Acinetobacter baumannii is a bacterial species classified as gram-negative bacteria. These bacteria are widespread in the environment, living in soil and water. Acinetobacter bacteria often infect you without causing any disease, but they can cause serious diseases of various organs and systems. People fear these bacteria because of their antibiotic resistance, and doctors face great difficulty treating Acinetobacter baumannii infections.
What Is Acinetobacter Baumannii?
Acinetobacter baumannii are bacteria that cause infections in the blood, lungs, kidneys, brain, and other organs. These bacteria are nonmotile (don't move on their own), strictly aerobic (need oxygen to survive), gram-negative (a pink appearance when stained with dyes and observed under a microscope), and nonfastidious (easy to grow in the laboratory for testing).
Their importance lies in their ability to develop mechanisms to avoid being killed by antibiotics. The different antibiotic classes have different mechanisms of action to destroy bacteria. Acinetobacter baumannii has developed mechanisms to evade the action of many types of antibiotics. This is called multidrug resistance.
These germs are frequent causes of hospital-acquired infections, especially in intensive care units (ICUs). Acinetobacter baumannii caused 8,500 infections in people in hospitals in 2017, and 700 of them died. Some hospitalized people are at high risk, including those:
- Admitted in ICUs
- On breathing machines (ventilators)
- With inserted urinary catheters and similar devices
- With long hospital stays
- With open surgical wounds
Healthy people outside hospitals don't often get Acinetobacter baumannii infections. Some people with diabetes, chronic lung disease, or weakened immune systems can get this infection in the community.
Acinetobacter baumannii can resist the action of different antibiotics. They do this by producing enzymes that destroy some antibiotics, changes in membrane proteins that prevent antibiotics from attaching to the bacteria, pumps that remove antibiotics, and changes in binding proteins. Carbapenem drugs (meropenem, imipenem, and others) are sometimes considered last-resort drugs for difficult-to-treat infections, but Acinetobacter baumanii can destroy them by producing enzymes called carbapenemases.
Acinetobacter Infection
Acinetobacter transmission can happen in the community, but it's rare. This infection is most likely in very sick people in hospitals. You're at highest risk if you're in an ICU or burns unit or have major wounds.
Acinetobacter infection can happen through:
- Hands of health care staff
- Contact with an infected person
- Airborne infection when an infected person coughs or sneezes
- Urinary catheters
- Venous catheters
Hospitals should take stringent precautions to prevent Acinetobacter baumannii infections. Health care-associated infections are a threat to patient safety. Such infections are associated with increased sickness, costs of treatment, lengths of hospital stay, and deaths.
Acinetobacter baumannii infections are not as common as other bacteria like Pseudomonas and Klebsiella, but they're often resistant to almost every antibiotic. The World Health Organization (WHO) has included Acinetobacter baumannii in the critical group of bacteria that are the greatest threat to human health.
Acinetobacter Symptoms
What is the Acinetobacter baumannii symptomatology? It depends on the organs and systems the germ infects. The underlying disorder that allowed the bacteria to infect you will also affect the expected symptoms.
Hospital-acquired pneumonia. This is the most frequent infection caused by Acinetobacter baumannii. Very sick people in intensive care units often have tubes placed in their airways to help them breathe. Ventilators can help people unable to breathe on their own. These situations often lead to hospital-acquired pneumonia.
Acinetobacter baumannii causes 5% to 10% of hospital-acquired pneumonia. Several other bacteria and fungi also cause hospital-acquired pneumonia. This complication prolongs ICU and hospital stays and can cause death.
If you're in a situation like this, your doctor will watch for fever, breathing difficulty, and a rapid heartbeat. You may also have chest pain, a poor appetite, and shivering. Your doctor will ask for X-rays of the chest to diagnose pneumonia.
Blood infections. Acinetobacter baumannii is a frequent cause of this deadly infection. Infection in the blood can spread all over the body. Bloodstream infections caused by Acinetobacter baumannii are more likely in the ICU than in the wards. This condition has a death rate of 34% to 43% in ICUs.
Central nervous system infections.Meningitis, an infection of the membranes covering the brain, is likely after brain surgery. Acinetobacter baumannii is one of several germs that can cause it. As many as 70% of people with this complication die.
The symptoms of meningitis are a high fever, unconsciousness, seizures (fits), neck stiffness, headache, and an inability to tolerate bright light (photophobia). Your doctor may ask for a spinal tap and cerebrospinal fluid examination to diagnose meningitis. Since meningitis can progress rapidly, they will start treatment as soon as possible without waiting for laboratory results.
Other infections Acinetobacter baumannii can cause include:
- Urinary tract infections
- Bone infections
- Skins and soft tissue infections
- Endocarditis (infection of the lining and valves of the heart)
- Wound infections
Acinetobacter Treatment
Doctors have difficulty treating these infections because Acinetobacter baumannii is often resistant to several antibiotics. They'll often send cultures to the microbiology laboratory and start medications based on their best guess. Your doctor's best guess is based on knowledge of which bacteria are common in the hospital and which medicines worked in the recent past.
Cultures are tests that grow the infecting organisms (bacteria, viruses, or fungi) in the laboratory. Your doctor will send appropriate specimens depending on your clinical condition — blood, sputum, cerebrospinal fluid, or others. The laboratory grows them on various dishes with nutrients for germs. They also place antibiotic discs in these dishes to see which are effective.
The culture results take a few days. If they show the germs are susceptible to the initial choice of antibiotic, your treatment will continue. If you're not better by the time these results are available, your doctor will decide based on the results. They will change your treatment based on which medicines are effective for your infection, the safety and adverse effects likely in your situation, and the possible interactions with your other medicines.
Acinetobacter baumannii has an uncanny ability to survive for a long time on surfaces, hospital equipment, and other places in health care settings. Some strains of this troublesome bacterium are resistant to all available antibiotics, making infections almost impossible to cure. This germ often targets people in ICUs and similar settings. These people are already very sick, and death rates are high. Good hygiene and aseptic procedures are the best hope for avoiding this difficult-to-treat germ.