- Email: [email protected]
Can ‘search and destroy’ reduce nosocomial meticillin-resistant Staphylococcus aureus in an Irish hospital?
Journal of Hospital Infection 75 (2010) 120–123
Available online at www.sciencedirect.com
Journal of Hospital Infection journal homepage: www.elsevierhealth.com/journals/jhin
Can ‘search and destroy’ reduce nosocomial meticillin-resistant Staphylococcus aureus in an Irish hospital? A. Higgins*, M. Lynch, G. Gethin Mater Private Hospital, Dublin 7, Ireland
a r t i c l e i n f o
s u m m a r y
Article history: Received 4 September 2009 Accepted 11 December 2009 Available online 16 March 2010
In Ireland, the Department of Health and Children recommends admission screening of patients at increased risk of meticillin-resistant Staphylococcus aureus (MRSA), isolation of these patients until proven negative, and eradication of any MRSA identified. These actions form the basis of a programme called ‘search and destroy’ that has successfully reduced MRSA in Scandinavia. There is, however, very little information published on the use of search and destroy in Ireland. This study was carried out using a quantitative, quasi-experimental design in the form of an interventional cohort study. The effect of reducing the turnaround time for MRSA results (2007) and the introduction of pre-emptive isolation (2008) was examined in a hospital with an established admission screening programme for MRSA. Rates of MRSA infection and colonisation were monitored post-intervention and compared to baseline rates prior to the intervention (2005–2006). Rates of hospital-acquired (nosocomial) MRSA infections and colonisation fell in both 2007 and 2008. However, due to the quasi-experimental design of the study and the low endemic level of MRSA in the hospital, a causal link could not be established. Ó 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Admission screening Meticillin-resistant Staphylococcus aureus Pre-emptive isolation Search and destroy
Introduction In 2006, the Health Protection and Surveillance Centre (HPSC) undertook a prevalence study of hospital-acquired infections in Ireland and the UK. According to this study, meticillin-resistant Staphylococcus aureus (MRSA) is responsible for 10% of healthcareassociated infections.1 MRSA is also well recognised internationally as being associated with increased morbidity, mortality and cost.2–4 Yet, certain countries such as Denmark have successfully reduced MRSA to less than 1% of Staphylococcus aureus isolates from blood cultures.5 The success of the Danish programme, labelled ‘search and destroy’, has centred around a number of actions.6 These include identification and screening of patients at admission who are considered to be ‘at increased risk of MRSA’; single room and pre-emptive isolation of these ‘at-risk’ patients until results are available and the instigation of eradication regimes to remove the MRSA once identified.7 The Health Service Executive (HSE) in Ireland recommends targeted admission screening and pre-emptive isolation of patients
* Address: Mater Private Hospital, Dublin 7, Ireland. Tel.: þ353 18858371; fax: þ353 18858541. E-mail address: [email protected] (A. Higgins).
colonised with MRSA, yet few studies on the effectiveness of any type of admission screening or the use of pre-emptive isolation have been published in Ireland.8 This information is essential to assess if international findings on control of MRSA by search and destroy can be effective in Ireland, where the majority of hospitals have inadequate numbers of single rooms.9–11 The aim of this study was to demonstrate a positive effect; that of a reduction in nosocomial MRSA, from a specific intervention – the introduction of a search and destroy programme for control of MRSA. Because of the difficulties with selecting a control group, a quasi-experimental approach in the form of an interventional cohort study was used. Methods The study was set in a 186-bed acute care tertiary referral private hospital. The majority of the 9553 average admissions per year were elective with 70% private and 30% public patients. The wards are made up of a mixture of four-bedded rooms and single rooms with single rooms accounting for 50% of the total 186 beds. The hospital has a nine-bedded intensive care unit and 11 stepdown beds mostly used for cardiac surgery. Specialties in the hospital include cardiothoracic surgery, orthopaedics including
0195-6701/$ – see front matter Ó 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhin.2009.12.014
A. Higgins et al. / Journal of Hospital Infection 75 (2010) 120–123
