Importance of the environment in methicillin-resistant Staphylococcus aureus acquisition: the case for hospital cleaning

Dr. Stephanie J. Dancer

Abstract


In the UK, we continue to debate the importance of hospital cleaning in relation to increasing numbers of patients acquiring methicillin-resistant Staphylococcus aureus (MRSA). However, there is little direct evidence for the effectiveness of cleaning because it has never been afforded scientific status. Hospital hygiene is usually assessed visually, but this does not necessarily correlate with microbiological risk. A more robust case for hospital cleaning can be presented by considering the evidence for all the stages of the staphylococcal transmission cycle between human beings and their environment. Cleaning has already been accepted as an important factor in the control of other hardy environmental pathogens, such as Clostridium difficile, vancomycin-resistant enterococci, norovirus, and Acinetobacter spp. This Review will show why the removal of dirt might have more impact on the control of MRSA than previously thought. Introduction of additional cleaning services is easier than improvements in hand-hygiene compliance.

 

Note: The complete article is available from Lancet Infectious Diseases.

 

Importance of the environment in methicillin-resistant Staphylococcus aureus acquisition: the case for hospital cleaning:  Created on March 3rd, 2008.  Last Modified on March 24th, 2010

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· 11 years ago

Schools are very different environments to healthcare environments, as my colleagues noted. However, the risk of acquiring potential pathogens from hand-touch sites still applies! The risk presumably increases for objects that are handled more frequently. Several sites could be targeted - door handles, faucet taps, computer keyboards and library (text) books are the ones that I would be interested in...perhaps also desk surfaces and buttons on a vending machine. If I were responsible for a school environment, I would want to include these in a cleaning specification, although tackling the cleaning of library books is way beyond my area of expertise.

My hypotheses could be investigated by seeding pieces of non-pathogenic marker viruses (cauliflower mosaic) onto a chosen site and then tracking it around the environment over hours and days. I would do this in a college as a project for the students! This has been done in hospitals, as well as in the community. The point is, that children could pick up microbes from commonly touched sites in a school; most of the time this doesn't matter. Perhaps dynamic transmission of minor ailments contributes towards the developing immune system. But maybe it is important if we start considering epidemic flu or C-MRSA.

Regarding this statement:

'Dr. Dancer doesn't really tackle the issue of how traditional cleaning methods simply spread contamination around rather than remove it. This really needs to be addressed by a study that has the spray-and-vac method go head to head with the traditional method.'

No, I didn't say much about this - but then, I think I included a reference which does; my own work has shown that the routine detergent-based methods for cleaning the floor do seem to spread S.aureus/MRSA around, although there is an overall reduction in dirt. Hand-touch sites are easier to clean - maybe it's the regular disposal or rinsing of the cloths/wipes used for these sites, while floors just get one mop and one pail of water. A study I have just finished - the first part accepted for publication and the second now in preparation - demonstrates the dynamic relationships between multiple strains of MRSA in two related ward environments and patients. We used molecular typing to track specific strains around for a year, to see whether environmental strains turned up in patients or vice-versa. We found both! We even saw a strain being introduced into a ward, then we found it at a hand touch site and then we saw it as a new acquisition in a patient. I am sorry, I do not know what the spray-and-vac system is, but it sounds better than what we do in the UK.

Regarding this comment:

'There is no doubt in my experience that the best way to transmit the MRSA is via person to person, however, it is important to note that these strains of staph can survive on surfaces as well as cloth for months, therefore the environment is very important also.'

I think that most patients in my hospital acquire MRSA from a person's hand that has just touched a contaminated site! So yes, person to person, but often via the environment. As I mentioned in the previous response, we have been doing some molecular typing to try and gain more insight into transmission on a ward.

Regarding this comment:

'Namely, about 30% of the general, asymptomatic, population are carriers of MRSA (and other infections).'

I would say that 1 in 5 persons always carry a coagulase-positive staph in their nose. Another 10% display transient carriage, giving us around 1 in 3 persons as staph carriers overall in prevalence studies. It varies according to age and race - Bill Noble wrote a fabulous book summarising all the findings from the staph pioneers of the 1950's and 60's on this subject. Of course, coagulase-positive means methicillin susceptible as well as methicillin-resistant S.aureus. What proportion of each are in the general population is difficult to assess.

Regarding this comment:

'This is controversial and probably depends on the bug species; but it seems to me that having often-touched surfaces contaminated is not a good situation. The problem with the controversy is that this is difficult to test experimentally. Hence, all the reported work (sparse) is based on epidemiological evidence leaving people to interpret what is meaningful and what is not.'

Again, please see previous response about the study looking at hand touch sites and patients and actually typing strains over a one year period to test the theory.

