Expression of internalin A and biofilm formation among Listeria monocytogenes clinical isolates.

Internalin A (InlA), a cell wall-bound protein of Listeria monocytogenes, is among the major components involved in the adhesion to and invasion of host cells expressing specific forms of E-cadherin. Some L. monocytogenes strains secrete truncated non-functional forms of InlA. The purpose of this study is to compare the biofilm-forming abilities of L. monocytogenes strains from clinical sources expressing InlA proteins in the different forms. A total of 70 L. monocytogenes strains were examined using SDS-PAGE, Western blot, DNA sequencing, and microtitre plate biofilm formation assays. We found that 8 of the 70 strains expressed truncated InlA, and that this group of strains exhibited significantly enhanced biofilm-forming ability compared to the group expressing full-length InlA. Further experiments showed that: (i) L. monocytogenes biofilms were detached by treatment with protease K; (ii) protein fragments resulting from proteolysis, rather than intact proteins, are responsible for biofilm enhancement, because biofilm formation was impaired by the protease inhibitor alpha2-macroglobulin; (iii) truncated and/or proteolytically cleaved InlA are likely involved in the biofilm enhancement, based on the effects that anti-InlA monoclonal antibodies produced on the biofilm formation of L. monocytogenes strains expressing either truncated or full-length InlA. These data provide a basis for further investigation of the molecular structure and composition of L. monocytogenes biofilms.

The role of neuroimaging in the diagnosis of headache in childhood and adolescence: a multicentre study.

Following the diagnostic indications of the Guidelines for the diagnosis and therapy of juvenile headache, we present the results of a prospective, multicentre study of headache patients aimed at evaluating the utility of neuroradiologic testing in the diagnosis of headache. A total of 6535 subjects up to age 18 were studied, and 1485 underwent neuroimaging testing based on the indications of the diagnostic Flow-Chart. Abnormal results were observed in 273 (18.5%) subjects. Incidental findings were observed in 138 (9.3%) subjects, not correlated with the headache pathology, whereas alterations that led to the diagnosis of secondary headache were observed in 135 (9.1%) subjects. In conclusion, our data support a greater incidence of positive neuroimaging examinations among patients who underwent testing based on suspicion of a secondary headache pathology when compared with the low percentages observed in study populations.