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Infection control of Staphylococcus aureus: spa typing to elucidate transmission
Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Staphylococcus aureus is a commensal of the human flora, primarily colonizing the anterior nares and throat, but it may also cause infections ranging from mild skin and soft tissue infections to severe diseases such as endocarditis and septicemia. S. aureus is also a major nosocomial problem increasing with the worldwide dissemination of methicillin-resistant S. aureus (MRSA). The main vector for bacterial cross-transmission in healthcare settings is the hands of healthcare workers (HCWs). No S. aureus was detected in the air in this thesis demonstrating that transmission through air is not important. Despite the fact that good compliance with hand hygiene is essential to prevent cross-transmission the compliance is generally less than 50 %. Gold standard to track bacterial transmission in healthcare settings has for long been pulsed-field gel electrophoresis (PFGE), a method that is labor- intensive, lacks consensus protocol and relies on semi-subjective analysis. Molecular typing by sequencing of the hypervariable part of the S. aureus protein A gene (spa typing) has overcome these problems and has shown promising results in epidemiological investigations.

The aims of this thesis were to study bacterial transmission with S. aureus colonization of newborn infants as a model and to evaluate spa typing as a molecular tool. Additionally, the influence of compliance with hygiene guidelines on S. aureus transmission was assessed.

Analysis of 280 MRSA isolates by spa typing revealed excellent typeability and epidemiological concordance and satisfactory discriminatory power. Additionally, spa typing was considered superior to PFGE thanks to its accessibility, ease of use and rapidity. Also, spa typing results are registered in a global database, facilitating inter-laboratory comparison.

The prevalence of S. aureus ranged from 41 % to 66 % in the populations studied and males had the highest colonization rate. Throat was the premier colonization site for adults and transmission from individuals colonized in the throat only was documented, suggesting that throat cultures should be included in S. aureus screening programs. The umbilicus was the premier colonization site for newborn infants. Incubating the swabs in enrichment broth prior to plating increased the prevalence of S. aureus positive samples by 46 %, resulting in prevalence ranging from 51 % to 70 % in the populations studied. Thus enrichment prior to plating is necessary to determine more truthful S. aureus colonization rates. There were no indications of an institutional flora, as the colonization rates, spa type distribution and antibiotic resistance prevalence were similar among parents and HCWs.

Direct observations and self-reporting by HCWs were both validated as tools for monitoring compliance with hygiene guidelines. The compliance with hygiene guidelines was significantly higher following a 10-point hygiene intervention as compared to baseline. The compliance was also higher three years after the intervention in three of four participating departments. These data show that it is possible to markedly improve the compliance with hygiene guidelines, but to achieve a long-term effect, continuous and varied reminders seems necessary.

Both at baseline and following the intervention almost 60 % of the colonized infants were colonized with an S. aureus of the same spa type as isolated from their own family. At baseline approximately 25 % of the colonized infants received their S. aureus from non-family individuals, indicating transmission directly or indirectly from HCWs. Despite the improvement in compliance with barrier precautions from 41 % at baseline to 86 % following the hygiene intervention, the transmission from non-family did not decrease. This indicates that other factors may have a prominent impact on bacterial transmission. One factor might be the quality of hand hygiene technique which therefore needs to be studied further. However, to ensure patient safety it is still recommended that all HCWs comply with hygiene guidelines at all time.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. , 77 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1454
National Category
Biochemistry and Molecular Biology Cell and Molecular Biology Microbiology
Identifiers
URN: urn:nbn:se:liu:diva-116703DOI: 10.3384/diss.diva-116703ISBN: 978-91-7519-096-9 (print)OAI: oai:DiVA.org:liu-116703DiVA: diva2:800043
Public defence
2015-05-08, Originalet, Qulturum, Länssjukhuset Ryhov, Jönköping, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2015-04-01 Created: 2015-04-01 Last updated: 2015-04-01Bibliographically approved
List of papers
1. Epidemiological typing of methicillin-resistant Staphylococcus aureus (MRSA): spa typing versus pulsed-field gel electrophoresis
Open this publication in new window or tab >>Epidemiological typing of methicillin-resistant Staphylococcus aureus (MRSA): spa typing versus pulsed-field gel electrophoresis
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2009 (English)In: SCANDINAVIAN JOURNAL OF INFECTIOUS DISEASES, ISSN 0036-5548, Vol. 41, no 6-7, 433-439 p.Article in journal (Refereed) Published
Abstract [en]

