Acinetobacter baumannii has emerged as one of the most challenging opportunistic pathogens in modern healthcare due to its remarkable ability to acquire and disseminate antimicrobial resistance determinants. Carbapenem-resistant A. baumannii (CRAB) is now recognized by the World Health Organization as a critical priority pathogen, highlighting the urgent need for improved diagnostic, surveillance, and therapeutic strategies. This review synthesizes current evidence on the relationship between phenotypic antimicrobial susceptibility patterns and underlying genetic determinants of resistance in A. baumannii. A structured literature search was conducted across major biomedical databases (PubMed/MEDLINE, Scopus, Web of Science, and the Cochrane Library), supplemented by citation tracking and relevant institutional sources, focusing on studies published between 2016 and 2026. The analysis integrates findings from studies examining phenotypic antimicrobial susceptibility testing (AST) with molecular and genomic investigations of resistance mechanisms, including carbapenemases, aminoglycoside-modifying enzymes, efflux pumps, and resistance-associated genomic islands. Particular attention is given to the complex and sometimes discordant relationship between genotype and phenotype, where the presence of resistance genes does not always translate directly into phenotypic resistance due to regulatory mechanisms, gene expression variability, and genomic context. The review further discusses methodological differences in AST standards and genomic prediction approaches that may contribute to variability across studies. Collectively, the evidence supports a multidimensional interpretation of antimicrobial resistance in A. baumannii, emphasizing the necessity of integrating phenotypic and genotypic data for accurate diagnostics, surveillance, and clinical decision-making. This integrated perspective may contribute to improved understanding of resistance evolution and support the development of more effective strategies for managing multidrug-resistant A. baumannii infections.

Acinetobacter baumannii is one of the most dangerous hospital-acquired infections, leading to death in patients with weakened immune systems, especially in intensive care units. Many strains resist carbapenems, the "antibiotics of last resort," making treatment extremely difficult. In this regard, the frequency of isolation and the level of resistance of A. baumannii strains in patients of the pediatric cardiac surgery department (PCSD) and the department of anesthesiology, resuscitation, and intensive care (DARIC) for the period 2015 to 2022 were studied. A retrospective analysis of the results of bacteriological culture of various biomaterials for the isolation of pathogenic flora taken from adult patients hospitalized in DARIC and PCSD patients over 8 years, with determination of antibiotic sensitivity was carried out. A total of 8696 clinical isolates were recovered, of which A. baumanniiaccounted for 629 cases, primarily from DARIC (203) and PCSD (426). Identification was carried out on a microbiological analyzer "Vitek 2 - Compact" (bioMerieux, Marcy I'Etoile, France). Antimicrobial activity was studied by the method of minimum inhibitory concentrations ("Vitek 2 - Compact"). Isolate distribution analysis shows a significant difference in the detection rate of A. baumannii in DARIC and PCSD: 13.5% in DARIC versus 5.8% in PCSD. Antibiotic resistance analysis revealed an increase in resistance to all antibiotics used, particularly in DARIC, where resistance to levofloxacin was 93.3%, meropenem 92.8%, gentamicin 90.6%, ciprofloxacin 89.7%, and imipenem 86.1%. PCSD also recorded an increase in resistance, but within 27%. Thus, the comparative analysis of the frequency of isolation of A. baumannii in DARIC units was higher than in PCSD. An increase in resistance to all tested antibiotics was noted in DARIC and PCSD units, except for colistin.

Acinetobacter baumannii is one of the most influential pathogens causing nosocomial infections characterized by high resistance to antibacterial drugs. Thus, this study aimed to evaluate the dynamics of A. baumannii isolation and the level of antibiotic resistance in a multidisciplinary hospital for the period 2021-2025. For this reason, a comparative retrospective analysis was conducted on 13 221 clinical isolates obtained from various departments. The analysis was conducted using phenotypic identification and susceptibility testing methods. Susceptibility testing (antibiograma) was performed using the Vitek 2 automated system and the disk diffusion method for nine antimicrobial drugs. These antibiotics included carbapenems (imipenem, meropenem), aminoglycosides (gentamicin, amikacin, tobramycin), fluoroquinolones (ciprofloxacin, levofloxacin), colistin, and a trimethoprim/sulfamethoxazole combination. The results showed a decrease in the frequency of A. baumannii isolation over the observation period (χ² = 19.29, p = 0.0007), with the majority of isolates retaining multiple-drug resistance (MDR). The highest resistance was detected to fluoroquinolones and carbapenems, while susceptibility to colistin remained high throughout all years. The lack of molecular analysis limits the interpretation of the results; however, the resulting resistance profile suggested genes that could act as pathogenicity factors. These comparative retrospective analyses of resistance highlight the need for ongoing local monitoring of A. baumannii antibiotic resistance and the rational use of antimicrobials in hospital settings.

Acinetobacter baumannii is a critical WHO priority pathogen due to its multidrug resistance and high mortality in carbapenem-resistant infections. Resistance is predominantly mediated by class D carbapenemase genes bla_OXA-23 and bla_OXA-40, which spread rapidly via horizontal gene transfer in healthcare settings. To address the lack of a rapid assay capable of detecting both blaOXA-23 and blaOXA-40 in a single analytical workflow, we developed a multiplex two-step RPA–CRISPR/Cas12a assay. Since infections caused by strains harboring either gene require identical therapeutic management, their co-detection in a single reaction is clinically justified. Although simultaneous use of two crRNAs within a single CRISPR/Cas12a reaction is often considered technically challenging due to potential inter-crRNA competition, here it advantageously enables dual-target coverage without compromising sensitivity. The assay demonstrated high specificity with no cross-reactivity against a panel of clinically relevant bacterial species, including closely related Acinetobacter spp. Evaluation using genomic DNA extracted from 63 cultured clinical A. baumannii isolates revealed bla_OXA-23 in 19 isolates (30.2%), bla_OXA-40 in 28 (44.4%), and co-carriage of both genes in 9 (14.3%), with at least one resistance gene detected in 60.3% of isolates. The complete workflow was accomplished within 45 min without specialized equipment, offering a rapid, sensitive, and cost-effective solution for point-of-care molecular surveillance of carbapenem-resistant A. baumannii in clinical and resource-limited settings.

Antibiotic resistance is one of the key problems of modern medicine, especially in relation to nosocomial infections caused by Acinetobacter baumannii, which has a high ability to accumulate drug resistance genes. One of the beta-lactam antibiotic resistance genes is blaTEM, which plays an important role in the formation of resistance in gram-negative microorganisms, including Acinetobacter baumannii. Standard molecular genetic methods for detecting antibiotic resistance genes, including PCR and real-time PCR, require the use of thermal cycling equipment. In this regard, the development of isothermal amplification methods with alternative methods of recording the result is of interest to laboratories with limited instrumentation. In this regard, the use of isothermal amplification methods in combination with CRISPR/Cas systems for sensitive detection of target genes is a promising direction. The purpose of this study was to develop and evaluate the sensitivity of a method for detecting the blaTEM gene based on recombinase polymerase amplification (RPA) in combination with the CRISPR/Cas12a system. The study showed that the RPA method provides specific amplification of the target gene with a detection limit of 104 copies/reaction. The results obtained confirm the fundamental operability of the RPA-CRISPR/Cas12a system for detecting a fragment of the blaTEM gene and fluorescence registration of the amplification product.