Improvement of the salt aggregation test to study bacterial cell-surface hydrophobicity

The Prolonged Treatment of Salmonella enterica Strains with Human Serum Effects in Phenotype Related to Virulence

Salmonella enterica as common pathogens of humans and animals are good model organisms to conduct research on bacterial biology. Because these bacteria can multiply in both the external environments and in the living hosts, they prove their wide adaptability. It has been previously demonstrated that prolonged exposition of Salmonella serotype O48 cells to normal human serum led to an increase in resistance to sera in connection with the synthesis of very long O-antigen. In this work, we have studied the phenotype connected to virulence of Salmonella enterica strains that were subjected to consecutive passages in 50% human serum from platelet-poor plasma (SPPP). We found that eight passages in SPPP may not be enough for the bacteria to become serum-resistant (S. Typhimurium ATCC 14028, S. Senftenberg). Moreover, C1q and C3c complement components bound to Salmonellae (S. Typhimurium ATCC 14028, S. Hammonia) membrane proteins, which composition has been changed after passaging in sera. Interestingly, passages in SPPP generated genetic changes within gene fljB, which translated to cells’ motility (S. Typhimurium ATCC 14028, S. Erlangen). One strain, S. Hammonia exposed to a serum developed a multi-drug resistance (MDR) phenotype and two S. Isaszeg and S. Erlangen tolerance to disinfectants containing quaternary ammonium salts (QAS). Furthermore, colonial morphotypes of the serum adaptants were similar to those produced by starter cultures. These observations suggest that overcoming stressful conditions is manifested on many levels. Despite great phenotypic diversity occurring after prolonged exposition to SPPP, morphotypes of colonies remained unchanged in basic media. This work is an example in which stable morphotypes distinguished by altered virulence can be confusing during laboratory work with life-threatening strains.

Gardnerella vaginalis and Neisseria gonorrhoeae Are Effectively Inhibited by Lactobacilli with Probiotic Properties Isolated from Brazilian Cupuaçu (Theobroma grandiflorum) Fruit

In recent years, certain Lactobacillus sp. have emerged in health care as an alternative therapy for various diseases. Based on this, this study is aimed at evaluating in vitro the potential probiotics of five lactobacilli strains isolated from pulp of cupuaçu fruit fermentation against Gardnerella vaginalis and Neisseria gonorrhoeae. Our lactobacilli strains were classified as safe for use in humans, and they were tolerant to heat and pH. Our strains were biofilm producers, while hydrophobicity and autoaggregation varied from 13% to 86% and 13% to 25%, respectively. The coaggregation of lactobacilli used in this study with G. vaginalis and N. gonorrhoeae ranged from 15% to 36% and 32% to 52%, respectively. Antimicrobial activity was present in all tested Lactobacillus strains against both pathogens, and the growth of pathogens in coculture was reduced by the presence of our lactobacilli. Also, all tested lactobacilli reduced the pH of the culture, even in incubation with pathogens after 24 hours. The cell-free culture supernatants (CFCS) of all five lactobacilli demonstrated activity against the two pathogens with a halo presence and CFCS characterization assay together with gas chromatography revealed that lactic acid was the most abundant organic acid in the samples (50% to 62%). Our results demonstrated that the organic acid production profile is strain-specific. This study revealed that cupuaçu is a promising source of microorganisms with probiotic properties against genital pathogens. We demonstrated by in vitro tests that our Lactobacillus strains have probiotic properties. However, the absence of in vivo tests is a limitation of our work due to the need to evaluate the interaction of our lactobacilli with pathogens in the vaginal mucosa. We believe that these findings may be useful in developing a product containing our lactobacilli and their supernatants in order to support with vaginal health.

