Review of a three-year meticillin-resistant Staphylococcus aureus screening programme

doi:10.1016/j.jhin.2011.02.012

Journal of Hospital Infection

Volume 78, Issue 2, June 2011, Pages 81-85

https://doi.org/10.1016/j.jhin.2011.02.012 Get rights and content

Summary

The Newcastle upon Tyne Hospitals NHS Foundation Trust (NuTH) implemented a seek and destroy (S&D) programme in 2006 to minimise meticillin-resistant Staphylococcus aureus (MRSA) colonisation and/or infection of patients. Using a phased introduction, all patient specialties were included in the scheme by September 2008, well in advance of the mandatory Department of Health, England (DoH) requirement for all patients to be screened. NuTH screens nose, throat and perineum samples from approximately 15 000 patients per month using a chromogenic culture method, showing a mean MRSA prevalence of 2.4%. Provision of seven-day microbiology and infection control services ensured that the turnaround time to prescribing decolonisation therapy was <24 h. Analysis of 168 073 results identified the necessity for inclusion of all three screening sites to maximise recovery of MRSA. Appraisal of the S&D policy demonstrated that MRSA detection rates did not increase despite an exponential increase in workload owing to mandatory inclusion of low risk areas in the screening programme. Review of data during a typical one-month period indicated that only seven day-case patients would not have been identified as MRSA carriers using our targeted S&D approach compared with the DoH universal screening. Detection of these additional patients incurred total laboratory costs of £20,000 and generated a further 4200 associated negative screens in one month alone. Our study indicates that a screening strategy based upon clinical risk is more pragmatic and more cost-effective than the universal programme currently required in England.

Introduction

Healthcare-associated infections (HAIs), including those caused by meticillin-resistant Staphylococcus aureus (MRSA), have become a global concern. Many strategies have been implemented to reduce significantly the risk of acquisition.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 The Department of Health, England (DoH) reported that about 9% of patients in hospitals in the UK acquire HAI, costing the National Health Service (NHS) about £1 billion per annum.¹² Concurrently, estimates from the Office for National Statistics up to 2005 had shown a rise in MRSA mortality rates.¹³ As a consequence, in 2006 all NHS Trusts in England were advised by the Chief Medical Officer to review their policies for screening and decolonisation of patients with MRSA. A targeted approach across all patient pathways was initially suggested by the DoH as the most effective measure for minimising the risk of infection.¹⁴

UK national protocols were subsequently modified in 2009 to encompass mandatory screening of all elective and day-case patients, with the proviso of including emergency patients by December 2010.15, 16, 17, 18 Each healthcare establishment has to provide documentary evidence of compliance. As the DoH guidance does not stipulate how to provide such a commitment, local decisions were advocated. This has resulted in a plethora of laboratory procedures to detect MRSA colonisation. Most testing algorithms incorporate either chromogenic culture with or without prior enrichment or rapid molecular methods.¹⁹ Even though molecular techniques have superior sensitivity and specificity, higher cost generally prevents their use in extensive screening regimes.20, 21 Such systems have also only been validated for use with material collected from the anterior nares, though some authors support the necessity for screening additional body sites to increase the likelihood of detection.22, 23, 24, 25, 26, 27

With regard to control strategies, international protocols suggest that extensive active surveillance cultures (ASCs) should only be advocated for use in intensive care units and that routine screening of all other hospital admissions be discouraged.²⁸ However, despite conflict of opinion, universal ASCs were introduced in England as a tool to minimise HAI caused by MRSA.²⁹

The Newcastle upon Tyne Foundation Hospitals NHS Trust (NuTH) initiated a locally devised seek and destroy (S&D) programme for MRSA in August 2006.¹⁴ As the microbiology department had processed screening swabs for more than three years there was a considerable dataset, covering about 300 000 patients, available for retrospective analysis. A review of local data was deemed essential to assess the outcomes against the recently implemented national screening initiative. The primary aims were: (i) to compare universal ASCs with a more targeted screening programme based upon patient-related risk defined by specialty; (ii) to determine local MRSA prevalence; (iii) to examine the sensitivity of various body sites for MRSA detection when using chromogenic culture methods.

