Reduction of capsular polysaccharide production in Klebsiella pneumoniae by sodium salicylate

Influence of capsule and extended-spectrum beta-lactamases encoding plasmids upon Klebsiella pneumoniae adhesion

Interaction with cells is believed to be a crucial step in the process of colonization by Klebsiella pneumoniae. In this study, we investigated the adhesion properties of 17 extended-spectrum beta-lactamases (ESBLs) producing clinical isolates using 2 intestinal cells (Int-407 and HT-29 cells) and components of the extracellular matrix (ECM) (fibrinogen, collagen, fibronectin). Since the capsule formed by K. pneumoniae potentially masks bacterial cell surface components, we created mutants defective in capsular synthesis. The levels of adhesion of the acapsulated mutants were higher than their corresponding wild-type strains for 7 and 4 isolates with Int-407 and HT-29 cells, respectively, whereas 2 mutants displayed lower adhesion indexes with HT-29 cells. Nine mutants adhered at higher levels than their corresponding wild-type strains to all 3 components of ECM tested and 13 only to collagen. Transfer by mating of ESBL-encoding plasmids did not correlate with the acquisition of adhesive properties by the transconjugants, which suggests that these plasmids were not involved in adhesion expression. The presence of ESBL-encoding plasmids alters the basal adhesion capacity of the recipient strain, and cured strains adhered more than the parental strains. The possessing of capsule or plasmid-encoded factors would have a bacterial cost, including a weaker capacity for adhesion.

Homologous response regulators KvgA, KvhA and KvhR regulate the synthesis of capsular polysaccharide in Klebsiella pneumoniae CG43 in a coordinated manner

On the basis of phenotypic analysis, the Klebsiella pneumoniae CG43 derived mutants with deletions of the gene encoding respectively the response regulators KvgA, KvhA, and KvhR were classified into two groups. Group I bacteria carrying either kvgA- or kvhR- exhibited less mucoidy, lower level of capsular polysaccharide (CPS) synthesis and higher LD50 than the parental strain. No apparent change of the group II, including kvhA- and kvhA- kvhR- mutants, was observed. However, the mucoidy of kvhA- kvhR- mutant was found to be diminished after introducing into a kvhA- expressing plasmid. Via promoter-lacZ fusion analysis, kvhA deletion was found to reduce kvhR expression. A regulatory role of KvhA for the expression of kvhR was supported further by EMSA showing a specific binding of KvhA to the putative promoter of kvhR. The promoter activity measurement and EMSA also revealed that KvgA acted as an autoregulator and an activator for the expression of kvhAS and kvhR. In addition, deletion of kvgA suppressed slightly the promoter activity of the cps-orf16-17, and the expression of all three cps transcripts orf1-2, orf3-15, and orf16-17 were reduced in the kvhR- mutant. These suggest that the three homologous response regulators interact to control, in coordination, the bacterial cps expression.

Comparative signature-tagged mutagenesis identifies Pseudomonas factors conferring resistance to the pulmonary collectin SP-A

The pulmonary collectin, surfactant protein A (SP-A), is a broad spectrum opsonin with microbicidal membrane permeabilization properties that plays a role in the innate immune response of the lung. However, the factors that govern SP-A's microbial specificity and the mechanisms by which it mediates membrane permeabilization and opsonization are not fully understood. In an effort to identify bacterial factors that confer susceptibility or resistance to SP-A, we used comparative signature-tagged mutagenesis to screen a library of 1,680 Pseudomonas aeruginosa mutants for evidence of differential pulmonary clearance in SP-A-sufficient (SP-A^+/+) and SP-A-deficient (SP-A^−/−) mice. Two SP-A-sensitive P. aeruginosa mutants harboring transposon insertions in genes required for salicylate biosynthesis (pch) and phosphoenolpyruvate-protein-phosphotransferase (ptsP) were recovered. The mutants were indistinguishable from the parental wild-type PA01 with regard to opsonization by SP-A, but they exhibited increased susceptibility to SP-A-mediated membrane permeabilization. These results suggest that bacterial gene functions that are required to maintain membrane integrity play crucial roles in resistance of P. aeruginosa to the permeabilizing effects of SP-A.