Molecular methods based on sequencing, such as spa typing, have facilitated epidemiological typing of bacterial isolates compared to the gold standard pulsed-field gel electrophoresis (PFGE), a technically more demanding method. We studied methicillin-resistant Staphylococcus aureus (MRSA) in 4 Swedish counties from 2003 through 2005, and compared spa typing and PFGE results to epidemiological data. Of 280 MRSA isolates, 91 were from sporadic cases and 189 were associated with 35 outbreaks. A total of 50 spa types and 74 PFGE patterns were detected. 60 (21%) of the MRSA isolates carried the Panton-Valentine leukocidin (PVL) genes. 12 of the PVL-positive MRSA were healthcare associated. 25 of the spa types and 31 of the PFGE patterns were associated with outbreaks. In 1 of the outbreaks we found isolates with different but closely related spa types, and in 6 of the outbreaks we observed isolates with different but related PFGE patterns. In this low-endemic setting, with outbreaks limited in time and place, we found spa typing to be a useful tool for epidemiological typing of MRSA, due to its rapidity, accessibility, ease of use, and standardized nomenclature.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-19886 (URN)10.1080/00365540902962749 (DOI)
Available from: 2009-08-14 Created: 2009-08-14 Last updated: 2015-04-01
2. Compliance with hygiene guidelines: The effect of a multimodal hygiene intervention and validation of direct observations
Open this publication in new window or tab >>Compliance with hygiene guidelines: The effect of a multimodal hygiene intervention and validation of direct observations
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2013 (English)In: American Journal of Infection Control, ISSN 0196-6553, E-ISSN 1527-3296, Vol. 41, no 5, E45-E48 p.Article in journal (Refereed) Published
Abstract [en]

Background

Good compliance with hygiene guidelines is essential to prevent bacterial transmission and health care-associated infections. However, the compliance is usually <50%.

Methods

A multimodal and multidisciplinary hygiene intervention was launched once the baseline compliance was determined through direct observations in 4 departments of obstetrics and gynecology. Detailed evaluations of the compliance rates were performed at point of stability (at 80%) and follow-up (3 years after hygiene intervention). Validation of direct observations was performed using blinded double appraisal and multiappraisal.

Results

At baseline, the compliance with barrier precautions and the dress code at the 4 departments were 39% to 47% and 79% to 98%, respectively. Point of stability was reached approximately 1 year after the hygiene intervention was launched. The compliance with barrier precautions was significantly higher at follow-up compared with baseline in 3 departments. In the validation by double appraisal, 471 of 483 components were judged identical between observers. In the multiappraisal, 95% to 100% of the observers correctly judged the 7 components.

Conclusion

It is possible to improve compliance with hygiene guidelines, but, to ensure a long-lasting effect, a continuous focus on barrier precautions is required. Observation is a valid method to monitor compliance.

Place, publisher, year, edition, pages
Elsevier, 2013
Keyword
Multidisciplinary, Adherence, Double appraisal, Multiappraisal, Self-reporting, Hand hygiene, Barrier precautions, Dress code
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-93971 (URN)10.1016/j.ajic.2012.09.008 (DOI)000318611200002 ()
Note

Funding Agencies|Futurum-the Academy for Healthcare, County Council, Jonkoping||Medical Research Council of Southeast Sweden||

Available from: 2013-06-13 Created: 2013-06-13 Last updated: 2017-12-06Bibliographically approved
3. The effect of improved compliance with hygiene guidelines on transmission of Staphylococcus aureus to newborn infants: The Swedish Hygiene Intervention and Transmission of S aureus study
Open this publication in new window or tab >>The effect of improved compliance with hygiene guidelines on transmission of Staphylococcus aureus to newborn infants: The Swedish Hygiene Intervention and Transmission of S aureus study
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2013 (English)In: American Journal of Infection Control, ISSN 0196-6553, E-ISSN 1527-3296, Vol. 41, no 7, 585-590 p.Article in journal (Refereed) Published
Abstract [en]

