[Microbiological diagnosis of medical device-associated infections]. / Diagnóstico microbiológico de las infecciones asociadas a dispositivos biomédicos.

The use of surgically implanted medical devices has increased greatly over the last few years. Despite surgical advances and improvements in the materials and design of devices, infection continues to be a major complication of their use. Device-associated infections are produced mainly during their implantation and, are caused by microorganisms that are part of the skin flora. Biofilm development on device surfaces is the most important factor to explain the pathophysiological aspects of infection. Microbiological diagnosis is difficult and can often only be achieved after removal of the device. Sonication of the removed device may be a useful tool, since this procedure dislodges and disaggregates biofilm bacteria from the device. Molecular techniques, especially PCR, applied to the tissues and material obtained after sonication have shown to have a high sensitivity and specificity for the diagnosis of cardiovascular device infections.

[Diagnosis of human brucellosis. Role of pH in the seroagglutination test and influence of pH on the agglutinating activity of IgM, IgG and IgA antibodies]. / Diagnóstico de la brucelosis humana. Influencia del pH en la prueba de seroaglutinación y sobre la actividad aglutinante de los anticuerpos IgM, IgG e IgA.

OBJECTIVE: To evaluate the role of pH in the seroagglutination test (SAT)and Rose Bengal (RB) test, and to determine the influence of pH on the agglutinating activity of IgM, IgG and IgA antibodies. MATERIALS AND METHODS: The SAT was performed at pH 7.2 or pH 5.0 in standard microtiter-type polystyrene plates using Ring Test antigen or the Brucella suspension (BRUCAPT) provided in the Brucellacapt kits. Specific antibodies against native hapten were determined by radial immunodiffusion. Additionally, IgG, IgA and IgM fractions were separated from 8 sera by absorption chromatography and their agglutinating capacity was studied at pH 7.2 and 5.0. RESULTS: We studied 72 sera from patients with clinical brucellosis taken at the time of hospitalization, 16 from persons in contact with infected animals, and 16 from healthy donors. SAT results at pH 5.0 correlated with those obtained with the Rose Bengal test. Four Rose Bengal-positive sera were found to be SAT-negative at pH 7.2 and SAT-positive at pH 5.0. SAT performed at pH 5.0 with BRUCAPT antigen yielded higher titers than tests performed at pH 7.2 or 5.0 with Ring Test antigen (p < 0.001), with highest titers in IDR-positive sera. Among the 8 IgG fractions, all but one agglutinated at pH 7.2, and in 4, IgG titers showed significant increases at pH 5.0. Three IgA fractions were SAT-negative at pH 7.2 and SAT-positive at pH 5.0; the other 5 agglutinated at both pH conditions and were DTT-sensitive. All IgA fractions but one were positive by Rose Bengal. Agglutinating activity of the IgM fraction was not affected by pH. CONCLUSION: The SAT performed with the buffer and antigen suspension included in the Brucellacapt kit (pH 5.0) is highly useful for detecting agglutinating and non-agglutinating antibodies at pH 7.2.