In vitro studies conducted by Garred et al. in 1999 found that MBL has a weak binding with Pseudomonas aeruginosa, which is the most common bacterial cause of tubotympanic CSOM [4], and, therefore, opsonization of Pseudomonas aeruginosa mediated by MBL cannot occur in in vivo conditions [22]. Here, MBL2 is linked to chronic purulent otitis media.