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After birth various bacterial species, mainly streptococci, colonize the oral cavity and are frequently isolated from carious lesions in children. Previous studies suggest that an earlier colonization of a child's mouth by cariogenic organisms might be related to a higher risk of caries. The aim of this study is to assess the influence of different milks for infant feeding on the growth of Streptococcus mutans (SM)colonies. Three human milk samples from three different mothers and five infant formulas were tested. To prepare the bacterial inoculum, SMwas grown in Brain Heart Infusion broth for 18 hours at 37°C in microaerophilic atmosphere. The growth of SMwas determined immediately after the inoculation of milks (T0) and after 24 hours (T24) of incubation. After 24 hours of incubation (?T= CFUs/ml at T24–CFUs/ml at T0) the bacterial growth changes were different among milks. Among the complementary milks tested, ?T of formulas supplemented with Lactobacillus reuteri and with Bifidobacterium lactiswas lower than those of non-supplemented formula. In conclusion, on the basis of the reduced SMgrowth in milks supplemented with probiotics, we may speculate that these formulas have a preventive effect on the development of caries in children.

In cystic fibrosis (CF) high iron concentration in airway secretion plays a pivotal role in bacterial multiplication and biofilm formation as well as in inflammatory response. Burkholderia cenocepacia, an opportunistic facultative pathogen responsible for chronic lung infections and cepacia syndrome, recurrently infects CF patients. Lactoferrin (Lf), an iron binding multifunctional glycoprotein synthesized by exocrine glands and neutrophils, has been found at higher concentration in the airway secretions of infected CF patients than in healthy subjects. Here the influence of milk derivative bovine lactoferrin (bLf), an emerging important regulator of iron and inflammatory homeostasis, on invasiveness of B. cenocepaciairon-modulated biofilm, as well as on inflammatory response by infected CF bronchial (IB3-1) cells, is reported, bLf did not significantly affect invasion efficacy by biofilm-forming B. cenocepaciaclinical strains. Conversely, the addition of bLf to cell monolayers during infection significantly decreased the pro-inflammatory Interleukin (IL)-1β and increased the antiinflammatory IL-11 expression compared to that observed in cells infected in the absence of bLf. The bLf ability to modulate genes expressed following B. cenocepaciainfection seems related to its localization to the nucleus of infected IB3-1 cells. These results provide evidence for a role of bLf in the protection of infected CF cells from inflammation-related damage, thus extending the therapeutic potential of this multifunctional natural protein.

Streptococcus mutansand Streptococcus sobrinus, the principal etiologic agents of caries decay of teeth, are generally acquired in oral cavity at the moment of tooth eruption. However, as S. mutanshas been detected in oral cavity of predentate children, the eruption of teeth seems not to be a necessary prerequisite, suggesting that this species may be not confined to dental plaque. Here, we evaluate the ability of S. mutansand S. sobrinusin planktonic and biofilm lifestyle to adhere, invade and survive within human gingival fibroblast (HGF-1) cells. Planktonic and biofilm streptococci adhered and invaded host cells to different extents, showing higher efficiencies of biofilm than planktonic counterparts. Moreover, planktonic and biofilm streptococci showed the same percentage of survival within host cells. Transmission electron and confocal microscopy observations confirmed intracellular localization of planktonic and biofilm bacteria. The adhesion, invasion and survival abilities within human oral cells may be considered S. mutansand S. sobrinusvirulence mechanisms to colonize and persist in the oral cavity in the absence of tooth surface.

Pseudomonas aeruginosaand Burkholderia cenocepaciaare two important opportunistic respiratory pathogens of cystic fibrosis (CF) patients. Infections caused by these microorganisms are particularly difficult to eradicate because they are usually highly resistant to several currently available broad-spectrum antibiotics. Lactoferrin (Lf), a glycoprotein found in physiological fluids of mammals and present at high concentrations in infected and inflamed tissues, plays an important role in the natural defence mechanism against pathogens and in immune regulation. In the present study, we evaluate the ability of bovine lactoferrin (bLf) to influence P. aeruginosaPAO1 and B. cenocepaciaPV1 adhesiveness and invasiveness, using the A549 human bronchial cell line. Three different iron-induced morphological forms of bacteria (free-living, aggregates and biofilm) were assayed. The addition of bLf to cells just before infection had little influence on adhesion efficiency for all three of the morphological forms of B. cenocepaciaPV1, while a slight increase in adhesion efficiency by P. aeruginosaPAO1 was noticed. Conversely, invasion of all three morphological forms of both P. aeruginosaand B. cenocepaciawas strongly inhibited by the presence of bLf, independently of its degree of iron-binding activity. This is the first report demonstrating an anti-invasive property of bLf for strains of P. aeruginosaand B. cenocepacia.

The aim of this work is to study a correlation between phenotype and genotype in clinical isolates of erythromycin-resistant Streptococcusspp. Among the 25 erythromycin-resistant S. pyogenes, we detected six strains with iMLSBnine with cMLSBand two with M phenotypes. Among 14 erythromycin-resistant S. agalactiae, we detected five strains with iMLSB, seven with cMLSBand none with an M phenotype. Moreover, 8 S. pyogenesand 2 S. agalactiaeshowed a phenotype not matching the known ones described in literature, defining an “unknown phenotype”. Upon examination, the genetic profiles, erm(A), erm(B) and mef(A), of the clinical isolates did not easily correlate with a specific phenotype. Our findings highlighted that the whole matter of phenotypic diversity in macrolide-resistant S. pyogenesand S. agalactiaestrains and the correlation with their genetic profiles should be submitted to a more careful analysis of phenotypic and genotypic characterization.

Pseudomonas aeruginosaand Burkholderia cenocepaciaare predominant opportunistic pathogens in cystic fibrosis (CF) patients. In healthy humans the lower respiratory tract as well as all mucosa, contains a very low free iron concentration (10-18M), while in CF patients' sputum iron concentration is very high, showing a median value of 63×10-6M. Accumulation of catalytic reactive iron heavily contributes to subsequent clinical complications in the lung disorders by the production of reactive oxygen species and increases bacterial growth and virulence. The data reported in this study indicate that low iron concentration (Fe3+1 µM) induced free-living forms and motility both in P. aeruginosaand B. cenocepacia, while high iron concentrations (Fe3+10 and 100 µM) stimulated aggregation and biofilm formation already in the fluid phases, so demonstrating that aggregation and biofilm formation are positively iron-modulated in these bacteria. Moreover, the different morphological forms (free-living, aggregates and biofilm) showed different capabilities of adhering and invading the bronchial cell line A549. P. aeruginosaPAO1 aggregates, and mostly biofilm, exerted the highest adhesion efficiency, while B. cenocepaciaPV1 aggregates or biofilm the lowest. A significant reduction in invasion efficiency by P. aeruginosabiofilm and a significant increase in cell internalization by B. cenocepaciabiofilm has been reported. Therefore, the iron availability is an important signal to which P. aeruginosaand B. cenocepaciacounteract by leaving the motile free-living forms and entering into a new lifestyle, i.e. biofilm. These data could contribute to explain that the iron-overload of the sputum of CF patients, inducing nonmotile forms, aggregates and biofilm, may facilitate penetration of host epithelial barriers contributing to the establishment of infection, colonization, persistence and systemic spread of these opportunistic pathogens.