Regarding this comment:

'According to Dancer, whenever hospital surfaces are cleaned with good sterilizers (e.g. bleach), the rate of infections goes down'

My own study has shown that if you target detergent-based cleaning of hand touch sites on a ward, the level of microbial dirt is reduced if measured weekly using a standardised method. There also appeared to be a favourable impact on patients regarding MRSA infections, but we are just analysing this data now.

Many thanks for these comments! I get so little feedback from my papers usually. How nice to be able respond like this.

Dr. Stephanie J. Dancer
Department of Microbiology
Hairmyres Hospital,
Eaglesham Road, East Kilbride G75 8RG, UK.
Tel +44 (0)1355 585000
stephanie.dancer@lanarkshire.scot.nhs.uk

March 7th, 2008 | 1:59pm Reply
· 11 years ago

Here is my summary of the article:

Much of what Dr. Dancer is pointing out has been known for over 100 years - crowded conditions and lack of good cleaning in hospitals spreads infection. Dancer acknowledges this and basically is frustrated that political considerations in the UK pressure hospitals to increase human throughput and thus make allocation of resources for cleaning scarce. The economics therefore continue to allow the spread of MRSA and other infections. She also makes the point (also known for a long time) that just because a room appears to the naked eye to be clean, it doesn't mean that it's clean in the sense that microbial populations on surfaces and in the air have been lowered by the cleaning procedures.

A newer point that she does mention, and that has been lost in much of the publicity about MRSA, is something that I wrote about several months ago: Namely, about 30% of the general, asymptomatic, population are carriers of MRSA (and other infections). She also mentions the recent awareness that bugs like MRSA can remain viable for long times (days to weeks or longer) on seemingly dry surfaces - especially floors, tables, doorknobs, etc.

Her major conclusion is that, in hospitals, near-patient hand-touch sites (gowns, bed rails, table surfaces, etc.) deserve to be cleaned on a much higher priority basis, and with more attention to getting rid of bugs, than they are currently. She believes that doing this, along with continued insistence on hand disinfection will help cut down the incidence of MRSA infections in hospitals.

Below is a response to questions received:

Question: What application does this information have to cleaning in schools?

School classrooms are probably more crowded than most hospital rooms. Probably the same percentage of the people (including teachers) are asymptomatic carriers of MRSA and help spread the bug to others. I think I actually sent KaiScience the results of a study from a Texas school district about the percentage of MRSA infections with the community species of bug. Cleaning and monitoring the cleaning for microbials is surely as important in schools as it is in hospitals. Dancer places less importance on floor cleaning than on touchable surface cleaning. This is probably going to hold true in schools. But I think that since floors are easier to clean than many touchables, and that microbial-contaminated airborne dirt from floors settles on touchable surfaces; floors should be cleaned with attention to microbial destruction.

Question: Do you agree or disagree with Dr. Dancer's application of data, conclusions, assertions?

It's impossible to disagree with it, knowing how rigorous applications of air cleaning, surface cleaning, garbing for reduced spread of microbials, can make cleanroom working environments cleaner than working environments anywhere else on earth: The air in a modern cleanroom is cleaner than the air in the Antarctic. Plus, as Dancer mentions, Florence Nightingale knew about most of the important things in the paper even before bugs were known to be causes of infection.

Question: What are the important "takeaways" from this paper?

a. Visual observation of cleaning effectiveness is not sufficient to determine if places are clean in the sense of absence of microbial contamination.

b. In public areas, crowded conditions and insufficient cleaning procedures that are known to destroy bugs, lead to spread of infection.

c. Emphasizing hand hygiene alone is not enough to halt the spread of infection: bugs fall on lots of surfaces from aerosolized respiratory sources, airborne dirt that contains infectious agents, etc.

d. Good cleaning methods can reduce microbial surface contamination.

Question: Is the fact that MRSA survives on many surfaces meaningful as a driver of what should be cleaned?

I think so; with priority being given to surfaces that are touched most frequently.

Question: CDC says that environmental surfaces are not very important as a transmitter. What about this?

This is controversial and probably depends on the bug species; but it seems to me that having often-touched surfaces contaminated is not a good situation. The problem with the controversy is that this is difficult to test experimentally. Hence, all the reported work (sparse) is based on epidemiological evidence leaving people to interpret what is meaningful and what is not.

Question: People seem to get infected most often from open wounds or sores?

For MRSA infections, yes, probably sometimes. But from my interpretation of the literature, respiratory aerosols from carriers of the community strains is probably the most important way.

Question: So, is surface cleaning that important for this bug?

Answer: According to Dancer, whenever hospital surfaces are cleaned with good sterilizers (e.g. bleach), the rate of infections goes down.

Question: Can you catch it from the air, water, surface to hand to mouth or nose?

