The debate over the use of standard precautions (SPs) versus contact precautions (CPs) for stopping the spread of multidrug-resistant organisms (MDROs) has been controversial for years [1,2,3,4,5] and still persists, despite recent high-quality cluster-randomized studies [6,7,8,9]. SPs are based on a universal (also called “horizontal”) approach to all patients, whether or not they are known to be as MDRO carriers; SPs include compliance with hand hygiene and cleaning the environment. CPs with a so-called “vertical” approach still include compliance with SPs for all patients, additional control barriers for colonized patients, i.e. gloves and gown, and placement in a single room if possible. Identification of MDRO carriage through screening is frequently associated with CPs.

The introduction of alcoholic handrub (AHR) in the early 2000s has been a major step in improving compliance with hand hygiene in healthcare settings. Many studies have demonstrated that including AHR in a multifaceted strategy, based on education, observation and feedback, and other bundled measures, is necessary for effective AHR implementation. Since CPs and SPs both aim to interrupt transmission, SPs now including AHR (as compared to handwashing) show higher efficacy, likely closer to that of CPs, thus fueling the debate between CPs and SPs.

The epidemiology of MDROs is rapidly changing. MDROs comprise methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum betalactamase-producing enterobacteriacae (ESBL-PE), vancomycin-resistant enterococci (VRE), carbapenemase-producing enterobacteriacae (CPE), and carbapenemase-producing Gram negative bacilli, Pseudomonas aeruginosa and carbapenem-resistant Acinetobacter baumannii (CRAB). In some countries, in the late 2010s, the latter, i.e. CPE, carbapenemase-producing Gram-negative bacilli, and VRE, were classified as extensively resistant.

In ICUs facing multiple endemic MDROs, placing a large proportion of patients to CPs may result in lower compliance for interrupting cross-transmission from each of these patients [10]. Priorities must be defined in order to select the most dangerous MDROs, in terms of the individual consequences of infection and the collective risk of dissemination, and thus the appropriate infection control practices can be selected.

This complexification of epidemiology and control measures, together with legal mandates issued in several countries, may have the effect of obscuring the central question relating to efforts to control the spread of MDROs: what is the most effective method of interrupting MDRO cross-transmission? Hospital epidemiologists are often faced with difficult choices, given that CPs have some benefits from the perspective of preventing the transmission of many MDROs, and the subsequent infections, but also have negative effects in terms of cost, environmental waste and healthcare worker dissatisfaction.

Many factors contribute to the mechanism of MDRO dissemination in the ICU, and these should be taken into consideration when designing a policy (Table 1). Some are of key importance:

Table 1 Circumstances in which standard or contact precautions are likely to be effective
Full size table

  • The particular MDRO in question and its local/regional and national epidemiology. Several MDROs can be more easily transmitted suggesting that CPs might be more appropriate for these bacteria: for example, non-E. coli ESBL as compared with ESBL E. coli [4, 11], or ESBL-PE (taken globally) as compared with MRSA [8]. Others may spread rapidly, e.g. VRE and CRAB, partially owing to their environmental reservoir; such organisms therefore require enhanced environmental cleaning.

  • National policies, strictly enforced by all health care facilities (HCFs), have resulted in several success stories relating to the control of MDROs, such as CPE in Israel [12], and MRSA in Northern European countries and, recently, in the UK and France as well [13]. Statistical modeling and regional surveillance of VRE and CPE showed that some HCFs may be hotspots for acquisition with subsequent dissemination in many other facilities, thus demonstrating the role that might be played by a policy enforced in all HCFs [14]; many of these national policies involved the use of active surveillance and CPs in their control measures.

  • This is especially true at the beginning of an epidemic, when extensive active surveillance of cultures and strict control measures including CPs have the highest chance of being effective. In contrast, an endemic situation with high prevalence at ICU admission can only be curtailed, and SPs may be preferred in this situation. Ideally, any strategy implemented should be evaluated, by performing admission and discharge screening.

  • Actually, compliance with hand hygiene in the context of SPs and CPs is lower than that measured through auditing, due to a Hawthorne effect [15]. The first objective in low compliance/low AHR consumption ICUs should be to improve hand hygiene practice, before implementing CPs.

  • Resources are critical for effective implementation of any precaution, including the availability of a single room for implementation of CPs. In ICUs in developing countries, it may be decided first to improve compliance with hand hygiene, while reserving CPs for the most aggressive MDROs.

As regards to Table 1 parameters to be considered before deciding a control strategy, we suggest that each ICU could implement its own policy, tailored to local epidemiology and resources. Leadership and effective implementation of recommended measures are crucial for success. For example, two multicenter ICU studies focusing on efforts to control MRSA were published simultaneously in 2011 [6, 7]. Both studies used essentially the same control measures, and both had methodological issues, yet their impact, in terms of controlling MDRO, differed. The successful intervention was conducted using a behavioral approach, with performance feedback and resolution of local challenges, in addition to technical measures consisting of screening and CPs. This illustrates the importance both of leadership and of involving health care workers (HCWs) in conducting such interventions.

CPs and SPs do not include measures for cleaning the environment. There is growing evidence that both dry surfaces and humid areas may be reservoirs of MDROs. This has long been demostrated for VRE and CRAB, and to a lesser extent for MRSA. Recent publications have shown that Multi-drug resistant Gram-negative bacteria (MDR-GNB), including CPE, may persist in humid reservoirs, responsible for outbreaks [16]. Any strategy, SPs or CPs, to control the spread of MDROs should include thorough environmental cleaning.

Although MDRO epidemiology varies across ICUs, it is of critical importance to adhere to a regional and national strategy. That said, evaluation of the local situation may help efforts to select targeted MDROs against which CPs have the best chance of being effective, and identify other MDROs that might be better tackled with SPs, having taken into account a maximum number of patients to be placed to CPs for higher efficacy.

In this very complex field, there are good arguments on both sides, that support the use of either SPs or CPs for controlling the spread of MDROs [1, 17]. There is, however, some solid evidence. CPs should be enforced only if compliance with hand hygiene is high enough, e.g. > 40–50%, otherwise the first objective should be to improve it. Conversely, implementing CPs may be futile in the presence of already very high compliance with hand hygiene. Moreover, given its potential drawbacks, the use of CPs is probably less appropriate for endemic situations. Local resources should be devoted to the most cost-effective measures, based on local epidemiology, whilst respecting national guidelines.