Genomic Analysis of Crispr-Cas3 (Subtype I-F/Ypest) in Acinetobacter Baumannii Clinical Isolates From Pakistan: Insights Into Phage Defense and Antimicrobial Resistance

Underlining a major danger to healthcare systems all over, Acinetobacter baumannii is an opportunistic pathogen linked to multidrugresistant infections. CRISPRCas systems especially the Cas3 nuclease/helicase Subtype IF/YPEST significantly contribute to bacterial adaptive immunity against phages and influence horizontal gene transfer, therefore influencing antimicrobial resistance (AMR) profiles. CRISPRCas3 in clinical isolates of A. baumannii from Pakistan was examined to understand its function in phage defense and antibiotic resistance (AMR). Total 50 non duplicate clinical isolates yielded through stratified random sampling. CRISPRCas loci were found using whole-genome sequencing and bioinformatics methods. Phylogenetic research and correlation between CRISPR presence and resistance patterns were done using chi-square and logistic regression analysis. Results showed that 36% of isolates carried CRISPRCas3 Subtype IF/YPEST, with preserved spacers pointing to historical phage exposure. Isolate with CRISPRCas3 showed much less lateral acquisition. These results highlight the double importance of CRISPRCas3 in phage of plasmid-mediated resistance genes (p< 0.05), therefore implying a possible protective role against gene transfer. immunity and modulation of AMR offer insights for phage therapy methods and other ways to fight multidrugresistant A. baumannii in clinical environments.