Molecular Characterization of OXA Carbapenemase Genes in Acinetobacter Baumannii Isolated from Different Clinical Samples.

Genotypic and Phenotypic Resistance Profiles of Invasive Acinetobacter baumannii Isolates at Bulgarian University Hospital

The relationship between genotypic and phenotypic resistance profiles in 36 non-duplicate invasive A. baumannii isolates collected at a tertiary care hospital in Bulgaria over a six-year period supports the use of targeted genes, such as armA, combined with phenotypic testing to guide empirical therapy and strengthen local surveillance of high-risk A. baumannii clones in hospital settings.

Characterization of blaNDM-1 and blaOXA-23-Type Carbapenemases in Acinetobacter baumannii Isolated from Post-Surgical Patients

This study substantiates an escalated incidence of carbapenem-resistant, MDR A. baumannii in post-surgical infections in Pakistan, highlighting the exigency for strengthened antimicrobial stewardship and infection control strategies in the hospitals of the region.

Genetic diversity and ERIC-PCR-based relationships of Acinetobacter baumannii isolates from hospitals

Comparative genomic insights into carbapenem-resistant versus susceptible Acinetobacter baumannii in Shanghai hospital settings: a multi-center molecular surveillance study

The ICU environment was critical for CRAB control, and CRAB exhibited stronger resistance, harbored more putatively conjugative plasmids and richer virulence-associated genes than CSAB, highlighting the need for targeted disinfection and surveillance of prevalent clones.

Molecular Characterization of Colistin Resistance Acinetobacter baumannii Isolates and Identification of Mutations in pmrA and lpxA Genes from a Tertiary Care Hospital in South India

Background/Objectives: Acinetobacter baumannii is a multidrug-resistant (MDR) nosocomial pathogen associated with significant morbidity and mortality. The emergence of strains resistant to multiple antibiotics has markedly reduced available treatment options. A. baumannii now demonstrates resistance to most first-line antibiotics, resulting in the extensive use of colistin, which in turn has led to the emergence of colistin-resistant strains. There are very limited studies from India on the mechanisms of colistin resistance. In this study, we focused on the molecular mechanisms leading to colistin resistance. Methods: A total of 225 clinical isolates of Acinetobacter baumannii were analyzed in this study. Antimicrobial susceptibility testing was done using the disk diffusion method for various classes of antimicrobial agents as per the Clinical Laboratory Standards Institute (CLSI M100 Ed 35,2025). Susceptibility to colistin was tested by the Microbroth dilution method. Colistin resistance mediated by the mcr gene and alterations in the pmrAB and lpxACD genes were investigated using conventional PCR followed by mutational analysis. Results: Among the 225 isolates, 4 isolates were found to be colistin resistant. All the resistant isolates had an MIC ≥ 16 mcg/mL. Mutations were found in lpxA and pmrB (c.391T > C, c.495T > C, c.516A > G, c.732A > G and c.966T > C). Mutations in pmrA, lpxC, and lpxD were not detected in this study. Mcr-1 gene was not detected in this study. Conclusions: Colistin is the last resort for the treatment of MDR strains, and the increase in resistance to colistin has become a huge concern among the medical community as it reduces the options available for treatment. This is the first report on the molecular mechanisms of colistin resistance in South India using PCR. The study is also the first to report four novel mutations in the genes that may be responsible for resistance. Early detection of resistance and swift control measures can help curb the morbidity and mortality rate among such A. baumannii strains.

Molecular analysis of clinical Acinetobacter baumannii isolates based on colistin resistance, biofilm formation, clonal relationships, and pmrA gene expression.

AIMS This study investigates the molecular characteristics of multidrug-resistant Acinetobacter baumannii (MDRAB) clinical isolates with particular emphasis on colistin resistance, biofilm formation, antimicrobial resistance determinants, clonal relatedness, and pmrA gene expression. METHODS Twenty MDRAB isolates were collected from intensive care unit patients at Afzalipour Hospital, Kerman, Iran. Antimicrobial susceptibility testing was performed using the broth microdilution method according to the EUCAST 2022 guidelines. Polymerase chain reaction (PCR) was used to detect extended-spectrum β-lactamase (ESBL), carbapenemase, biofilm-associated genes, and class 1 integrons. Clonal relatedness was assessed using Repetitive-element PCR (Rep-PCR), and the pmrA gene (GenBank accession no. MN787072.1) expression analyzed through quantitative RT-PCR (qRT-PCR). RESULTS The isolates demonstrated high minimum inhibitory concentrations (MICs) particularly against carbapenems. Many isolates showed strong biofilm, while carrying biofilm-associated genes bap, csuE, pgaA, and ompA. Class 1 integrons and the blaCTX-M gene detected in 94% and 65% of isolates, respectively. Colistin-resistant (ColR) isolates shared a distinct Rep-PCR profile (singleton) and harbored both the pmrA and blaCTX-M-15 genes. DNA sequencing and qRT-PCR analysis revealed that, the Q218→K mutation had marginal effect on pmrA gene expression. CONCLUSION These findings underscore the urgent need for effective antibiotic stewardship to address rising incidence of carbapenemase-producing, colistin resistance in A. baumannii.