joint implant surgery, oncology, haematology, general medicine and general and vascular surgery. Since January 2000 all cardiac surgery patients, patients with a history of MRSA and patients transferred from other hospitals have been screened for MRSA on admission. In January 2005 this was extended to include patients hospitalised in the past month. All patients colonised with MRSA were placed in single rooms with contact precautions including hand hygiene and the wearing of plastic aprons and disposable gloves instigated for all patient contact until three negative screens were obtained. Eradication of MRSA was carried out as per national guidelines.8 All practices in place were actively audited. Surveillance for MRSA continued during the patients’ stay. Patients were screened on admission to intensive care unit (ICU) and weekly while in the ICU. Patients in the hospital for more than 12 days were screened fortnightly on all wards. All clinical samples reserved during any inpatient or daypatient stay were cultured for MRSA. There was no change to these procedures from 2005 until the end of the study. Following the introduction of the infection control programme in 2000 and the gradual introduction of targeted admission screening over the next few years, MRSA levels in the hospital declined. However, while these results were sustained, they became the new endemic level of MRSA for the hospital and did not fall any further when the screening programme was extended in 2004 and 2005. Reviewing these results in 2006, a decision was taken to expand the MRSA control programme using the method of targeted screening and pre-emptive isolation until results of screening swabs were available known as ‘search and destroy’ from January 2007.8,9 This study details the results following these interventions. Prior to the study the average turnaround time for MRSA screening swabs was 72 h from receipt in the laboratory. A change in the method of identifying MRSA was implemented in 2006. The new process involved direct plating of swabs onto Pastores coagulase, cefoxitin-based, Serosep agar (BioRad) plates and incubating for 18 h. Absence of pink colonies after 18 h indicated that MRSA was not present. The turnaround time for negative results was therefore reduced from 72 to 24 h. Pink colonies were further identified as MRSA by tube coagulase, if necessary, and sensitivity testing using the disc diffusion method. Patients with suspected MRSA were isolated and treatment commenced pending confirmation by culture. From January 2008, pre-emptive isolation was introduced. This involved identification of patients at risk of colonisation with MRSA at admission and assigning these patients single rooms until screening results were available. Contact precautions were instigated for those with a history of MRSA in the past year. Due to the lack of randomisation in the study groups, it was decided to randomly select 100 patients from the cardiac surgery specialty. These patients were selected using stratified random
121
sampling, ensuring inclusion of 25 patients from each year of the study. A number of commonly recognised risks for infection – length of stay, age, National Nosocomial Infection Surveillance (NNIS) risk score, body mass index, and presence of diabetes – were examined.12 The groups were then compared using Levine’s test for equality of variance in order to confirm the similarities in the cohort groups and thus add to the strength of the quasiexperimental design. The numbers of confirmed MRSA bacteraemias and surgical site infections (SSIs) were recorded for each of the two study periods. All microbiology reports were reviewed daily and positive wound swabs and blood cultures were followed by review of each patient to assess whether the patient had signs of infection as per specific Centers for Disease Control and Prevention (CDC) definitions.13 These were then confirmed with the microbiologist before inclusion on the database as an infection. Infections occurring after discharge but within one month of surgery were included if the surgeon later reported the infection or if the patient was readmitted to our hospital with an infection. Patients who had implant surgery such as joint replacement, pacemaker insertion or valve surgery were included if the infection occurred within one year of the surgery. All patients found to have nosocomial colonisation with MRSA were also included in the numbers recorded in the study. Ethics approval was sought and obtained from the Ethics Committee in the adjacent Mater Misericordiae University Hospital. Results From 1996 to 1999, nosocomial rates of MRSA colonisation and infection were recorded as 0.48 per 1000 bed-days. With the introduction and expansion of the targeted screening programme in 2000, rates over the next few years fell to a mean of 0.29 per 1000 bed-days. Despite the introduction of faster turnaround times for MRSA screening swabs, the hospital’s rates for nosocomial MRSA colonisation and infection did not fall in 2007 and were recorded as 0.27 per 1000 bed-days. However, MRSA infections were lower in 2007. In 2008, when pre-emptive isolation was introduced, a reduction to 0.14 per 1000 bed-days was seen in rates of nosocomial infection and colonisation (Figure 1). MRSA infection rates also fell further in 2008. In 2005 rates for MRSA bacteraemias were recorded as 42% of Staphylococcus aureus isolated from blood cultures. This was similar to rates for Ireland recorded by the European Antimicrobial Resistance Surveillance System (EARSS).14 These rates fell to 10% in 2007 and there were no MRSA bacteraemias in the hospital in 2008 (Figure 2). In the two years preceding the intervention (2005 and 2006), MRSA SSI rates were recorded as 0.09 per 1000 bed-days. The faster turnaround times appeared to have an impact on the acquisition rates in
0.7
MRSA rate
0.6 0.5 0.4 0.3 0.2 0.1 0
1996
1997
1998
1999
2000
2001
2002 Year
2003
2004
2005
2006
Figure 1. Nosocomial meticillin-resistant Staphylococcus aureus (MRSA) per 1000 bed-days.
