Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen that colonizes various body sites, including the nares, skin, and vagina. During pregnancy,colonization can lead to dysbiosis, adverse pregnancy outcomes, and invasive disease. To identify genes contributing to MRSA vaginal fitness, we performed transposon sequencing (Tn-seq) using a murine model of vaginal colonization, identifying over 250 conditionally essential genes. Five genes were validated in our murine model, including those encoding the aerobic respiration protein QoxB, bacillithiol biosynthesis component BshB2, sialic acid catabolism enzyme NanE, and staphylococcal regulator of respiration SrrAB. RNA sequencing and comparative analysis identified over 30 SrrAB-regulated genes potentially important for fitness in vaginal-like conditions, particularly under oxygen stress. These findings highlight pathways such as aerobic respiration, bacillithiol biosynthesis, sialic acid catabolism, and transcriptional regulation that support MRSA's competitive fitness in the vaginal tract.