Phenotypic and transcriptional analysis of the antimicrobial effect of lactic acid bacteria on carbapenem-resistant Acinetobacter baumannii: Lacticaseibacillus rhamnosus CRL 2244 an alternative strategy to fight it

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a recognized nosocomial pathogen with limited therapeutics options. Lactic acid bacteria (LAB) constitute a promising therapeutic alternative. Here we aimed to study the antibacterial properties of a collection of LAB strains using phenotypic and transcriptomic analysis against A. baumannii clinical strains. One strain, Lacticaseibacillus rhamnosus CRL 2244, exerts a strong inhibitory capacity on A. baumannii with a strong killing activity. Scanning electron microscopy images showed changes in the morphology of A. baumannii with an increase formation of outer membrane vesicles. Significant changes in the expression levels a wide variety of genes were observed. Interestingly, most of the modified genes were involved in metabolic pathway known to be associated with bacterial survival. The paa operon, Hut system, and fatty acid degradation were some of the pathways that have been induced. The data reveals the impact of Lcb. rhamnosus CRL 2244 on A. baumannii response, resulting in bacterial stress and subsequent cell death. These findings highlight the antibacterial properties of Lcb. rhamnosus CRL 2244 and its potential as an alternative or complementary strategy for treating infections. Further exploration and development of this LAB as a treatment option could provide valuable alternatives for combating CRAB infections. Overnight cultures of Acinetobacter baumannii AB5075 and Lacticaseibacillus rhamnosus CRL 2244 with OD adjusted to 600 nm at 4.0 were centrifuged and resuspended in 3 mL of BHI broth and incubated for 90 min at 37°C. Total RNA extractions of Acinetobacter baumannii AB5075 or Acinetobacter baumannii AB5075 coincubated with Lacticaseibacillus rhamnosus CRL 2244 were performed in three biological replicates for each condition. RNA-seq reads corresponding to A. baumannii AB5075 exposed to CRL 2244 were analyzed.