If MRSA Is Airborne, then CDC Guidance on “Enhanced Barrier Precautions” in Nursing Homes Is Wrong (and Lethal)

If MRSA Is Airborne, then CDC Guidance on “Enhanced Barrier Precautions” in Nursing Homes Is Wrong (and Lethal) 1

MRSA infections had dropped for years, but the COVID-19 pandemic erased years of progress. During the pandemic, some infections caused by MRSA rose 41%, according to the Society for Healthcare Epidemiology of America.

Given that MRSA is said to spread by contact (fomite transmission), hand-washing — Hospital Infection Control loves them their handwashing — is one appropriate remedy, along with disinfecting surfaces. From CDC’s page on “Cleaning & Disinfection” (last reviewed February 27, 2019):

If MRSA Is Airborne, then CDC Guidance on “Enhanced Barrier Precautions” in Nursing Homes Is Wrong (and Lethal) 2

But what if MRSA is also airborne?

Is MRSA Airborne?

Here is a list of studies suggesting that it is (with, sadly, some link rot, though generally searching on the title does the trick). For example, Journal of Hospital Infection, “Reduction in MRSA environmental contamination with a portable HEPA-filtration unit” (2006):

The aim of this study was to evaluate the effectiveness of a portable high-efficiency particulate air (HEPA)-filtration unit (IQAir Cleanroom H13, Incen AG, Goldach, Switzerland) at reducing MRSA environmental surface contamination within a clinical setting. The MRSA contamination rate on horizontal surfaces was assessed with agar settle plates in ward side-rooms of three patients who were heavy MRSA dispersers. … Without air filtration, between 80% and 100% of settle plates were positive for MRSA… Air filtration at a rate of 140 m(3)/h (one patient) and 235 m(3)/h (two patients), resulted in a highly significant decrease in contamination rates compared with no air filtration…. In conclusion, this portable HEPA-filtration unit can significantly reduce MRSA environmental contamination within patient isolation rooms, and this may prove to be a useful addition to existing MRSA infection control measures.

If MRSA were not airborne, HEPA filters would hardly reduce it, amiright or amiright? Here’s another one, from JAMA, “Significance of Airborne Transmission of Methicillin-Resistant Staphylococcus aureus in an Otolaryngology–Head and Neck Surgery Unit” (2001):

The MRSA samples were collected from the air in single-patient rooms during both a period of rest and when bedsheets were being changed. Isolates of MRSA were detected in all stages (from stage 1 [>7 µm] to stage 6 [0.65-1.1 µm]). About 20% of the MRSA particles were within a respirable range of less than 4 µm. Methicillin-resistant S aureus was also isolated from inanimate environments, such as sinks, floors, and bedsheets, in the rooms of the patients with MRSA infections as well as from the patients’ hands. An epidemiological study demonstrated that clinical isolates of MRSA in our ward were of one origin and that the isolates from the air and from inanimate environments were identical to the MRSA strains that caused infection or colonization in the inpatients.

Methicillin-resistant S aureus was recirculated among the patients, the air, and the inamimate environments, especially when there was movement in the rooms. Airborne MRSA may play a role in MRSA colonization in the nasal cavity or in respiratory tract MRSA infections. Measures should be taken to prevent the spread of airborne MRSA to control nosocomial MRSA infection in hospitals.

And one more, from Anesthesia and Intensive Care (PDF), “The Correlation Between Airborne Methicillin-resistant Staphylococcus aureus with the Presence of MRSA Colonized Patients in a General Intensive Care Unit” (2004):

Air sampling directly onto a methicillin-resistant Staphylococcus aureus (MRSA) selective agar was performed at six locations three times weekly over a period of 32 weeks in a new, initially MRSA-free Intensive Care Unit to examine if MRSA is present in air sample cultures and, if so, whether it is affected by the number of MRSA colonized patients present. A total of 480 air samples were collected on 80 days. A total of 39/480 (8.1%) samples were found to be MRSA positive of which 24/160 (15%) positive air samples were from the single rooms, where MRSA colonised patients were isolated, and 15/320 (4.7%) were from the open bed areas. A significant correlation was found between the daily number of MRSA colonized or infected patients in the Unit and the daily number of MRSA positive air samples cultures obtained (r2=0.128; P<0.005). The frequency of positive cultures was significantly higher in the single rooms than in the open bed areas (relative risk=3.2; P<0.001). The results from one of the single rooms showed a strong correlation between the presence of MRSA patients and MRSA positive air samples (relative risk=11.4; P<0.005). Our findings demonstrate that the presence of airborne MRSA in our unit is strongly related to the presence and number of MRSA colonized or infected patients in the Unit.

Influence of bed making on loads of airborne and surface-associated drug-resistant bacteria in patient rooms” (2023):

A transient increase in MRSA in room air was detected in most samples 1 min and 15 min after bed making…, Surface samples showed that MRSA… was isolated regularly in the patient environment. Correlation between airborne and surface pathogen loads after bed making was demonstrated. The study results indicate the importance of wearing a face mask in combination with cautious handling techniques when making the beds of patients carrying multi-drug-resistant bacteria. If the carrier status of a patient is unknown, consideration should be given to protective measures for staff and other patients present during and shortly after bed making. Surface disinfection should not be started until at least 30 min after bed making.

Duh, you have to let the bacteria settle before you clean the surfaces! (Of course, MRSA is airborne in factory farms — but not, apparently, in hospitals!)

