A set of training materials for professionals working in intervention epidemiology, public health microbiology and infection control and hospital hygiene.
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1. Environment and Risk of Infection.
Many scientific evidences support the role of the inanimate environment as a source of Healthcare-Associated Infections (HAIs). Transmission can happen through air or through contact.
1.1 Air transmission.
Potential reservoirs of infections conveyed through air are the following:
building materials, during maintenance and/or renovation works: in this case Aspergillus and other filamentous fungi are most likely to be involved as infectious agents. Subjects with low immune defenses are at highest risk;
water reservoirs, such as humidifiers, nebulizers and sinks can be the source for Acinetobacter spp, Pseudomonas aeruginosa, Aspergillus, and Legionella pneumophila. Legionella can also be spread by the hot water network and the heating, ventilation and air conditioning system.
1.2 Contact transmission.
The transmission can occur through direct or indirect contact. The potential sources of infection are:
These microorganisms can spread through the colonized or infected patient (who is also sometimes carrier of invasive devices such as tracheal or tracheostomy tubes, central venous catheters - CVC, urinary catheters), can survive on surfaces for a long time and are difficult to eradicate by cleaning and disinfection [1,2].
Environmental contamination can occur directly, through shared use of contaminated medical devices, and, most frequently, indirectly, usually through the hands of healthcare workers (HCW).
Alternative healthcare settings (outpatient treatment services, homecare, rehabilitation and long-term care facilities), which may not warrant the standards required to acute care hospitals in terms of HCWs numbers and competence and environmental cleanliness and maintenance, and the emergence and spread of antibiotic multidrug or pan-resistant organisms, especially of gram-negative bacteria, may be also at risk.
2. Environmental localization and survival of microorganisms
In 2003 the CDC pointed out the need to ensure proper environmental hygiene standards, especially for high touch surfaces .
The environmental surfaces most commonly involved as a source of contamination / transmission are:
surfaces in the immediate surrounding patient's area (e.g. bed rails, bedside table, bed table, call buttons );
surfaces commonly touched by patients and healthcare workers (e.g. toilet door handles, toilets);
shared use devices (e.g. stethoscopes, glucometers);
Gram-positive (such as MRSA and VRE, even in dry conditions) and Gram-negative MDR organisms have been documented to survive on environmental surfaces, especially on those closest to the patient. According to many authors, the most common way of transmission is due to gloves contaminated while delivering care to the patient.
Distribution of microorganisms on environmental surfaces depends on the prevalence of contaminants in the treated population and on their ability to survive in the environment in different conditions (e.g. dryness or wetness).
There are some microbiological factors that may facilitate transmission of pathogens from environmental surfaces, particularly:
Biofilm is an assemblage of surface-structured communities of one or more species in which microorganisms are wrapped and protected by esopolymeric substances (EPS). It protects microorganisms from drying, helps their attachment to surfaces, and reduces the effectiveness of both chemical (disinfectants) or physical (e.g. UV rays) biocides and antibiotics.
Microorganisms adhering to the surfaces represent an intermediate step and have a lower susceptibility to biocides than planktonic cells; susceptibility becomes much lower when biofilm is structured. Occasionally, biofilm releases free microorganisms and, although they regain their original sensivity to biocides, they are still potential agents of infection.
Biofilm can affect healthcare wet surfaces, such as medical devices ( including endoscope channels and prosthetic devices), as well as dry surfaces, including environmental ones.
Moreover, adhesion to surfaces increases the resistance to physical removal, made through cleaning (resilience), mostly due to the esopolymeric matrix. [4,5].
Many evidences show that an environment previously occupied by a patient colonized or infected with a pathogen, and not properly treated, constitutes an important risk factor for colonization or infection with the same pathogen for the next patient [6-9].
Consequently, all healthcare workers need to be educated about the importance of maintaining a clean and safe care environment for patients. Every healthcare worker needs to know their specific responsibilities for cleaning and decontaminating the clinical environment and the equipment used in patient care.
Otter JA, Yezli S, Salkeld JA, French GL. Evidence that contaminated surfaces contribute to the transmission of hospital pathogens and an overview of strategies to address contaminated surfaces in hospital settings. Am J Infect Control. 2013 May;41 (5 Suppl): S6-11.
Moore G, Muzslay M, Wilson AP. The type, level, and distribution of microorganisms within the ward environment: a zonal analysis of an intensive care unit and a gastrointestinal surgical ward. Infect Control Hosp Epidemiol. 2013May; 34 (5): 500-6.
Guidelines for environmental infection control in health-care facilities. Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC). Atlanta: U.S. Department of Health and Human Services; 2003.
