MRSA Infection: What it Is, How it Spreads, and How to Avoid Getting Infected

October 29, 2021

This article was medically reviewed by Dr. Donald T. Allegra.

According to the Centers for Disease Control, methicillin-resistant Staphylococcus aureus (MRSA) is commonly found on skin or in the nose. Once the bacteria enter the bloodstream, however, they can cause a Staphylococcus (Staph) infection that is difficult to treat due to its resistance to some antibiotics. When MRSA spreads in hospitals, nursing homes, and other healthcare facilities, it is referred to as hospital-acquired or HA-MRSA, and when it arises in community settings where people live, work, play sports, and go to school, it is known as community-acquired or CA-MRSA. In this article, ID Care’s Dr. Donald T. Allegra provides you with a guide to understanding MRSA, its dangers, diagnosis, treatment, and prevention.

MRSA Infection Overview

Methicillin is an antibiotic that was developed around 1960 and targeted at treating Staph aureus infections. Within about a year, hospitals began identifying isolates of the bacteria that were resistant to methicillin. Now, after six decades of evolution, the methicillin-resistant Staphylococcus aureus has become a significant healthcare challenge. As recently as 2009, it was estimated that about 70% of Staph aureus infections found in ICU patients are MRSA variants.

70% of Staph aureus infections found in hospitals ICU patients are methicillin-resistant Staphylococcus aureus (MRSA) variants.

After emerging in England, HA-MRSA was first detected in the United State in 1968. It spreads through physical contact, usually within hospitals and other care facilities, exploiting the vulnerability of people with existing health problems. The disease can also become airborne if it infects a patient’s lungs. HA-MRSA can lead to severe, invasive disease if left untreated, including bacteria in the blood stream (sepsis), pneumonia, and other life-threatening effects. Fortunately, it is easy to detect and very treatable with antibiotics not related to methicillin, especially in the early stages. A fever is usually the first symptom of HA-MRSA, and if the disease is present, a simple culture test will reveal it.

CA-MRSA is a different strain first described in the 1980s and tends to target healthy people. According to Dr. Allegra, this variant “was first seen in IV drug users, but since then has spread across the general population of people who don’t have other health risk factors.” CA-MRSA spreads through physical contact only and is now common where active healthy people congregate and share equipment or contact each other directly, for example, on sports teams or in health clubs, schools, prisons, military barracks, and even in families. “In those cases,” Dr. Allegra notes, “it’s usually associated with skin and soft-tissue infections, which are often just recurrent boils. While it’s not really a threat to people’s lives, CA-MRSA is a painful nuisance that can cause a lot of suffering if not treated.”

MRSA Colonization

In some cases, bacteria directly cause an infection. Others are cases of colonization, where the bacteria are present but haven’t yet caused infection. “Many hospitalized patients who are MRSA-colonized have no current symptoms,” warns Dr. Allegra, “but they can spread symptomatic MRSA without even realizing it, and as time passes, many colonized patients eventually get infected and show symptoms.”

The most common place MRSA is carried is in the nose, near the opening of the nostrils. According to Dr. Allegra, “we’re always reaching up to our nose and then touching other parts of our body, and that’s often how MRSA spreads to other parts of our skin. In the hospital setting, patients with catheters in place can get colonized by it, as well as those with surgical wounds or diabetic ulcers.”

MRSA has been called “the superbug” because it tends to stay colonized within people, and they can carry it for months or even years without experiencing an infection. It also clings to surfaces and to prosthetic devices in people’s bodies, including artificial hips and knees, pacemaker wires, and intravenous lines. It forms a slimy barrier around these devices that protects the bacteria from attack by antibiotics. Within its protective slime barrier, MRSA can remain for long periods and be difficult to eradicate.

Why MRSA is So Contagious

MRSA is highly contagious because it spreads by air, like COVID-19, and by contact with contaminated surfaces (called fomites) or someone else’s contaminated skin. It can live on the hands of healthcare workers, on stethoscopes and other devices, and even on hospital bed rails, so it’s everywhere that patients are. Also, MRSA has evolved to be more virulent, potent, and harder to kill than the regular Staph aureus typically encountered.

Worse, some highly contagious strains of MRSA produce an enzyme called panton valentine. It’s a tissue-damaging toxin that can lead to more severe skin and soft tissue infections (SSTIs), and sometimes even to tissue death or necrosis. ID Care’s guide to avoiding SSTIs, including those caused by MRSA, is located here.

