Bacterial adherence ability and adherence factors of quinolone sensitive and resistant E. coli strains isolated from cirrhotic patients
Abstract number: 902_p1060
Prolonged use of norfloxacin as secondary prophylaxis of spontaneous bacterial peritonitis entails an appearance of 40% of E. coli quinolone-resistant (QR) in stools. However, the development of infections caused by these QR bacteria is not so frequent as expected. Our aim was to assess bacterial adherence (BA) of either quinolone-sensitive (QS) or QR strains to oral epithelial cells in presence/absence of sub-MIC concentrations of norfloxacin and to evaluate the influence of some relevant adherence factors presence on adherence to cells.
59 strains of E. coli obtained from rectal swabs of cirrhotic patients were studied and their MIC was determined by E-test. Twenty strains from healthy volunteers were also tested as controls. Strains were incubated with oral epithelial cells in presence/absence of sub-MIC of norfloxacin. BA was measured by the percentage of epithelial cells with attached bacteria (marked with fluorescein). Adherence factors were determined by PCR of specific sequences for type I fimbriae, intimin and afimbrial adhesin. Type I fimbriae expression was also measured by agglutination inhibition with manose. Statistical analysis was performed with the SPSS package. Student's t-test or U-MannWhitney test was applied for quantitative variables, and Ji-Square test or Exact Fisher test were applied for qualitative ones.
22 QR and 37 QS strains were isolated. BA was similar in both series (78.2 vs. 80.6%, P = NS), and these percentages were similarly and significantly reduced when norfloxacin was added (48.5 vs. 45.0%, P = NS) (P < 0.001). The most frequent factor was type I fimbriae (71%), whose expression was shown in 52.3%. Eighteen per cent of the strains lacked the adherence factors studied. Adherence factors presence was less frequent in QR strains than in QS. Adherence observed is independent of the presence/absence of the adherence factor studied. The joint presence of various adherence factors is correlated with a slightly increase in BA, independently of the sensitivity to quinolones. No differences were found respect to the control strains results.
BA capacity of E. coli is independent of its sensitivity to quinolones, although QR strains seemed to be less infective. Subminimal concentrations of norfloxacin decreases BA in both bacterial phenotypes in the same degree. This result would support the continuous use of norfloxacin in this patients, in spite of the selection of QR strains in stools."
|Session name:||XXIst ISTH Congress|
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