Everyday, normal breathing deposits numerous microorganisms on the surfactant membrane that lines the air-exchanging surfaces of the lung. Surfactant protein SP-A, a component of the surfactant membrane, helps to maintain the lung in a germ-free state by aggregating inhaled microorganisms and facilitating their ingestion by immune cells, and by increasing the permeability of their cell membranes. However, the bacterial pathogen Pseudomonas aeruginosa is resistant to SP-A-mediated membrane disruption.

Using a genetic tool called comparative signature-tagged mutagenesis, the authors have identified two P. aeruginosa genes, pch and ptsP, that are required to resist SP-A-mediated membrane permeabilization. Molecular analyses indicate that the pch gene encodes an enzyme that synthesizes salicylate, a compound utilized by bacteria to acquire essential metal ions. The ptsP gene encodes an enzyme called phosphoenolpyruvate-protein-phosphotransferase. The loss of salicylate and phosphoenolpyruvate-protein-phosphotransferase weakens the P. aeruginosa cell membrane, which allows SP-A to poke holes on the membrane and kill the bacteria.

This is the first known report of the roles played by salicylate and phosphoenolpyruvate-protein-phosphotransferase in maintenance of bacterial membrane, and consequently, protecting bacteria from killing by SP-A, through disruption of membrane integrity.

Salicylic acid attenuates virulence in endovascular infections by targeting global regulatory pathways in Staphylococcus aureus

Aspirin has been previously shown to reduce the in vivo virulence of Staphylococcus aureus in experimental endocarditis, through antiplatelet and antimicrobial mechanisms. In the present study, salicylic acid, the major in vivo metabolite of aspirin, mitigated two important virulence phenotypes in both clinical and laboratory S. aureus strains: alpha-hemolysin secretion and fibronectin binding in vitro. In addition, salicylic acid reduced the expression of the alpha-hemolysin gene promoter, hla, and the fibronectin gene promoter, fnbA. Transcriptional analysis, fluorometry, and flow cytometry revealed evidence of salicylic acid-mediated activation of the stress-response gene sigB. Expression of the sigB-repressible global regulon sarA and the global regulon agr were also mitigated by salicylic acid, corresponding to the reduced expression of the hla and fnbA genes in vitro. Studies in experimental endocarditis confirmed the key roles of both sarA and sigB in mediating the antistaphylococcal effects of salicylic acid in vivo. Therefore, aspirin has the potential to be an adjuvant therapeutic agent against endovascular infections that result from S. aureus, by downmodulating key staphylococcal global regulons and structural genes in vivo, thus abrogating relevant virulence phenotypes.

RmpA2, an activator of capsule biosynthesis in Klebsiella pneumoniae CG43, regulates K2 cps gene expression at the transcriptional level

The rmpA2 gene, which encodes an activator for capsular polysaccharide (CPS) synthesis, was isolated from a 200-kb virulence plasmid of Klebsiella pneumoniae CG43. Based on the sequence homology with LuxR at the carboxyl-terminal DNA-binding motif, we hypothesized that RmpA2 exerts its effect by activating the expression of cps genes that are responsible for CPS biosynthesis. Two luxAB transcriptional fusions, each containing a putative promoter region of the K. pneumoniae K2 cps genes, were constructed and were found to be activated in the presence of multicopy rmpA2. The activation is likely due to direct binding of RmpA2 to the cps gene promoter through its C-terminal DNA binding motif. Moreover, the loss of colony mucoidy in a K. pneumoniae strain deficient in RcsB, a regulator for cps gene expression, could be recovered by complementing the strain with a multicopy plasmid carrying rmpA2. The CPS production in Lon protease-deficient K. pneumoniae significantly increased, and the effect was accompanied by an increase of RmpA2 stability. The expression of the rmpA2 gene was negatively autoregulated and could be activated when the organism was grown in M9 minimal medium. An IS3 element located upstream of the rmpA2 was required for the full activation of the rmpA2 promoter. In summary, our results suggest that the enhancement of K2 CPS synthesis in K. pneumoniae CG43 by RmpA2 can be attributed to its transcriptional activation of K2 cps genes, and the expression level of rmpA2 is autoregulated and under the control of Lon protease.

