ORIGINAL RESEARCH

Blood pressure cuffs as a vector fortransmission of multi-resistant organisms:Colonisation rates and effects of disinfectionHarjeet Grewal,1 Kavita Varshney,1 Lee C Thomas,2 Jen Kok2,3 and Amith Shetty1

1Emergency Department, Westmead Hospital, Sydney, New South Wales, Australia, 2Centre forInfectious Diseases and Microbiology Laboratory Services, Institute of Clinical Pathology and MedicalResearch, Westmead Hospital, Sydney, New South Wales, Australia, and 3Sydney Institute for EmergingInfections and Biosecurity, Centre for Research Excellence in Critical Infections, University of Sydney,Sydney, New South Wales, Australia

Abstract

Objective: Blood pressure (BP) cuffs are potential vectors for transmission of multi-resistant organ-isms (MROs). The present study aims to determine MRO colonisation rates in BP cuffsfrom areas of high patient flow as an assessment of the quality of disinfection and infectioncontrol practices.

Methods: BP cuffs in the ED, high dependency unit (HDU) and operating theatres (OT) wereprospectively examined after routine disinfection procedures. Swabs collected from theinner and outer surfaces of BP cuffs during inter-patient intervals were plated onto repli-cate organism detection and counting, methicillin-resistant Staphylococcus aureus (MRSA)and vancomycin-resistant Enterococcus (VRE) chromogenic agar plates to detect rates ofbacterial, MRSA and VRE colonisation, respectively.

Results: High bacterial colonisation rates were detected in BP cuffs from all three areas. BP cuffsfrom OT were significantly less colonised compared with cuffs from HDU and ED; 76%versus 96% and 100% (P < 0.0001) for inner surfaces and 86% versus 98% and 100% (P <0.0001) for outer surfaces, respectively. Equivalent or higher bacterial growth was observedon the inner surface compared with outer surface in 54%, 84% and 86% of BP cuffs fromOT, HDU and ED, respectively. MRSA was detected in 3 of 150 (2%) swabs collected, butno VRE was detected.

Conclusion: Although MRSA and VRE were infrequently isolated, current disinfection and infectioncontrol protocols need to be improved given the greater recovery of organisms from theinner compared with outer surfaces of BP cuffs.

Key words: blood pressure cuffs, disinfection, methicillin-resistant Staphylococcus aureus, transmission,vancomycin-resistant Enterococcus.

Correspondence: Dr Amith Shetty, Emergency Department, Westmead Hospital, Westmead, Sydney, NSW 2145, Australia. Email:samit36@hotmail.com

Harjeet Grewal, MBBS, MS, Emergency Medicine Advanced Trainee; Kavita Varshney, MBBS, FACEM, Staff Specialist; Lee C Thomas, MSc,Senior Hospital Scientist; Jen Kok, MBBS, FRACP, FRCPA, Staff Specialist; Amith Shetty, MBBS, FACEM, Staff Specialist.

doi: 10.1111/1742-6723.12076Emergency Medicine Australasia (2013) 25, 222–226

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© 2013 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine

Introduction

Nosocomial infections occur frequently, resulting inincreased mortality rates while adding significant coststo the treatment of hospitalised patients.1 Healthcare-associated acquisition of multi-resistant organisms(MRO) including methicillin-resistant Staphylococcusaureus (MRSA) and vancomycin-resistant Enterococcus(VRE) has been associated with increased nosocomialinfections.2,3 Within the hospital environment, inani-mate objects including inadequately disinfected bloodpressure (BP) cuffs serve as reservoirs for MROs, result-ing in the transmission of MROs to patients.4–7 Reducingpotential reservoirs and acquisition of pathogens is thusa key measure in preventing nosocomial infections.

Although a direct correlation between BP cuff con-tamination rates and risks of MRO transmission cannotbe made, increased contamination of BP cuffs is likely toincrease the risk of nosocomial infections. Both patientsand health-care workers might be colonised with MROupon contact with inadequately disinfected BP cuffs,thus establishing a cycle for ongoing transmission ofMRO in the hospital environment. Previous studieshave also demonstrated that colonisation rates betweenthe inner and outer surfaces of BP cuffs are different,suggesting that the area of skin in contact with the BPcuff is important in determining the efficiency of colo-nisation and transmission.8

Our hospital’s infection control policy recommendsthat between patient use, BP cuffs are disinfected withTuffie Wipes® (Vernacare, Lancashire, UK), whichcontain the neutral detergent alkyl dimethyl benzylammonium chloride 0.5%.9 However, for patients colo-nised with MROs, the policy recommends that BP cuffsbe disinfected with polychlorophenoxyphenol contain-ing Triclosan® after each patient use.10,11 Few studieshave investigated the efficacy of these cleaningagents when applied in routine clinical use for BP cuffdisinfection.2,8,11

The present study aims to determine BP cuff coloni-sation rates in three hospital departments with differ-ent patient dynamics and adherence to disinfectionprocedures.

