The sink as a potential source of transmission of carbapenemase-producing Enterobacteriaceae in the intensive care unit

The prevalence of infections with multidrug resistant (MDR) GN bacteria such as CPE is increasing worldwide [9] and there is probably a wider range of environmental reservoirs for those bacteria compared with Gram positive MDR bacteria [10].

Both the results in the literature and in this work show that the sink is an ideal moist reservoir for (waterborne) GN bacteria to survive. The fact that fluids, often containing antibiotics, were flushed through the drains, promotes the selection of resistant bacterial strains. Despite the efforts made and the discontinuation of the outbreak with CPE on ICU A room six, even after replacing the complete sinks, we could find multiresistant Pseudomonas species and Stenotrophomonas maltophilia. Both bacteria can also colonize/infect patients and indeed, we noticed that some patients showed positive respiratory samples with those species after a few days of hospitalization on the ICU (data not shown). However, we didn’t do molecular characterization to prove this hypothesis.

Air sampling experiments taught us that the air above and the environment of the sink got contaminated with bacteria after tap water was running. Hands of health care workers can be contaminated via this way. This underlines the primordial importance of hand hygiene. A limitation of the study is that although we could pick-up bacteria in the air and the environment of the sink after water was running, we could not prove that these bacteria really came from the biofilm of the siphon and we were not able to pick up CPE in the air above the sink. This is possibly due to the limited time and availability of the siphons for the measurements in order to not disturb the critical ill patients in the room.

In the next years, a new ICU will be built in the UZ Brussels. A few propositions according to the architecture of the room and sinks can be made. First of all, it was considered not to place sinks in the rooms. Sinks were used to wash reusable medical devices before disinfection, as waste bins and as water suppliers for shaving men. Reprocessing of reusable medical devices should be centralized, shaving can be done by means of a separate wash basin and fluids have to be removed in special containers that provide easy transport to the utility room. Body fluids should not be flushed through the sink anymore. A second possibility is to build a room with two separate sinks. One sink should be rigorously restricted to hand washing. The sinks used for waste disposal should be systematically considered as potentially contaminated. In our ICUs, the distance between the sink and the patient’s bed is less than one meter. There are no guidelines about the minimum distance required and it depends also on the sink’s architecture, but as seen in literature, aerosols and splashes coming from the plughole of the sink can be propagated up to 1 m from the sink when the tap is turned on [11]. Therefore, we suggest that the distance between a sink and a patient’s bed should be at least two meter.

In our ICU, there are two types of taps. The taps in the isolation rooms are designed well with a distance between tap and inlet of 40 cm. In contrast, the taps in the standard rooms are not ergonomically designed: the distance between the tap and the inlet of the wash basin is too small (20 cm) which makes it possible to contaminate the tap when water is running. In the future, we will replace them. Moreover, in the sinks of the standard rooms, water from the tap is directed straight into the outlet, allowing splash-back from the sink’s drain trap.

A German company brought a self-disinfecting siphon on the market (MoveoSiphon ST24, MoveoMed, Dresden, Germany). That device prevents the formation of a biofilm in the sink by means of permanent physical disinfection, electromagnetic cleaning and antibacterial coating [12]. This siphon was tested during five months (July- November 2016) in the ICU A room 1 for the presence of GN bacteria. During that entire period, we could not pick up any GN bacteria (data not published). However; there still need to be investigated whether that siphon could really prevent nosocomial transmissions in our ICUs and whether this intervention will be cost-effective.