Vergara, N. (Nuria)
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- Cavitary pneumonia in an AIDS patient caused by an unusual Bordetella bronchiseptica variant producing reduced amounts of pertactin and other major antigens(American Society for Microbiology, 2002) Rodriguez-Cuesta, J. (Juan); Garcia-Curiel, A. (Andrés); Vergara, N. (Nuria); Villanueva, J.L. (José Luis); Bernabeu, M. (Máximo); Martinez-de-Tejada, G. (Guillermo); Lorenzo, B. (Benito)Although Bordetella bronchiseptica can infect and colonize immunocompromised humans, its role as a primary pathogen in pneumonia and other respiratory processes affecting those patients remains controversial. A case of cavitary pneumonia caused by B. bronchiseptica in an AIDS patient is presented, and the basis of the seemingly enhanced pathogenic potential of this isolate (designated 814) is investigated. B. bronchiseptica was the only microorganism recovered from sputum, bronchoalveolar lavage fluid, and samples taken through the protected brush catheter. Unlike previous work reporting the involvement of B. bronchiseptica in cases of pneumonia, antibiotic treatment selected on the basis of in vitro antibacterial activity resulted in clearance of the infection and resolution of the pulmonary infiltrate. Although isolate 814 produced reduced amounts of several major antigens including at least one Bvg-activated factor (pertactin), the molecular basis of this deficiency was found to be BvgAS independent since the defect persisted after the bvgAS locus of isolate 814 was replaced with a wild-type bvgAS allele. Despite its prominent phenotype, isolate 814 displayed only a modest yet a significant deficiency in its ability to colonize the respiratory tracts of immunocompetent rats at an early time point. Interestingly, the antibody response elicited by isolate 814 in these animals was almost undetectable. We propose that isolate 814 may be more virulent in immunocompromised patients due, at least in part, to its innate ability to produce low amounts of immunogenic factors which may be required at only normal levels for the interaction of this pathogen with its immunocompetent natural hosts.
- Evaluation of the role of the Bvg intermediate phase in Bordetella pertussis during experimental respiratory infection(American Society for Microbiology, 2005) Rodriguez-Cuesta, J. (Juan); Chavarri, A. (Alberto); Vergara, N. (Nuria); Martinez-de-Tejada, G. (Guillermo); Cotter, P.A. (Peggy A.); Miller, J.F. (Jeff F.)The BvgAS system of Bordetella pertussis was traditionally considered to mediate a transition between two phenotypic phases (Bvg(+) and Bvg(-)) in response to environmental signals. We characterized a third state, the intermediate (Bvg(i)) phase, which can be induced by introducing a 1-bp substitution into bvgS (the bvgS-I1 mutation) or by growing B. pertussis under conditions intermediate between those leading to the Bvg(+) and Bvg(-) phases. Like B. bronchiseptica, B. pertussis displays in its Bvg(i) phase a characteristic colony morphology and hemolytic activity and expresses a Bvg(i)-phase-specific polypeptide called BipA, whose synthesis is regulated by bvgAS at the transcriptional level. Based on our results, we hypothesize that the Bvg(i) phase of B. pertussis may be involved in facilitating transmission between hosts. Thus, a B. pertussis mutant carrying the bvgS-I1 mutation (GMT1i) persisted at wild-type levels only in the upper murine respiratory tract. Interestingly, a bipA deletion derivative of GMT1i displayed a reduced ability to colonize the nasal cavity of mice compared with GMT1i. However, in experimental mixed infections GMT1i expressing the Bvg(i) phase could establish an initial colonization in the nose and trachea of mice as efficiently as GMT1, but the wild-type strain outcompeted GMT1i at a later time point at all sites of the respiratory tract, suggesting that the Bvg(i) phase does not serve as a phenotypic phase specialized in colonization. