October 10, 2014

PHILADELPHIA —Acinetobacter baumannii was not only present in the air of infected patients, but was also more frequent among those rectally colonized, according to data presented at IDWeek 2014.

“We wanted to see how long A. baumannii can be in the air for patients who are colonized with it, so we relied on sedimentation to sample the air,” Luis Shimose, MD, of the Jackson Memorial Hospital in Miami, told Infectious Disease News. “We found that these patients who are colonized in the rectum had a higher degree of air contamination with A. baumannii, and that when we did [polymerase chain reaction], the A. baumannii in the air was identical to the one from the patients.”

Luis Shimose, MD, of the Jackson Memorial Hospital in Miami, and colleagues identified 30 patients with A. baumannii (57% respiratory, 17% rectal, 27% other) across seven adult ICUs. Open blood agar plates were exchanged daily for 10 consecutive days in infected patients’ rooms, with control plates collected from adjacent rooms belonging to uninfected patients. Presence of A. baumannii in incubated plates was determined based on colony color, morphology and final identification by Vitek II (bioMerieux, Inc.).

Researchers reported A. baumannii was present in the air of infected patients for a mean proportion of 0.21 days (95% CI, 0.14-0.29). Among rectally colonized patients, researchers found a mean proportion of 0.26 (95% CI, 0.15-0.44), compared with 0.11 among patients with respiratory colonization (95% CI, 0.07-0.16) and 0.14 among patients with other areas of colonization (95% CI, 0.08-0.26). Rooms adjacent to the infected patients recordedA. baumannii in the air a mean proportion of 0.11 days (95% CI, 0.07-0.18).

There were six cases where both patient and air A. baumannii isolates were available; four matching isolates shared more than 95% similarity, however none of the air isolates from the neighboring rooms were closely related with those of the patient, according to researchers.

“When we did PCR, those A. baumannii that were contaminating the air next-door to the patient did not match. It wasn’t the same strain, so we cannot say that it is expanding,” Shimose said. “We only have proven that the A. baumannii is in the air; we cannot prove anything else from our study yet, so there is more research to be done.”

While it is premature to say that airborne A. baumannii is directly spreading from the infected patients, Shimose said ICUs should still be cautious when placing uninfected patients nearby until more information is available. — by Dave Muoio

For more information:

Shimose L. Abstract 336. Presented at: IDWeek 2014; Oct. 8-12, 2014; Philadelphia.

Disclosure: The researchers report no relevant financial disclosures.