Bacterial attachment to immobilized extracellular matrix proteins in vitro.

Meat surfaces are contaminated with bacteria during slaughter and processing. Understanding bacterial attachment properties to specific structures of meat could result in more targeted interventions to improve its safety and quality. However, the influence of temperatures relevant to abattoir environments on bacterial attachment to specific meat structures is not known. In this study, the effect of temperature and protein concentration on attachment of 10 Escherichia coli and seven Salmonella strains to extracellular matrix (ECM) proteins (collagen I, fibronectin, collagen IV and laminin) was measured using crystal violet stain and epifluorescence microscopy assays. By crystal violet assay, only five of 17 strains showed significant attachment to any ECM protein and only one strain attached to all proteins. Strains that attached at all tested temperatures (4, 25, 37°C) were E. coli M23Sr and M23 (collagen I); E. coli M23Sr (fibronectin); E. coli M23Sr, O157:H12 and M23, (collagen IV); and E. coli M23Sr, O157:H12, O78:K80:H1, O26:H11 and M23 (laminin). A higher proportion of strains attached to basement membrane proteins (laminin and collagen IV) than to interstitial proteins (collagen I and fibronectin). Highest attachment levels occurred at 4°C for collagen I and at 25°C for the other three proteins. Generally, the attachment levels of Salmonella strains to all ECM proteins were lower than for E. coli. No significant effect was found for concentration of collagen I, fibronectin and collagen IV, but was for higher laminin concentration. A strong positive correlation was found between results of both the crystal violet and epifluorescent methods (r≥0.905, p<0.05). This study demonstrated that attachment properties to ECM proteins displayed distinct variation among strains, that temperature highly influenced attachment and that protein concentration had a minor effect.