Editorials
Ageing Infectious diseases
Volume 195 - Issue 9

Multiresistant Escherichia coli in aged care: the gathering storm

Authors:  Timothy J J Inglis and Christopher D Beer

Med J Aust 2011; 195 (9): 489-490. || doi: 10.5694/mja11.11202
Published online: 7 November 2011
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The growing infection control challenges facing an ageing population

In this issue of the Journal, a study of multiresistant bacterial intestinal carriage by Stuart and colleagues adds important detail to the emerging picture of multiple antibiotic resistance in non-hospital settings.1 The higher colonisation rate they found for Escherichia coli than for vancomycin-resistant enterococci (VRE) or Clostridium difficile in residential aged care facilities is a timely reminder that our surveillance and infection control resources should not be exclusively targeted at VRE or C. difficile. The simultaneous presence of these potential pathogens in the same aged care population raises the ugly spectre of carriage of two or more resistant organisms. The risk of contemporaneous multiresistant E. coli, C. difficile-associated diarrhoea and faecal incontinence might be considered the perfect infection control storm.

As Stuart and colleagues rightly point out, data are lacking on the prevalence of community-acquired multiresistant gram-negative bacteria in Australia. By extrapolation from northern hemisphere studies, it appears that nursing homes and other long-term care facilities can function as potent reservoirs of multiresistant E. coli.2 Measuring the duration of enteric carriage after initial colonisation by a multiresistant strain may help determine the potential window for onward transmission, but we can anticipate variable and possibly strain-dependent transmissibility. The relatively small size of Stuart et al’s study, the presence of a single-strain case cluster and other specific features make it difficult to generalise from their results. However, observation of a dominant genotype of multiresistant E. coli in one aged care facility concords with a previous observation of single genotype clusters in long-term care facilities.3

The observed dominance of CTX-M (cefotaxime-hydrolysing) β-lactamase-mediated resistance is also consistent with the wider international trend, as noted in a recent nationwide study from Belgium.4 The mechanism of antibiotic resistance designated CTX-M-15 has been particularly successful on a global scale — the result of carriage of resistance-determining genes on multireplicon plasmids, combined with international travel.5 CTX-M-15 has become a prominent multiresistance determinant detected in the faeces of international travellers, particularly those returning from the Indian subcontinent or Africa.6 The route followed by multiresistant gram-negative bacteria brought to Australia by healthy, young international travellers to reach the residents of aged care facilities is unclear. But once aged care residents are colonised, Stuart et al’s data suggest spread of resistance among them, possibly assisted by transmissible bacterial genetic elements.1,3 In a survey of resistant E. coli in western Sydney, where CTX-M-15 predominates, 11 different conjugative plasmids were found, most of which had multiresistance regions.7

The challenges of aged care are many and will continue to grow as the number of people in need of residential care expands. There are many potential contributors to the emergence of multiresistant bacteria in residents of aged care facilities: multiple hospital admissions, excessive use of antibiotics (in terms of courses, duration and antimicrobial spectrum), incontinence, dementia, venous stasis ulcers, and difficulty implementing infection control practices in institutions where residents are free to move outside their rooms and mingle with others.

Well established multiresistant bacteria such as community-acquired methicillin-resistant Staphylococcus aureus (MRSA) pose a significant problem in some aged care facilities and other long-term care units. Our failure to hold the MRSA threat at bay, even with the most stringent measures, should make us wary of trying to apply failed control strategies to a group of bacteria with a substantially different ecology. The “search-and-destroy” approach to infection control, with its heavy reliance on screening swabs and decolonisation, risks interfering with movement of aged care facility residents to and from hospital (when admission or discharge depends on documented screening status or completion of decolonisation) for little, if any, demonstrable benefit. The value of alternative approaches is also uncertain. To date, attempts to control intestinal carriage of multiresistant E. coli in long-term care residents using probiotic E. coli have been unsuccessful.8 This indicates the durability of multiresistant E. coli as a gastrointestinal coloniser.

A control method for multiresistant bacteria that relies on surveillance and targeted infection control measures may seem appealing, but in reality is likely to be costly, impractical and ineffective. An alternative strategy9 is to use multiple measures targeting improvements in the skilled nursing care of those at identifiably higher risk of multiresistant bacterial infection, without prior surveillance culture. We recognise that this proposal will not sit comfortably with those who have long advocated a post-hoc, species-specific, search-and-destroy approach to organisms of interest. But with an estimated multimillion dollar annual cost of multiresistant bacteria control measures, and a residential aged care sector facing many challenges, we will be forced to explore all options. This should include considering a more public health-based approach, as long-term care facilities lie outside the remit of conventional hospital infection control.

These options cannot be properly debated without additional, nationally representative data addressing the key questions raised by Stuart and colleagues, particularly the duration of gastrointestinal colonisation, the relationship between colonisation and subsequent infection, and the consistency of epidemiological data across a wider range of residential aged care facilities. Their timely study highlights a need for informed discussion of new measures to control multiresistant gram-negative bacteria in long-term residential care facilities. This could include a gamut of aged care measures aimed at reducing transmission, such as decreasing long-term care facility–hospital transfers through the use of advance care planning10 and hospital-in-the-home treatment.

Authors

  • Timothy J J Inglis DM, PhD, FRCPA1
  • Christopher D Beer MB BS, PhD, FRACP2
  • 1. Division of Microbiology and Infectious Diseases, PathWest Laboratory Medicine WA, Perth, WA.
  • 2. Western Australian Centre for Health and Ageing, University of Western Australia, Perth, WA.

Correspondence: tim.inglis@health.wa.gov.au

Competing interests

No relevant disclosures.

References

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