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A. Higgins et al. / Journal of Hospital Infection 75 (2010) 120–123
100 90 80 70
%
60 50 40 30 20 10 0 2005
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Year Figure 2. Percentage of Staphylococcus aureus bloodstream infections caused by meticillin-resistant S. aureus (MRSA).
surgical wounds with MRSA SSI rates recorded as 0.02 per 1000 bed-days in 2007. No MRSA SSIs were recorded in 2008. The cardiac surgery ward accommodated both cardiac surgery and cardiology patients and had the highest levels of MRSA acquisition prior to the interventions. Rates of acquisition on the ward (colonisation and infection) averaged at 0.75 per 1000 beddays in 2005–2006. Four percent of admissions to the ward were identified as colonised with MRSA at admission and the average length of stay was 15.2 days. Acquisition rates dropped to 0.33 per 1000 bed-days in 2007 when results from MRSA screening became available after 24 h (Figure 3). This reduction was sustained in 2008 when pre-emptive isolation was introduced and no patient acquired MRSA colonisation or infection on the ward in the 12 months following this intervention. The patient profile did not change during the four years of the study. While the numbers in the study were small and statistical significance thus not achievable, the reduction in MRSA infections was considered to be significant for the hospital. Discussion Much of the debate in the literature in recent years has centred around whether screening specific high risk groups of patients or screening all patients is more effective at reducing hospitalacquired MRSA.15–17 Some have deduced that the speed of
turnaround for results from this screening impacts on the effect of the screening programme.18,19 Others still have argued that it is a combination of admission screening, eradication of MRSA identified and pre-emptive isolation – also known as search and destroy – that have provided the best results.20–22 Internationally benefits from reducing turnaround time for MRSA screening swabs have been mixed.19,21–23 In our study there was no impact on overall MRSA acquisition rates following a reduction in turnaround times from 72 to 24 h. However, the screening programme for MRSA was well established and rates had already fallen significantly in the previous few years. The faster turnaround times for results did positively impact on rates of MRSA acquisition on the cardiac surgery ward. The benefits seen on this ward were related to the availability of results before the patient was transferred back to the ward from the intensive care unit postsurgery, thus ensuring that the patient was placed directly into a single room. This prevented patients colonised with MRSA from unknowingly sharing rooms with other patients and MRSA acquisition rates fell. Examination of variables recognised by other researchers as risk factors for MRSA acquisition demonstrate that the profile of patients in the ward did not change during the study.24–27 Levine’s test for equality of variances demonstrated both groups of patients (pre-intervention and post-intervention) were statistically similar, thus reducing the possibility that a change in patient profile might have influenced the results.
0.8 0.6 Nosocomial MRSA per 0.4 1000 bed-days 0.2 0
2005
2006 Target screening
2007 Faster turnaround time for MRSA swabs
2008 Pre-emptive isolation
Figure 3. Total nosocomial meticillin-resistant Staphylococcus aureus (MRSA) (colonisation and infection) on cardiac surgery ward.
