Implementation of perineural catheters may lead to infection by catheter colonization. Catheters may be colonized by the bacteria present on the skin. This is most often commensal organisms as Staphylococcus or gram negative bacilli. In a large study of 1416 peripheral nerve catheters, 28.7% of catheters were cultured positive. This colonization is most often silent because in the same study only 3% of patients had signs of local inflammation and one psoas abscess was observed (0.07%). The germs are most often coagulase negative staphylococci (61%) and gram negative bacillus (21.6%).