Bacterial adherence to intravenous catheters and needles and its influence by cannula type and bacterial surface hydrophobicity.

Bacterial adherence to intravenous (IV) catheters and needles (cannulas) was studied morphologically by scanning electron microscopy and determined quantitatively with radiolabeled bacteria. Electron micrographs showed that bacteria adhered well to IV cannulas with formation of microcolonies. The adherence process was studied quantitatively, as related to cannula composition and bacterial surface hydrophobicity. The adherence of the bacteria examined (per square centimeter) was lowest to siliconized steel needles, higher to Teflon catheters, and highest to polyethylene catheters. The results for Staphylococcus aureus were (9.9 +/- 0.9) X 10(5) bacteria/cm2 adhered to steel needles, (37.2 +/- 2.8) X 10(5) bacteria/cm2 to Teflon catheters, and (168.4 +/- 15.6) X 10(5) bacteria/cm2 to polyethylene catheters. Hydrophobic bacteria (S. aureus and Serratia marcescens), as determined by their adherence to liquid hydrocarbons, adhered better than less hydrophobic species (Escherichia coli). The role of hydrophobicity was documented by showing that hydrophobic S. marcescens adhered to IV catheters 18- to 27-fold better than its less hydrophobic mutants. It is concluded that IV steel needles have an advantage over plastic cannulas regarding bacterial adherence in vitro, and inasmuch as infectious complications in vivo were indeed shown to be lower with IV needles, their usage should be preferred.