MRSA Risk and Spread

Those at highest risk for MRSA are the immunocompromised, people with debilitated immune systems due to older age, cancer chemotherapy, or drugs that modify the immune system such as steroids. If they have MRSA-colonizable devices in their bodies, their infection risk is also elevated. Even hospital respirators can get colonized and spread MRSA.

The other risky patient profile for MRSA is someone using a lot of antibiotics. For example, Dr. Allegra reports that some of his nursing home patients suffer continually from sinus infections or bronchitis. “When they are prescribed antibiotics,” he said, “those antibiotics will select for resistant organisms such as MRSA, and then the patient gets colonized. From colonization, the next step is infection, and particularly in hospitalized patients, those infections need prompt treatment to avoid progressing.”

On the other end of the patient spectrum, CA-MRSA often affects the very healthiest people in our community. For example, athletes who share equipment, including towels and water bottles, are at increased risk. Big outbreaks on athletic teams have happened this way, as well as from skin-to-skin contact during game play. Wrestling is especially conducive to spreading MRSA, but all contact sports can be vectors. So can using health club equipment that has been contaminated and not properly cleaned after use.

Close-contact transmission also means that MRSA spreads very easily in families. Even dogs and cats can carry it and pass it to their human companions.

MRSA’s Most Serious Outcomes

Part of the reason HA-MRSA causes higher mortality rates than non-resistant Staph infections is the typical condition of people who get it. Usually, it’s someone who is already ill and has been on antibiotics, may have been in a nursing home, and may have MRSA-friendly invasive devices like pacemakers and IVs. They’re a generally sicker population, and so more likely to succumb.

The great majority of MRSA infections are detected and treated successfully. However, if left untreated, a MRSA infection can progress to involve one or more of these serious concerns, in order of their frequency:

  • Chronic Wounds: skin and surgical-site infections (SSIs) that won’t heal;
  • Bloodstream Infections: sepsis, usually due to patients’ intravenous lines becoming infected
  • Lower Respiratory Tract Infections: mostly pneumonia and;
  • Urinary Tract Infections (UTIs):

Preventing MRSA Infection

MRSA infection is common, easily spread and potentially deadly if ignored, so preventing it should be part of every healthcare facility’s infection control program. According to Dr. Allegra, step one is to create distance and barriers between the patient and everyone else. “At ID Care’s offices and at the hospitals where we operate,” he said, “the first thing we do for actual or suspected MRSA patients is to put them into contact isolation. That means we wear gloves, gowns, masks when near those patients, and we usually put them in private rooms.” When a MRSA patient is discharged or moved, a terminal cleaning of their room to make sure all surfaces have been disinfected and rendered safe.

For high-risk surgeries, patients are often screened for MRSA as part of pre-surgery protocols. If found to be MRSA colonized, Dr. Allegra’s team will try to decolonize the patient with topical and systemic medications to reduce the possibility of a post-operative infection.

ID Care also tries to remove invasive IV lines as soon as possible. While “these catheters can get infected, we limit how long they’re in use and take special precautions when cleaning, inserting and removing them. Everything is done in a very sterile environment, so we’ve cut our rate of MRSA bloodstream infections close to zero. In some hospitals, we’ve gone up to 18 months without a single infection. This proves that major infection control efforts are effective in producing tangible, real-world results.”

MRSA and Antibiotic Stewardship

A big factor in the spread of MRSA infection has been the inappropriate use of antibiotics, a widespread and long-lived problem across medicine. In the United States, it’s been estimated that a third of people who get antibiotics don’t need them, largely because they have viral infections which are not responsive to antibiotics.

When appropriately prescribed, the type, dosage and duration of antibiotic use must be managed. “If not,” Dr. Allegra warns, “then bacteria such as MRSA can flourish and predominate — antibiotic stewardship refers to the close monitoring of antibiotic use, and it’s fundamentally important.”

For people who traditionally have been prescribed multiple broad-spectrum antibiotics, Dr. Allegra advises using only the narrowest spectrum antibiotic that is really needed, and for the shortest effective period: “If someone doesn’t absolutely need antibiotics or if they’ve already had a reasonable course of antibiotic treatment, they don’t need more for a simple infection. Limiting antibiotic use decreases the pressure to develop resistance to those antibiotics.”

MRSA Diagnosis

To diagnose the disease, healthcare providers first need a good sense of MRSA awareness to order a test. Dr. Allegra advises that “any skin or soft tissue infection is a source of concern.” He added that “surgical wounds often get infected with MRSA and must be watched carefully.”