Hydrophobic features of EPS extracted from anaerobic granular sludge: an investigation based on DAX-8 resin fractionation and size exclusion chromatography

The hydrophobic fractionation of extracellular polymeric substances (EPS) extracted from anaerobic granular sludge was performed on the DAX-8 resin (two elution pH conditions, i.e., pH 2 and pH 5 were tested). The impact of seven different EPS extraction methods on EPS hydrophobicity features was assessed. The results showed that the extraction methods and bulk solution pH influenced dramatically the biochemical composition of the EPS, and in turn, the hydrophobicity determined. Besides, EPS extracting reagents i.e., formaldehyde, ethanol, sodium dodecyl sulfate (SDS), and Tween 20 not only introduced extra carbon content in the total organic carbon (TOC) measurement but also interacted with the DAX-8 resin. By comparing the apparent molecular weight (aMW) distribution of untreated and pH-adjusted EPS samples, more complete EPS aMW information was preserved at pH 5. Thus, elution at pH 5 was preferred in this study for the qualitative analysis of EPS hydrophobic features. The hydrophobic fraction of EPS retained by the resin at pH 5 was ascribed to a wide aMW range, ranging from >440 to 0.3 kDa. Within this range, EPS molecules ranging from 175 to 31 kDa were mostly retained by the DAX-8 resin, which indicates that these EPS molecules are highly hydrophobic.

Lactobacilli reduce chemokine IL-8 production in response to TNF-α and Salmonella challenge of Caco-2 cells

The probiotic properties of two selected lactobacilli strains were assessed. L. salivarius and L. plantarum displayed higher hydrophobicity (48% and 54%, resp.) and coaggregation ability with four pathogens (from 7.9% to 57.5%). L. salivarius and L. plantarum had good inhibitory effects on S. aureus (38.2% and 49.5%, resp.) attachment to Caco-2 cells. Live lactobacilli strains and their conditioned media effectively inhibited IL-8 production (<14.6 pg/mL) in TNF-α-induced Caco-2 cells. Antibiotic-treated and the sonicated lactobacilli also maintained inhibitory effects (IL-8 production from 5.0 to 36.3 pg/mL); however, the heat-treated lactobacilli lost their inhibitory effects (IL-8 production from 130.2 to 161.0 pg/mL). These results suggest that both the structural components and the soluble cellular content of lactobacilli have anti-inflammatory effects. We also found that pretreatment of Caco-2 cells with lactobacilli inhibited S. typhimurium-induced IL-8 production (<27.3 pg/mL). However, lactobacilli did not inhibit IL-8 production in Caco-2 cells pretreated with S. typhimurium. These results suggest that the tested lactobacilli strains are appropriate for preventing inflammatory diseases caused by enteric pathogens but not for therapy. In short, L. salivarius and L. plantarum are potential candidates for the development of microbial ecological agents and functional foods.

"Biofilmology": a multidisciplinary review of the study of microbial biofilms

The observation of biofilm formation is not a new phenomenon. The prevalence and significance of biofilm and aggregate formation in various processes have encouraged extensive research in this field for more than 40 years. In this review, we highlight techniques from different disciplines that have been used to successfully describe the extracellular, surface and intracellular elements that are predominant in understanding biofilm formation. To reduce the complexities involved in studying biofilms, researchers in the past have generally taken a parts-based, disciplinary specific approach to understand the different components of biofilms in isolation from one another. Recently, a few studies have looked into combining the different techniques to achieve a more holistic understanding of biofilms, yet this approach is still in its infancy. In order to attain a global understanding of the processes involved in the formation of biofilms and to formulate effective biofilm control strategies, researchers in the next decade should recognise that the study of biofilms, i.e. biofilmology, has evolved into a discipline in its own right and that mutual cooperation between the various disciplines towards a multidisciplinary research vision is vital in this field.

Evaluation of adherence, hydrophobicity, aggregation, and biofilm development of Flavobacterium johnsoniae-like isolates

