*Acinetobacter baumannii (A. baumannii)* is a pathogenic bacterial species that causes disease in humans. It is commonly found in soil and water. *A. baumannii* is the most important member of the Acinetobacter genus associated with infections gained in hospitals. A.*Baumannii is resistant* to a specific class of antibiotic called carbapenems. Carbapenems-resistant *Acinetobacter* infection is common in hospitals and is very dangerous. In 2017, it resulted in an estimated 8,500 infections in hospital patients and 700 deaths in the United States. The World Health Organisation (WHO) released a list of top bacteria pathogens of concern, called ESKAPE pathogens, due to their high levels of antibiotic resistance. *A. baumannii* was named as one of the most dangerous ESKAPE pathogens. In order to treat *A. baumannii* effectively, it is important to understand how it acts as pathogen and its mechanism of antibiotic resistance.

Biology
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*A. baumannii* are short and rod-shaped. They average between 1.0 and 1.5 micrometers in length. They do not all look the same and can vary in size and shape. *Acinetobacter* do not have a flagella, a tail-like structure used by many bacteria to move around. They are immobile but sometimes twitch and swarm to move around.

Habitat
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The first *Acinetobacter* was found in the soil by M.W. Beijerink in 1911. Since then, it has also been found in water, animals, and humans. *A. baumannii* are often found in hospitals and makeup almost 15% of infections that are transmitted in hospitals.  *A. baumannii* target moist environments. The respiratory tract, blood, open wounds, skin, and eyes are all possible sites of infection.

Hospital infections
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*A. baumannii* can cause many different diseases with different symptoms. Types of infection include pneumonia, bloodstream infections, meningitis, skin and bone infections and urinary tract infections. The most common infections are pneumonia and bloodstream infections. Factors that increase the risk of infection include a weak immune system, long hospital stays, hospital ventilators, and having an open wound.

It can be difficult to tell the difference between symptoms of *A. baumannii* infection and symptoms of other hospital infections. Symptoms include fever, rash, confusion, urinating pain, nausea, muscle and chest pains, breathing difficulties, and coughing.

*A. baumannii* is spread through contact with contaminated surfaces, objects, and skin of contaminated patients. It can survive on surfaces for a long time before infecting new patients making it an effective pathogen.

Treatment
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Carbapenems are a type of antibiotics that have been used to treat *Acinetobacter baumannii* infections. These antibiotics are effective in treating infection. However, *A. baumannii* can develop tolerance to this antibiotic. This tolerance makes it harder to treat infections. Carbapenems-resistant *A. baumannii* can spread their tolerance to other types of bacteria. This is dangerous in healthcare settings because if many bacteria are tolerant to carbapenems, the antibiotic cannot be used to treat infections anymore. *A. baumannii* can be tolerant to multiple antibiotics making infections difficult to treat.

Polymyxins are another antibiotic used to treat *A. baumannii* infection. These are effective against infection but polymyxins can be toxic to the kidneys.

Combination therapies can also be used to treat *A. baumannii* which is tolerant to many different types of antibiotics. This means treating the infection with a combination of different drugs at the same time. Different combinations are still being tested against *A. baumannii* infections.

Prevention of infection
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Preventing and controlling outbreaks of *A. baumannii* is very important. Preventing infections will reduce the number of infections in hospitals and help stop the spread of antibiotic resistance.

*A. baumannii* can be controlled with strict infection control measures such as educating hospital staff about the dangers of spreading hospital infections, proper hand washing, cleaning of hospitals and actively testing surfaces for the presence of *A. baumannii**.* These measures have been shown to reduce the spread of *A. baumannii* and reduce tolerance to antibiotics. However, all measures must be followed strictly to control infection.