Luckily, unlike some bacteria, MRSA is not one that hides. It often grows easily in routine cultures. Dr. Allegra has observed that “when we do routine cultures of sputum, an abscess cavity, urine, or an abdominal wound due to recent surgery, we usually know in a couple of days whether a patient is truly infected with MRSA.”

Treating MRSA

MRSA got its name for methicillin-resistance, but there are many other antibiotics that do treat MRSA infection. Some people are unduly frightened at the mention of MRSA, but Dr. Allegra advises against panic: “It’s not a hopeless situation when you get this infection. Even though we can’t use methicillin-type drugs, commonly available intravenous vancomycin usually works. There’s also daptomycin, and a few oral agents for community-acquired MRSA called doxycycline and bactrim. These have been around for a long time and cover this organism quite well.” In addition to oral antibiotics, CA-MRSA strains can be treated with special soaps and medicated creams designed to rid the skin of MRSA infection.

Usually, when MRSA is suspected, a wary doctor will cover for it by prescribing antibiotics even before the test cultures return from the laboratory. Because final lab results can take two or three days, treatment with MRSA-effective antibiotics is often begun immediately. “This way,” Dr. Allegra counsels, “we’re not three days behind the eight-ball before we get a positive culture, and then begin treatment. We always try to start MRSA treatment as soon as possible.”

MRSA Prevalence and Interventions

Some parts of the world have more MRSA than others, and New Jersey is one of them. Conversely, Scandinavian countries have lower levels. Some of the disparity is related to local patient characteristics, differing healthcare coverage policies, and how infection control procedures are implemented. Taking aggressive steps sustained over time has been shown to bring MRSA infection rates down, and that is what guides ID Care’s efforts in New Jersey.

Anti-MRSA interventions can be fruitful even with non-human animals. For example, giving antibiotics to make livestock grow is a long-time practice in the United States, but it contributes to the development of drug-resistant infectious organisms. In response to mounting evidence of this, many large chicken processors have recently begun phasing it out. “As members of the same ecosystem,” Dr. Allegra instructs, “when animals get antibiotics for growth, they develop antibiotic-resistant bacteria that can spread to humans and cause us disease. It’s a very complicated, interdependent ecology we’re dealing with, and ID Care is trying to reduce MRSA and other problem infections at many different levels, with multi-pronged attacks.”

CA-MRSA Infection Control

Beyond treating complicated internal MRSA infections and developing infection-control strategies, Dr. Allegra and his colleagues see patients daily who have recurrent boils due to CA-MRSA. The symptoms are commonly why ID Care gets referrals from other physicians, and if patients have recurrent infections, we try to decolonize or eliminate the bacteria from their skin to prevent future infections. “It might seem mundane,” Dr. Allegra said, “but our patients feel it’s a critical aspect of the care we provide.”

ID Care’s Role in MRSA Prevention and Treatment

Studies have shown that patients with MRSA bloodstream infections do much better if they have an infectious disease consultant on the case from day one. Mortality goes down, a clearly positive indicator.

The transmissible disease specialists at ID Care regularly see patients with serious infections like MRSA, and they also serve on infection control committees for hospitals and other healthcare facilities. Typically, ID Care staff will lead those committees, spearheading the design of strategies to minimize MRSA’s spread. Within the next decade, it is projected that antibiotic-resistant infections may result in up to 10 million deaths worldwide and MRSA is a main driver of those potentially preventable deaths. In response, ID Care is making a big push to ensure that infection control committees have the expertise and resources necessary to do their jobs effectively.

“Each year in the United States,” Dr. Allegra reports, “about 2.8 million people get antibiotic-resistant infections and about 35,000 die. But at ID Care, we have zero tolerance for these organisms. We regard even one case as a serious threat to investigate and determine how it occurred, how we can stop the spread, and how we can prevent a recurrence. Since we’ve adopted the zero-tolerance approach, we’ve seen a marked decrease in hospital-acquired MRSA infections.”

As New Jersey’s largest infectious disease practice, ID Care is a leader in the prevention and treatment of MRSA and other serious infections. To learn more, call 908-281-0610 or visit to schedule a consultation with an ID Care infectious disease expert.

Allegra, Donald, Antibiotic Stewardship, Bacteremia, Boils, Infectious Disease Blog, Infectious Disease Care, Infusion Care, MRSA, Pneumonia, Sepsis, Skin Infections, UTIs, Wound Care, Wound Infections