Flavobacterium spp. isolates have been identified in diverse biofilm structures, but the mechanism of adherence has not been elucidated. The absence of conventional biofilm-associated structures such as fimbriae, pili, and flagella suggest that surface hydrophobicity, and/or autoaggregation and coaggregation may play an important role in adherence and biofilm formation. The biofilm-forming capacity of 29 Flavobacterium johnsoniae-like isolates obtained from South African aquaculture systems was assessed using microtiter plate assays. The role of hydrophobicity [salting aggregation test (SAT) and bacterial adherence to hydrocarbons (BATH) assays], autoaggregation, and coaggregation on biofilm formation by Flavobacterium spp. was also investigated, while biofilm structure was examined using flow cells and microscopy. All isolates displayed a hydrophilic nature, but showed varying levels of adherence in microtiter assays. Significant negative correlations were observed between adherence and biofilm-forming capacity in nutrient-poor medium at 26 degrees C and BATH hydrophobicity and motility, respectively. Isolates displayed strain-to-strain variation in their autoaggregation indices and their abilities to coaggregate with various Gram-negative and Gram-positive organisms. Microcolony and/or biofilm development were observed microscopically, and flavobacterial isolates displayed stronger biofilm structures and interaction with a Vibrio spp. isolate than with an Aeromonas hydrophila isolate. The role of extracellular polysaccharides and specific outer membrane proteins will have to be examined to reveal mechanisms of adherence and coaggregation employed by biofilm-forming F. johnsoniae-like strains.

Enterotoxigenic Escherichia coli associated diarrhoea among infants aged less than six months in Calcutta, India

The role of enterotoxigenic Escherichia coli (ETEC) as etiologic agents of diarrhoea in infants aged less than six months was assessed in a hospital based study in Calcutta, India. Of the 218 cases examined, ETEC strains were isolated from 26 (11.9%) cases. Among these, in 17 cases ETEC was the sole infecting pathogen (p = 0.0085). Of the 26 isolates (each isolate representing a case), 24 were distributed among seven different O:K:H serotypes and two different colonization factor antigens (CFAs) I and II. Two of the remaining isolation were untypable, non-haemagglutinating, and were non-hydrophobic as measured by the salt aggregation test (SAT). Of the 26 ETEC strains detected, 15 (57.7%) produced heat-labile toxin (LT) only, 8 (30.8%) liberated heat-stable toxin (ST) only, and the remaining 3 (11.5%) produced both LT and ST. No ETEC strain was isolated from the 102 age-matched controls included in this study. All the ETEC isolates were multiple drug resistant. The study showed that the diarrhoea due to ETEC was of brief duration, mostly within the range of 3 to 7 days.

Pathogenicity and virulence of coagulase negative staphylococci in relation to adherence, hydrophobicity, and toxin production in vitro

AIMS

To study the pathogenicity and virulence characteristics of Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus sapro-phyticus.

METHODS

BALB/c mice were challenged intraperitoneally with graded doses of three strains belonging to each species. LD50s were measured for each strain. Haemolysin (alpha- and delta-) and enzyme (DNAase, lipase, and esterase) production in vitro were measured qualitatively and quantitatively. Adhesion to plastic was measured and related to cell surface hydrophobicity among the strains.

RESULTS

S saprophyticus proved the most virulent (LD50 = 2.7-2.9 x 10(7) cfu/g body weight) while S epidermidis was the least virulent (LD50 = 6-8 x 10(7) cfu/g body weight). An enlarged spleen was the most common macroscopic pathological feature. Kidney, liver, and more rarely peritoneal abscesses were also seen in the infected animals. No direct correlation was found between adherence in vitro, cell surface hydrophobicity, or toxin/enzyme biosynthesis and virulence in mice.

CONCLUSION

The results show that coagulase negative staphylococci are pathogenic in BALB/c mice. It is clear that these bacteria can cause invasive disease. However, the in vitro characteristics of coagulase negative staphylococci are not related to the pathogenicity of the organisms in mice.

Effects of nutrients on exopolysaccharide production and surface properties of Aeromonas salmonicida

Extracellular polysaccharide (EPS) and capsular polysaccharide (CPS) production by Aeromonas salmonicida A450 and the influence of the capsule on cell surface properties were studied. A. salmonicida did not produce CPS or EPS when glucose, phosphate, magnesium chloride, or trace mineral components were absent from the medium. The addition of yeast extract improved capsule production. Neither EPS nor CPS formation depended on the C/N ratio, although it appeared to be influenced by the level of carbon and nitrogen in the culture. Both EPS and CPS production started at the end of the logarithmic growth phase. The amounts of EPS and CPS produced were not influenced by temperature changes between 15 and 20 degrees C and was maximal from pH 7 to 7.5. Cell surface properties were strongly influenced by capsule production; high CPS production was associated with enhanced cell hydrophilicity and autoagglutination. The effect of CPS on cell surface properties was independent of the presence of the surface protein array (A-layer).

