MALDI-TOF is not useful in the diagnosis of catheter colonization based on superficial cultures: results from an in vitro study

We compared in an vitro model the yields of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and conventional culture (CC) for the detection of catheter colonization with superficial catheter samples (SS). We used blood culture bottles (BCB) with an inserted cannula and incubated at 37 °C. The BCB were manipulated with different contaminations and when a BCB turned positive, SS were obtained to perform both techniques. To compare both techniques we analyzed the mean time to colonization (MTC) and the mean time to a result (MTR). The MTC (SD, days) by CC and MALDI-TOF was as follows: hub, 0.59 (0.79) versus 1.07 (1.39), P = 0.06; surface: 0.62 (0.67) versus 0.82 (0.81), P < 0.001. The MTR (SD, days) of CC and MALDI-TOF was as follows: hub: 1.58 (0.79) versus 2.25 (1.48), P = 0.04; surface: 1.62 (0.67) versus 1.95 (0.80), P < 0.001. In general, the use of MALDI-TOF performed directly with SS was no better than CC and did not anticipate colonization results.