A. Higgins et al. / Journal of Hospital Infection 75 (2010) 120–123
While the faster turnaround time for MRSA screening swabs was successful in reducing rates of MRSA acquisition on the cardiac surgery ward, it was not until 2008 when pre-emptive isolation was introduced that rates of MRSA acquisition in the whole hospital fell. Harbarth had noted a similar finding in his study, deducing that it was the single room isolation of colonised patients that reduced MRSA rates.22 Although there are few data concerning the impact of isolation on rates of MRSA in hospitals, the benefits of programmes that combine some form of admissions screening with isolation of colonised patients are well established.5–7,24,25 Furthermore, recent studies by MacKenzie, Moore and others have added to the body of knowledge on impact of sharing rooms with patients colonised with MRSA.26–30 Our study found that, by assigning patients at risk of MRSA colonisation a single room from time of admission, rates of MRSA acquisition for the hospital fell. This study does, however, have limitations. The results must be examined with some caution as rates of MRSA infection in the hospital were already low and the quasi-experimental design of the study makes a cause-and-effect link difficult to establish. Because the study compared data from 2007 and 2008 with data retrospectively correlated from 2005 and 2006, the time scale of this study must also be taken into account when reviewing the findings. In Ireland in 2005, there was little public awareness of MRSA compared with 2007 and 2008. Improved visitor awareness may have improved adherence to hand washing over the course of the study. The fact that this may have impacted on numbers of infections and acquisition rates cannot be excluded. Antibiotic use is also recognised by some researchers as impacting on MRSA levels.26 However, use of antibiotics in this hospital was not monitored during this study. Whereas no change to antibiotic prescribing policy was implemented while this study was in progress, some changes may have occurred that could have impacted on the results. This study was carried out in a single private hospital with 50% single rooms. The majority of hospitals in Ireland have only 6% single rooms and thus comparison with other Irish hospitals is not possible.11 Although numbers in the study were high (w38 000 patients in total) the ideal would have been to replicate the study in a number of other settings in Ireland. For hospitals with sufficient single room availability, this study demonstrates the possible reductions in infection rates that can be achieved by actively searching for MRSA colonisation, eradicating MRSA identified and reducing contact with carriers by preemptively assigning single rooms and practising contact precautions for those with highest risks. However, many hospitals in Ireland have inadequate single rooms in which to isolate patients. Further research is needed to examine whether search and destroy can realistically be implemented in this context. Conflict of interest statement None declared. Funding sources No external funding.
References 1. Health Protection Surveillance Centre. Prevalence study of healthcare associated infections in Ireland and United Kingdom. Dublin: HSE; 2007. 2. Jevons MP. ‘‘Celbenin"-resistant Staphylococci. Br Med J 1961;I:124–125. 3. Cosgrove SE, Sakoulas G, Perencevich EN, Schwaber MJ, Karchmer AW, Carmeli Y. Comparison of mortality associated with methicillin-resistant and methicillin-sensitive Staphylococcus aureus bacteremia; a meta analysis. Clin Infect Dis 2003;36:53–59.
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4. Thompson DS, Workman R, Strutt M. Contribution of acquired methicillin resistant Staphylococcus aureus bacteraemia to overall mortality in a general intensive care unit. J Hosp Infect 2008;70:223–227. 5. Wertheim H, Vos M, Boelens H, Voss C, Vandenbroucke-Grauls C. Low prevalence of MRSA at hospital admission in the Netherlands: the value of search and destroy and restrictive antibiotic use. J Hosp Infect 2004;56:321–325. 6. Van Trijp M, Melles D, Hendriks W, Parlevliet G, Gommans M. Successful control of widespread MRSA colonization in a large teaching hospital in the Netherlands. Infect Control Hosp Epidemiol 2007;28:970–975. 7. Kluytmans J. Control of methicillin resistant Staphylococcus aureus (MRSA) and the value of rapid tests. J Hosp Infect 2007;65(Suppl. 2):100–104. 8. Strategy for the Control of Antimicrobial Resistance in Ireland. The control and prevention of MRSA in hospitals and the community. Dublin: Health Service Executive, Health Protection and Surveillance Centre; 2005. 9. Cunney R, Humphreys H, Murphy N. Survey of acute hospital infection control resources and services in the Republic of Ireland. J Hosp Infect 2006;64:63–68. 10. Department of Health and Children. Report of the commission on patient safety and quality assurance. Building a culture of patient safety. Dublin: Stationery Office; 2008. 11. Doherty T, Thomas T, Walsh J, Morris-Downes M, Smyth E, Humphreys H. Isolation facilities for patients with MRSA; how adequate are they? J Hosp Infect 2007;65:274–282. 12. Society for Healthcare Epidemiology of America. Strategies to prevent surgical site infections in acute care hospitals. Infect Control Hosp Epidemiol 2008;29: 51–61. 