Otter JA, Vickery K, Walker JT, de Lancey Pulcini E, Stoodley P, Goldenberg SD, et al. Surface-attached cells, biofilms and biocide susceptibility: implications for hospital cleaning and disinfection. J Hosp Infect. 2015 Jan;89 (1): 16-27.
Vickery K, Deva A, Jacombs A, Allan J, Valente P, Gosbell IB. Presence of biofilm containing viable multiresistant organisms despite terminal cleaning on clinical surfaces in an intensive care unit. J Hosp Infect. 2012 Jan;80 (1): 52-5.
Huang SS, Datta R, Platt R. Risk of acquiring antibiotic-resistant bacteria from prior room occupants. Arch Intern Med. 2006 Oct 9;166 (18):1945-51.
Drees M, Snydman DR, Schmid CH, Barefoot L, Hansjosten K, Vue PM, et al. Prior environmental contamination increases the risk of acquisition of vancomycin-resistant enterococci. Clin Infect Dis. 2008 Mar1;46 (5): 678-85.
Nseir S, Blazejewski C, Lubret R, Wallet F, Courcol R, Durocher A. Risk of acquiring multidrug-resistant Gram-negative bacilli from prior room occupants in the intensive care unit. Clin Microbiol Infect. 2011 Aug;17 (8): 1201-8.
Shaughnessy MK, Micielli RL, De Pestel DD, Arndt J, Strachan CL, Welch KB, et al. Evaluation of hospital room assignment and acquisition of Clostridium difficile infection. Infect Control Hosp Epidemiol. 2011 Mar;32 (3): 201-6.
Original contribution from:
Gaetano Privitera, Dept of Translational Medicine, University of Pisa, Italy.
Cesarina Curti, Scientific Committee, SIMPIOS, Società Italiana per la Prevenzione delle Infezioni nelle Organizzazioni Sanitarie, Italy.
Join the discussion about this article in the forum!
Mike Catchpole posted on 3/30/2010 11:54:18 AM:
The definitions of different types of bias should be reconciled with the definitions included in the ECDC internal lexicon (ie that developed by Laszlo)
Vladimir Prikazsky replied on 6/4/2010 8:36:54 AM:
Current status of the terminology services - answer from Laszlo:
The current version as such is running behind the firewall, within our internal network. However, as it has a machine interface, there could be a method to feed a list in the wiki with proper terms queried from the Term Server and updated regularly. This will need some work to tag our categories with the attribute `is required by fem wiki`. That way the users of the wiki could consult the derived lists in the wiki itself.
For this we have discuss what term sets are needed. Now a systematic audit of all systems / applications is ongoing to check their information objects regarding the core metadata standard implementation. We could join these two tasks in a single work process.
*** I hope this answer is promising. However at present we have to refer to books or other ready to use services.
Arnold Bosman replied on 8/6/2010 12:07:47 PM:
Reading through the chapter again, I was wondering if it could be useful to add the 2x2 tables that we have as examples in the EPIET Powerpoint lecture for each form of bias. What do you think?
Aileen Kitching replied on 9/7/2010 2:03:18 PM:
thanks for the suggestion! and apologies for the delayed reply. I have added the 2x2 tables from the EPIET lectures we had in Menorca (these still need some editing, up/down arrows put in etc), and some other examples also from the lectures, and from Rothman and other books/ articles.
Please let me know if you would like an changes made to the additions to the text/ edits of the text.
All the best,
Aileen Kitching replied on 9/7/2010 2:06:12 PM:
This is a question for Arnold & Vladimir :-).
In the original text of my chapter 'biases in epi studies' , it says that random error will be dealt with in a separate chapter. I realise that not all chapters are finished yet, but was wondering which chapter will deal with random error, confidence intervals, p-values etc?
Derval Igoe replied on 9/22/2010 10:29:50 AM:
This chapter is well written, accurate and clear overall. I have made some editing suggestions. (My machine crashes each time I am in the information bias section and try to edit, so I havent edited from there on - not sure if this is a local, or global issue)
The definition of bias could perhaps be introduced earlier. There is another broader definition used by Daly which defines bias as "any factor or process that tends to produce results or conclusions that differ systematically from the truth" (Interpretation and uses of medical statistics, Leslie E Daly, Geoffrey J Bourke, 5th edition, 2007). Perhaps this could be used, and then lead on to the more focused definition given later
Also, has what we mean by an association been defined elsewhere in the text? If not, suggest that this is discussed too.
I have suggested including outcome as well as disease wherever its mentioned in the first section, as we are not only interested in diseases, rather outcomes too.
