Acinetobacter baumannii- An Overview


Acinetobacter baumannii is a bacterial species that belongs to the genus Acinetobacter, which comprises a group of gram-negative, coccobacillary, aerobic bacteria that are widely distributed in soil and water . The name Acinetobacter derives from the Greek words "akinetos", meaning nonmotile, and "bakterion", meaning small rod . The species baumannii is named after Paul Baumann, a Swiss microbiologist who first described the genus in 1968 .

Acinetobacter baumannii is an opportunistic pathogen that can cause serious infections in humans, especially in those with compromised immune systems or in healthcare settings . It can affect various organs and systems, such as the lungs, bloodstream, urinary tract, and wounds, causing diseases such as pneumonia, bacteremia, urinary tract infection, wound infection, meningitis, and sepsis . It can also colonize the skin, respiratory tract, and gastrointestinal tract of healthy or asymptomatic individuals .

One of the major challenges posed by Acinetobacter baumannii is its remarkable ability to develop resistance to multiple antibiotics, including carbapenems, which are considered the last-resort drugs for treating gram-negative infections . Acinetobacter baumannii can acquire resistance through various mechanisms, such as modifying or inactivating antibiotics, altering or expressing efflux pumps, changing the permeability of the outer membrane, or acquiring resistance genes from other bacteria . As a result, some strains of Acinetobacter baumannii have become resistant to all available antibiotics, making them extremely difficult to treat and control .

Acinetobacter baumannii is one of the ESKAPE pathogens, a group of bacteria that are responsible for most hospital-acquired infections and have the potential to escape the action of antibiotics . The other ESKAPE pathogens are Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Enterobacter species . In addition, Acinetobacter baumannii is one of the critical-priority pathogens on the World Health Organization priority list of antibiotic-resistant bacteria for which new antibiotics are urgently needed .

Acinetobacter baumannii is a relatively new pathogen that emerged in the late 1970s and has since become a global threat to public health . It has been associated with outbreaks in hospitals and intensive care units worldwide, as well as with infections in military personnel and civilians during wars and natural disasters . Its emergence and spread are likely related to its environmental persistence, survival ability under stress conditions, genetic diversity, adaptation to different hosts and niches, and rapid evolution of resistance .

Acinetobacter baumannii is an important cause of morbidity and mortality among infected patients. It has been estimated that Acinetobacter baumannii infections account for 10% of gram-negative hospital-acquired infections and 20% of ventilator-associated pneumonias in intensive care units in Europe and North America . The mortality rate of Acinetobacter baumannii infections ranges from 19% to 54%, depending on the type and site of infection, the severity of illness, the presence of comorbidities, and the availability of effective antibiotics .

The diagnosis of Acinetobacter baumannii infection is based on the isolation and identification of the bacterium from clinical specimens using microbiological methods. However, distinguishing between infection and colonization can be challenging, as Acinetobacter baumannii can be present in various body sites without causing disease. Therefore, clinical criteria such as signs and symptoms of infection, inflammatory markers, radiological findings, and response to treatment should also be considered. Molecular methods such as polymerase chain reaction (PCR) or whole-genome sequencing (WGS) can be used to detect specific genes or variants associated with resistance or virulence in Acinetobacter baumannii isolates.

The treatment of Acinetobacter baumannii infection depends on the susceptibility profile of the isolate and the severity of the disease. Empirical therapy should be initiated promptly after obtaining appropriate specimens for culture and susceptibility testing. Combination therapy with two or more antibiotics from different classes is usually recommended to increase the likelihood of efficacy and to prevent the emergence of resistance. However, the optimal choice and duration of therapy are not well established and should be guided by clinical judgment and local guidelines. In addition to antibiotic therapy, supportive care and infection control measures are essential to improve the outcome and prevent the transmission of Acinetobacter baumannii.