Fibronectin binding by Salmonella strains: evaluation of a particle agglutination assay

Thirty-five Salmonella strains isolated from human cases of salmonellosis were tested and compared for their fibronectin (fn) binding capacities by using two fn-particle agglutination assays (fn-PAAs) prepared by coating with human fn either (i) latex beads (Difco; 0.81-micron diameter) (L-fn-PAA) or (ii) heat-killed formalin-treated Staphylococcus aureus Cowan 1 cells (C-fn-PAA). Six S. aureus strains were also included in this study as controls. The strains were cultured on colonization factor antigen agar and blood agar and in tryptic soy broth and brain heart infusion broth. The Salmonella and S. aureus strains were cultured at 33 and 37 degrees C, respectively, for optimal expression of fn-binding proteins. Bacterial cells (approximately 10(10) cells per ml) harvested from growth in various culture media and suspended in 0.02 M potassium phosphate buffer (pH 6.8) agglutinated the fn-PAA reagents. These reactions were scored semiquantitatively from + to + depending on the speed or intensity of the reactions within 2 min. Maximum agglutination in fn-PAA systems was observed when the cells were grown in brain heart infusion broth, while tryptic soy broth proved to be least suitable media for culturing cells for fn-PAAS. Although a statistically highly significant correlation was obtained between results of assays of radiolabeled fn and 29-kDa fragment binding, no significant correlation was observed (i) between the results of strains cultured in different media or (ii) when semiquantitative score results of the two fn-PAA systems were compared with those of the conventional radiolabeled fn assay. To enhance the efficiency of the test system, the C-fn-PAA reagent was stained with methylene blue (2% in 0.17 M glycine-NaOH buffer [pH 6.8]). This facilitated easy interpretation of results, which could be performed on hydrophobic paper instead of glass slides. The results obtained with both unstained C-fn-PAA and stained C-fn-PAA were comparable to each other and reproducible. Although the fn-PAAs are simple and easy to perform, the results did not differentiate between negative, low, moderate, and high binding abilities when Salmonella strains were evaluated for fn binding, and the results were not comparable to those obtained by the conventional radiolabeling method.

Toxin profiles, and cell-surface properties of Salmonella strains isolated from Swedish travelers

Toxin production, cell-surface hydrophobicity and fibronectin-binding properties of 21 Salmonella strains of different species, isolated from Swedish travelers to different parts of the world, were studied. Cell sonicate supernatants from blood agar grown cultures of 80% of the strains induced rabbit skin permeability reaction in the form of induration and/or blueing while 33% of the strains also produced cell necrotizing factor on rabbit skin. Four strains were negative in the rabbit skin permeability test, while only two were negative when tested on CHO cells. When cultured on blood agar, a majority of the strains (17/21) showed low cell-surface hydrophobicity, showing no aggregation even at 1.5 M ammonium sulfate concentration in salt aggregation test (SAT), while only four strains showed high cell-surface hydrophobicity. Furthermore, these strains could be classified as low fibronectin binders due to their poor interaction with fibronectin or its 29 kDa N-terminal fragment.

Contribution of silver ion resistance to the pathogenicity of Pseudomonas aeruginosa with special reference to burn wound sepsis

The virulence of a silver-ion-resistant (AgR) clinical isolate of Pseudomonas aeruginosa and its silver-sensitive mutant (AgS) was compared in the murine burn-wound sepsis model. The AgR strain showed significantly higher colonization of burned skin vis-a-vis the AgS strain. The altered pathogenicity may in part be due to the decrease in capsular content and cell surface hydrophobicity, accompanying the loss of silver ion resistance. The AgR and AgS strains, however, did not exhibit quantitatively significant differences in the production of extracellular hemolysins and proteinases.