Eradication of biofilm-forming Staphylococcus epidermidis (RP62A) by a combination of sodium salicylate and vancomycin

Staphylococcus epidermidis is a major cause of infections associated with indwelling medical devices. Biofilm production is an important virulence attribute in the pathogenesis of device-related infections. Therefore, elimination of these biofilms is an ideal treatment. Salicylate (5 mM) combined with 1 microg of vancomycin per ml inhibited biofilm formation by S. epidermidis (RP62A) by >or=99.9%. When biofilm-coated polystyrene beads were exposed to 5 mM sodium salicylate and 4 microg of vancomycin per ml (one-half the minimum biofilm eradication concentration), there was a >99.9% reduction in viable count.

Capsule impedes adhesion to and invasion of epithelial cells by Klebsiella pneumoniae

The adhesion of K21a, K26, K36, and K50 capsulated Klebsiella strains to ileocecal (HCT-8) and bladder (T24) epithelial cell lines was significantly lower than that of their corresponding spontaneous noncapsulated variants K21a/3, K26/1, K36/3, and K50/3, respectively. Internalization of the bacteria by both epithelial cell lines was also significantly reduced. Similarly, a capsule-switched derivative, K2(K36), that exhibited a morphologically larger K36 capsule and formed more capsular material invaded the ileocecal epithelial cell line poorly compared to the corresponding K2 parent strain. None of the capsulated strains exhibited significant mannose-sensitive type 1 fimbriae, whereas two of the noncapsulated variants K21a/3 and K50/3 exhibited potent mannose-sensitive hemagglutinating activity. Although hemagglutinating activity that could be attributed to mannose-resistant Klebsiella type 3 fimbriae was weak in all strains, in several cases the encapsulated parent strains exhibited lower titers than their corresponding noncapsulated variants. Although the level of adhesion to the ileocecal cells is not different from adhesion to bladder cells, bacterial internalization by bladder cells was significantly lower than internalization by ileocecal cells, suggesting that bladder cells lack components required for the internalization of Klebsiella.

The effects of salicylate on bacteria

Salicylate and related compounds, such as aspirin, have a variety of effects in eucaryotic systems and are well known for their medicinal properties. Salicylate also has numerous effects on bacteria, yet only a handful of individuals within the scientific community appreciate these findings. From a bacterial viewpoint, growth in the presence of salicylate can be both beneficial and detrimental. On one hand, growth of certain bacteria in the presence of salicylate can induce an intrinsic multiple antibiotic resistance phenotype. On the other hand, growth in the presence of salicylate can reduce the resistance to some antibiotics and affect virulence factor production in some bacteria. This review provides an overview of the effects salicylate has on various bacterial species.

Binding to and opsonophagocytic activity of O-antigen-specific monoclonal antibodies against encapsulated and nonencapsulated Klebsiella pneumoniae serotype O1 strains

The high mortality of nosocomial infections caused by Klebsiella spp. has acted as a stimulus to develop immunotherapeutic approaches targeted against surface molecules of these bacteria. Since O-antigen-specific antibodies may add to the protective effect of K antisera, we tested the functional and binding capacity of O-antigen-specific monoclonal antibodies (MAbs) raised against different Klebsiella O antigens. The MAbs tested were specific for the O-polysaccharide partial antigens D-galactan II (MAb Ru-O1), D-galactan I (MAb IV/4-5), or core oligosaccharide (MAb V/9-5) of the Klebsiella serogroup O1 antigen. In enzyme-linked immunosorbent assay binding experiments, we found that all MAbs recognized their epitopes on intact capsule-free bacteria; however, binding to encapsulated wild-type strains belonging to different K-antigen serotypes was significantly reduced. The K2 antigen acted as the strongest penetration barrier, while the K7 and K21 antigens allowed some, though diminished, antibody binding. In vitro phagocytic killing experiments showed that MAb Ru-O1 possessed significant opsonizing activity for nonencapsulated O1 serogroup strains and also, to a much lesser extent, for encapsulated strains belonging to the O1:K7 and O1:K21 serotypes. MAbs or antisera specific for the D-galactan II antigen may thus be the most promising agents for further efforts to develop a second-generation Klebsiella hyperimmune globulin comprising both K- and O-antigen specificities.