13. Horan TC, Gaynes RP, Martone WJ, Jarvis WR, Emori TG. CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Infect Cont Hosp Epidemiol 1992;13:606–609. 14. EARSS (European Antimicrobial Resistance Surveillance System). Annual Report 2005. 15. Gopal Rao G, Michalczyk P, Nayeem N, Walker G, Wigmore L. Prevalence and risk factors for methicillin resistant Staphylococcus aureus in adult emergency admissions – a case for screening all patients? J Hosp Infect 2007;66:15–21. 16. Harbarth S, Sax H, Uckay I, et al. A predictive model for identifying surgical patients at risk of MRSA carriage on admission. J Am Colorect Surg 2008;207:683–689. 17. Dancer SJ. Considering the introduction of universal MRSA screening. J Hosp Infect 2008;69:315–320. 18. Raboud J, Saskin R, Simor A, et al. Modeling transmission of methicillin resistant Staphylococcus aureus among patients admitted to a hospital. Infect Control Hosp Epidemiol 2005;26:607–615. 19. Keshgar M, Khalili A, Coen G, et al. Impact of rapid molecular screening for methicillin resistant Staphylococcus aureus in surgical wards. Br J Surg 2007;95:381–386. 20. West T, Guerry C, Hiott M, Morrow N, Ward K, Salgado C. Effect of targeted surveillance for control of methicillin resistant Staphylococcus aureus in a community hospital system. Infect Control Hosp Epidemiol 2006;27:233–237. 21. Chaberny I, Schwab F, Ziesing S, Suerbaum S, Gastmeier P. Impact of routine surgical ward and intensive care unit admission surveillance cultures on hospital wide nosocomial MRSA in a university hospital: an interrupted time series analysis. J Antimicrob Chemother 2008;62:1422–1429. 22. Harbarth S, Masuet-Aumatell C, Schrenzel J, et al. Evaluation of rapid screening and pre-emptive contact isolation for detecting and controlling methicillin resistant Staphylococcus aureus in critical care: an interventional cohort study. Crit Care 2006;10:1–8. 23. Aldeyab MA, Kearney MP, Hughes CM, et al. Can the use of a rapid polymerase chain screening method decrease the incidence of nosocomial MRSA? J Hosp Infect 2009;71:22–28. 24. Cooper BS, Stone SP, Kibbler C, Cookson B, Roberts J, Medley G. Isolation measures in the hospital management of MRSA: systematic review of the literature. Br Med J 2004;329:533. 25. Lucet JC, Chevret S, Durand-Zaleski I, Chastang C, Regnier B. Prevalence and risk factors for carriage of methicillin-resistant Staphylococcus aureus at admission to the intensive care unit: results of a multicenter study. Arch Inter Med 2003;163:181–188. 26. MacKenzie FM, Bruce J, Struelens MJ, Gossens H, Mollison J, Gould IM. Antimicrobial drug use and infection control practice associated with the prevalence of MRSA in European hospitals. Clin Microbiol 2007;13:269–276. 27. Eveillard M, Lancien E, Barnaud N, et al. Impact of screening for MRSA carriers at hospital admission on risk adjusted indicators according to the imported MRSA colonization pressure. J Hosp Infect 2005;59:254–258. 28. Wernitz M, Swissinski S, Weist K, et al. Effectiveness of a hospital wide elective screening programme for methicillin resistant Staphylococcus aureus (MRSA) carriers at hospital admission to prevent hospital acquired MRSA infections. Clin Microbiol 2005;11:457–461. 29. Moore C, Dhaliwal J, Tong A, Eden S, Wigston C, Willey B. Risk factors for MRSA acquisition in roommate contacts of patients colonized or infected with MRSA in an acute care hospital. Infect Control Hosp Epidemiol 2008;29: 600–606. 30. Rohr U, Kaminski A, Wilhelm M, Jurzik L, Gatermann S, Muhr G. Colonization of patients and contamination of the patient’s environment by MRSA under conditions of single-room isolation. Int J Hyg Environ Health 2008;212:209–215.
Available online at www.sciencedirect.com
Journal of Hospital Infection journal homepage: www.elsevierhealth.com/journals/jhin
Can ‘search and destroy’ reduce nosocomial meticillin-resistant Staphylococcus aureus in an Irish hospital? A. Higgins*, M. Lynch, G. Gethin Mater Private Hospital, Dublin 7, Ireland
a r t i c l e i n f o
s u m m a r y
Article history: Received 4 September 2009 Accepted 11 December 2009 Available online 16 March 2010
In Ireland, the Department of Health and Children recommends admission screening of patients at increased risk of meticillin-resistant Staphylococcus aureus (MRSA), isolation of these patients until proven negative, and eradication of any MRSA identified. These actions form the basis of a programme called ‘search and destroy’ that has successfully reduced MRSA in Scandinavia. There is, however, very little information published on the use of search and destroy in Ireland. This study was carried out using a quantitative, quasi-experimental design in the form of an interventional cohort study. The effect of reducing the turnaround time for MRSA results (2007) and the introduction of pre-emptive isolation (2008) was examined in a hospital with an established admission screening programme for MRSA. Rates of MRSA infection and colonisation were monitored post-intervention and compared to baseline rates prior to the intervention (2005–2006). Rates of hospital-acquired (nosocomial) MRSA infections and colonisation fell in both 2007 and 2008. However, due to the quasi-experimental design of the study and the low endemic level of MRSA in the hospital, a causal link could not be established. Ó 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.
