MRSA Research Center

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For Infection Control Professionals – FAQs

Infection Control Professionals and Issues Related to MRSA Spread in Healthcare Facilities

What is the benefit of MRSA screening?

Many people have the logical perception that it is beneficial to have programs aimed at determining whether individuals who enter a healthcare institution (such as a hospital) are colonized with MRSA.

Indeed, some states have even developed legislation that mandates MRSA screening. These mandates have provided for different approaches and different programs. Some legislation mandates screening at the time of hospital admission. Others mandate screening at the time of admission to an Intensive Care Unit. Some practices have extended the identification of positive individuals to include attempts at decolonizing these individuals with various antibiotic and antiseptic regimens.

Various problems have been identified with these MRSA screening approaches, however. First, they are expensive. Second, they may focus only on one of many antibiotic-resistant pathogens and provide no potential benefit for other healthcare associated infections. Third, they may not take into account the considerably less expensive intervention of enforcing hand washing by healthcare personnel when moving from one patient to another.

Most locales that mandate screening place individuals designated as positive for MRSA in contact isolation. While this is intended to prevent the spread of MRSA from the colonized individual, it may also have unintended consequences such as decreasing the quality of nursing and/or patient care, as nurses have to gown up and glove to participate in even minor patient activities. Moreover, physicians and others who provide patient care may consequently enter an isolation room less frequently than they would a room of a patient not in isolation.

Such approaches may nevertheless be worthwhile if they clearly prevented the spread of MRSA. However, spread from a colonized individual in the hospital to another colonized individual in the hospital is but a small part of the overall MRSA transmission fabric. Also, expensive screening programs are unlikely to be tipping points for decreasing the MRSA burden in the population.

Does MRSA spread in hospitals and healthcare facilities?

Most MRSA infections that are encountered while staying in a hospital or healthcare facility are acquired by one of two major mechanisms. First, the patient may become infected with the MRSA organism that was part of their own flora. This may well be flora that the patient entered the facility with, the most likely scenario. A colonized individual who undergoes a surgical procedure (such as the insertion of a venous catheter or other indwelling device) that requires breaking the skin to install the device provides the MRSA organisms already on the patient's skin an opportunity to breech the barrier of the integument. Thus, the patient appears to have acquired a nosocomial MRSA infection but in actuality the infecting organism was from the patient's own flora.

That having been said, there is no doubt that MRSA does sometimes spread in healthcare facilities and nursing homes from one patient to another. Most often, this is facilitated by healthcare workers who fail to wash their hands between handling patient A and patient B. An aggressive program to enforce hand washing would probably diminish spread of MRSA in healthcare facilities. Furthermore, careful attention to catheter maintenance guidelines and adherence to indwelling device guidelines has the potential to decrease MRSA infections caused by autologous flora. In fact, the Centers for Disease Control and Prevention (CDC) recently reported that careful attention to such procedures reduces the occurrence of MRSA infections in healthcare facilities.

What is a MRSA outbreak and how is it managed?

Experts differ on the definition of an outbreak. All agree that an outbreak is the occurrence of “several” cases of MRSA in a defined time period. The word “several” may refer to 2, more than 2, 3, more than 3, or some other number. The term “cases” may refer to individuals with actual infections or individuals who are colonized. Different institutions have developed different guidelines with respect to “outbreaks.”

What is the management of a MRSA outbreak in an institution?

Experts differ and there is no single answer to this question. When an outbreak, however it is defined, does occur in an institution such as a healthcare facility, many individuals believe that it is appropriate to culture all individuals residing in that facility, be it an Intensive Care Unit, a ward, or some other healthcare facility unit simultaneously. It is not clear how this culturing should be accomplished. Some believe that a nasal culture of all individuals is appropriate. Others prefer an approach that takes into account the fact that individuals with MRSA colonization may be colonized at multiple sites including the skin. Healthcare workers are generally not included in this initial screening process, in part because the management of the colonized healthcare worker is problematic. It is customary to cohort individuals found to be positive during a patient colonization screen. It is less clear what to do when healthcare workers are included.

