Dear Editor,

In 2012 five patients of an 18 bed ICU whose rectal swabs were negative on admission turned positive for VRE in routine surveillance cultures over the same 2 week period during their prolonged ICU stay. The colonization outbreak investigation (Table 1) revealed a reusable transport ventilator breathing circuit as presumed vector, similar to a previously described case for transmission of an ESBL Klebsiella oxytoca [1].

Table 1 Summary of the colonization outbreak investigation
Full size table

Because the manufacturer and current German guidelines [2] allow use of the breathing circuits for up to 7 days when bacterial filters are in use, we tested the effectiveness of surface disinfection measures to reduce the transmission potential of the outside surface.

A single use and a multiple use breathing circuit for the Dräger Oxylog 2000® transport ventilator (Dräger AG; Lübeck, Germany) were wiped with fluorescent solution and disinfected with a commercially available disinfectant cloth to visually assess the surface coverage and decontamination. In addition, three representative surface spots were contaminated with 100 μL of a standardized sheep blood/Enterococcus faecium solution (containing 1.1 × 109 CFU E. faecium ATCC 6057). 24 h after contamination the breathing circuits were wiped down with commercially available disinfectant cloths (Schülke mikrozid AF®, Schülke & Mayr GmbH; Norderstedt, Germany) and the contaminated spots sampled with moist swabs. Reduction of CFU was measured in log units.

A single wipe disinfection process resulted in a coverage/decontamination of more than 95 % of the surface area of the breathing circuit by visual estimate. Measurements showed reduction of contaminated E. faecium by seven log units on the circuit surface and patient adapter (no difference between single and multiple use), 4.4 log units (single use) and 3.9 log units (multiple use) on the processing unit connector.

Breathing circuits have large surface areas with direct patient contact (when laying in the patient's bed) and are frequently touched by health care workers. They are often not routinely disinfected or discarded after every patient use. A wipe disinfection of these breathing circuit surfaces seems to be feasible and effective, in a range recommended for items such as ECG wires, blood pressure cuffs, etc. [3]. “Hidden” contact surfaces (other examples include ultrasound units, mobile ECG carts etc.) might contribute to the spread of VRE, especially if handling is not associated with a mandatory hand disinfection (such as carrying the transport ventilator to a room to help a colleague without directly touching the patient); thus, surface disinfection after use becomes essential.

Multiple-use circuits seem to be easier to treat with wipe disinfection because of the larger and more flexible rifles. The disinfectants used for wiping and the validated reprocessing cycle of those multiple use circuits need to be checked for compatibility.

Hübner et al. [4] describe relevant outer surface contamination of the breathing circuit and the breathing bag of anesthesia machines with staphylococcus aureus, Escherichia coli and klebsiella pneumoniae, which confirms our observation.

We therefore recommend either discarding these breathing circuits after each patient, or at least performing a thorough wipe disinfection of the outer surfaces before reuse.