The Long Arm of MRSA

Infection Control Today, Infection Control Today, November 2021 (Vol. 25 No. 9), Volume 25, Issue 9

Preliminary data for the last quarter of 2020 revealed a jump of 34% in methicillin-resistant Staphylococcus aureus (MRSA) compared with the same quarter in 2019. Several states had much higher increases. In Arizona, for instance, rates leapt 80%; in New Jersey, that figure was 99%.

The patient’s room may be a sanctuary of cleanliness, but what about outside? Outpatient clinics, radiology, physical therapy, and other such areas may be “underappreciated sources” of transmission of multidrug-resistant organisms, according to investigators from the Louis Stokes Cleveland VA Medical Center in Ohio. In a 6-month observational study, they found environmental shedding of methicillin-resistant Staphylococcus aureus (MRSA) during 45% of appointments outside hospital rooms or during outpatient clinic visits.1

Patients were screened for MRSA or multidrug-resistant gram-negative bacilli (MDR-GNB) upon admission, ward transfer, and discharge. Those with MRSA colonization or infection were placed in contact precautions (as were any patients with cultures positive for extended-spectrum β-lactamase–producing gram-negative bacilli or carbapenem-resistant gram-negative bacilli). For appointments outside patient rooms, staff at the appointment locations were alerted that the patient was in contact precautions. Clinical staff in subspecialty clinics, radiology, hemodialysis, and physical therapy were responsible for cleaning surfaces between patient visits.

Of 50 enrolled patients, 39 were colonized with MRSA and evaluated for shedding during 53 procedures. Eleven MDR-GNB carriers were evaluated during 14 procedures. Patients were classified as shedding if 1 or more environmental cultures were positive during 1 or more procedures. All preprocedure cultures collected after cleaning and disinfection of surfaces were negative for the pathogens. The investigators performed χ2 tests to identify patient-level factors associated with shedding.

Hardy Pathogen

No MDR-GNB were recovered from surfaces during 14 appointments. “We probably recovered more MRSA because it tends to be [hardier] and more able to survive on surfaces than multidrug-resistant gram-negative bacilli,” says Curtis Donskey, MD, director of infection control at Louis Stokes Cleveland VA Medical Center, chair of the Infection Control Committee at the Cleveland Department of Veterans Affairs, and an author of the study. He adds that conclusions that can be drawn about shedding of MDR-GNB are limited by the small number of colonized patients studied.

It was a different story for the MRSA carriers. Of those 39, 15 (38.5%) shed MRSA to the environment during 1 or more procedures, including 10 of 24 (41.7%) inpatients evaluated during appointments outside their rooms and 5 of 15 (33.3%) evaluated during outpatient clinic visits.

In all, 17 appointments resulted in environmental MRSA contamination. In those 17 instances, cultures were positive in the patient area. In 2 of the 17 cases, the provider work area was also contaminated, due to the provider touching the patient without gloves followed by contact with the work area without performing hand hygiene.

The 15 clinic visits were for infectious diseases, general internal medicine, and surgery. Contamination was present only in the patient area after 4 appointments and only in the provider work area after 1 appointment (the provider used the computer after patient contact without prior hand hygiene).

Given that none of the shedding was due to MDR-GNB carriers, the investigators subsequently focused their analysis on factors associated with shedding by the MRSA-colonized patients. The only factor significantly associated with shedding, they found, was a wound positive for MRSA.

On the Rise?

Before last year, hospital-acquired MRSA infections had been in decline since 2010. Then came the COVID-19 pandemic. Investigators who used data from more than 3000 hospitals in the National Healthcare Safety Network (NHSN) to determine the impact of COVID-19 on health care–acquired infections (HAIs) say that, compared with 2019, 2020 saw “large and significant” increases in prevalence for hospital-acquired bacteremia.2 Preliminary data for the last quarter of 2020, for instance, revealed a jump of 34% in MRSA compared with the same quarter in 2019. Several states had much higher increases. In Arizona, for instance, rates leapt 80%; in New Jersey, that figure was 99%.

The investigators attribute some of the rise to the larger number of laboratory-identified events reported during those quarters in 2020. They also considered that the increase in MRSA bacteremia in 2020 might have been a result of inadequate central line insertion and maintenance practices, but preliminary NHSN data showed no substantial changes in 2020 in the proportion of central line bloodstream infections (CLABSIs) caused by S aureus, or in the proportion of S aureus CLABSIs resistant to methicillin.

Theirs is the first comprehensive look at the impact of COVID-19 on HAI incidence at the national and state levels, the investigators say. Their data analysis is still preliminary and doesn’t reflect all HAIs in the United States in 2019 and 2020. However, they also point to a meta-study that found more than 25% of all coinfections in COVID-19 patients were related to S aureus, more than half of which were MRSA. Whether some of the MRSA bacteremia events reported to NHSN in 2020 were secondary infections in COVID-19 patients remains unknown, they add.

