[DNA probe for the detection of uropathogenic strains of P-fimbriated Escherichia coli]. / Sonda de ADN para la detección de cepas uropatógenas de Escherichia coli P fimbriadas.

BACKGROUND: P fimbria is one of the main factors of virulence of the uropathogenic Escherichia coli strains thus developing methods for its detection is of interest. P fimbriation may manifest through associated characteristic hemagglutination patterns. Another way of directly detecting its expression is by the PF test consisting in a specific agglutination test with latex particles which have the specific receptor of the fimbria incorporated. METHODS: The two phenotypic techniques (hemagglutination pattern using human, bovine, and sheep erythrocytes, and the PF test) were compared with colony hybridization with a specific DNA probe (pap1) in 35 strains of uropathogenic E. coli. RESULTS: Eight of the 35 strains studied were positive for the PF test with 7 strains presenting mannose-resistant agglutination to human erythrocytes without agglutinating the other erythrocytes tried. However, with hybridization with the DNA probe the number of positives was higher (25/35). CONCLUSIONS: The difference found in the number of positive strains may be due to the probe used corresponding to cluster pap, thus the use of a smaller more specific probe for fimbrial expression obtained from pap should be used given that the hybridization technique is easy to perform and is carried out in less time than phenotypic detection which requires long periods of culture prior to the test.

[Detection of virulence factors using DNA probes in uropathogenic strains of Escherichia coli]. / Detección de factores de virulencia mediante sondas de DNA en cepas de Escherichia coli uropatógenas.

BACKGROUND: There are several bacterial determinants that contribute to the onset of urinary tract infection by E. coli. The present study focuses on some of the virulence factors considered to be most important, as P fimbriae, the siderophore aerobactin and bacterial capsule, which were studied among 123 uropathogenic E. coli strains isolated from outpatients from the Basque Community. METHODS: Virulence factors were detected using Molecular Biology techniques, namely DNA hybridization to specific probes prepared in our laboratory. RESULTS: When probe pap2, specific for fimbrial adherence was used, 36.5% of the strains showed positive hybridization, and 66 and 73% of the strains hybridized to probes for aerobactin and common capsule region, respectively. CONCLUSIONS: We believe that this technology provides a very useful tool for rapid and easy screening of strains harbouring different virulence factors. Nevertheless, the fact that these methods detect genetic determinants that are not always being expressed must be borne in mind.

[Modulation of P-fimbriation by ciprofloxacin in uropathogenic Escherichia coli]. / Modulación de la fimbriación P por ciprofloxacina en Escherichia coli uropatógena.

BACKGROUND: The aim of this study was to determine the effect of ciprofloxacin at subinhibitory concentrations on the expression of P fimbriae of uropathogenic Escherichia coli. Thirty-nine strains of Escherichia coli isolated from out patients with urinary tract infection were studied. Thirty-nine of these strains had been previously characterized as P-fimbriated and the remaining non fimbriated strain was used as a negative control. METHODS: Fimbriation was quantitatively studied by electron microscope observation of the strains before and after treatment. To determine possible qualitative variations in the fimbrial proteins and in the external membrane (OMPs), extraction and electrophoretic separation was performed in polyacrylamide gels. RESULTS: No qualitative differences were observed in the OMPs profile and fimbrial proteins induced by ciprofloxacin in any of the strains studied. However, electron microscopic observation generally showed a decrease in the percentage fimbriated bacterial cells by the antimicrobial effect. CONCLUSIONS: The mechanism of action of ciprofloxacin at subinhibitory doses may correspond to a process of fimbrial protein synthesis inhibition secondary to the initiation of general repair mechanism of the cell exposed to the antimicrobial and not to a process of specific mutations which qualitatively affect fimbrial protein composition.

[Virulence factors and 0 serogroups of Escherichia coli as a cause of community-acquired urinary infections]. / Factores de virulencia y serogrupos 0 de Escherichia coli causantes de infecciones urinarias comunitarias.

BACKGROUND: The aim of this study was to determine the virulence factors and 0 serogroups of E. coli strains that cause community acquired urinary tract infections (UTI). METHODS: We examined 103 E. coli strains isolated from the urine of patients with UTI. The following virulence factors were investigated using phenotypic techniques: the alpha-haemolysin (Hly), the cytotoxic necrotizing factor type 1 (CNF-1) and the mannose-resistant haemagglutination (MRHA) types III, IVa and IVb expressed by P fimbriated E. coli. Serotyping of 0 antigen was carried out by means of a microtechnique using 163 antisera. RESULTS: Fifty-five (53%) of the 103 E. coli strains examined showed some of the virulence factors investigated in this study; 41% of the strains were Hly+, 28% were CNF-1+ and 48% expressed MRHA types III, IVa or IVb. The uropathogenic strains characterized belonged to 27 different 0 serogroups. However, 68% were from one of 10 serogroups (01, 02, 04, 06, 09, 018, 027, 073, 075 and 077) and 36% were from one of only 3 serogroups (02, 04 and 06). Furthermore, the virulence factors were concentrated in strains belonging to the 3 serogroups most frequently detected. Thus, 36 (97%) of the 37 strains of these 3 serogroups showed virulence factors, versus only 19 (29%) of 66 belonging to other serogroups (p < 0.001). CONCLUSIONS: Our results support the special pathogenicity theory and suggest that many cases of community acquired UTI may be caused by a limited number of uropathogenic E. coli strains that produce toxins (Hly+ and/or CNF-1+) and possess P fimbriae or P-related adhesins (with MRHA types III, IVa or IVb), and that usually belong to 02, 04 and 06 serogroups.