The effects of three non-antibiotic, antimicrobial agents on the surface hydrophobicity of certain micro-organisms evaluated by different methods

The effects of three non-antibiotic, antimicrobial agents (taurolidine, chlorhexidine acetate and providone-iodine) on the surface hydrophobicity of the clinical strains Escherichia coli, Staphylococcus saprophyticus, Staphylococcus epidermidis and Candida albicans were examined. Three recognized techniques for hydrophobicity measurements, Bacterial Adherence to Hydrocarbons (BATH), the Salt Aggregation Test (SAT) and Hydrophobic Interaction Chromatography (HIC) were compared. At concentrations reported to interfere with microbial-epithelial cell adherence, all three agents altered the cell surface hydrophobicity. However, these effects failed to exhibit a uniform relationship. Generally, taurolidine and povidone-iodine treatments decreased the hydrophobicity of the strains examined whereas chlorhexidine acetate effects depended upon the micro-organism treated. Subsequently, the exact contribution of altered cell surface hydrophobicity to the reported microbial anti-adherence effects is unclear. Comparison of the three techniques revealed a better correlation between the results obtained with the BATH test and HIC than the results obtained with the BATH and SAT or SAT and HIC. However, these differences may be due to the inaccuracy associated with the visual assessment of results employed by the SAT.

Phagocytosis and virulence of different strains of Porphyromonas gingivalis

In this study 17 strains of Porphyromonas gingivalis, both reference and clinical isolates, were investigated for their in vitro interaction with human polymorphonuclear leukocytes, hydrophobicity, density, and virulence in a mouse model. The results of the phagocytosis, hydrophobicity, and density experiments showed that P. gingivalis strains could be divided into two distinct groups. One group of strains were readily attached and phagocytosed when exposed to the leukocytes. These bacteria were hydrophobic and had a higher buoyant density than the other group, which were poorly phagocytosed, had a low buoyant density, and were hydrophilic. This latter group also exhibited an extracellular meshwork resembling a glycocalyx when examined by electron microscopy. There were also significant differences between strains in the mouse pathogenicity model. Two strains caused an invasive, spreading infection compared with the other 15 strains which produced small, localized abscesses. There was no clear correlation between the results of the phagocytosis assay and the virulence of the bacteria when injected subcutaneously in mice. Resistance to phagocytosis may be important for survival of these bacteria, but it does not in itself imply the ability to cause damage to the host.

The susceptibility of in vivo-grown Pasteurella haemolytica to ovine defence mechanisms in vitro

Pasteurella haemolytica organisms grown in vivo were examined for their susceptibility to ovine immune mechanisms in vitro. Compared with in vitro grown organisms they were less susceptible to opsonophagocytosis and, in contrast, susceptible to complement-dependent killing in the absence of exogenous antibody. These differences were not associated with phenotypic changes in the surface of the bacterial cell. However, overproduction and de novo synthesis of proteins was observed in in vivo grown organisms. Also, bound host-immunoglobulin was observed on in vivo grown organisms and a role for this in modifying the interaction with immune mechanisms is discussed.

Fibronectin, vitronectin, and collagen binding to Escherichia coli of intestinal and extraintestinal origin

Strains of enteropathogenic Escherichia coli (EPEC, 157 strains), enterotoxigenic E. coli (ETEC, 10 strains), enteroinvasive E. coli (EIEC, 40 strains), enterohaemorrhagic E. coli (EHEC, 10 strains), and enteroadherent E. coli (EAEC, 6 strains), all isolated from children and adults with diarrhoea, uropathogenic E. coli (25 strains) and faecal E. coli (36 strains) isolated from healthy persons were tested for binding to subepithelial connective tissue proteins, viz. fibronectin, collagen and vitronectin (S-protein). Strains expressing high and moderate binding to these proteins were found in all groups including normal stools. The highest incidence of binding strains were found among EAEC, EHEC and EPEC strains. Many strains bound collagen only whereas no strain bound vitronectin only. Binding to these proteins was generally best expressed after overnight growth on CFA agar at 37 degrees C. It is not correlated to surface hydrophobicity, and it is not influenced by O antigens or K1 and K5 antigens. The presence of fimbrial adhesins on extraintestinal isolates did not enhance the binding to soluble form of the matrix proteins. During pathological conditions when subepithelial connective tissue proteins are exposed, strains with the ability to bind fibronectin, collagen and/or vitronectin may have a selective advantage to colonize the tissue.

