By sequencing the genome of MRSA, scientists may be able to predict the severity of infection in an individual, according to a new study published in Genome Research.
Although most "staph" germs can be easily cured by antibiotics, MRSA - or "methicillin-resistant Staphylococcus aureus," the origins of which can be traced back to cattle infections - is a staph infection that is resistant to antibiotics.
Like other staph germs, MRSA is spread by touching. The germ can be spread from a patient's body to a doctor, nurse or other health care provider, who could then pass the pathogen on to other patients.
People who have a weakened immune system are more at risk from getting serious staph infections, such as MRSA. These include people who are in the hospital for a long time, people on kidney dialysis or who are receiving cancer treatment, or people who have had surgery in the past year.
Outside of clinical settings, factors that can make someone more at risk include injecting illegal drugs, getting a tattoo, sharing towels and razors or being in the military.
MRSA infections can be severe if they enter the bloodstream, heart, lungs or other organs. Symptoms of this include:
By sequencing the whole genome of 90 MRSA isolates, Massey and her colleagues were able to identify more than 100 genetic loci linked to toxicity.
- Chest pain
- Cough or shortness of breath
- Fever and chills
- General ill feeling
- Wounds that do not heal.
Because it is so easily transmitted and so resistant to antibiotics, MRSA presents a considerable problem to public health - both in terms of treatment and prevention.
For instance, last year, Medical News Today reported on a study that found wearing gloves or gowns in intensive care units does not reduce overall rates of acquiring MRSA.
Determining appropriate treatment options for patients is especially challenging, as the toxicity of the pathogen can vary, which influences the course of the disease.
Lead author of the new study, Dr. Ruth Massey, from the University of Bath, UK, says that when assessing MRSA's toxicity, "the standard approach has always been to focus on a single or small number of genes and proteins." But due to the complex nature of toxicity - which involves many genetic loci - this approach has not always been successful.
Cheaper and faster than ever before, could genome sequencing improve treatment?
"As the cost and speed of genome sequencing decreases, it is becoming increasingly feasible to sequence the genome of an infecting organism," says Dr. Massey.
By sequencing the whole genome of 90 MRSA isolates, Dr. Massey and her colleagues were able to identify more than 100 genetic loci linked to toxicity. The researchers found that the MRSA isolates varied greatly in toxicity.
But the researchers also found that the isolates that were highly toxic shared a common genetic signature. Looking for this signature in the MRSA genomes allowed the researchers to predict which isolates were the most toxic.
Knowing the toxicity of the strain of MRSA that a patient is infected with could greatly influence their treatment. A highly toxic infection could be treated more aggressively, or a patient isolated from others to control the spread of the infection.
But further research is needed before the scientists know how each of the genetic loci identified by the study influences disease. Next, Dr. Massey and hear team will apply their methodology from this study to examining the highly antibiotic-resistant USA300 strain of MRSA, as well as other bacteria such as Streptococcus pneumonia.
Written by David McNamee