Section snippets

Methods

NuTH is a large multi-sited teaching hospital with approximately 1800 beds. The infection prevention and control team (IPCT) used a phased approach for the introduction of S&D; prioritising using evidence-based risk assessment of MRSA acquisition.¹⁴ Table I shows the order of implementation, assigned risk category according to hospital specialty, and the number of MRSA screens submitted to the laboratory each month.

The S&D programme required admission, transfer and discharge screens from those

Efficacy and cost-effectiveness of the universal screening and targeted approach

The number of patients screened for MRSA in our organisation has increased each month since S&D was initiated in August 2006, with the most recent figures exceeding 12 000 NTP screens per month. Despite this increase, the number of MRSA-positive patients detected remained relatively constant throughout the four phases of screening at an average of 159 patients (range: 118–201) per month during the 27 months of study. Figure 1 illustrates the monthly totals and highlights the relative proportion

Discussion

The introduction and subsequent expansion of the S&D programme at NuTH has required an investment of about £1.6 million since August 2006. This encompassed microbiology consumables, decolonisation therapy, expansion of the laboratory footprint, plus additional laboratory and infection control staff to allow introduction of a dedicated seven-day service specifically for infection prevention and control.

Current sample turnaround times of 21–22 h for all microbiology MRSA results and prompt

Acknowledgements

The authors gratefully acknowledge the support of Dr A. Gascoigne (Director of Infection Prevention and Control) and his team, and also the microbiology staff who assisted throughout the evaluation.

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Cited by (21)