Methods

A prospective cohort study was conducted at WestmeadHospital, New South Wales, Australia, an adult tertiaryreferral hospital. Ethical approval from the Sydney

West Area Health Service Human Research Ethics Com-mittee as quality assurance audit study was gained.

We determined bacterial colonisation rates in 50 BPcuffs from three hospital areas with different patientpopulations and turnover of patients but similar proto-cols for disinfection procedures; ED with a higher rate ofturnover of patients (approximately 58 000 presenta-tions per annum), high dependency unit (HDU) withlower rates of patient turnover and operating theatre(OT), where there is a high turnover of patients butpotentially greater adherence to disinfection protocols.The intensive care unit was not studied as BP monitor-ing is not done using sphygmomanometers.

Bacterial growth on replicate organism detection andcounting (RODAC; Becton Dickinson, Sparks, MD,USA) plates collected after disinfection (measured ascolony-forming units [cfu]/25 cm2) was utilised to deter-mine the adequacy of the disinfection process. Bacterialswabs (Copan Italia Spa, Brescia, Italy) were also col-lected and plated onto MRSA and VRE chromogenicagar to determine MRSA and VRE colonisation rates,respectively. Two RODAC plates and four bacterialswabs were taken from each cuff (one plate and twoswabs from the inner [the surface in contact with theskin] and outer [the surface in contact with the health-care staff]) surfaces.8,12 BP cuffs of different materials(nylon or plastic) and types (manual, automatic, port-able or walled units) were randomly selected. A singleinvestigator collected all the specimens, and randomlysampled BP cuffs in each area to reduce sample bias. BPcuffs already in use on a patient were excluded. Staffworking in the three areas was not informed of thestudy in order to eliminate the Hawthorne effect.13

RODAC plates were incubated overnight at 37°C, andthe bacterial cfu were counted the following day. Fivelevels of growth were categorised: no growth, minimal(<10 cfu/25 cm2), mild (11–50 cfu/25 cm2), moderate (51–100 cfu/25 cm2) and severe (>100 cfu/25 cm2). Swabs ofBP cuffs (surface area measuring 25 cm2, correspondingto area of contact plate contact) were plated directlyonto MRSA (BrillianceTM MRSA, Basingstoke, Hants,UK) and VRE (ChromID VRE, bioMérieux, Marcyl’Etoile, France) chromogenic agar plates and placedinto enrichment broth. Following overnight incubationat 37°C, the presence of MRSA and/or VRE was deter-mined. If MRSA or VRE was not detected, enrichmentbroth fluid was plated onto chromogenic agar plates forenhanced detection of MRSA and/or VRE.

Colony counts from RODAC plates obtained fromthe inner and outer surfaces of BP cuffs, as well asthe growth of MRSA or VRE in the three areas of the

Blood pressure cuffs as transmission vectors

223© 2013 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine

hospital was compared. Data were analysed using SPSS

software, version 17 (IBM, Somers, NY, USA). Univari-ate analyses were performed using c2 (or Fisher’s exacttest, where number was small) or Wilcoxon rank-sumtest as appropriate. A two-sided P-value of <0.05 wasconsidered statistically significant.

Results

Bacterial colonisation rates on the inner and outer sur-faces of BP cuffs in OT were less compared with that ofthe ED and HDU (76% vs 100% and 100%, P < 0.01 and86% vs 100% and 98%, P < 0.01, respectively). Thecolonisation rates of the inner surface of cuffs was alsogreater compared with the outer surface in the ED, HDUand OT (Table 1).

The degree of bacterial colonisation of cuffs was alsohigher in the ED and HDU compared with OT. BP cuffsin ED were more likely to be severely contaminated(>100 cfu/25 cm2) compared with OT. When no growthand minimal growth counts were grouped together, sig-nificant differences were noted between BP cuffs; OT(75% [95% confidence interval [CI] 67–83%]), HDU(22% [95% CI 15–31%]) and ED (2% [95% CI 1–7%]).Most BP cuffs from OT had minimal growth or nogrowth. When cuffs with moderate and severe colonisa-tion rates were grouped together, the rate of colonisationof BP cuffs in ED, HDU and OT were 69% (95% CI59–77%), 54% (95% CI 44–63%) and 8% (95% CI4–15%), P < 0.01, respectively.

One cuff from ED and two cuffs from HDU isolatedMRSA on the outer surface. A single BP cuff from HDUisolated MRSA on the inner surface but VRE was notisolated on any cuff. Two cuffs from HDU isolated fungion the outer surface, but the identification of these werenot pursued.

