Effect of Pili on Susceptibility of Escherichia coli to Phagocytosis

Abstract

The degree of piliation of 20 clinical isolates of Escherichia coli was correlated with their susceptibility to phagocytosis by human polymorphonuclear leukocytes. Piliation was quantitated by negative staining, and phagocytosis was quantitated by a monolayer technique. Ingestion was confirmed by electron microscopy. In the absence of source of opsonins, there was a positive correlation between the degree of piliation and susceptibility to phagocytosis (y = 0.83x + 19.58; correlation coefficient = 0.65; P < 0.01). Heavily piliated strains were no longer phagocytized after their pili were removed by ultraviolet irradiation. Phagocytosis was reduced 75% in the presence of 0.1 M D-mannose, an agent which competitively inhibits binding of pili to cell surfaces. L-Mannose, D-glucose, and D-galactose were much less inhibitory. The viability of piliated organisms was reduced by 1 log after 1 h of incubation with polymorphonuclear leukocytes. Addition of 10% fresh human serum increased both the rate and completeness of killing. These observations suggest that polymorphonuclear leukocytes may interact with the pili of E. coli to promote phagocytosis. This phenomenon may have clinical relevance in situations where normal opsonic activity is poor, such as the renal medulla.

Phagocytosis and virulence of different strains of Porphyromonas gingivalis

“…Pili and fimbriae are other surface structures which may influence the susceptibility to phagocytosis by human neutrophils. A direct correlation has been demonstrated between degree of piliation and susceptibility to phagoeytosis for bacteria of the species E. coli, Pseudomonas aeruginosa, and B. fragilis (48)(49)(50). P. gingivalis has been reported to show the presence of fimbriae on the phagocytosis-susceptible strains 381 and ATCC 33277 (51)(52)(53)(54)(55).…”

The mannose-specific lectin activity of Escherichia coli type 1 fimbriae assayed by agglutination of glycolipid-containing liposomes, erythrocytes, and yeast cells and hydrophobic interaction chromatography

“…Type 1 fimbriae are bacterial lectins, that are associated with increased adherence of the bacteria to different kinds of epithelial cells [1], phagocytes [2][3][4] and mucus [5]. The monosaccharide D-mannose inhibits adhesion mediated by type 1 fimbriae [6] suggesting that mannose residues on eukaryotic cell surfaces serve as receptor molecules [7].…”

Pili and the interaction of Aeromonas species with humanperipheral blood polymorphonuclear cells

“…It interacted to the same extent with PMN even when pili expression was varied markedly by culture manipulation. Despite some reported amino acid homology, these results suggest that Aeromonas S/R pili are different from morphologically similar pili on Escherichia coli and Proteus mirabilis which promote phagocytosis [12,14,15]. Many very poorly piliated faecal strains showed high interaction with PMN confirming such interaction was not due to S/R pili.…”

“…The degree of bacterial association to human peripheral blood polymorphonuclear cells (PMN) was quantitated by a monolayer method adapted from Silverblatt et al [14]. Human PMN were obtained from peripheral blood by density eentrifugation on Polymorphprep (Nycomed Pharma AS, Oslo, Norway).…”

“…Pili are known to enhance the phagocytosis of several Gram-negative bacterial pathogens. For these species, phagocytosis in blood and beyond mucosal barriers is thought to explain observed shifts in pilus phenotype [14][15][16][17]. Aeromonas species associated with severe gastroenteritis, especially Aeromonas veronii biotype sobria in Australia, would encounter phagocytic cells as a result of the inflammatory response induced by the powerful cytotoxic enterotoxin or invasive ability of these bacteria.…”