Septicemia-inducing Escherichia coli O115:K"V165"F165(1) resists killing by porcine polymorphonuclear leukocytes in vitro: role of F165(1) fimbriae and K"V165" O-antigen capsule

Abstract

Escherichia coli 0115:K'"V165":F1651 wild-type strain 5131 survives in the bloodstream of experimentally inoculated gnotobiotic pigs and induces septicemia, whereas its afimbriate (F1651-negative) TnphoA mutant M48 and its acapsular (K"V165"-negative) spontaneous mutant 5131a are both nonpathogenic. We evaluated the role of the mannose-resistant F1651 fimbrial system and of the 0-antigen K"V165" capsule in resistance to phagocytosis by porcine polymorphonuclear leucocytes (PMNLs) in vitro. F1651-positive strains (5131 and

Pseudomonas aeruginosa selective adherence to and entry into human endothelial cells

“…Following the gentamicin treatment, in some uptake assays, cells were fixed and processed for TEM to further confirm the presence of intracellular P. aeruginosa. The extinction of acridine orange fluorescence by crystal violet has been largely used to distinguish internalized from surface-bound microorganisms in phagocytosis assays (13,26,28,30). Accordingly, a modification of the fluorescencequenching technique (15,34) was used to demonstrate further the uptake of P. aeruginosa PAK by endothelial cells.…”

F1651fimbriae of the P fimbrial family inhibit the oxidative response of porcine neutrophils

“…Extraintestinal infections such as septicemia, caused by Escherichia coli , are commonly encountered in domestic animals and poultry [1,2].…”

“…Bacterial phagocytosis involves attachment of bacteria to phagocytic cells (polymorphonuclear neutrophils, monocytes, and macrophages) by means of opsonins and lectins, ingestion, and lysis of the prey [2]. Destruction of invading microorganisms by phagocytes may involve one of the oxygen‐dependent or oxygen‐independent mechanisms.…”

“…F165 1 is a member of the P fimbrial family with an F11‐like major fimbrial subunit and expresses a class III Prs‐G adhesin (commonly associated with E. coli causing human cystitis) with specificity for the galactose‐ N ‐acetyl‐α‐(1‐3)‐galactose‐ N ‐acetyl (GalNac‐GalNac) moiety [15]. We have shown that F165 1 fimbriae mediate bacterial attachment to porcine polymorphonuclear leukocytes (pPMNLs) with subsequent ingestion by the phagocytes [2]. However, in contrast to the findings for F1 fimbriae or other MR fimbriae, the presence of F165 1 fimbriae on pathogenic wild‐type E. coli strain 5131 was strongly associated with the resistance of bacteria to pPMNL killing as compared to the F165 1 ‐negative Tn pho A mutant M48 [2].…”

“…We have shown that F165 1 fimbriae mediate bacterial attachment to porcine polymorphonuclear leukocytes (pPMNLs) with subsequent ingestion by the phagocytes [2]. However, in contrast to the findings for F1 fimbriae or other MR fimbriae, the presence of F165 1 fimbriae on pathogenic wild‐type E. coli strain 5131 was strongly associated with the resistance of bacteria to pPMNL killing as compared to the F165 1 ‐negative Tn pho A mutant M48 [2]. One of the mechanisms involved in the resistance of the F165 1 ‐positive strain to phagocytosis seemed to be the inhibition of the phagocyte oxidative response as detected by hydrogen peroxide release.…”