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Acinetobacter baumannii

An emerging pathogen with a high propensity for broad antibiotic resistance, it initially gained global attention as “Iraqibacter”, due to its prevalence in US military personnel returning from the Middle East. A. baumannii has been labeled as an “Serious Threat” pathogen by the US Centers for Disease Control (CDC) and is the #1 priority pathogen in the World Health Organization’s (WHO) “Global Priority Pathogens List for Combatting Antibiotic Resistance”.

The Pathogen

A. Baumannii is a gram-negative coccobacillus that is commonly classified as an opportunistic pathogen. Found among a group of bacteria (known as Acinetobacter) that all can cause human disease, A. baumannii accounts for about 80% of reported infections. Several virulence factors have been reported, including outer membrane porins, phospholipases, proteases, LPS, capsular polysaccharides, protein secretion systems, and iron-chelating systems.

"Iraqibacter" Infections

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Acinetobacter are one of the most successful pathogens responsible for hospital-acquired infections in the modern healthcare system. A. Baumannii is responsible for opportunistic infections of the skin, bloodstream, urinary tract, and other soft tissues. Most of these infections occur in critically ill patients in the intensive care unit (ICU), accounting for 20% of infections in ICUs worldwide. However, rare infections can also be acquired from both community and environmental sources. Common diseases include pneumonia, urinary tract, serious blood, or wound infections, and sepsis, but A. baumannii can also colonize without causing any symptoms.

Acinetobacter Antibiotic Resistance

Approximately 50% of all A. baumannii infections are multi-drug resistant in the United States. A. baumannii has several resistance mechanisms, including β-lactamases, aminoglycoside-modifying enzymes, efflux pumps, permeability defects, and modifications of target sites. Resistance to carbapenems has been increasing gradually, mediated through the production of carbapenemases or metallo-β -lactamases, and soon will no longer be a reliable treatment for A. baumannii. Compounding the problem, carbepenem-resistant A. baumannii are often resistant to all other commonly used antibiotics, leaving few treatment options. Fluoroquinolone resistance is also high in clinical A. baumannii isolates, due to target site mutations in the genes encoding DNA gyrase and topoisomerase IV, as well as enhanced efflux mechanisms.  

 

Personalized bacteriophage to fight infection

Using personalized bacteriophages, CHARM Investigators saved the life of a patient with an MDR A. baumannii infection. After the failure of multiple antibiotic courses, administration of bacteriophages was associated with reversal of the downward clinical trajectory and a return to health.

 Read the article from Antimicrobial Agents and Chemotherapy