Specific binding of lactoferrin to Escherichicr coli isolated from human intestinal infections. APMIS 99: 1142-1 150, 1991.The degrees of human lactoferrin (HLf) and bovine lactoferrin (BLf) binding in 169 Esclierichiu c.01; strains isolated from human intestinal infections. and in an additional 68 strains isolated from healthy individuals. were examined in a ''51-labelled protein binding assay. The binding was expressed as a percentage calculated from the total labelled ligand added to bacteria. The HLf and BLf binding to E. coli was in the range 3.7 to 73.4% and 4.8 to 61.6'%,, respectively. Enterotoxigenic strains demonstrated a significantly higher HLf binding (median = 19%) than enteropathogenic, enteroinvasive, enterohaemorrhagic strains or normal intestinal E. coli isolates (medians 6 to 9). Enteropathogenic strains belonging to serotypes 0 4 4 and 01 27 demonstrated significantly higher HLf binding compared to 026. 0 5 5 , 01 1 I , 01 19 and 0126. No significant differences in the degree of HLf or BLf binding were found between aerobactin-producing and non-producing strains. The interaction was further characterized in a high Lf-binding EPEC strain, E34663 (serotype 0127). The binding was stable in the pH range 4.0 to 7.5, did not dissociate in the presence of 2M NaCl or 2M urea, and reached saturation within two h. Unlabelled HLf and BLf displaced the '"I-HLf binding to E34663 in a dosedependent manner. Apo-and iron-saturated forms of Lf demonstrated similar binding to E34663. Among various unlabelled subepithelial matrix proteins and carbohydrates tested (in 1O4-fold excess) only fibronectin and fibrinogen caused a moderate inhibition of '"I-HLf binding. According to Scatchard plot analysis. 5,400 HLf-binding sitesicell, with an affinity constant (K,) of 1.4 x lo-' M, were estimated in strain E34663. These data establish the presence of a specific Lf-binding mechanism in E. coli.

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Escherichia coli H10407 demonstrated low '25I-human lactoferrin (IlLf) binding (7%) and was insusceptible to group A (A, El, E2, E3, E6, and K) and group B (B, D, Ta, Ib, and V) colicins. Conversely, a spontaneous HLf high-binding (44%) variant, H10407(Lf), demonstrated an increased susceptibility to both colicin groups.Colicin-insusceptible E. coli wild-type strains 75ColT, 84ColT, and 98lColT showed a low degree of HLf binding, i.e., 4, 8, and 10%, respectively. The HLf binding capacity was high in the corresponding colicin-susceptible mutants 75ColS (43%), 84ColS (32%), and 981ColS (43%). Furthermore, HLf low-(<5%) and high-(>35%) binding E. coli clinical isolates (10 in each category) were tested for susceptibility against 11 colicins. Colicin V susceptibility did not correlate with HLf binding in either categories. However, with the remaining colicins, three distinct HLf-binding, colicin susceptibility patterns were observed; (i) 10 of 10 HLf low-binding strains were colicin insusceptible, (ii) 6 of 10 HLf high-binding strains were also colicin insusceptible, and (iii) the remaining HLf high binders were highly colicin susceptible. Certain proteins in the cell envelope and outer membrane of wild-type H10407 (HLf low binder, colicin insusceptible) showed a lower mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis compared to the corresponding proteins of mutant H10407(Lf) (HLf high binder, colicin susceptible). These mobility differences were also associated with HLf-binding proteins in Western blot (ligand blot) analysis. The wild type showed a smooth form of lipopolysaccharide (LPS) with a distinct ladder of 0-chains, compared to the rough LPS of the mutant.Exogenous smooth LPS from wild-type H10407 inhibited 125T-HLf binding to mutant H10407(Lf) in a dose-dependent manner, while rough LPS was ineffective. These data establish a correlation between HLf binding and colicin susceptibility in E. coli. The LPS seems to be associated with the HLf binding components and the colicin receptors in a similar manner and interferes with the interaction of these eucaryotic and procaryotic antimicrobial agents with E. coli.

The integron content of 52 DT104/U302 phage type strains and 53 non-DT104/U302 strains of Salmonella enterica serotype Typhimurium (S. Typhimurium) was studied in PCR experiments using a 5'-CS/3'-CS primer pair (Lévesque et al., 1995). Forty-three out of 44 streptomycin-and/or ampicillinresistant DT104 and related phage type strains were found to carry a 1 kb and/or 1.2 kb long integron. The other resistance markers did not affect the number and size of integrons; no integron-free multidrug-resistant (MDR) DT104 strains were found. The two large groups of DT104 strains (Felix-Callow's phage types 2 and 2c) proved to be identical in respect of integron patterns (IPs), supporting the views of those authors who consider DT104 a single clone. Strains of human and animal origin did not differ from each other in their IPs. Within the non-DT104 phage types, ampicillin-and/or streptomycin-resistant, integron-free MDR strains were also found. Based on amplicons varying between 290 and 3500 bp an IP system was suggested. The commonest amplicon sizes in non-DT104 strains were 1450 and 2050 bp. The IPs of DT104 strains and of non-DT104 strains containing an integron of 1 and 1.2 kb size were stable. In contrast, the IPs of other non-DT104 strains showed a varying degree of instability. Integron loss was frequently associated with spontaneous plasmid elimination and changes of R-type among the descendants of a given strain.Key words: Typhimurium, phage type, DT104, integron pattern, instability, PCR Since the early 1990s, the DT104 phage type of Salmonella enterica serotype Typhimurium (S. Typhimurium) has spread all over the world (Threlfall et al

Aims: The aim of the study was to develop a colony blot immunoassay to detect Shigella and enteroinvasive Escherichia coli (EIEC) in water. Methods and Results: Spiked samples were ®ltered through nitrocellulose membranes. Colony prints on the ®lters were tested with a monoclonal antibody speci®c to IpaC, an antigen coded by the invasion plasmid of Shigella and EIEC. Invasive pathogens could be successfully detected with the technique, even in the presence of a large number of non-pathogenic bacterial cells. The method was signi®cantly more sensitive in identifying pathogen-containing samples then the traditional culture-based approach. Conclusions: The IpaC-speci®c colony blot immunoassay is an inexpensive method for identifying the aetiological agents of bacillary dysentery in water samples. Signi®cance and Impact of the Study: The technique could be particularly useful in detecting enteroinvasive E. coli which often remains undetected by bio-and serotyping.