Meticillin-resistant Staphylococcus aureus Contact Screening Strategy in a Low Prevalence Setting; a Nested Case-Control Study
2022, Infection Prevention in Practice
The optimal screening strategy in hospitals to identify secondary cases after contact with a meticillin-resistant Staphylococcus aureus (MRSA) index patient in a low prevalence setting is not well defined. We aimed at identifying factors associated with documented MRSA transmissions.
Single center, retrospective, nested case-control study. We evaluated the screening strategy in our 950 bed tertiary care hospital from 2008 – 2014. Room and ward contacts of MRSA index patients present at time of MRSA identification were screened. We compared characteristics of Staphylococcus aureus Protein A (spa)-type matched contact patients (cases) to negative or spa-type mismatched contact patients (controls).
Among 270,000 inpatients from 2008 – 2014, 215 MRSA screenings yielded 3013 contact patients, and 6 (0.2%) spa-type matched pairs. We included 225 controls for the nested case-control study. The contact type for the cases was more frequently “same room” and less frequently “same ward” compared with the controls (P = 0.001). Also, exposure time was longer for cases (median of 6 days [IQR 3–9]) than for controls (1 day [0–3], P=0.016).
The extensive MRSA screening strategy revealed only few index/contact matches based on spa-typing. Prolonged exposure time and a shared room were significantly associated with MRSA transmission. A targeted screening strategy may be more useful in a low prevalence setting than screening entire wards.
Detection of meticillin-resistant Staphylococcus aureus and carbapenemase-producing Enterobacteriaceae in Danish emergency departments – evaluation of national screening guidelines
2020, Journal of Hospital Infection
Multi-resistant bacteria (MRB) are an emerging problem. Early identification of patients colonized with MRB is mandatory to avoid in-hospital transmission and to target antibiotic treatment. Since most patients pass through specialized emergency departments (EDs), these departments are crucial in early identification. The Danish National Board of Health (DNBH) has developed exposure-based targeted screening tools to identify and isolate carriers of meticillin-resistant Staphylococcus aureus (MRSA) and carbapenemase-producing Enterobacteriaceae (CPE).
To assess the national screening tools for detection of MRSA and CPE carriage in a cohort of acute patients. The objectives were to investigate: (i) if the colonized patients were detected; and (ii) if the colonized patients were isolated.
This was a multi-centre cross-sectional survey of adults visiting EDs. The patients answered the DNBH questions, and swabs were taken from the nose, throat and rectum. The collected samples were examined for MRSA and CPE. Screening performances were calculated.
Of the 5117 included patients, 16 were colonized with MRSA and four were colonized with CPE. The MRSA screening tool had sensitivity of 50% [95% confidence interval (CI) 25–75%] for carrier detection and 25% (95% CI 7–52%) for carrier isolation. The CPE screening tool had sensitivity of 25% (95% CI 1–81%) and none of the CPE carriers were isolated.
The national screening tools were of limited use as the majority of MRSA and CPE carriers passed unidentified through the EDs, and many patients were isolated unnecessarily.
Implications of targeted versus universal admission screening for meticillin-resistant Staphylococcus aureus carriage in a London hospital
2014, Journal of Hospital Infection
Citation Excerpt :
The Department of Health in England introduced universal screening of patients at hospital admission for MRSA carriage (‘MRSA admission screening’) in 2010, which replaced the previous policy of targeted screening based on risk factors.2,3 Recent UK studies showing a lower rate of MRSA at admission than when the policy was first introduced have brought the cost-effectiveness of the national universal screening policy into question.3–8 Another change in the epidemiology of MRSA in the UK has been the emergence of community-associated MRSA (CA-MRSA).9
Universal admission screening for meticillin-resistant Staphylococcus aureus (MRSA) has been performed in England since 2010. We evaluated the predictive performance of a regression model derived from the first year of universal screening for detecting MRSA at hospital admission. If we had used our previous targeted screening policy, 75% fewer patients (21,699 per year) would have been screened. However, this would have identified only ∼55% of all MRSA carriers, 65% of healthcare-associated MRSA strains, and 40% of community-associated strains. Failing to identify ∼45% of patients (262 per year) carrying MRSA at hospital admission may have implications for MRSA control.
Low prevalence of meticillin-resistant Staphylococcus aureus carriage at hospital admission: Implications for risk-factor-based vs universal screening
2013, Journal of Hospital Infection
Citation Excerpt :
However, no significant difference in the proportion of HA-MRSA and CA-MRSA strain types from patients with prior hospital admission or previous MRSA episodes was identified, reflecting the continuing breakdown of purely epidemiological definitions of CA-MRSA.9 The finding of a 2% overall rate of colonization is comparable with hospitals performing universal screening in England between 2006 and 200916 and Scotland in 2010.17 Rates from six Scottish hospitals performing universal screening in 2008–2009 were somewhat higher at 3.9%.15
There is debate over the optimal policy for detecting meticillin-resistant Staphylococcus aureus (MRSA) colonization at hospital admission. The emergence of community-associated (CA)-MRSA may compromise targeted screening strategies based on risk factors for healthcare-associated (HA)-MRSA.
To determine the prevalence of MRSA colonization at admission, and the genotype and molecular epidemiology of the strains involved.
A 12-month observational study was performed at a 1200-bed London tertiary referral hospital from 1 April 2008 to 1 March 2009. All available MRSA isolates were genotyped by spa and staphylococcal cassette chromosome mec (SCCmec) typing.
The overall MRSA colonization rate was 2.0% of 28,892 admissions (range 6.6% in critical care to 0.8% in obstetrics/gynaecology/neonatology). The overall frequency of previously unknown carriage of MRSA on admission was 1.4%. Most colonizing strains were epidemic HA-MRSA-15 and -16. However, heterogeneous CA strains accounted for 18% of recovered isolates, including 37.5% of MRSA from accident and emergency and 23.1% of MRSA from surgery. The CA-MRSA strain types had significantly different epidemiological associations from the HA-MRSA strains, so risk factors used for the identification of HA-MRSA may not detect CA-MRSA reliably.