DiscussionSecular trends highlight an increasing rate ofhealthcare-associated infections both nationally andinternationally, in particular those caused by organismsthat are readily transmissible including, but not limitedto, MRSA, VRE and Clostridium difficile.14,15 The inci-dence of healthcare-associated infections allows anassessment of the quality of infection control practice atan institution and also serves as a measure for qualityimprovement. Minimising the transmission of MROshould reduce the number of healthcare infections.Although fomites have been previously identified aspotential vectors for MRO transmission, there is limiteddata on the prevalence of colonisation rates and thequality of the disinfection process in different areas ofhospitals. In theory, a standardised protocol shouldresult in fairly uniform rates of disinfection regardlessof the area within an institution.

Our study herein identified that bacterial colonisationrates of BP cuffs were high in all three areas. BP cuffs inED and HDU had similar colonisation rates, whereascuffs from OT had significantly lower colonisationrates. These findings are similar to those reported by deGialluly et al.8 Although the disinfection process of BPcuffs should be similar in ED, HDU and OT, our resultssuggest that disinfection procedures are suboptimal inED and HDU. Furthermore, the inner surface wassubject to more rigorous disinfection given the lowercolonisation rates, which is fortuitous given that is itmore likely to be in direct contact with patients. Ourstudy also highlights that the disinfection process couldbe improved further in all three areas. Nevertheless,it was reassuring that MRO rates on BP cuffs werereasonably low given the acuity of the hospital andthe complexity of patients that are treated, whichpotentially have numerous risks factors for MROcolonisation.

Previous studies have also noted significant coloni-sation rates of BP cuffs,8 although the criterion forcolonisation is not standardised between the differentstudies. Some investigators have defined contaminatedcuffs using bacterial counts of >100 cfu/25 cm2 andhighly contaminated as >300 cfu/25 cm2, although spe-cific evidence for using such criterion is lacking.8 Stern-licht et al. defined a significant colonisation rate as>20 cfu/16 cm2 after swabbing the medial aspect of thearms of anaesthetists.16 The lack of standardisationacross the different studies makes them difficult todefine a significant level of contamination for inani-mate objects.

Table 1. Inner and outer surface colonisation rates of bloodpressure cuffs in the emergency department (ED), high depend-ency unit (HDU) and operating theatre (OT)

Source Number colonised % colonised 95% CI

Inner surfaceED 50 100 96–100HDU 48 96 91–100OT 38 76 64–88

Outer surfaceED 50 100 96–100HDU 49 98 94–100OT 43 86 76–96

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224 © 2013 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine

Disposable BP cuffs could be an effective approach toreduce BP cuff contamination but are expensive ($80–90per cuff).17 Other options include thermal disinfection ofsuitable cuffs as practiced by some OT ($6 per cuff),although not all BP cuffs are able to withstand the hightemperatures (up to 85°C) involved in the washing anddrying process. Turnaround times for the disinfection ofcuffs are also prolonged compared with current disin-fection procedures. Although disposable BP cuff covers($2–20 per cover) are cost-effective (particularly in areasof prolonged use such as HDU), there is limited evidenceon their efficacy in reducing transmission of MROs.18–20

Disposable cuffs and more aggressive disinfectionmight be suitable options in HDU where prolonged skinexposures and slow patient turnover make these optionsmore viable.

The aim of our study was to determine colonisationrates of BP cuffs ready for subsequent patient use andso no record of adherence to cleaning protocols weremade during the study. Although staff in the threestudied areas was not informed of the study, the reason-ably long study period of 4 months might have pre-sented an opportunity for staff members to improve thedisinfection process.

Although we reported the incidence of MRO (MRSAand VRE) on the cuffs, we did not further identify theindividual bacterial growth. The colonisation ratescould represent normal skin flora, or other potentiallypathogenic or innocuous bacteria. It was also notedduring the study that BP cuffs from OT underwentthermal disinfection at the end of the working day. Theeffect of such an intervention could not be gauged asswabs were not collected at the beginning of the day inall three areas. It is difficult to decipher if this interven-tion by itself resulted in significant change in colonisa-tion rates.

Conclusion

Although MRSA and VRE were infrequently isolated,current disinfection and infection control protocolsneed to be improved given the greater recovery oforganisms from the inner compared with outer surfaceof BP cuffs. Departments with high patient turnoverrates can achieve higher rates of adequate disinfec-tion by improving adherence to disinfection proto-cols. Randomised controlled studies to determine theoptimal disinfection method of BP cuffs should bepursued.

Acknowledgements

We thank Ms Karen Byth for statistical advice andanalysis of results.

Author contributions

Conception of study and study design: HG, KV, JK andAS; data collection, collation and analysis: HG; labora-tory testing: JK and LCT; preparation of manuscript:HG; review and critique of manuscript: AS and JK.

Competing interests

None declared.

Accepted 12 April 2013

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