Vaporized Hydrogen Peroxide as Part of a Control Intervention during an Outbreak of Acinetobacter in an ICU

Background:

In December 2008, the rate of Acinetobacter baumanii (ACBA) infected or colonized patients in a six ICU tower increased by 80% from the rate observed in the preceding three months.  A review of cases demonstrated a dominant antibiogram.   Molecular strain typing, performed on a subset of isolates, confirmed the presence of two epidemic strains from this cohort.  Although geographic clustering and time in the hospital supported that nosocomial acquisition was highly likely for most patients, some patients referred from outside institutions shared this strain.   

An intervention consisting of amplified Contact Precautions, patient and personnel cohorting, environmental cleaning with bleach, education for workers and vaporized hydrogen peroxide (VHP) was instituted.

Objective: To determine the effectiveness of vaporized hydrogen peroxide to reduce bacterial contamination above the effect seen by bleach based environmental cleaning

Methods:

13 rooms of ACBA case patients in 4 ICUs had bleach based cleaning performed before any environmental cultures were obtained. VHP was used as a final disinfectant for these same rooms.

96 cultures were obtained from the immediate room environment. Additionally, 69 cultures from shared nursing equipment from two ICUs and shared respiratory therapy devices (e.g. oxygen meters and pulse oximeters) were obtained. Isolates were reported as ACBA or other gram negative organisms.

Results:

Of 56 cultures obtained from ICU rooms before VHP, 25 (45%) were positive for microorganisms; 13 (23%) grew gram-negative rods and two (4%) were positive for ACBA.  Of 40 cultures obtained after VHP 2 (5%) were positive; none with gram-negative organisms.  The relative risk (RR) of positive culture following VHP in rooms was 0.11; CI=0.03 – 0.45; p = .00002.

Of 39 cultures obtained from the shared equipment before VHP, 15 (38%) were positive; 3 (7%) grew gram negative rods and 1 (3%) from a pulse oximeter grew ACBA.  Of 30 cultures obtained after VHP, 3 were positive; none with gram-negatives.   RR of positive cultures from shared equipment following VHP was .26; CI = 0.08 – 0.82; p = .008.

The ACBA infection rate of 3.7 cases per 1000 ICU days at  baseline and 6.6 cases during the epidemic resolved to a sustained 1.7cases in the following 8 months.

Conclusions: VHP was effective in decreasing bacterial burden from ICU rooms and equipment.   The rate of infection and colonization in this setting improved to pre- baseline rates following the use of a comprehensive bundle of interventions including VHP.  The relative contribution of VHP could not be measured from this review, but may have played a beneficial role. Many items in the ICU setting have intricate mechanical structures, rendering them difficult to clean by usual methods. Other items are not appropriate for bleach cleaning, making VHP an attractive, albeit expensive alternative.