The effect of different cultivation temperatures (30 and 37 degrees C) and pH of the media (5.5, 7.5, 8.5) on the biofilm production was compared in Pseudomonas aeruginosa, Klebsiella pneumoniae, and Vibrio cholerae non-O1 and O1 using the crystal-violet test for estimation of quantitative production of the biofilm. Decrease (46.4-98.4 %) in the biofilm production was observed at 37 degrees C in 8 of the tested strains (P. aeruginosa three strains, K pneumoniae two, V. cholerae non-O1 two, and V. cholerae O1 one strain) compared with the production at 30 degrees C. On the other hand, five strains (P. aeruginosa 1, K. pneumoniae 3, V. cholerae non-O1 1) exhibited under these conditions a higher biofilm production (103-143 %). However, this difference was not significant (p = 0.196). Increased pH lead to a higher biofilm production using all media tested. In P. aeruginosa the biofilm production at pH 8.5 was 139-244 %, at pH 7.5 136-164 % in comparison with pH 5.5. Similarly, in K. pneumoniae the biofilm production increased to 151-319 % at pH 8.5 while with the drop of pH to 7.5 the biofilm production was 113-177 % compared with pH 5.5. In V. cholerae non-O1 and O1 the biofilm production reached 204-329 % at pH 8.5, and 123-316 % at pH 7.5 (compared with the production at pH 5.5). An increase in biofilm production represented an average of 169 % (p = 0.001) at pH change from 5.5 to 7.5, with the rise of pH from 5.5 to 8.5 caused an average difference of 229 % (p = 0.001).

No abstract

No abstract

cš y¢ SummaryHost protection by humoral immunity against Vibrio cholerae O1 confers lipopolysaccharide (LPS)-specific vibriocidal antibodies. Levels of relevant specific antibodies are closely related to complement-mediated inactivation of the vibrios inoculum, especially on the mucosal surface of intestine. We have tested complex V. cholerae O1 Ogawa-detoxified lipopolysaccharide (dLPS) conjugates. The first conjugate contained glucan both as the immunomodulator and the matrix; the second conjugate contained immunologically inert amylose as matrix. Both d-LPS conjugates contain multiply attached dLPS antigen. These conjugates elicited a statistically significant increase of antigen-specific IgG levels in mice ( P < < < < 0·001 and P < < < < 0·05, respectively). The specific anti-conjugate IgG and IgA response after the second (booster) dose were significantly higher compared to pre-immune and whole-cell response. The most effective vibriocidal activity was observed in the case of conjugate, with glucan as the matrix. The highest correlation was found between vibriocidal activity and specific IgG2b ( r = = = = 0·765) and IgA ( r = = = = 0·887) sera levels. The determination of specific IgG subclasses and IgG2a + + + + 2b/IgG1 ratio revealed a dominant T H 1 cell response crucial for effective vaccine candidate.

Resistance to 17 antimicrobials, surface hydrophobicity, motility, biofilm, production of N-acylhomoserine lactone signal molecules (N-butyrylhomoserine lactone and N-3-oxolauroylhomoserine lactone) and response to oxidative stress were analyzed in 47 clinical Pseudomonas aeruginosa strains. In addition to natural resistance, the strains demonstrated the greatest level of resistance to cefotaxime (91.5%). Isolates in the range of 44.7-57.4% were resistant to aminoglycosides and ciprofloxacin, of 25.5-36.2% to cephalosporins. On the other hand, 97.9% remained susceptible to meropenem, 93.6% to piperacillin + tazobactam and 87.2% to piperacillin. The majority of the strains (72.3%) manifested their hydrophilic character. Higher zones of motility showed 12 isolates (in average 54.8 mm) as compared to the others (30.2 mm). Approximately 1/3 of the strains (29.8%) produced a higher amount of biofilm quantified by measuring the absorbance of solubilized crystal violet (0.20-0.46) than the rest of isolates (0-0.19). All but two strains produced N-3-oxolauroylhomoserine lactone and in 48.9% of samples N-butyrylhomoserine lactone were detected. Only four isolates with higher biofilm production showed both types of homoserine lactone. Majority of the strains (70.2%) manifested higher resistance to H2O2 than the rest of the strains. The group of strains resistant to aminoglycosides and ciprofloxacin revealed a significantly higher number of hydrophobic strains (compared with the sensitive ones). In contrast, higher number of strains sensitive to aminoglycosides and ciprofloxacin or only to ciprofloxacin produced N-butyrylhomoserine lactone and biofilm (compared to the resistant ones). Such association was not found among the rest of the tested parameters. The results indicate that the resistance to antimicrobials in P. aeruginosa isolates was not generally associated with changes in the production of the pathogenicity factors.