Physical chemical description of bacterial adhesion

For the description of general bacterial adhesion phenomena two different physicochemical approaches are available. The first one, based on a surface Gibbs energy balance, assumes intimate contact between the interacting surfaces. According to this approach adhesion is solely related to the Gibbs energies of the surfaces involved. The second approach, based on colloid chemical theories (DLVO theory), allows for two types of adhesion: 1. secondary minimum adhesion, which is often weak and reversible, and 2. irreversible primary minimum adhesion. In the first case a thin water film is present between the interacting surfaces. In the DLVO approach adhesion is determined by long range interactions, i.e., Van der Waals and electrostatic interactions. Van der Waals interactions may be related to the hydrophobicity of the cell wall. For the measurement of bacterial hydrophobicity and electrokinetic potential several macroscopic methods are available. Based on a literature review of the influence of both surface characteristics on adhesion, it is concluded that the surface Gibbs energy balance approach is not adequate to describe the majority of adhesion phenomena. On the other hand the DLVO-theory describes the observations fairly well, especially in the case of reversible (secondary minimum) adhesion. The influence of adsorbing (in)organic compounds, extracellular polymers and cell surface appendages on adhesion can also be predicted by a DLVO-type approach.

Kinetics of Pseudomonas aeruginosa adhesion to 304 and 316-L stainless steel: role of cell surface hydrophobicity

Fifteen different isolates of Pseudomonas aeruginosa were used to study the kinetics of adhesion to 304 and 316-L stainless steel. Stainless steel plates were incubated with approximately 1.5 X 10(7) CFU/ml in 0.01 M phosphate-buffered saline (pH 7.4). After the plates were rinsed with the buffer, the number of adhering bacteria was determined by a bioluminescence assay. Measurable adhesion, even to the electropolished surfaces, occurred within 30 s. Bacterial cell surface hydrophobicity, as determined by the bacterial adherence to hydrocarbons test and the contact angle measurement test, was the major parameter influencing the adhesion rate constant for the first 30 min of adhesion. A parabolic relationship between the CAM values and the logarithm of the adhesion rate constants (In k) was established. No correlation between either the salt aggregation or the improved salt aggregation values and the bacterial adhesion rate constants could be found. Since there was no significant correlation between the bacterial electrophoretic mobilities and the In k values, the bacterial cell surface charge seemed of minor importance in the process of adhesion of P. aeruginosa to 304 and 316-L stainless steel.

Staphylococcus aureus exopolysaccharide in vivo demonstrated by immunomagnetic separation and electron microscopy

Staphylococcus aureus strains were separated from mastitis milk samples without cultivation by using monodisperse magnetic polymer particles coated with polyclonal antiserum against an encapsulated S. aureus strain. Exopolysaccharide was verified by transmission electron microscopy and the serum soft-agar culture technique. Capsular polysaccharide was found on virtually all clinical isolates. Surface protein A and S. aureus-specific cell wall components were masked when the strains were cultured on an exopolysaccharide-promoting medium. Masking of surface determinants was dependent on their concentration on the bacterial surface as well as on exopolysaccharide abundance. The polysaccharide layer on in vivo bacteria was reduced markedly after just one transfer from milk to blood agar plates but was reexpressed after culturing was done on a capsule-generating medium.

Prevalence of enterotoxigenic Escherichia coli strains in outbreaks and sporadic cases of diarrhoea in Spain

Escherichia coli strains isolated 1985-1988 in Spain from patients with diarrhoea were examined; 1170 strains were isolated from 582 sporadic cases of diarrhoea in children, and seven strains were associated with seven outbreaks of diarrhoea. Strains positive for STa enterotoxin production in the infant mouse test were also assayed for production of LT enterotoxin on Vero cells and by a coagglutination test. Thirty-one strains were STa positive: 28 were isolated from 16 (2.7%) sporadic cases of diarrhoea and three were responsible for outbreaks. The majority of STa+LT- strains from both outbreaks and sporadic cases were serotype O153:H45 and expressed the CFA/I colonization factor antigen. Enterotoxigenic STa+LT- strains of serotype O27:H7 and STa+LT+ CFA/II+ strains of serotype O6:K15:H16 were also isolated frequently from sporadic cases.

