lactoferrin and Actinobacillus-Infections

Actinobacillus pleuropneumoniae (App) is a Gram-negative bacterium that causes porcine pleuropneumonia, leading to economic losses in the swine industry. Due to bacterial resistance to antibiotics, new treatments for this disease are currently being sought. Lactoferrin (Lf) is an innate immune system glycoprotein of mammals that is microbiostatic and microbicidal and affects several bacterial virulence factors. The aim of this study was to investigate whether bovine iron-free Lf (BapoLf) has an effect on the growth and virulence of App. Two serotype 1 strains (reference strain S4074 and the isolate BC52) and a serotype 7 reference strain (WF83) were analyzed. First, the ability of App to grow in iron-charged BLf was discarded because in vivo, BapoLf sequesters iron and could be a potential source of this element favoring the infection. The minimum inhibitory concentration of BapoLf was 14.62, 11.78 and 10.56 µM for the strain BC52, S4074 and WF83, respectively. A subinhibitory concentration (0.8 µM) was tested by assessing App adhesion to porcine buccal epithelial cells, biofilm production, and the secretion and function of toxins and proteases. Decrease in adhesion (24-42 %) was found in the serotype 1 strains. Biofilm production decreased (27 %) for only the strain 4074 of serotype 1. Interestingly, biofilm was decreased (60-70 %) in the three strains by BholoLf. Hemolysis of erythrocytes and toxicity towards HeLa cells were not affected by BapoLf. In contrast, proteolytic activity in all strains was suppressed in the presence of BapoLf. Finally, oxytetracycline produced synergistic effect with BapoLf against App. Our results suggest that BapoLf affects the growth and several of the virulence factors in App.

Topics: Actinobacillus Infections; Actinobacillus pleuropneumoniae; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Apoproteins; Bacterial Adhesion; Bacterial Toxins; Biofilms; Cattle; Drug Synergism; HeLa Cells; Humans; Iron; Lactoferrin; Oxytetracycline; Pleuropneumonia; Swine; Swine Diseases; Virulence

Concentrations and output of lactoferrin and of low-Mr mucin MG2 were determined in saliva of subjects suffering from Actinobacillus actinomycetemcomitans-associated periodontal disease and healthy subjects. Periodontal patients were clinically examined and a microbiological sample was taken from the deepest bleeding pockets in each quadrant. The number of viable A. actinomycetemcomitans was determined in the sampled sites of each patient. The MG2 output in the diseased subjects (13.6 microg protein/min) was decreased at least by a factor three compared to periodontal healthy subjects (44.3 microg protein/min). On the other hand, output of lactoferrin was not significantly different in healthy (9.5 microg/min) and diseased subjects (7.6 microg/min). Western analyses demonstrated a higher iron-saturation of lactoferrin in diseased subjects in comparison with the healthy subjects. Lactoferrin degrading enzymes, probably derived from microbial sources, could be detected in saliva of the periodontally diseased subjects, but not in saliva of healthy subjects. The combination of iron-saturation and degradation of lactoferrin suggests that anti-microbial properties of lactoferrin are diminished in periodontitis patients. Moreover, the low concentration of mucin MG2 suggests a decline in mucin defence and consequently a higher susceptibility for oral infection. A negative correlation (r= -0.4, p < 0.05) between the number of subgingival A. actinomycetemcomitans and lactoferrin in saliva suggested that low concentrations of lactoferrin favour the growth of the bacterium. These data indicate that a decline in the salivary defence system might increase the risk for oral infection by A. actinomycetemcomitans.

Topics: Actinobacillus Infections; Adolescent; Adult; Aggregatibacter actinomycetemcomitans; Albumins; Blotting, Western; Colony Count, Microbial; Cystatins; Cysteine Proteinase Inhibitors; Electrophoresis, Polyacrylamide Gel; Female; Humans; Immunoblotting; Iron; Lactoferrin; Male; Middle Aged; Mucins; Periodontal Pocket; Periodontitis; Risk Factors; Saliva; Salivary Proteins and Peptides