I believe: Surface to nose, for sure, air to nose, for sure. The problem is again, doing controlled experiments with humans.

Question: Also, in the article referenced here -

http://www.infectioncontroltoday.com/articles/striving-for-cleanliness.html

- Jennifer S. mentions development of microbe resistance as a danger with chemical disinfectants. Does this actually occur?

This comes under the heading of a widely believed "urban myth". Even cleanroom QA/QC people seem to believe it. But it's based on a lack of understanding of how bugs develop antibiotic resistance. I can send KaiScience a paper disputing the myth. If you had a mixed population of bug species; one which ate the disinfectant and one that was killed by it; you could wind up with a growing population of the species that liked the disinfectant. Does this happen on this planet? Probably not.

Jay Glasel

(Dr. Glasel is the Managing Member and Founder of Global Scientific Consulting, LLC. He is a Professor Emeritus in the Department of Microbial, Molecular and Structural Biology at the University of Connecticut.)

March 3rd, 2008 | 5:46pm Reply
· 11 years ago

There is no doubt in my experience that the best way to transmit MRSA is via person to person, however, it is important to note that these strains of staph can survive on surfaces as well as cloth for months, therefore the environment is very important also. It is much like the problem we are having with C diff spores in the environment.

Philip M. Tierno, Jr, PhD
Director, Clinical Microbiology & Immunology
New York University Medical Center
Associate Professor, Departments of Microbiology & Pathology
New York University School of Medicine
560 First Avenue
New York, NY 10016
phone- 212-263-5905
fax- 212-263-7922
cell- 646-279-6082
e-mail- philip.tierno@nyumc.org

March 3rd, 2008 | 5:37pm Reply
· 11 years ago

Please see my comments regarding the questions below:

1) What application does this information have to cleaning in schools?

I doubt this study can be extrapolated to schools. Hospitals and schools house vastly different populations, largely very ill adults and largely very healthy children, respectively. Hospitalized patients live there 24 hours per day, but schoolchildren go home at night and on the weekends, and are absent during the summers. There are no invasive procedures and in-dwelling catheters in schools. Many schoolchildren bring their food to school, while patients have it prepared for them in a central location. Near-touch objects such as telephones and nurse call buttons that are sequentially touched by sick people don’t really have a counterpart in schools.

2) Do you agree or disagree with Dr. Dancer’s application of data, conclusions, assertions?

I agree with Dr. Dancer entirely.

3) What are the important “takeaways” from this paper?

a. The standard of “visible cleanliness”, while important for a hospital’s image and PR, is absolutely worthless when it comes to infection control. There must be a scientifically quantifiable standard such as cultured colony counts or ATP bioluminescence.

b. Housekeeping personnel must be better educated in how to clean. The fact that the lowest paid employees are frequently housekeeping staff who don’t speak English as their native tongue is a huge barrier that has to be overcome.

c. Housekeeping must receive funding priority at hospitals, and there must be open communication channels between the housekeeping department and the infection control service.

d. Dr. Dancer doesn’t really tackle the issue of how traditional cleaning methods simply spread contamination around rather than remove it. This really needs to be addressed by a study that, for example, has the spray-and-vac method go head-to-head with the traditional method, etc.

Paul S. Darby, MD, PhD, MPH
MD PhD Services, PLLC

March 3rd, 2008 | 5:31pm Reply

About Dr. Stephanie J. Dancer

Formerly a consultant microbiologist at the Southern General Hospital in Glasgow, Scotland (2005-7), Stephanie now works in NHS Lanarkshire and is the current editor of the Journal of Hospital Infection. She trained at St. Bartholomew's hospital in London (1977-83) followed by postgraduate studies in Pathology at Guy's hospital, where she produced a thesis on the epidemiology and biochemistry of toxin-producing staphylococci. She has worked in various remote areas of the world, including Papua New Guinea, Thailand, Vietnam and the Canadian High Arctic, where she resuscitated 30,000 year old organisms from glacial ice. She spent six years as the Infection Control Officer for Argyll before moving to Health Protection Scotland as their inaugural microbiologist (2002-5). There she set up MRSA surveillance for Scotland, evaluated real-time PCR for the rapid identification of MRSA and helped establish the Scottish Microbiology Forum. She has been an active member of several national working groups on antibiotic prescribing and hospital cleaning, and was a formal referee for the Scottish Health Technology Assessment on MRSA screening. At present she balances clinical and editorial duties with various research projects, specifically the role of antibiotics, screening and cleaning in the control of MRSA.

 

Dr. Stephanie J. Dancer

Department of Microbiology
Hairmyres Hospital,

Eaglesham Road, East Kilbride G75 8RG, UK.

Tel +44 (0)1355 585000

stephanie.dancer@lanarkshire.scot.nhs.uk

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