Klebsiella pneumoniae 35 and 36 kDa porins are common antigens in different serotypes and induce opsonizing antibodies

BACKGROUND

Klebsiella pneumoniae is a major cause of neonatal sepsis and nosocomial infections in Mexico. Antibiotic therapy is the first choice for treatment but the increase in multiple resistance strains has forced scientists to look for alternative treatments, such as immunotherapy. In this work, we propose that porins could be a common antigen among four different capsular serotypes of Klebsiella pneumoniae for the production of immune sera with opsonizing capacity.

METHODS

The 35 and 36 kDa porins from four different serotypes of the bacteria were isolated by the Nikaido method followed by purification in Sephacryl column chromatography. The 36 kDa of serotype K8 was further purified by electroelution. The 35 and 36 kDa porins were used to obtain rabbit polyclonal antibodies (PolyAb) to the four serotypes and the 36 kDa from K8 for the production of monoclonal antibodies (MoAb). Antigenic reactivity of PolyAb and MoAb were analyzed by ELISA and WB and their opsonizing capacity for human PMN was measured by chemiluminescence (CL) using capsulated and non-capsulated bacteria.

RESULTS

Porins from the four strains showe electrophoretic homology and cross reaction by ELISA and WB. CL assays indicated that PolyAb opsonized heterologous strains and that MoAb perform this in the absence of capsule.

CONCLUSIONS

K.pneumoniae 35 and 36 kDa porins are common antigens for the four serotypes studied and induce opsonizing antibodies.

Inability of encapsulated Klebsiella pneumoniae to assemble functional type 1 fimbriae on their surface

We screened phase variants of Klebsiella pneumoniae isolates for the expression of capsule and type 1 fimbriae and found that all of the 22 blood isolates were encapsulated and did not express type 1 fimbriae while 10 of 11 urinary tract isolates expressed type 1 fimbriae but were unencapsulated. Phase variants from selected isolates were found to be either unencapsulated and fimbriated or lacked both structures. Variants expressing both structures were not detected. Fimbrial subunits FimH and FimA were localized in the periplasmic space of the parent strain and on the surface of the unencapsulated variants. The results suggest that capsule formation impedes assembly of pre-formed fimbrial subunits on the bacterial surface.

Surface antigen exposure by bismuth dimercaprol suppression of Klebsiella pneumoniae capsular polysaccharide

The bacterial capsule is an important virulence determinant in animal and plant disease. Bacterial capsule and slime can be inhibited by bismuth compounds, especially when complexed with lipophilic thiol chelators. Bismuth dimercaprol (BisBAL) at 1 ppm of Bi3+ repressed Klebsiella pneumoniae capsule expression in defined medium by nearly 90%, which exposed subsurface structures. The phagocytic index for BisBAL-treated bacteria increased from <10 to 360 bacteria per 100 neutrophils in the presence of complement and anticapsular or anti-O antigen antiserum. BisBAL treatment also enhanced the reactivity of monoclonal antibodies (MAbs) specific for the O1-antigen lipopolysaccharide (LPS) or the LPS core in a dose-dependent manner as indicated by the results of enzyme-linked immunosorbent assays. When anti-O1 MAb was used, the reactivity increased significantly for fully encapsulated O1:K1 or O1:K2 cells but not for O1:K- cells. Deposition of C3b also increased significantly for BisBAL-treated O1:K1 or O1:K2 cells but not for O1:K- cells. Survival of a serum-sensitive strain was <0.1% when nonimmune human serum absorbed with O1:K1 cells was used and 107% when BisBAL-treated cells were used for absorption. Outer membrane proteins were also more accessible on the surface of K. pneumoniae after BisBAL treatment. Thus, at subinhibitory levels, BisBAL inhibited capsule expression, which promoted phagocytosis, enhanced the reactivity of specific antibodies for LPS O antigen, LPS core epitopes, or outer-membrane proteins, and enhanced complement interaction with encapsulated K. pneumoniae. By unmasking bacterial surface structures and enhancing the immune system reactivity to bacteria, bismuth thiols may prove useful as adjuncts for vaccination.