The increased focus on hand hygiene, environmental cleaning, patient isolation, and use of personal protective equipment during 2020, combined with continued inpatient antimicrobial stewardship programs, could only have been for the good. But these days, with patients, staff, and families still at risk for COVID-19 and its variants, “there’s a need for more attention to the risk for transmission of all kinds of pathogens in outpatient and ancillary care settings,” Donskey says. “In our VA facility, we found that most clusters of COVID-19 with nosocomial transmission occurred in outpatient clinics and ancillary care areas and predominantly involved health care personnel.”3 

Donskey says the Department of Veterans Affairs has had a strong national program focused on control of MRSA and other resistant pathogens for more than a decade. “The intervention has been associated with significant reductions in MRSA transmission and infections. One component of the program has been routine screening of hospital admissions for MRSA carriage. Knowing which patients are colonized with MRSA allows providers to implement control measures in inpatient settings and after discharge.”


Donskey has spent the better part of his career narrowing down the who, what, why, where, when, and how of pathogen shedding. “At this point there’s a lot of evidence on how pathogens are being shed. The next step is to see if there are some practical interventions we can implement to reduce shedding,” he says. “We’re currently testing interventions like patient hand hygiene, antimicrobial clothing, and improved patient bathing.”

The investigators suggest that measures such as chlorhexidine bathing may provide “source control.” Only 2 MRSA carriers in their study were receiving chlorhexidine bathing—and neither shed MRSA. Of course, some basics should be de rigueur. Donskey cites a 2019 study that found intermittent decolonization of MRSA carriers with nasal mupirocin and chlorhexidine bathing after hospital discharge reduced the risk of MRSA infections.4 This type of intervention, he notes, could also potentially reduce the risk for shedding of MRSA during postdischarge outpatient visits.

“In outpatient settings, personnel typically don’t know what pathogens their patients may be carrying,” Donskey points out. “Simple practices like encouraging all patients to use hand sanitizer when they arrive for outpatient clinic visits or procedures can reduce MRSA and other pathogens on hands.”

Other steps include ensuring that mobility does not affect the disinfection. “We’re cleaning and disinfecting hospital rooms much better and now realize that we need to improve cleaning of equipment that goes from room to room and in outpatient clinics and ancillary care areas,” Donskey says. Transferring patients also carries risk of triggering a super-spreader event. Researchers in Belgium and Sweden developed a MRSA contagion model based on a data-driven model of contact patterns among 743,182 patients in a large hospital system. They found that, conservatively speaking, it would take 3.5 weeks for the infection to appear in a second hospital. Even for low infectious rates, they say, MRSA might reach up to 10 hospitals within a year after the initial infection.5

Infections can be managed or prevented, but it will be a while before they disappear. Donskey is optimistic but realistic. “I think basic practices like hand hygiene and environmental cleaning have improved a lot over the past 20 years,” he says. “However, once we improve in 1 area, we always find other areas that need attention.”

JAN DYER is a writer and editor specializing in clinical topics. She lives in Suffern, New York.


  1. Alhmidi H, Cadnum JL, Koganti S, Jencson AL, Wilson BM, Donskey CJ. Shedding of methicillin-resistant Staphylococcus aureus and multidrug-resistant gram-negative bacilli during outpatient appointments and procedures outside hospital rooms. Am J Infect Control. 2021;49(8):991-994. doi:10.1016/j.ajic.2021.03.002
  2. Weiner-Lastinger LM, Pattabiraman V, Konnor RY, et al. The impact of coronavirus disease 2019 (COVID-19) on healthcare-associated infections in 2020: a summary of data reported to the National Healthcare Safety Network. Infect Control Hosp Epidemiol. Published online September 3, 2021. doi:10.1017/ice.2021.362
  3. Jinadatha C, Jones LD, Choi H, et al. Transmission of SARS-CoV-2 in inpatient and outpatient settings in a Veterans Affairs Health Care System. Open Forum Infect Dis. 2021;8(8):ofab328. doi:10.1093/ofid/ofab328
  4. Huang SS, Singh R, McKinnell JA, et al; Project CLEAR Trial. Decolonization to reduce postdischarge infection risk among MRSA carriers. N Engl J Med. 2019;380(7):638-650. doi:10.1056/NEJMoa1716771
  5. Rocha LEC, Singh V, Esch M, Lenaerts T, Liljeros F, Thorson A. Dynamic contact networks of patients and MRSA spread in hospitals. Sci Rep. 2020;10(1):9336. doi:10.1038/s41598-020-66270-9