: Domains Bacteria and Archea. “Microbiology: An Introduction.” Tenth ed. San Francisco, CA: Pearson Benjamin Cummings