Consequences of reduction of Klebsiella pneumoniae capsule expression on interactions of this bacterium with epithelial cells

Most Klebsiella pneumoniae clinical isolates are fully encapsulated and adhere in vitro to intestinal cell lines with an aggregative pattern. In this study, the influence of the capsule on interactions with epithelial cells was investigated by creating an isogenic mutant defective in the synthesis of the capsule. Determination of the uronic acid content of bacterial extracts confirmed that the mutant did not produce capsular polysaccharides whereas, with the wild-type strain, the level of encapsulation was growth phase dependent and reached a maximum during the lag and early log phases. Assays performed with different epithelial cell lines, Int-407, A-549, and HEp-2, showed that the capsule-defective mutant demonstrated greater adhesion than did the wild-type strain and that the aggregative pattern was maintained, indicating that the capsule was not related to the adhesion phenotype. In contrast, when the mucus-producing HT-29-MTX cells were used, the encapsulated wild-type strain adhered more strongly than did the capsule-defective mutant. No invasion properties were observed with any of the capsular phenotypes or cell lines used. The K. pneumoniae adhesin CF29K was detected by Western blot analysis and enzyme-linked immunosorbent assay on the surface of transconjugants obtained after transfer of a conjugative plasmid harboring the CF29K-encoding genes into both the wild-type and the capsule-defective strains. The amounts of adhesin detected were greater in the capsule-defective background strain than in the wild-type encapsulated strain and were associated with an increase in the level of adhesion to Caco-2 cells. Moreover, RNA slot blot experiments showed that transcription of the adhesin-encoding gene was markedly increased in the capsule-defective mutant compared to the wild-type encapsulated background. These results suggest (i) that the capsule plays an active role during the initial steps of the pathogenesis by interacting with mucus-producing cells but is subsequently not required for the adhesin-related interaction with the epithelial cell surface and (ii) that the expression of the adhesin is modulated by the presence of a capsule at a transcriptional level.

Inhibition of bacterial adherence to a high-water-content polymer by a water-soluble, nonsteroidal, anti-inflammatory drug

Deposition and aggregation of lachrymal proteins on the contact lens surface can promote bacterial adherence. Lysozyme is the major tear protein and is also mainly responsible for the formation of protein deposits on contact lenses. Nonsteroidal anti-inflammatory drugs (NSAID) prevent protein aggregation. The effect of a water-soluble NSAID drug on bacterial adherence to high-water-content/ionic disposable contact lenses was examined in a radiolabeling study. Dose-related inhibition of adherence of Staphylococcus aureus, S. epidermidis, and Pseudomonas aeruginosa on both pretreated lenses and after adding the drug to the medium was investigated. When the drug was added to the media, maximal inhibition of S. aureus adherence was observed in trypticase soy broth (59-98% at the lower and higher drug concentrations, respectively); inhibition progressively decreased in calf aqueous humor (48-75%), lysozyme (34-63%), and saline (12-20%) solutions. Inhibition of adherence varied with the three bacterial species; it was maximal with S. aureus, intermediate with S. epidermidis, and minimal with P. aeruginosa. When lenses were pretreated with the drug, consistent, and even higher, inhibitory effects were observed. The results suggest that water-soluble NSAIDs could be used in preventive treatments for conjunctivae and corneal infections in contact lens wearers, and may provide a clue as to which compounds might inhibit protein interaction and bacterial adhesion.

