Evaluation of the bactericidal efficacy of three different alcohol hand rubs against 57 clinical isolates of S. aureus

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Summary

We tested the efficacy of three alcohol hand rubs (AHRs) used in two local Welsh intensive therapy units (ITUs) against Staphylococcus aureus. The test protocol was based on a carrier test and parameters (concentration, contact time) were chosen following observation of hand-sanitising practices in the ITUs. Following AHR exposure, surviving bacteria were enumerated using a standard plate count method plus a Bioscreen C Microbial Growth Analyser. The AHRs demonstrated variable efficacy against the clinical isolates: the mean log10 reduction after 10 s exposure to Soft Care Med H5, Cutan and Guest Medical AHRs was 2.67, 0.696 and 1.96, respectively, and after 30 s exposure was 4.58, 1.74 and 3.60, respectively. Since the average time taken by healthcare workers (HCWs) to rub AHR onto their hands was 11 s and 15 s at the two hospitals, the efficacy of these AHRs may be significantly limited against the S. aureus isolates under the conditions observed in practice. In addition, differences observed in log10 reduction in bacterial number post-exposure using the Bioscreen compared to the plate count method provided evidence that S. aureus may be able to recover following Guest Medical AHR treatment within 2 min exposure, whereas after 5 min exposure bacterial damage caused by the AHR was irreversible. Although the introduction of AHRs improved hand hygiene compliance among HCWs, our observations highlighted that contact time is an important factor to ensure the efficacy of these products.

Introduction

Staphylococcus aureus causes significant morbidity and mortality in hospital intensive therapy units (ITUs).1 The most common mode of transmission of micro-organisms in the healthcare environment is via the hands of healthcare workers (HCWs).2, 3

Alcohol hand rubs (AHRs) were introduced in the healthcare environment as an alternative to hand washing for use when hands are physically clean. Their introduction resulted in much higher compliance rates and this has led to a reduction in infection rates.4, 5 There are many AHRs commercially available, each with a different formulation. Although these products all claim to kill a number of pathogenic micro-organisms, different efficacy test protocols are being used by manufacturers. These include methods such as EN1500, and EN12054 and EN1276, which measure efficacy against a small number of standard bacterial strains in suspension.6, 7, 8 For safety and ethical reasons, pathogenic micro-organisms cannot be tested on volunteers with EN1500, and suspension tests in particular may not be appropriate to measure the activity of such products since micro-organisms on skin are more difficult to kill than planktonic ones.9

As part of a surveillance programme for the effectiveness of hand disinfection measures in Welsh ITUs against meticillin-resistant Staphylococcus aureus (MRSA), the efficacy of three AHRs used in local ITUs was investigated using a common carrier test protocol. Parameters used in the methodology were based on observation of ITU staff to ensure that conditions in practice were reflected.

Section snippets

Bacterial strains

Fifty-seven S. aureus isolates from positive blood cultures of clinically infected ITU patients between 2004 and 2006 were provided by two hospitals in Wales. Thirty-one isolates were MRSA and 26 meticillin-sensitive S. aureus (MSSA). S. aureus NCIMB 9518 was also used. Freezer stocks were stored at −80 °C and subcultured to working slopes, from which Tryptone soya agar slopes (TSA; Oxoid, Basingstoke, UK) were prepared for testing. Suspensions were prepared by washing the TSA slope

Observation of hand-sanitising practices in ITU

A summary of hand-sanitising observations is shown in Table I. One of the most important findings was the exposure time of the AHRs on hands, which was ≤15 s in both hospitals. However, it was observed that the majority of staff applied AHRs to the required areas of hands as stated in the hospital hand hygiene guidelines. These observations highlighted the importance of measuring the efficacy of AHRs using a short exposure time.

The volume of AHR delivered on the hand after the application of one

Discussion

The overall compliance in hand hygiene observed was high in hospital A and low in hospital B (Table I) when compared with other findings.11 Of great importance is the short exposure time observed for AHRs to be applied to the hands of HCWs and the variability in their application (Table I). The volume of AHR was found to be low compared with manufacturer's recommendation. The volume of AHR delivered on hand after the application of one pump varied between the different products as well as the

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