Surface properties of Staphylococcus aureus isolated from caprine mastitis

A total of 53 Staphylococcus aureus strains isolated from caprine mastitis were tested for surface hydrophobicity, surface Protein A (SpA), and binding capacity of fibronectin, fibrinogen and type II collagen. Strong positive correlation was found between surface hydrophobicity and SpA, and between surface hydrophobicity and 125I-fibronectin-binding. Regardless of hydrophobicity, the binding of fibrinogen was moderate and type II collagen binding was low. The results indicate that SpA and fibronectin-binding protein contribute to the high relative surface hydrophobicity of S. aureus associated with caprine mastitis.

Growth conditions for the expression of fibronectin and collagen binding to Salmonella

Binding of 125I-fibronectin, its 125I-labelled 29-kDa aminoterminal fragment, and 125I-collagen to cells of 13 Salmonella strains grown in broth and agar media at three different temperatures was studied. Of the 13 strains, 7 had only smooth colony morphologies while three strains were pairs of both smooth strains and their corresponding rough variants. The three rough variants showed higher binding to fibronectin, it's 29-kDa fragment and to collagen, than the corresponding smooth forms. However, the percentage of 125I-protein bound was greatly influenced by the growth conditions. In these three pairs of strains, there was a direct correlation between cell-surface hydrophobicity and the binding activity, but this correlation was not observed in the remaining strains. Thus, some of the strains showed high cell-surface hydrophobicity but low binding activity under optimal growth conditions. The highest binding rates of fibronectin and of it's 29-kDA fragment were obtained with bacteria grown on colonisation factor antigen (CFA) agar at 33 degrees C, while the binding to collagen was slightly higher when bacteria were cultured on tryptic soy agar.

Interaction of sub-epithelial connective tissue components with Staphylococcus aureus and coagulase-negative staphylococci from bovine mastitis

Staphylococcus aureus and coagulase-negative staphylococci (CNS) isolated from bovine mastitis were examined for their ability to interact with 125I-labelled fibronectin, fibrinogen and type II collagen. Their relative surface hydrophobicity and production of extracellular capsule were also investigated. Almost all S. aureus strains bound fibronectin (mean value 23%), fibrinogen (mean value 12%) and type II collagen (mean value 16%). CNS bound fibronectin (mean value 6%) and type II collagen (mean value 7%), but not fibrinogen (mean value 2%). The specificity of binding of these proteins to S. aureus strain F1440 and to coagulase-negative Staphylococcus chromogenes strain BO52 was studied by adding an excess of unlabelled proteins. Fibronectin and collagen binding were observed to be specific, varying between 50 and 75%, whereas the specificity of fibrinogen binding to S. aureus strain F1440 was lower (26%). Most of the S. aureus strains (63%) showed very high surface hydrophobicity (autoaggregation) or lower hydrophobicity (29% of the strains) and the rest were hydrophilic. None of the CNS strains autoaggregated, 44% were classified as hydrophilic strains. Hydrophilic strains (except the reference strains) did not show extracellular capsule production. However, the encapsulated (reference) strains showed low binding to these proteins as compared to their unencapsulated variants. Pre-treatment of S. aureus strain F1440 and S. chromogenes strain BO52 with trypsin decreased their fibronectin binding capacity and surface hydrophobicity, whereas pre-treatment with bovine milk (except on collagen binding to strain F1440) did not significantly affect binding to these proteins. These data indicate that S. aureus and CNS isolated from bovine udder infection have the ability to bind to tissue matrix and plasma proteins which may be exposed in the traumatized or toxin-damaged udder epithelial lesions.

Relative cell surface hydrophobicity of Escherichia coli strains with various recognized fimbrial antigens and without recognized fimbriae

