Overview of β-Lactam-Resistance Genes in Pandemic Multidrug-Resistant Acinetobacter baumannii: A Troublesome Pathogen in the Indian Intensive Care Unit
Authors: Paneri Manita , Sevta Prashant , Yagnik Vipul D. , Gupta Pooja , Bansal Vikasdeep , Sevta Gurupreet , Saini Ram Gopal , Singh Manju , Kaur Sukhchain 
Published: November 2024

Objectives:
Acinetobacter baumannii is responsible for many infections in admitted patients, especially in the intensive care unit (ICU). Several risk factors may lead to an enhanced risk of A. baumannii colonization and infections. β-lactam antibiotics are frequently administered to treat Gram-positive and Gram-negative bacterial infections due to their minimum side effects, but the acquisition of β-lactamase genes has been the most challenging and troublesome situation and an imminent threat to the world as it increases mortality, medical expenses, and hospital stays. Hence, the present systematic review focused on the screening of β-lactam resistance genes that have been identified in the A. baumannii isolates’ genome and the nosocomial infections they cause in the Indian ICU.

Material and Methods:
This review has been done according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline 2020. After screening, 317 genomes were included in this systematic review. We downloaded data from the bv-brc.org website on an Excel spreadsheet for statistical analysis. We presented categorical data in percentages (%) and in the form of a graph and pie chart.

Results:
Among the 317 isolates, pneumonia was caused by 189 strains (59.62%), bacteremia was caused by 109 strains (34.38%), respiratory infection by 12 isolates (3.79%), sepsis by 5 isolates (1.58%), and wound infection by 2 isolates (0.63%), which indicated that A. baumannii strains are highly involved in pneumonia followed by bacteremia. We did comparative genome analysis and found 26 β-lactamase genes; among them, the ADC2 gene was found to be in higher frequency (312) and was identified in 98.42% of A. baumannii isolates, followed by the OXA23 gene (303), which was found in 95.58% of isolates. The NDM-1 gene was identified in 181 (57.09%) isolates. OXA66 was found in 156 (49.21%) isolates. Our findings show a higher frequency of the ADC2 gene, followed by the OXA23 gene, in all these nosocomial infections. We have found that NDM-1, ADC2, OXA23, and OXA-66 genes coexisted in higher frequency in the A. baumannii isolates (137; 43.21%), followed by OXA23, OXA-66, and ADC2 (52; 16.40%).

Conclusion:
A. baumannii is a notorious pandemic pathogen, designated as a “priority of concern” by the World Health Organization. Our study indicates a high prevalence of the ADC2 gene, which gives resistance against the cephalosporin group and co-existence of β-lactamase genes (ADC2, OXA23, OXA66, and NDM-1) in various A. baumannii isolates’ genomes. This is a worrisome situation. Global molecular surveillance and the “One Health Concept” are crucial, as are research studies on plant extracts’ in vitro and in vivo efficacy against A. baumannii. Combating multidrug-resistant A. baumannii requires a multifaceted approach that involves infection control measures, antimicrobial stewardship, surveillance, education, research, and collaboration. Implementing these strategies and staying vigilant in the face of this resilient pathogen is essential to minimize its impact on health-care systems and public health.