Maura Millesimo

Pseudomonas aeruginosa clinical isolates: Serotypes, resistance phenotypes and plasmid profiles

Abstract78 Pseudomonas aeruginosa strains were isolated from the respiratory tract of 56 patients, 15 of which were affected by cystic fibrosis (CF). The epidemiological typing scheme was based on serotyping, antibiotic resistance pattern and plasmid DNA profile. All strains (except 2 mucoid strains) were typed using a rapid slide O-agglutination technique. Most common serotypes in both group were 0:1, 0:10 and 0:6. Moreover we observed a correlation among 0:12 serotype and CF patients. Plasmid DNA analysis showed that 45.2% (on average) of strains isolated from patients with and w/o CF harboured 1–3 plasmids ranging in size from 1 to 15 Md. Plasmid prevalence was higher in strains isolated from CF patients in specimens collected after antibiotic therapy. A correlation was found between 1 and 1.9 Md plasmids and resistance to aminoglycosides. Our results indicate that the analysis of antibiotic resistance phenotypes combined with plasmid analysis may be useful, in association to serotyping, to characterize the circulation of P. aeruginosa strains and the spread of resistance in these bacteria.

Evaluation of the immune response in visceral leishmaniasis

Detection of parasites in culture or by microscopy is still necessary to make diagnosis of visceral leishmaniasis (VL). Serological methods still need assessment, as they are quick but not very sensitive, especially in immunosuppressed subjects. This paper compares the results obtained with three serological methods (indirect immunofluorescence test (IFAT), direct agglutination test (DAT), and enzyme-linked immunosorbent assay (ELISA) and the specific cell-mediated immune response, evaluated as proliferation and IFN-gamma production by peripheral blood lymphocytes (PBL) following stimulation with heat-killed L. infantum promastigotes. PBL and sera were obtained from 10 healthy donors, 3 VL patients in acute phase, and 3 patients recovering after two glucantim treatment courses. No false positive results were observed with the serological methods. IFAT can be considered the most sensitive and best suited for follow-up, as it allowed a good discrimination between the acute and remission phase. DAT did not discriminate between healthy donors and remission-phase patients, whereas ELISA is unsuited for follow-up, as it did not show any significant difference between remission- and acute-phase patients. Assessment of the cellular response is not recommended for making a diagnosis, because false positive results are frequent. However, a strong cellular response in a patient stands for a successful treatment. IFN-gamma titration is preferable to the proliferation test, because it gives earlier results and does not require the use of radioactive isotopes.