Keywords: Admission screening Meticillin-resistant Staphylococcus aureus Pre-emptive isolation Search and destroy
Introduction In 2006, the Health Protection and Surveillance Centre (HPSC) undertook a prevalence study of hospital-acquired infections in Ireland and the UK. According to this study, meticillin-resistant Staphylococcus aureus (MRSA) is responsible for 10% of healthcareassociated infections.1 MRSA is also well recognised internationally as being associated with increased morbidity, mortality and cost.2–4 Yet, certain countries such as Denmark have successfully reduced MRSA to less than 1% of Staphylococcus aureus isolates from blood cultures.5 The success of the Danish programme, labelled ‘search and destroy’, has centred around a number of actions.6 These include identification and screening of patients at admission who are considered to be ‘at increased risk of MRSA’; single room and pre-emptive isolation of these ‘at-risk’ patients until results are available and the instigation of eradication regimes to remove the MRSA once identified.7 The Health Service Executive (HSE) in Ireland recommends targeted admission screening and pre-emptive isolation of patients
* Address: Mater Private Hospital, Dublin 7, Ireland. Tel.: þ353 18858371; fax: þ353 18858541. E-mail address: [email protected] (A. Higgins).
colonised with MRSA, yet few studies on the effectiveness of any type of admission screening or the use of pre-emptive isolation have been published in Ireland.8 This information is essential to assess if international findings on control of MRSA by search and destroy can be effective in Ireland, where the majority of hospitals have inadequate numbers of single rooms.9–11 The aim of this study was to demonstrate a positive effect; that of a reduction in nosocomial MRSA, from a specific intervention – the introduction of a search and destroy programme for control of MRSA. Because of the difficulties with selecting a control group, a quasi-experimental approach in the form of an interventional cohort study was used. Methods The study was set in a 186-bed acute care tertiary referral private hospital. The majority of the 9553 average admissions per year were elective with 70% private and 30% public patients. The wards are made up of a mixture of four-bedded rooms and single rooms with single rooms accounting for 50% of the total 186 beds. The hospital has a nine-bedded intensive care unit and 11 stepdown beds mostly used for cardiac surgery. Specialties in the hospital include cardiothoracic surgery, orthopaedics including
0195-6701/$ – see front matter Ó 2009 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhin.2009.12.014
A. Higgins et al. / Journal of Hospital Infection 75 (2010) 120–123
joint implant surgery, oncology, haematology, general medicine and general and vascular surgery. Since January 2000 all cardiac surgery patients, patients with a history of MRSA and patients transferred from other hospitals have been screened for MRSA on admission. In January 2005 this was extended to include patients hospitalised in the past month. All patients colonised with MRSA were placed in single rooms with contact precautions including hand hygiene and the wearing of plastic aprons and disposable gloves instigated for all patient contact until three negative screens were obtained. Eradication of MRSA was carried out as per national guidelines.8 All practices in place were actively audited. Surveillance for MRSA continued during the patients’ stay. Patients were screened on admission to intensive care unit (ICU) and weekly while in the ICU. Patients in the hospital for more than 12 days were screened fortnightly on all wards. All clinical samples reserved during any inpatient or daypatient stay were cultured for MRSA. There was no change to these procedures from 2005 until the end of the study. Following the introduction of the infection control programme in 2000 and the gradual introduction of targeted admission screening over the next few years, MRSA levels in the hospital declined. However, while these results were sustained, they became the new endemic level of MRSA for the hospital and did not fall any further when the screening programme was extended in 2004 and 2005. Reviewing these results in 2006, a decision was taken to expand the MRSA control programme using the method of targeted screening and pre-emptive isolation until results of screening swabs were available known as ‘search and destroy’ from January 2007.8,9 This study details the results following these