MRSA in the Air: How Hospitals Can Protect Patients from Infection - Part 1

VRE, CRE, C. diff., CRKP — healthcare facilities have no shortage of dangerous bacteria to contend with. Among the most worrisome in this alphabet soup of superbugs: MRSA.

Easily spread and notoriously resilient, methicillin-resistant Staphylococcus aureus continues to invade the bloodstreams and attack the lungs and joints of hospital and nursing-home patients, entering via cuts, open wounds, burns, feeding tubes, catheters, nasal passages, and airways. Declines in MRSA bloodstream infections have stalled, and aggressive, community-based strains are on the rise.

“MRSA infection is still a major global healthcare problem,” an American research team concluded in Critical Care.

The World Health Organization (WHO) deems MRSA “a serious threat,” while the U.S. Centers for Disease Control (CDC) calls the bacteria “a common and severe threat.” Worldwide, the death rate from invasive MRSA infections is an estimated 20%. In the United States alone, more than 80,000 invasive MRSA infections are diagnosed annually; treatment can last months and cost nearly $40,000 per patient.

With new, lethal strains emerging and new treatments still years away, facilities must broaden their approach to MRSA prevention, deploying new technology to disinfect surfaces and indoor air, in addition to improving hand hygiene.

Studies show MRSA contaminates all manner of surfaces: bed linens, towels, floors, privacy curtains, stretchers, stethoscopes, door handles. At the same time, MRSA particles — propelled airborne when privacy curtains are drawn or an MRSA pneumonia patient coughs — hover in operating theatres, intensive care units, and patient rooms. Clearly, containing MRSA will require more than diligent use of antibacterial hand rub and surgical gloves.

"Hospitals should not just rely upon hand hygiene alone for protecting patients,” asserted American MRSA researcher Neal Goldstein, Ph.D. “Infection control is a multipronged strategy.”

MRSA: Resilient and Widespread

MRSA is particularly concerning to infection-control experts because it has proven, over decades, to be remarkably adaptable.

In the pre-antibiotic era, patients treated for Staphylococcus aureus blood infections, a scourge on the World War I battlefield, had an 82% mortality rate. Among patients over age 50, only 2% survived such infections.

Penicillin, discovered in 1941, changed everything — but only briefly. Within two years, staph infections had become resistant to penicillin and, just a few years later, to its replacement, methicillin. Staphylococcus aureus also outwitted amoxicillin and oxacillin.

Today’s most effective treatment, vancomycin, is a crumbling firewall. Several S. aureus strains exhibit partial resistance to the drug, and isolates with total resistance —  vancomycin-resistant S. aureus (VRSA) — have been reported. There is no “next” drug.

“The ability of S. aureus to become completely resistant to vancomycin is disconcerting,” cautioned a U.S. government research team.

Also disconcerting: the prevalence of MRSA among the public. According to the CDC, 2% of the general population and 5% of hospital patients are colonized with MRSA. Even if asymptomatic, carriers can transmit infection to the vulnerable, such as the elderly, infants, and patients with cancer, diabetes, or chronic skin diseases.

Worldwide, 4.6% of healthcare workers carry MRSA, and 5.1% of carriers have symptomatic infections, but MRSA may be even more widespread than these statistics suggest.

"We underestimate how much MRSA is out there in the general public," asserts Texas State professor Rodney Rohde, Ph.D., whose research has found MRSA in the nostrils of 4% to 5% of prisoners and up to 8% in a sample of college students.

In nursing homes, the prevalence is demonstrably higher. “One in four nursing home residents harbour MRSA in some settings,” said Mary-Claire Roghmann, M.D., infectious disease specialist at the University of Maryland School of Medicine.

How MRSA Spreads

Healthcare workers’ hands are the primary vectors for the spread of MRSA, and transmission is astonishingly easy.

An MRSA carrier visiting the hospital might shake the hand of a busy nurse, who misses a spot while washing her hands and then changes a patient’s bandage. In nursing homes, research shows, MRSA is often transmitted when healthcare workers simply help residents brush their teeth or comb their hair.

Better hand hygiene has long been considered the key to halting MRSA transmission. Compliance among doctors and nurses is “abysmally low,” according to WHO, so there is much room for improvement.

However, even perfect compliance would not halt MRSA spread, according to American researchers who found potential for infant-to-infant transmission in a simulated neonatal intensive care unit.

"Even under optimal hygiene conditions, horizontal transmission of MRSA is possible,” the researchers concluded.

Furthermore, skin-to-skin contact with an MRSA carrier is not necessary to transmit infection. It’s enough for the sleeve of a doctor’s lab coat to brush against a patient’s wound.

MRSA’s staying power on surfaces makes the bacteria particularly hard to contain. MRSA can survive for days, even weeks, on floors, door handles, sinks, mops, blood pressure cuffs, call buttons, and fabrics.

When Canadian researchers tracked freshly laundered privacy curtains at a hospital, they found that by day 14, 87.5% of the curtains tested positive for MRSA, whereas curtains not placed in patient rooms stayed clean the entire 21 days of the study.  

Notably, none of the rooms were occupied by MRSA patients. "Privacy curtains pose a high risk for cross-contamination because they are frequently touched but infrequently changed," concluded lead study author, Kevin Shek.

Nursing scrubs are another reservoir for MRSA. In a study of 120 nurse shifts, researchers found new contamination on scrubs during 39 shifts. MRSA was among the most commonly transmitted pathogens.

And an American team called hospital floors “an underappreciated source” of MRSA transmission, finding that high-touch objects such as medical devices, personal items, and linens were often in direct contact with MRSA-contaminated floors.

Read part 2 of this blog post here.

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