Acinetobacter baumannii is a bacterium commonly found in healthcare environments. When this bacterium develops resistance to carbapenems, a powerful class of antibiotics, it becomes Carbapenem-Resistant Acinetobacter baumannii (CRAB). This organism presents a significant challenge in healthcare settings. Its ability to withstand many treatments has led to its designation as a “superbug,” making infections difficult to manage.
The Nature of the Threat
Acinetobacter baumannii is a Gram-negative, rod-shaped bacterium that acts as an opportunistic pathogen, primarily affecting individuals with compromised immune systems. It is particularly notable for its ability to survive for extended periods, sometimes months, on dry surfaces in hospital settings. This persistence, partly due to its capacity to form biofilms, makes the bacterium difficult to eradicate from environmental surfaces and medical equipment.
Carbapenems are broad-spectrum antibiotics considered a last resort for treating severe bacterial infections. The emergence of resistance renders these powerful drugs ineffective against Acinetobacter baumannii. Public health organizations like the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) classify CRAB as an urgent or critical threat, highlighting the pressing need for new treatment options.
Transmission and Risk Factors
Carbapenem-resistant Acinetobacter baumannii primarily spreads within healthcare environments through direct contact with contaminated surfaces or medical equipment. Transmission also occurs from person to person, often facilitated by the hands of healthcare personnel. The bacterium’s ability to survive on dry surfaces for prolonged periods contributes significantly to its widespread presence and challenges in controlling its dissemination.
Patients in intensive care units (ICUs) face an elevated risk of acquiring CRAB infections. Other factors increasing vulnerability include the use of medical devices such as ventilators or urinary and central venous catheters, which provide direct entry points for the bacteria. Individuals with weakened immune systems, those with open wounds from surgery or trauma, and patients with prolonged hospital stays or previous exposure to broad-spectrum antibiotics are also more susceptible to infection.
Clinical Manifestations and Diagnosis
Carbapenem-resistant Acinetobacter baumannii can cause a variety of serious infections, primarily in hospitalized patients. These commonly include ventilator-associated pneumonia, bloodstream infections, urinary tract infections, and infections in surgical wounds.
Symptoms vary depending on the site of infection; for instance, pneumonia might present with fever and difficulty breathing. To diagnose a CRAB infection, clinicians collect biological samples such as blood, sputum, or urine. These samples are sent to a microbiology laboratory for culture and identification. Subsequent antibiotic susceptibility testing determines if the A. baumannii strain is indeed resistant to carbapenems and other antibiotics.
Treatment Strategies
Treating infections caused by carbapenem-resistant Acinetobacter baumannii is challenging due to the limited number of effective antibiotic options and the bacterium’s high resistance rates. Older antibiotics, such as colistin and polymyxin B, have been reintroduced as primary treatments. These polymyxin-based therapies are effective but can be associated with side effects like kidney damage.
Combination therapy, where multiple antibiotics are administered together, is often employed to enhance effectiveness and overcome resistance. Examples of such combinations include colistin with tigecycline, ampicillin-sulbactam, meropenem, or fosfomycin. Minocycline combined with high-dose sulbactam, polymyxins, or even carbapenems has also shown promise in some cases.
Newer or investigational treatments are emerging to address this persistent threat. Cefiderocol, a siderophore cephalosporin, represents a novel approach for Gram-negative infections, including CRAB. Sulbactam-durlobactam is another recently developed combination that prevents the breakdown of sulbactam. Additionally, bacteriophage therapy, which uses viruses that specifically target and destroy bacteria, is being explored as a future treatment option.
Prevention and Control Measures
Controlling the spread of carbapenem-resistant Acinetobacter baumannii in healthcare settings relies on implementing strict infection control protocols. Consistent and thorough hand hygiene is fundamental for all healthcare staff, patients, and visitors, using alcohol-based hand rubs or soap and water. This practice helps prevent the transfer of bacteria from contaminated surfaces or individuals.
Enhanced environmental cleaning and disinfection of patient rooms and medical equipment are also paramount. A. baumannii can persist for weeks to months on surfaces, making rigorous cleaning of high-touch areas, such as bed rails and call buttons, with effective disinfectants an important measure. Implementing contact precautions, and isolating infected or colonized patients in private rooms or designated areas, further limits transmission. These efforts are complemented by antibiotic stewardship programs, which aim to optimize antibiotic use, reducing overuse and inappropriate prescribing. Such programs are important for minimizing the selection pressure that drives antibiotic resistance.