While it is possible to acquire A. baumannii infections outside of hospital (in the community), it is healthcare settings where they are most problematic and pose a significant risk, particularly to patients who are in intensive care, chronically ill, or have cancer. These bacteria have the ability to adhere to the surfaces of objects and people, including catheters, ventilators and sutures, and form biofilms (a sticky matrix/community of bacteria on surfaces) that are incredibly resilient and difficult to kill.  

Some drug-resistant A. baumannii can colonize patients and live on their skin or other parts of the body. This ability aids person-to-person transmission, because patients can shed the bacteria and pass it on to others even if they do not show any symptoms themselves.

A. baumannii infections first started to become common in the 1960s and 1970s with the advent of more complex intensive care. But it wasn’t until the 1990s, when it emerged as a common cause of infection among injured soldiers during desert conflicts in Iraq, that it became a global concern. The dry, sandy conditions, combined with the challenges of achieving good infection prevention and control during a conflict, provided ideal conditions for these bacteria to infect open wounds and for antibiotic resistance to develop and then spread.

The high incidence of US troops returning home with multiple serious injuries infected by multidrug-resistant bacteria quickly earned this superbug the nickname “Iraqibacter”. Today, while multidrug-resistant A. baumannii infections continue to emerge in conflict zones, such as in Ukraine and Gaza, it has also become entrenched in hospital settings infecting vulnerable patients in countries all over the world. All this makes A. baumannii very difficult to eliminate.  

Like other types of Gram-negative bacteria, A. baumannii has a number of tricks up its sleeve to develop resistance to antibiotics. Examples including producing enzymes that stop the drugs from binding to their targets, and efflux pumps that literally pump antibiotics back out of the bacterial cell.  

Also the pore-like proteins on its outer membrane are considerably smaller compared to other Gram-negative bacteria, making it far less permeable and harder for antibiotics to enter. But what makes A. baumannii especially resilient and versatile is its ability to evolve drug resistance as well as acquire drug-resistant genes, not just from other A. baumannii bacterium but from other species of bacteria too.  

Carbapenem-resistant A. baumannii, or CRAB infections, are particularly problematic. With one million cases a year globally and a mortality rate of around 35%, these are resistant to almost all antibiotics, including broad-spectrum carbapenem drugs. This can make CRAB infections extremely challenging to treat and stop from spreading. CRAB infections have been known to cause large and deadly outbreaks in clinical settings, such as hospitals and nursing homes.