We have shown how the anatomic source of colonization impacts air contamination with carbapenem-resistant Acinetobacter baumannii (CRAB) using settle plates. Nonetheless, this method did not allow us to obtain colony counts and might not have had enough sensitivity for patients with low “bacterial loads”. Now we aimed to compare the yields between settle plates and an air impactor.
This project occurred in a large teaching hospital in Miami, FL in 2 adult ICUs. Settle plates consisted of leaving open blood agar plates (2-ft from roof) exchanged daily. Upon collection, plates were swabbed with sterile Q-tips, inoculated on TSB, incubated overnight, and then plated on MaConkey.
The second method was performed using an impactor (AirTrace® Environmental Sampler) which accommodates 150 mm blood agar plates, which spins 360° in 2 hour period. We used 3 plates consecutively for a total of 6hrs/day. Subsequently, plates were incubated overnight. Selected colonies were streaked on MacConkey.
AB was determined based on colony color, morphology; final identification with Vitek II. Carbapenem susceptibility was checked with meropenem disks, and results interpreted based on CLSI criteria.
During this 4-month surveillance, 4 CRAB pts were followed. Pts 1 & 2 were located in an open layout ICU, while pts 3 & 4 were in a close ICU. With regards to the settle plate method, 22 plates were obtained from all 4 pts. Of those, 5 (22.7%) were CRAB+. The impactor concomitantly tested 87 plates across all 4 patients. Of those, 34 (39%) were CRAB+.
The number of CFUs/positive plate detected by impactor was as follows: Patient 1, ranged from 2 to 135, median of 16; with the highest amount of CFU obtained with bed linens change. Patient 2, from 1-86, median of 28; with the highest amount of CFU obtained with physical therapy. Patient 3, from 2-9, median of 4; with highest CFU obtained with colostomy bag change. Patient 4, from 1-7, median of 2; with highest CFU obtained when repositioning the pt. The percentage of agreement between both methods was 12.5, 11 and 33 for patient 1, 2 & 3 respectively.
The impactor is superior for detecting air contamination with CRAB when compare to settle plates. Air contamination also seems to be higher when activities occurred around the pts (e.g. linens change, etc).
A. Berbel Caban, None
D. Depascale, None
T. Cleary, None
L. S. Munoz-Price, None