It is certainly prudent to culture healthcare workers' should the initial attempt to control the outbreak by screening the patients and cohorting those that are positive not be effective (e.g., the initial intervention of culture and cohorting results in additional cases occurring). Most individuals agree that healthcare workers should be cultured when they are clearly implicated in MRSA transmission. This is sometimes difficult to demonstrate.

What to do with the healthcare worker found to be colonized? Many programs initially approach such individuals with counseling, informing the colonized healthcare worker that they are positive, and insisting on an aggressive hand washing policy for that individual as they move in their work setting. Some might ask such a healthcare worker to work while masked or gowned, although this has implications for identifying this person as a carrier. While removal from employment is an option for controlling the outbreak, this fairly drastic measure is reserved for the colonized healthcare worker when simple measures like those mentioned above are not effective.

Decolonization of colonized patients or healthcare workers is generally not recommended in part because a good decolonization strategy is not currently available. Closing the unit rather than trying to cohort the patients in the management of an outbreak is generally not recommended. Discharging patients from a facility where an outbreak is occurring is generally considered to be acceptable. An institution should have an internal working group to monitor the course of the outbreak. This generally includes the existing Infection Control Service and members of the facility affected by the outbreak.

How is MRSA transmitted?

MRSA is almost always transmitted by person-to-person contact from an infected lesion that is touched by a healthcare worker or from touching a colonized individual. The healthcare worker now has MRSA organisms on their hands. This individual may fail to wash their hands before contacting the next patient and help MRSA to spread in this manner. The great majority of MRSA spread is person-to-person and the majority is by hand contact. Institutional spread of MRSA in this fashion does occur but is infrequent. Spread of MRSA in the community by these same means is considerably more frequent.

It is true that MRSA organisms are found on inanimate objects or “fomites.” It is important to recognize that fomite colonization is not rare, particularly in the hospital room, for example, and probably even in the home of a patient with an active MRSA infection. But, healthcare workers disagree as to whether the finding of colonized fomites implies transmissibility from the fomite surface to an individual who is not colonized. It is not clear whether this occurs or if it does, how often it occurs.

What is decolonization and is it effective?

Decolonization is an attempt to remove Staphylococcus aureus or MRSA or both from an individual's body environment known to be colonized. At first glance this appears to be relatively simple. However, years of experience with decolonization strategies taught us that this is difficult to do. Also, it is not certain whether it is an effective practice (i.e., whether it reduces transmissibility of the organism or whether it reduces the risk to a colonized person of becoming infected).

Routine use of decolonization in managing MRSA infections is not recommended.

Various strategies have been employed to decolonize individuals; none can be recommended as routinely effective. Intranasal mupirocin is a favorite agent to use in this situation. Mupirocin cream is applied to the nose, often twice a day, for some defined period (e.g., five days). Most studies that employ this technique have demonstrated that there is a decrease in nasal colonization. Most studies further demonstrate that following such decolonization, in a time frame of weeks to months, the colonization often returns. Obviously, the strategy of intranasal topical antibiotics assumes that there is only one site by which a patient is colonized. This is seldom known with certainty.

Applying an antiseptic to a patient's body such as chlorhexidine or bathing in bathwater with diluted bleach are other strategies frequently employed. Neither of these has been proven to be an effective decolonization strategy, however. With chlorhexidine it is uncertain what strength to use, how long to leave it on the skin, whether it should be washed off, etc. With bleach baths, it is uncertain how frequently to take them, how much bleach to put in them, or what end-point to measure.

Some healthcare providers have even employed oral antibiotics in a decolonization regimen, usually combined with one or more of the modalities described above. There are insufficient data at this time to determine if the use of such oral antibiotics—an expensive strategy that has the potential to create additional resistant antibiotic flora#8212;is an effective adjunct.

Whether colonized inanimate objects need to be routinely approached with disinfectants, whether household pets need to be included in decolonization regimens employed in a family with recurrent disease, whether all individuals in the family need to attempt the designated decolonization strategy at once, or whether only the affected individual needs to do it, these are all questions with uncertain answers at this time.

The views on this page are of the MRSA Research Center, not necessarily those of the institutional infection control program at the University of Chicago Medical Center.