In the non-response bias section, I think that it would be helpful to have some text to explain the scenarios more fully
In the preventing non-response bias section one additional method to achieve high response rates (as well as incentives) is to make it easy to contribute, eg by using questionnaires that are not too long, and dont take too much time to complete
Arnold Bosman replied on 9/27/2010 4:23:14 PM:
These sound like good points to me. There may be a challenge in finding the right balance between the amount of text per screen, and keeping the overview of the topic.
Still, it is in my view worth to try and put these concepts in the chapter. Derval, would you care to try an attempt in editing? This will also allow us to test how that part of our process will work out once the WIKI is open to the public. We will definitely get users who start modifying the texts, and that is exactly what we want.
So if you feel inspired, please go ahead, and we can check out how that works for the chief-chapter-editor :)
Arnold Bosman replied on 9/27/2010 4:26:13 PM:
sorry for the tardy reply, and we have already touched upon the solution in our last teleconference. There will not soon be a 'random error' chapter, as it seems to have been described sufficiently for the time being in the lines within the Bias chapter.
However, the chapter on 'P-value' would in my view indeed be a useful next priority.
Perhaps an idea for the current facilitators in Menorca? :)
Aileen Kitching replied on 10/5/2010 12:23:28 AM:
Many thanks Derval for the review of the chapter, and Arnold for additional comments!
Derval, I was also having the same problem with the Information Bias page - it kept crashing every time I tried to edit it - it didn't seem to be able to be fixed, so I have written the page again, and if you would like to take another look again, that would be great!
I have incorporated some of your other suggestions already in case you want to review those:
- I have added Leslie Daly's definition of bias to the existing paragraph, and added a definition of an association in the 2nd paragraph in that page (feel free to adapt it if you would like)
- disease/outcome is now throughout the text
- I added your suggestion about the questionnaire to the 'preventing non-response bias' section
I would be happy for you to try some editing, as Arnold suggested, and if you feel inspired :-)
Lisa Lazareck replied on 10/5/2010 12:40:10 PM:
Aileen + Derval,
Great work! Please do try editing with Internet Explorer...in case the browser freezing/crashing problem is stemming from the use of Firefox.
Another message to follow shortly, Aileen, about your table formatting query.
Aileen Kitching replied on 10/5/2010 4:00:27 PM:
Many thanks for your reply!
I have been using Internet Explorer all the time as a browser - I mentioned this also at the last telco. I really don't think it;s a browser issue, else why would it only happen on one page?? and not on others while editing.
I did wonder whether it could be related to the amount of editing on the page? e.g. if many changes are made to a page, could that be causing the problem?
if so, I would be concerned that this would cause issues when the wiki goes live......
I would be grateful if you & Martin could take a look at this. Perhaps you could also check with the others whether any of them are having problems with editing formatting, etc. as I also find that sometimes I have changed things & this is not reflected in the View page afterwards.
Derval Igoe replied on 10/5/2010 4:40:58 PM:
Hi Aileen and Lisa
Sorry about this, but its crashing again. The first page worked, I made a couple of suggestions, but cant access it from there on. I am using internet explorer
Aileen Kitching replied on 10/5/2010 5:06:45 PM:
There is definitely a problem with the "selection bias and case-control studies" page (it kept crashing on me too), but the others (e.g. Info Bias, Preventing Bias etc) were ok for me earlier, if you would like to try those?
all the best,
Lisa Lazareck replied on 10/6/2010 6:43:36 PM:
Really sorry to read about your troubles - and Martin has indeed been looking into this..a response should follow ASAP tomorrow - and if this hinders your meeting the Friday (8th) deadline, then by all means, we will extend it for you.
Thank you and more to come,
Theodore Lytras replied on 3/20/2015 9:50:04 PM:
The plot showing the random vs systematic error is erroneous. The measure of random error is the standard error, which (regardless of outcome type) is proportional to the inverse square root of sample size. Therefore the plot should actually look like this:
Arnold Bosman replied on 3/20/2015 10:02:55 PM:
Thanks so much Theodore, this is very good. Feel free to modify the article. That is why this is a Wiki: to be improved where needed.
Arnold Bosman replied on 3/20/2015 10:06:08 PM: By the way, I believe Rothman shoUld have a Femwiki account :)
Theodore Lytras replied on 3/21/2015 1:01:21 PM:
OK, replaced the plot with a modified version. I guess even Rothman can make a slight mistake now and then! :)
sbpmebxu replied on 7/29/2015 7:20:20 PM: 1
sbpmebxu replied on 7/29/2015 7:59:24 PM: 1
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