The low rate of HA-MRSA in the UK increases the relative proportion due to CA-MRSA, for which conventional risk-factor-based screening strategies may be less effective. Cost–benefit analyses of universal MRSA admission screening will need to take account of this new epidemiology.
Development of a simple, low-density array to detect methicillin-resistant Staphylococcus aureus and mecA dropouts in nasal swabs
2012, Journal of Microbiological Methods
Citation Excerpt :
There is now significant interest in understanding how these molecular tests can contribute to infection control and surveillance programs worldwide. While the clinical value of universal versus targeted molecular screening is still debated (Collins et al., 2011; Garcia et al., 2011; Holmes and Williams, 2010; Hombach et al., 2010; Leonhardt et al., 2011; Witteck et al., 2011; Wolk et al., 2009), there is an increasing incidence of mecA dropouts (defined herein as S. aureus lacking a functional mecA gene but containing an SCCmec junction), diversity of SCCmec junction sequences, and incorrect assignment of coagulase-negative staphylococci (CoNS) as MRSA (false positives; e.g., (Bartels et al., 2009; Blanc et al., 2011; Farley et al., 2008; Laurent et al., 2010; Liu et al., 2010; Malhotra-Kumar et al., 2010; Pereira et al., 2011; Snyder et al., 2009; Stamper et al., 2011)). False-positive results may lead to several undesirable actions, such as (i) treatment with glycopeptide compounds instead of beta-lactam antibiotics, (ii) decolonization treatments, and (iii) isolation of patients or other constraining and expensive infection control measures.
Detection of methicillin-resistant Staphylococcus aureus (MRSA) is important for prevention and control of MRSA infections, but the discovery of mecA dropouts and SCCmec junction sequences with homology to coagulase-negative staphylococci (CoNS) has challenged several real-time PCR tests. The objective of this study was to develop a user-friendly, gel element microarray test for MRSA detection, to estimate the analytical performance characteristics of the test on bacterial isolates, and to perform an initial evaluation of the test on nasopharyngeal swabs from patients known to have a high prevalence of S. aureus containing mecA dropouts. The assay limit of detection for the test was 250 fg (or less) of genomic DNA per amplification reaction (approximately 80 cell equivalents) and MRSA was consistently detected at a ratio of 1:12,000 in a non-target background. Of 87 bacterial isolates, the test accurately classified 86 (98.8%) overall, and correctly identified 14 mecA dropout specimens that were falsely positive in the BD GeneOhm MRSA test or BD GeneOhm StaphSR test. A retrospective analysis of 246 nasal swab samples acquired from a high-risk patient population (overall prevalence = 10.8% by culture) resulted in 80.5% sensitivity (95% CI = 68.4%, 92.6%) and 96.6% specificity. Of these 246 samples, 174 (71%) were positive for mecA, 86 (35%) were positive for S. aureus tufA and 46 (19%) were positive for a SCCmec junction sequence. To estimate method repeatability, 48 samples representing the full range of phenotypes, genotypes and microarray probe SNR values were tested in triplicate, with three discordant results for a concordance rate of 97.9% (141/144 tests). These data demonstrate that a very simple microarray test can identify mecA dropouts with high specificity in either cultured isolates or nasal swabs from a high-prevalence, high-risk patient population. However, the clinical sensitivity of the test will likely depend on local microbial ecology and the prevalence of mecA positive CoNS in any given patient population.
Evaluation of chromogenic meticillin-resistant Staphylococcus aureus media: Sensitivity versus turnaround time
2012, Journal of Hospital Infection
Citation Excerpt :
Our results also demonstrate that incubation of chromogenic MRSA media for 42–48 h can improve further upon test sensitivity. Perry et al. described the development and evaluation of ChromID MRSA and reported that an overnight incubation period of 22–24 h resulted in the recovery of 89.9% of the total MRSA isolates identified after 48 h.11 We note that in a recent publication the same group again reported their results using ChromID MRSA following culture for ‘a minimum of 20 hours’, with sample turnaround times of 21–22 h, indicating that extended incubation was not used.19 In the media comparison part of the present study, the sensitivity of ChromID MRSA was 73% after 24 h, rising to 93.2% after 48 h. Cherkaoui et al. also reported a low sensitivity (76%) for this medium after incubation for 24 h, which increased to 90% after 48 h.9 Athanasopoulos et al. reported a higher sensitivity of 85% after 24 h incubation but again observed an increase in sensitivity to 92% after 48 h; similarly Malhotra et al. reported a sensitivity of 82.8% at 24 h rising to 93.5% with prolonged incubation.15,20
Chromogenic media offer the potential for improved detection of meticillin-resistant Staphylococcus aureus (MRSA). Incubation times in a clinical setting vary, generally between 16 and 48 h.
To investigate the effects of incubation time on the performance of commercial chromogenic MRSA media.
We initially compared the early recovery of MRSA isolates from routine screening swabs following 16–23 h to that after 22–24 h of incubation using ChromID MRSA (bioMérieux). We also compared ChromID MRSA, ChromID MRSA V2 (bioMérieux), Brilliance MRSA 2 Agar (Oxoid) and Colorex MRSA (E&O Laboratories Ltd) as selective media for 6035 MRSA screening swabs.
Only 303 of 623 (48.6%) MRSA isolates detected by this medium after 48 h were recovered after 16–23 h compared with 726 of 1018 (71.3%) isolates after 22–24 h. Following implementation of the 22–24 h incubation period, 50 (4.4%) isolates exhibiting a positive chromogenic reaction gave conflicting coagulase latex and DNase results. In 88% of these cases, DNase gave the correct result of non-MRSA. ChromID MRSA demonstrated the highest sensitivity overall at 93.2%, followed by Colorex MRSA Agar (87.1%), ChromID V2 (83.7%) and Brilliance Agar (78.2%). All media exhibited specificities of >99.7%.
Early detection of MRSA using ChromID MRSA is best achieved after incubation for 22–24 h. Latex agglutination coagulase tests alone should not be relied upon for identification of MRSA isolates from this medium. Although ChromID MRSA was deemed the superior medium in terms of MRSA recovery, the disadvantages of increased turnaround time (48 vs 24 h) must be considered.

