Gram staining is still the most frequent staining procedure and cornerstone in clinical microbiology (Samuel et al., 2016, Deleers et al., 2015) and if appropriately performed can substantially decrease mortality of invasive infections (Barenfanger, et al., 2008, Morris et al., 2003). Even though some modification of Gram stain procedure were introduced over the years none of them with the exception of one histological modification (Becerra et al., 2016) tried to solve the limitation of color contrast between Gram-negative bacteria (GNB) and host tissue (Siguenza et al., 2019).
Removing this limitation would also be advantageous, especially in the case of a low number of bacteria, as is the case with false-negative blood cultures (Peretz et al., 2015).