Now, it’s clear that fomite transmission is a pathway for MRSA transmission — almost certainly the main pathway, given successful MRSA reductions in the past. However, unless we are willing to accept a level of continued MRSA transmission, it seems clear to me that airborne MRSA must be addressed, certainly at the level of the precautionary principles. And if the HEPA filters set up — one assumes — to trap SARS-CoV-2 also trap MRSA, is that so very bad? Or [dread word] the masks? (Of course, I have big priors on resistance to airborne, given the unconscionable and unscientific “massive resistance” to airborne transmission by WHO, CDC, and the Hospital Infection Control community. Another way of saying that is that these institutions have form. And not good form. Or accountability.)

Fortunately, the FDA has approved a mask that blocks MRSA. So now let’s turn to current precautions to prevent MRSA.

Do Enhanced Barrier Precautions Address Airborne MRSA Transmission?

We must fit Enhanced Barrier Precautions (EBP) within the larger framework of Infection Control as understood by CDC. From “Infection Control Basics“:

There are 2 tiers of recommended precautions to prevent the spread of infections in healthcare settings:

Standard Precautions and Transmission-Based Precautions.

Standard Precautions (Page last reviewed: January 26, 2016):

Standard Precautions are used for all patient care. They’re based on a risk assessment and make use of common sense practices and personal protective equipment use that protect healthcare providers from infection and prevent the spread of infection from patient to patient.

More specifically:

If MRSA Is Airborne, then CDC Guidance on “Enhanced Barrier Precautions” in Nursing Homes Is Wrong (and Lethal) 3

Transmission Precautions (Page last reviewed: January 7, 2016):

Transmission-Based Precautions are the second tier of basic infection control and are to be used in addition to Standard Precautions for patients who may be infected or colonized with certain infectious agents for which additional precautions are needed to prevent infection transmission.

Transmission Precautions at least has an airborne section. Here it is:

If MRSA Is Airborne, then CDC Guidance on “Enhanced Barrier Precautions” in Nursing Homes Is Wrong (and Lethal) 4

Obviously these “precautions” are wholly inadequate to prevent transmission of an airborne, asymptomatic Level 3 Biohazard (SARS-CoV-2) that moves like smoke through the entire facility. I’m not sure they’re adequate for MRSA either; that MRSA rose by 41% during the early phases of the Covid pandemic would argue no. (Isn’t it amazing how these “Precautions” don’t take account of the Precautionary Principle?)

And now we arrive at “Enhanced Barrier Precautions”, which are a third tier of Precautions for Andrew “Ratface Andy” Cuomo’s death traps nursing homes only. From the CDC’s FAQ:

What are Enhanced Barrier Precautions?

Enhanced Barrier Precautions are an infection control intervention designed to reduce transmission of multidrug-resistant organisms (MDROs) in nursing homes. Enhanced Barrier Precautions involve gown and glove use during high-contact resident care activities for residents known to be colonized or infected with a MDRO as well as those at increased risk of MDRO acquisition (e.g., residents with wounds or indwelling medical devices).

What are the differences between Enhanced Barrier Precautions and Standard Precautions?

As part of Standard Precautions, which apply to the care of all residents, the use of PPE is based on the “anticipated exposure” to blood, body fluids, secretions, or excretions. For example, gloves are recommended when contact with blood or other potentially infectious materials, mucous membranes, non-intact skin, or contaminated equipment could occur. A gown is recommended to protect skin and prevent soiling of clothing during procedures and activities that could cause contact with blood, body fluids, secretions, or excretions.

Enhanced Barrier Precautions expand the use of gown and gloves beyond anticipated blood and body fluid exposures. They focus on use of gown and gloves during high-contact resident care activities that have been demonstrated to result in transfer of MDROs to hands and clothing of healthcare personnel, even if blood and body fluid exposure is not anticipated. Enhanced Barrier Precautions are recommended for residents known to be colonized or infected with a MDRO as well as those at increased risk of MDRO acquisition (e.g., residents with wounds or indwelling medical devices). Standard Precautions still apply while using Enhanced Barrier Precautions. For example, if splashes and sprays are anticipated during the high-contact care activity, face protection should be used in addition to the gown and gloves.

See anything about airborne there? Masks? Thought not. Kevin Kavanaugh once more:

EBP allows contact precautions only to be used some of the time, and the resident is allowed to roam around the facility. “Residents are not restricted to their rooms and do not require placement in a private room.” Even with low transmission risk activities, such as passing medications, these activities are performed so frequently that transmission can still occur.

Enhanced barrier precautions and not advocating for admission screening of major pathogens is the opposite of determining and modifying a patient’s microbiome to prevent spread to other individuals.

Once again, there is no concept that whatever is airborne can — certainly with SARS-CoV-2, possibly with MRSA — spread throughout the facility.


Why then, given that airborne tranmission is a massive loophole for all CDC’s tiers of precaution, are Enhanced Barrier Precautions even being adopted by health (putatively) facilities? The letter announcing CDC’s new EBP guidance provides a clue:

If MRSA Is Airborne, then CDC Guidance on “Enhanced Barrier Precautions” in Nursing Homes Is Wrong (and Lethal) 5

Money (musical interlude). Exactly as with CDC’s guidance on school ventilation, as I show here. So if somebody in your care is in a nursing home and gets MRSA, remember that CDC didn’t protect them from airborne tranmission, and why.


[1] Abaluck et al., where a natural experiment permitted a randomized trial is not listed, oddly. Or not.

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