Complex sentence: Biofilms of "P. aeruginosa" can cause chronic opportunistic infections, which are a serious problem for medical care in industrialized societies, especially for immunocompromised patients and the elderly.
Split into simpler sentences: Biofilms of "Pseudomonas aeruginosa" can cause chronic opportunistic infections. These kinds of infections are a serious problem for medical care in industrialized societies, especially for immunocompromised patients and the elderly.