interventions. Prior to the study the average turnaround time for MRSA screening swabs was 72 h from receipt in the laboratory. A change in the method of identifying MRSA was implemented in 2006. The new process involved direct plating of swabs onto Pastores coagulase, cefoxitin-based, Serosep agar (BioRad) plates and incubating for 18 h. Absence of pink colonies after 18 h indicated that MRSA was not present. The turnaround time for negative results was therefore reduced from 72 to 24 h. Pink colonies were further identified as MRSA by tube coagulase, if necessary, and sensitivity testing using the disc diffusion method. Patients with suspected MRSA were isolated and treatment commenced pending confirmation by culture. From January 2008, pre-emptive isolation was introduced. This involved identification of patients at risk of colonisation with MRSA at admission and assigning these patients single rooms until screening results were available. Contact precautions were instigated for those with a history of MRSA in the past year. Due to the lack of randomisation in the study groups, it was decided to randomly select 100 patients from the cardiac surgery specialty. These patients were selected using stratified random
121
sampling, ensuring inclusion of 25 patients from each year of the study. A number of commonly recognised risks for infection – length of stay, age, National Nosocomial Infection Surveillance (NNIS) risk score, body mass index, and presence of diabetes – were examined.12 The groups were then compared using Levine’s test for equality of variance in order to confirm the similarities in the cohort groups and thus add to the strength of the quasiexperimental design. The numbers of confirmed MRSA bacteraemias and surgical site infections (SSIs) were recorded for each of the two study periods. All microbiology reports were reviewed daily and positive wound swabs and blood cultures were followed by review of each patient to assess whether the patient had signs of infection as per specific Centers for Disease Control and Prevention (CDC) definitions.13 These were then confirmed with the microbiologist before inclusion on the database as an infection. Infections occurring after discharge but within one month of surgery were included if the surgeon later reported the infection or if the patient was readmitted to our hospital with an infection. Patients who had implant surgery such as joint replacement, pacemaker insertion or valve surgery were included if the infection occurred within one year of the surgery. All patients found to have nosocomial colonisation with MRSA were also included in the numbers recorded in the study. Ethics approval was sought and obtained from the Ethics Committee in the adjacent Mater Misericordiae University Hospital. Results From 1996 to 1999, nosocomial rates of MRSA colonisation and infection were recorded as 0.48 per 1000 bed-days. With the introduction and expansion of the targeted screening programme in 2000, rates over the next few years fell to a mean of 0.29 per 1000 bed-days. Despite the introduction of faster turnaround times for MRSA screening swabs, the hospital’s rates for nosocomial MRSA colonisation and infection did not fall in 2007 and were recorded as 0.27 per 1000 bed-days. However, MRSA infections were lower in 2007. In 2008, when pre-emptive isolation was introduced, a reduction to 0.14 per 1000 bed-days was seen in rates of nosocomial infection and colonisation (Figure 1). MRSA infection rates also fell further in 2008. In 2005 rates for MRSA bacteraemias were recorded as 42% of Staphylococcus aureus isolated from blood cultures. This was similar to rates for Ireland recorded by the European Antimicrobial Resistance Surveillance System (EARSS).14 These rates fell to 10% in 2007 and there were no MRSA bacteraemias in the hospital in 2008 (Figure 2). In the two years preceding the intervention (2005 and 2006), MRSA SSI rates were recorded as 0.09 per 1000 bed-days. The faster turnaround times appeared to have an impact on the acquisition rates in
0.7
MRSA rate
0.6 0.5 0.4 0.3 0.2 0.1 0
1996
1997
1998
1999
2000
2001
2002 Year
2003
2004
2005
2006
Figure 1. Nosocomial meticillin-resistant Staphylococcus aureus (MRSA) per 1000 bed-days.
2007
2008
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A. Higgins et al. / Journal of Hospital Infection 75 (2010) 120–123
100 90 80 70
%
60 50 40 30 20 10 0 2005
2006
2007
2008
Year Figure 2. Percentage of Staphylococcus aureus bloodstream infections caused by meticillin-resistant S. aureus (MRSA).
