Staphylococcus aureus infections can be resistant to methicillin – an antibiotic – or susceptible to it. MRSA is resistant to methicillin while MSSA is susceptible. The Food and Drug Administration (FDA) has cleared the first test – the KeyPath MRSA/MSSA Blood Culture Test – that can tell one from the other rapidly.

Methicillin, also known as Staphcillin, is a semisynthetic penicillin-related antibiotic. It used to be effective against staphylococci resistant penicillin. Methicillin has been largely taken over by Vancomycin and is rarely used today. Over the last five decades, staphylococci (staph) bacteria have become increasingly resistant to several antibiotics, including methicillin and many other commonly used penicillin-related medications. These bacteria are known as MRSA, which stands for methicillin-resistant Staphylococcus aureus.

Staph bacteria can cause skin infections, blood poisoning, pneumonia and other infections.

Within five hours of detecting any bacterial growth in a blood sample, the KeyPath MRSA/MSSA Blood Culture Test can tell whether the bacteria are MRSA or MSSA – one, two, or more days faster than standard AST testing. All the test requires is blood culture equipment, making it ideal for laboratory use.

Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostics Device Evaluation and Safety in the FDA’s Center for Devices and Radiological Health, said:

“Clearing this test gives health care professionals a test that can confirm S.aureus and then identify whether the bacteria is MRSA or MSSA. 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.”

Although MRSA infections can occur in any type of setting, those that develop in hospitals tend to have more severe and life-threatening complications, because they house a considerable number of patients with weakened immune systems who have undergone surgery. Surgery gives bacteria an ideal opportunity to enter the body.

The FDA examined a clinical study involving 1,116 blood samples from four major hospital centers in the USA. The identification of MRSA within S. aureus organisms was 98.9% accurate – 178 correct identifications out of 180. Identifying MSSA was 99.4% accurate, 153 out of 154.

According to MicroPhage Inc., the makers of this test, death rates are increasing, largely because of antibiotic resistance. Diagnostic methods today take a long time; doctors cannot base their treatments on clinical data if it takes form 48 to 72 hours to come back, they have to base treatment decisions on experience – some of these decisions may not result in effective results.

On its website, MicroPhage wrote:

“MicroPhage’s bacteriophage amplification platform enables early identification of S. aureus and determination of methicillin resistance (MRSA) or methicillin susceptibility (MSSA) to deliver actionable results when clinicians need them. Simple to perform and without the need for expensive equipment, MicroPhage is making high-value diagnostics accessible to all institutions, large and small.

“KeyPath MRSA/MSSA Blood Culture Test” (page includes a video)

Sources: Food and Drug Administration, MicroPhage Inc.

Written by Christian Nordqvist