Salicylate-enhanced exposure of Klebsiella pneumoniae subcapsular components

The capsular polysaccharide (CPS) of Klebsiella pneumoniae is an important virulence factor. Salicylate, which inhibits CPS production, was used to expose subcapsular antigens and components that may play an important role in host defense. Salicylate treatment greatly increased phagocytosis of five O1 serotypes by human polymorphonuclear leukocytes with normal rabbit serum and rabbit antisera against purified O1 lipopolysaccharide (O1LPS) as opsonins (p < 0.01 or < 0.05). Similar results were obtained with rabbit antiserum against a non-encapsulated isogenic strain. To further determine how salicylate increases susceptibility to phagocytosis, the binding of monoclonal antibodies against O1LPS or the LPS core and the binding of complement component C3b were measured by ELISA. The data indicate that salicylate reduced the barrier of CPS in serotypes O1:K1, O1:K10, and O1:K16 and unmasked subcapsular antigenic components in serotypes O1:K2 and O1:K66 so that bound opsonins could react with receptors on phagocytes. Serum bactericidal assays supported this conclusion. Therefore, decapsulating agents such as salicylate accentuate phagocytosis of K. pneumoniae by making subcapsular antigens and components accessible to immune and nonimmune host defences and vaccination with subcapsular antigens may exhibit optimal protection against lethal infection when combined with salicylate therapy.

Effect of salicylate on expression of flagella by Escherichia coli and Proteus, Providencia, and Pseudomonas spp

Osmotic stress, salicylate, and Mar (multiple antibiotic resistance) mutation are known to block the expression of the OmpF porin. Since these conditions have also been shown to inhibit the expression of P and CFA fimbriae in Escherichia coli, we speculated that they might affect the expression of flagella as well. Hyperosmotic conditions have been shown to block the synthesis of flagellin and expression of flagella in E. coli (C. Li, C. J. Louise, W. Shi, and J. Adler, J. Bacteriol. 175:2229-2235, 1993). In the current study, sodium salicylate was found to inhibit the motility of E. coli, Proteus mirabilis, Proteus vulgaris, Providencia rettgeri, and Providencia stuartii in a reversible, concentration-dependent manner. Swarming did not occur at 20 mM sodium salicylate. Salicylate also blocked the synthesis of flagellin in E. coli. Phenotypic Mar mutants of E. coli derived from motile strains were amotile. Flagella were markedly reduced as determined by scanning electron microscopy when P. mirabilis was grown in broth containing 20 mM salicylate. Salicylate had no apparent effect, however, on expression of a 40-kDa porin protein in P. mirabilis. This finding suggests that the noted effect of salicylate on Proteus spp. may be mediated through a mechanism other than porin production or that the Proteus porin may not be analogous to OmpF in E. coli. Salicylate decreased the motility of Pseudomonas cepacia but had no effect on Pseudomonas aeruginosa. The exact mechanism by which salicylate exerts its effect is not known, but it appears to be related to osmoregulation.

Polysaccharide capsule-mediated resistance to opsonophagocytosis in Klebsiella pneumoniae