surgical wounds with MRSA SSI rates recorded as 0.02 per 1000 bed-days in 2007. No MRSA SSIs were recorded in 2008. The cardiac surgery ward accommodated both cardiac surgery and cardiology patients and had the highest levels of MRSA acquisition prior to the interventions. Rates of acquisition on the ward (colonisation and infection) averaged at 0.75 per 1000 beddays in 2005–2006. Four percent of admissions to the ward were identified as colonised with MRSA at admission and the average length of stay was 15.2 days. Acquisition rates dropped to 0.33 per 1000 bed-days in 2007 when results from MRSA screening became available after 24 h (Figure 3). This reduction was sustained in 2008 when pre-emptive isolation was introduced and no patient acquired MRSA colonisation or infection on the ward in the 12 months following this intervention. The patient profile did not change during the four years of the study. While the numbers in the study were small and statistical significance thus not achievable, the reduction in MRSA infections was considered to be significant for the hospital. Discussion Much of the debate in the literature in recent years has centred around whether screening specific high risk groups of patients or screening all patients is more effective at reducing hospitalacquired MRSA.15–17 Some have deduced that the speed of
turnaround for results from this screening impacts on the effect of the screening programme.18,19 Others still have argued that it is a combination of admission screening, eradication of MRSA identified and pre-emptive isolation – also known as search and destroy – that have provided the best results.20–22 Internationally benefits from reducing turnaround time for MRSA screening swabs have been mixed.19,21–23 In our study there was no impact on overall MRSA acquisition rates following a reduction in turnaround times from 72 to 24 h. However, the screening programme for MRSA was well established and rates had already fallen significantly in the previous few years. The faster turnaround times for results did positively impact on rates of MRSA acquisition on the cardiac surgery ward. The benefits seen on this ward were related to the availability of results before the patient was transferred back to the ward from the intensive care unit postsurgery, thus ensuring that the patient was placed directly into a single room. This prevented patients colonised with MRSA from unknowingly sharing rooms with other patients and MRSA acquisition rates fell. Examination of variables recognised by other researchers as risk factors for MRSA acquisition demonstrate that the profile of patients in the ward did not change during the study.24–27 Levine’s test for equality of variances demonstrated both groups of patients (pre-intervention and post-intervention) were statistically similar, thus reducing the possibility that a change in patient profile might have influenced the results.
0.8 0.6 Nosocomial MRSA per 0.4 1000 bed-days 0.2 0
2005
2006 Target screening
2007 Faster turnaround time for MRSA swabs
2008 Pre-emptive isolation
Figure 3. Total nosocomial meticillin-resistant Staphylococcus aureus (MRSA) (colonisation and infection) on cardiac surgery ward.
A. Higgins et al. / Journal of Hospital Infection 75 (2010) 120–123
While the faster turnaround time for MRSA screening swabs was successful in reducing rates of MRSA acquisition on the cardiac surgery ward, it was not until 2008 when pre-emptive isolation was introduced that rates of MRSA acquisition in the whole hospital fell. Harbarth had noted a similar finding in his study, deducing that it was the single room isolation of colonised patients that reduced MRSA rates.22 Although there are few data concerning the impact of isolation on rates of MRSA in hospitals, the benefits of programmes that combine some form of admissions screening with isolation of colonised patients are well established.5–7,24,25 Furthermore, recent studies by MacKenzie, Moore and others have added to the body of knowledge on impact of sharing rooms with patients colonised with MRSA.26–30 Our study found that, by assigning patients at risk of MRSA colonisation a single room from time of admission, rates of MRSA acquisition for the hospital fell. This study does, however, have limitations. The results must be examined with some caution as rates of MRSA infection in the hospital were already low and the quasi-experimental design of the study makes a cause-and-effect link difficult to establish. Because the study compared data from 2007 and 2008 with data retrospectively correlated from 2005 and 2006, the time scale of this study must also be taken into account when reviewing the findings. In Ireland in 2005, there was little public awareness of MRSA compared with 2007 and 2008. Improved visitor awareness may have improved adherence to hand washing over the course of the study. The fact that this may have impacted on numbers of infections and acquisition rates cannot be excluded. Antibiotic use is also recognised by some researchers as impacting on MRSA levels.26 However, use of antibiotics in this hospital was not monitored during this study. Whereas no change to antibiotic prescribing policy was implemented while this study was in progress, some changes may have occurred that could have impacted on the results. This study was carried out in a single private hospital with 50% single rooms. The majority of hospitals in Ireland have only 6% single rooms and thus comparison with other Irish hospitals is not possible.11 Although numbers in the study were high (w38 000 patients in total) the ideal would have been to replicate the study in a number of other settings in Ireland. For hospitals with sufficient single room availability, this study demonstrates the possible reductions in infection rates that can be achieved by actively searching for MRSA colonisation, eradicating MRSA identified and reducing contact with carriers by preemptively assigning single rooms and practising contact precautions for those with highest risks. However, many hospitals in Ireland have inadequate single rooms in which to isolate patients. Further research is needed to examine whether search and destroy can realistically be implemented in this context. Conflict of interest statement None declared. Funding sources No external funding.
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