TTR and infection: Enzymatically active forms of cysteine cathepsins such as Cts B, H, K, L, and S are not correlated with bacterial colonization, because comparable activities of these enzymes were found in sputum of P. aeruginosa-positive and P. aeruginosa-negative CF patients, and therefore, they are not suitable markers for this type of infection (Naudin et al., 2011).