The polysaccharide capsule of Klebsiella pneumoniae is an important virulence factor that confers resistance to phagocytosis. The treatment of encapsulated bacteria with salicylate to inhibit capsule expression was found to enhance the phagocytosis of encapsulated bacteria by human neutrophils only in the presence of cell surface-specific antibodies. Both type-specific rabbit antisera and anticapsular human hyperimmune globulin were employed as opsonins. Salicylate significantly enhanced phagocytosis with homologous, but not heterologous, whole-cell antisera. Antisera, diluted 1:40, no longer opsonized fully encapsulated bacteria but promoted the uptake of multiple salicylate-treated bacteria in > 90% of neutrophils. Salicylate (0.25 to 1.0 mM) also enhanced opsonization with globulin against homologous bacteria. Higher salicylate levels (1 to 2.5 mM) enhanced the opsonization of heterologous serotypes with human globulin. The nature of antibody attachment to encapsulated bacteria was determined by immunofluorescence. Even after the addition of purified capsular polysaccharide to prevent phagocytosis, K-specific antibodies attached in large amounts to bacteria. K-specific antibodies reacted with antigens throughout the capsule and showed a predilection for a denser inner layer of the capsule, indicating that many of the K-specific antibodies may be masked underneath the capsule surface. K-specific antibodies can also be rendered nonfunctional by soluble, cell-free capsular antigen. In culture, large quantities of soluble capsular polysaccharide extrude from bacteria after overnight growth. The reduction in capsule expression caused by salicylate largely affected the soluble, cell-free fraction. Purified capsular polysaccharide was shown to retard the opsonophagocytosis of salicylate-treated bacteria in a concentration-dependent manner. However, extensive washing of encapsulated bacteria to remove loosely attached capsular material did not significantly enhance opsonophagocytosis. In conclusion, cell-free capsule and cell-associated capsule are antiphagocytic; both act to neutralize K-specific antibodies by binding or concealment. Salicylate-mediated inhibition of capsule expression, particularly of the cell-free fraction, improved K-specific opsonization dramatically.

Urethral cytology in spinal cord injury patients performing intermittent catheterisation

Local reactions of the urethral wall are known to occur by repeated introduction of a catheter in the urethra. Urethritis was found in 2-19% of patients practising intermittent catheterisation. Although the use of catheters of smaller size and the liberal use of lubricants may prevent urethral irritation and trauma, it was postulated that hydrophilic catheters (LoFric, Astra Tech Ltd, Stroud, England) induce significantly less trauma than PVC catheters because of the binding of the water molecules to the catheter surface which consists of polyvinylpyrrolidone and sodium chloride. Although urethritis and urethral stricture may represent one end of the spectrum of repeated urethral trauma, minor degrees of inflammation need to be quantitatively determined while assessing two different catheters for intermittent catheterisation. The degree of urethral inflammation in patients practising intermittent catheterisation was studied by urethral cytology and staining the smear by Papanicolaou's method. The number of neutrophil polymorphs and epithelial cells in three random high power fields in the urethral smear was counted and the percentage ratio of polymorphs to epithelial cells was calculated. Group 1 comprised 14 patients practising intermittent catheterisation with a PVC catheter and group 2 comprised 17 patients performing intermittent catheterisation with a LoFric catheter. There was no significant difference between the two groups as regards the age, diagnosis, size of the catheter used for intermittent catheterisation and the number of times that they performed catheterisation during a 24 hour period. Urethral cytology revealed a percentage (mean ratio) ratio of polymorphs to epithelial cells of 66 in group 1 and 0.04 in group 2. (< 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of salicylate, bismuth, osmolytes, and tetracycline resistance on expression of fimbriae by Escherichia coli

Adherence of Escherichia coli is facilitated by fimbriae and several outer membrane proteins (OMPs). Hypertonic conditions, salicylate, and Mar mutations are known to reduce OmpF expression. We speculated that OMPs involved in export or assembly of fimbrial subunits might be similarly affected. To explore this hypothesis, E. coli expressing P, type 1, S, colonization factor antigen I (CFA/I), or CFA/II fimbriae was grown in the presence of salicylate, bismuth salts, NaCl, and nonfermented sugars. Tetracycline-resistant clones were derived from several P-fimbriated strains. The bacteria were tested for the ability to agglutinate erythrocytes, yeast cells, and alpha-D-Gal(-4)-beta-D-Gal-bonded latex (Gal-Gal) beads and were examined for fimbriae by electron microscopy. Hyperosmolar conditions decreased fimbrial expression for all strains. Expression of P fimbriae by pyelonephritic strains, all of which were OmpF+, was reversibly repressed by salicylate and bismuth salts. CFA strains were similarly affected. Tetracycline-resistant P-fimbriated strains were OmpF deficient, were unable to agglutinate erythrocytes and Gal-Gal beads, and lacked fimbriae as observed by electron microscopy. Strains with plasmid-encoded P-fimbrial genes did not demonstrate OmpF on polyacrylamide gel electrophoresis profiles and were not affected by salicylate. The type 1-fimbriated phenotype was not affected by salicylate or bismuth unless the strains also expressed P fimbriae. S-fimbriated strains were not affected. The mechanism by which salicylates, bismuth salts, and tetracycline resistance inhibit or modulate the expression of P fimbriae may be mediated through OmpF and other OMPs.