Background: Newborn infants are often colonized with Staphylococcus aureus originating from health care workers (HCWs). We therefore use colonization with S aureus of newborn infants to determine the effect of an improved compliance with hygiene guidelines on bacterial transmission. Methods: Compliance with hygiene guidelines was monitored prior to (baseline) and after (follow-up) a multimodal hygiene intervention in 4 departments of obstetrics and gynecology. spa typing was used to elucidate transmission routes of S aureus collected from newborn infants, mothers, fathers, staff members, and environment. Results: The compliance with hygiene guidelines increased significantly from baseline to follow-up. The transmission of S aureus from HCWs to infants was however not affected. Fathers had the highest colonization rates. Persistent carriage was indicated in 18% of the HCWs. The most commonly isolated spa type was t084, which was not detected in a previous study from the same geographic area. Conclusion: It is possible to substantially improve the compliance with hygiene guidelines, by using multimodal hygiene intervention. The improved compliance did not decrease the transmission of S aureus from sources outside the own family to newborn infants. Furthermore, we show the establishment of a new spa type (t084), which now is very common in our region. Copyright (C) 2013 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2013
Keyword
Compliance rates; The Swedish HITS-study; spa typing; Persistent carriage; Colonization; Carriage; Multimodal hygiene intervention
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-96178 (URN)10.1016/j.ajic.2012.09.014 (DOI)000321046300004 ()
Available from: 2013-08-14 Created: 2013-08-14 Last updated: 2017-12-06
4. The role of broth enrichment in Staphylococcus aureus cultivation and transmission from the throat to newborn infants: results from the Swedish hygiene intervention and transmission of S-aureus study
Open this publication in new window or tab >>The role of broth enrichment in Staphylococcus aureus cultivation and transmission from the throat to newborn infants: results from the Swedish hygiene intervention and transmission of S-aureus study
2013 (English)In: European Journal of Clinical Microbiology and Infectious Diseases, ISSN 0934-9723, E-ISSN 1435-4373, Vol. 32, no 12, 1593-1598 p.Article in journal (Refereed) Published
Abstract [en]

Staphylococcus aureus is detected by direct plating, whereas incubation in enrichment broth prior to plating to increase the proportion of positive samples has not been fully evaluated. S. aureus throat colonization has been suggested to be more common than colonization of the anterior nares, but no data are available on the transmission of S. aureus from the throat. Swab samples were collected from the anterior nares and umbilicus from newborn infants (n = 168), anterior nares, throat, skin lesions, and vagina from parents (n = 332), and anterior nares, throat, and skin lesions from healthcare workers (n = 231) at three maternity wards. spa typing was used to elucidate the transmission routes of S. aureus. The use of enrichment broth prior to plating increased the proportion of positive samples by 46 %. The prevalence of S. aureus colonization in adults was 58 %. Throat colonization (47 %) was significantly more common than colonization in any of the other screened sites (p andlt; 0.001). In total, 103 out of 168 (61 %) newborn infants were colonized during their hospital stay. Overall, 124 S. aureus transmissions to newborn infants were detected. Although we detected an increased risk of transmission from the nares as compared to the throat, with an odds ratio of 4.8 [95 % confidence interval (CI) 1.8-12.7], we detected a transmission rate of 7 % from the throat. We show that S. aureus throat colonization is more common than colonization in any of the other sites among the parents and staff. We also show evidence of transmission from the throat.

Place, publisher, year, edition, pages
Springer Verlag (Germany), 2013
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-102493 (URN)10.1007/s10096-013-1917-6 (DOI)000326896700014 ()
Note

Funding Agencies|Futurum-the Academy for Healthcare||Jonkoping County Council||Medical Research Council of Southeast Sweden||

Available from: 2013-12-13 Created: 2013-12-12 Last updated: 2017-12-06

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