Peptidoglycans in cutting fluids - a good indicator of bacterial contamination?

Abstract

The aim of this study was to estimate the content of peptidoglycans in cutting fluids (CFs) and to assess the possibility of using them as a marker of bacterial contamination in this type of occupational environment. A total of 11 samples of CFs were collected: 8 were taken from the working machine systems and 3 were unused CF samples. The peptidoglycans were determinated with the kinetic version of the Silkworm Larvae Plasma (SLP) test. The average concentration of bacteria was 5.58×10⁵ CFU/mL, and peptidoglycans - 28.2 ng/mL. The variability for peptidoglycans concentration was less pronounced than that for bacteria (GSD 6 and 13.3, respectively). Taking into consideration the National Research and Safety Institute (INRS - Institut National de Recherche et de Sécurité) limit value the concentrations of bacteria and peptidoglycans, as well as the usage of the fluids, the analysis showed that peptidoglycans reflect the differences between the studied factors much more accurately than bacteria. The correlation analysis, however, showed that the levels of peptidoglycans in the examined CFs strongly correlated with the concentrations of viable bacteria (R² = 0.50, p<0.05). The study confirmed that the CFs may contain immunologically active substances of bacterial origin even though they did not show any bacterial growth. Moreover, it showed that the concentrations of peptidoglycans in CFs precisely reflect the exposure to bacteria, and as a structural component of the cell wall can be treated as their marker.