Browsing by Author "Ferres, M."

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    Evaluation of direct immunofluorescent assay (DFA) and rapid antigen test (RAT) for diagnosis of new pandemic influenza A H1N1 2009 (FLU AH1N1) during first wave in Santiago, Chile
    (ELSEVIER SCI LTD, 2010) Vizcaya, C.; Ferres, M.; Perret Pérez, Cecilia; Martinez, C.; Godoy, P.; Contreras, A. M.; Ferrer, P.; Azocar, T.
    Background: Since May 17th 2009 (epidemiological week 20th), the new strain of influenza A H1N1 was detected in respiratory samples of symptomatic patients in Santiago, Chile. The circulation of the virus lasted 11 weeks, with a peak between weeks 25-27th. The objective of our study was to evaluate the performance of influenza tests for diagnosis of FLU AH1N1. Methods: Nasopharyngeal swabs were taken from in and outpatients with influenza like illness (ILI), between June 1st and July 19th of 2009 (weeks 23-29th) and the results of DFA and RAT were compared using RT-PCR FLU AH1N1 (Light mix Kit Influenza A virus M2 and Light Mix Kit FLU A swine H1Ò of TIB MOLBIOL) as gold standard. We analyzed sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of DFA (D3 Ultra 8 DFA Respiratory & Identification Kit ä de Diagnostic Hybrid) and RAT (QuickVeuÒ of Biomerieux). Results were compared by age group and over three different periods of the outbreak: increasing, peak and decreasing. Results: 510 patients had RT-PCR for FLU AH1N1 with simultaneous DFA, 385 with RAT and 48 with both tests. Average age with DFA was 25,8 years (1 month-108 years, 53% females) and with RAT 32,9 years (2 months-108 years, 51% females), (p <0,0001). Comparing periods of the outbreak, DFA sensitivity was 58%, 77% and 81% in ascending, peak and descending period, respectively (p <0,001) and specificity was 90%, 83% and 91% respectively (p>0,05). Evaluating RAT, sensitivity was 41%, 61% and 67% (p<0,001) and specificity was 87%, 96% y 92% (p> 0,05) in different periods.
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    Infection by Bartonella henselae in immunocompetent patients: Cat scratch disease
    (SOC MEDICA SANTIAGO, 1996) Abarca Villaseca, Katia; Vial, P. A.; Rivera, M.; Garcia, C.; Oddo, D.; Prado, P.; Ferres, M.
    Background: Cat scratch disease, whose etiologic agent is Bartonella benselae, is a benign disease in immunocompetent subjects, characterized by lymphadenopathy of prolonged course and occasional involvement of other organs such as liver, spleen, central nervous system, eye and lung. In immunocompromised patients, the infection is bacteremic and disseminated. Aims: To report Chilean cases of cat scratch disease. Patients and methods: Ten children (seven male, aged between 6 and 13 years old) with histologically or serologically confirmed cat scratch disease are reported. Results: Lymphadenopathy location was pre auricular in four cases, axillary in two, inguinal in two and epitrochlear in two. Three children had fever over 39 degrees C and two had a Parinaud syndrome. Nine children had a history of cat scratch and one of a cat byte. Six had an erythrocyte sedimentation rate over 40. Lymph node ultrasound examination was a useful diagnostic tool. Two patients had splenic granulomas. Lymph node biopsies were obtained in four cases, showing a suppurative granulomatous lymphadenitis in all and a positive Wartbin-Starry stain in two. Serology, done in patients without histological confirmation was positive with titles ranging from 1:64 to 1:8192. All patients had a satisfactory outcome with regression of lymphadenopathy. Conclusions: Infections by Bartonella hemselae occur in the Chilean population and must be considered in the differential diagnosis of regional lymph node enlargement.
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    Is Gamma (P.1) Variant Associated with a Higher Severity in ICU Patients with SARS-CoV-2 Infection
    (2022) Vera, M.; Angulo, J.; Medina, R.; Ferres, M.; Bruhn, A.; Castro, R.; Pardo-Roa, C.
    The Omicron variant of SARS-CoV-2 has been shown to evade neutralizing antibodies elicited by vaccination or infection. Despite the global spread of the Omicron variant, even among highly vaccinated populations, death rates have not increased concomitantly. These data suggest that immune mechanisms beyond antibody-mediated virus neutralization may protect against severe disease. In addition to neutralizing pathogens, antibodies contribute to control and clearance of infections through Fc effector mechanisms. Here, we probed the ability of vaccine-induced antibodies to drive Fc effector activity against the Omicron variant using samples from individuals receiving one of three SARS-CoV-2 vaccines. Despite a substantial loss of IgM, IgA, and IgG binding to the Omicron variant receptor binding domain (RBD) in samples from individuals receiving BNT162b2, mRNA-1273, and CoronaVac vaccines, stable binding was maintained against the full-length Omicron Spike protein. Compromised RBD binding IgG was accompanied by a loss of RBD-specific antibody Fc gamma receptor (Fe gamma R) binding in samples from individuals who received the CoronaVac vaccine, but RBD-specific Fc gamma R2a and Fc gamma R3a binding was preserved in recipients of mRNA vaccines. Conversely, Spike protein-specific antibodies exhibited persistent but reduced binding to Fc gamma Rs across all three vaccines, although higher binding was observed in samples from recipients of mRNA vaccines. This was associated with preservation of Fc gamma R2a and Fc gamma R3a binding antibodies and maintenance of Spike protein-specific antibody-dependent natural killer cell activation. Thus, despite the loss of Omicron neutralization, vaccine-induced Spike protein-specific antibodies continue to drive Fc effector functions, suggesting a capacity for extraneutralizing antibodies to contribute to disease control.