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Review of a three-year meticillin-resistant Staphylococcus aureus screening programme

Summary

Introduction

Section snippets

Methods

Efficacy and cost-effectiveness of the universal screening and targeted approach

Discussion

Acknowledgements

Int J Antimicrobiol Agent

Clin Microbiol Infect

Clin Microbiol Infect

J Hosp Infect

J Hosp Infect

J Hosp Infect

Am J Infect Control

Lancet Infect Dis

J Hosp Infect

J Hosp Infect

Hospital policies and practices on prevention and treatment of infections caused by methicillin-resistant by Staphylococcus aureus

Am J Health Syst Pharm

Rapid detection of methicillin-resistant Staphylococcus aureus directly from clinical samples: methods, effectiveness and cost considerations

Ger Med Sci

Targeted MRSA surveillance and its potential use to guide empiric antibiotic therapy

Antimicrob Agents Chemother

5 years of experience implementing a methicillin-resistant Staphylococcus aureus search and destroy policy at the largest university medical center in the Netherlands

Infect Control Hosp Epidemiol

Impact of routine intensive care unit surveillance cultures and resultant barrier precautions on hospital-wide methicillin-resistant Staphylococcus bacteraemia

Clin Infect Dis

Effects of selective patient screening for MRSA on overall MRSA hospital-acquired infection rates

Crit Care Nurs Q

Saving lives. A delivery programme to reduce healthcare associated infection including MRSA