Salicylic acid prevents the adherence of bacteria and yeast to silastic catheters

During the pathogenesis of catheter-related urinary tract infection, bacteria attach to the catheter and migrate along a biofilm into the bladder. We studied the effect of coating silastic catheters with salicylic acid on bacterial and yeast adherence. An agar roll technique, bioluminescent assay, and radiolabeling study all produced consistent results. There was a dose related inhibition of adherence with Pseudomonas aeruginosa, Enterobacter aerogenes, Klebsiella pneumoniae, Candida albicans, and Enterococcus faecalis. Inhibition of over 90% was noted with Enterobacter and Pseudomonas. Similar results were obtained in broth and synthetic urine. A dose related reduction in adherence was seen with all gram-negative rods and yeast as measured by a radiolabeling assay. TDMAC was used to bind the salicylic acid to the catheters with > 95% inhibition of the gram-negative rods. These studies suggest the potential role of coating catheters with salicylic acid to reduce bacterial adherence and urinary tract infection.

The use of salicylic acid to prevent the adherence of Escherichia coli to silastic catheters

We studied the effect of salicylic acid on the attachment of Escherichia coli to silastic catheters. Silastic catheters were exposed to organisms grown in the presence of subinhibitory concentrations (1 and 5 mM.) of salicylic acid. An agar rolling technique demonstrated 59% and 79% inhibition of adherence with the 2 concentrations, respectively. Silastic catheters were also pretreated by heating and then incubating in 200 mM. and 600 mM. salicylic acid in 95% ethanol at -20C. After incubation in 10(4) CFU/ml. E. coli for 5 hours at 37C, 62% and 93% inhibition of adherence was observed. Acetylsalicylic acid and ibuprofen did not demonstrate similar results. Similar inhibition (82% and 95%) was observed despite preincubation of the treated catheters in sterile urine for 4 days. A bioluminescent assay of bacterial adherence also revealed inhibition only with salicylic acid. Studies using 3H-leucine demonstrated a decrease in adherence with higher concentrations of salicylic acid. Finally, tridodecylmethylammonium was used to bind salicylic acid to silastic catheters. After a 5-hour incubation in 10(4) CFU/ml. at 37C, 94% and 99% inhibition were observed with 200 and 600 mM. salicylic acid. Salicylic acid decreases adherence of E. coli to silastic catheters. This observation may be of value in designing catheters less likely to cause urinary tract infection.

Salicylate or bismuth salts enhance opsonophagocytosis of Klebsiella pneumoniae

After treatment of encapsulated Klebsiella pneumoniae with salicylate or bismuth compounds, phagocytic uptake by human peripheral white blood cells or rat alveolar macrophages was assessed. Without salicylate pretreatment of bacteria, a 30-60% net increase in viable bacteria resulted in phagocytic assays after a 1 hour incubation. With salicylate pretreatment, dose-related decreases in bacterial counts were seen, achieving a maximal reduction of 60% with 240 microM salicylate pretreatment. Bacterial variants producing less capsule were more serum sensitive and more readily phagocytosed. Micrographs of Giemsa-stained cells revealed phagocytic uptake of multiple bacteria after salicylate pretreatment, but virtually no uptake of untreated bacteria. Opsonization with polyclonal antiserum decreased bacterial cell counts by 20% without and by 90% with salicylate pretreatment of bacteria. Pretreatment of bacteria with bismuth salts also enhanced opsonophagocytosis of encapsulated bacteria. Thus, agents known to reduce capsule expression in K. pneumoniae also enhance phagocytic uptake of bacteria.