Bacterial surface hydrophobicity as well as mannose-sensitive haemagglutinating (MSHA) and mannose-resistant haemagglutinating (MRHA) activities were studied in Escherichia coli strains with and without recognized fimbrial antigens grown under different conditions. Relative bacterial surface hydrophobicity was measured by the salt aggregation test. Four kinds of bacterial aggregations depending on fimbrial antigens were observed: bacteria with CFA/I, CFA/II, CFA/III and K88 aggregated in a particulated form, bacteria with type 1 pilus in a granular form, and bacteria with K99 in a tiny granular form. Some strains, mainly when grown under non-optimal conditions at 18 degrees C or when heated at 80 degrees C, aggregated in a non-typical filamentous form. Among MRHA- MSHA+ (type 1 pilus positive), two classes of bacteria were detected: hydrophobic bacteria aggregating in 0.2-0.4 M ammonium sulphate, and non-hydrophobic bacteria aggregating in 2.0 to 1.6 M ammonium sulphate. The hydrophobicity levels in strains possessing different recognized fimbrial antigens, when grown under optimal conditions to express fimbriae and their typical haemagglutination pattern, were of a decreasing order, viz. CFA/III = CFA/I greater than CFA/II greater than MRHA-MSHA+ hydrophobic = MRHA+ greater than P987 greater than K99-F41 = K88 greater than MRHA- MSHA+ non-hydrophobic greater than MRHA- MSHA- without recognized fimbriae.

Hydrophobicity of Candida albicans related to their adherence to mucosal epithelial cells

A total of 150 Candida albicans strains were examined, using a salt aggregation test (SAT) and an improved salt aggregation test (ISAT). The fungal strains were isolated from patients or taken from a collection. Out of 150 strains, 20.7% were autoaggregating in the ISAT. In the SAT, 12% of the strains were autoaggregating in saline and 14% in phosphate buffer. The remaining strains did not clump. Pretreatment of the autoaggregating strains with detergents (Tween 80 and ethylene glycol) prevented aggregation in some of them. The adherence capacity to buccal epithelial cells of the fungal strains autoaggregating in the SAT and ISAT, was compared to that of the nonaggregating ones. The autoaggregating strains revealed significantly higher adherence values (p less than 0.002). The adherence ability to buccal epithelial cells of the autoaggregating strains before and after their pretreatment with detergents was compared. The adherence values after pretreatment were significantly lower (p less than 0.001).

Surface properties of lactobacilli isolated from the small intestine of pigs

One hundred wild-type strains of the genus Lactobacillus were isolated from the small intestine of newly-slaughtered pigs up to 6 months of age. Cell surface hydrophobicity and capsule formation were studied on a number of strains. Strains showing high surface hydrophobicity as measured by the salt-aggregation test and hydrophobic interaction chromatography on Octyl Sepharose were commonly found to adhere in high numbers to isolated pig intestinal epithelial cells. Heat and protease treatment of bacteria of high surface hydrophobicity, including autoaggregating strains in phosphate-buffered saline, showed a drastic decline in this surface property. Three hydrophilic strains (LBp 1044, 1068 and 1073) also showed binding to intestinal cells but at a lower level (approx. 5 bacteria/cell) as compared with the best binding hydrophobic strain (LBp 1063, approx. 11 bacteria/cell). These findings suggest that different or multiple adhesion mechanisms may be involved in the colonization of the small intestinal mucosa of pigs. Cultures of selected strains grown in liquid media rich in carbohydrates did not affect their hydrophobic cell surface character. Therefore it seems less likely that carbohydrate capsule polymers are the major determinants of intestinal colonization of lactobacilli in pigs.

Binding of fibronectin, fibrinogen and type II collagen to streptococci isolated from bovine mastitis

Binding of 125I-labelled fibronectin, fibrinogen and type II collagen to group B (S. agalactiae), group C (S. dysgalactiae and S zooepidemicus), group E (S. uberis) and nontypable streptococci isolated from bovine mastitis was studied. S. agalactiae and S. uberis were found to bind low levels of all three proteins, while S. zooepidemicus bound high levels. Binding of the proteins to S. dysgalactiae varied, i.e. fibronectin was high, fibrinogen moderate and collagen low. Nontypable strains showed moderate or low binding of all proteins. Both hydrophobic and hydrophilic strains were found to bind fibronectin. For S. dysgalactiae the specific fibronectin binding ranged from 70% to 10% and for S. zooepidemicus it was more than 80% and this binding was sensitive to papain treatment. The binding of 29K-fibronectin fragment to one S. dysgalactiae strain showed an affinity of KD = 2.6 x 10(-8) M and the number of binding sites per colony forming unit (CFU) was calculated at 11,000.