A new study by Chinese researchers suggests a highly resistant, healthcare-associated bacterial pathogen could be transmitted through the air.

In the study, published yesterday in the American Journal of Infection Control, researchers from Sichuan University investigated the extent of air contamination with carbapenem-resistant Acinetobacter baumannii (CRAB) in an intensive care unit (ICU) at West China Hospital. CRAB is a multidrug-resistant pathogen that tends to infect severely ill hospital patients, and is known to spread in ICUs through contact with contaminated high-touch surfaces and shared medical devices. 

The study authors note that while CRAB air contamination has been detected in previous studies or infected or colonized patients, airborne transmission has not been documented.

A challenge for infection prevention and control

On February 26, 2025, the researchers collected air samples from five rooms in the ICU that had at least one patient who had CRAB recovered from a clinical specimen or screening swab, along with nasal or rectal swabs. Whole-genome sequencing (WGS) was used to analyze CRAB colonies recovered from 13 of 88 (10%) of air samples and nine swab samples. All the CRAB colonies from air samples were collected from multipatient rooms

WGS revealed two sequence types (STs) of CRAB among air and patient samples: ST2, a well-known high-risk lineage, and ST164, an emerging high-risk lineage. Further analysis showed four of nine ST2 isolates were associated with transmission within rooms or between rooms, while all of the ST164 isolates belonged to a common clone and were found in two rooms.

The researchers suggest that daily activities conducted for ICU patients—including mechanical ventilation, endotracheal suctioning, diaper changing, and bed making—could facilitate the air dispersal of CRAB. While multicenter studies are needed to demonstrate that air transmission is a common problem, they say air contamination poses serious challenges for infection prevention and control.

"The route through the air may represent a yet-to-be-recognized, important mode of CRAB spread in ICUs. Without addressing such a route, infection control of CRAB transmission in healthcare settings could be compromised in effectiveness and even fail," they wrote.

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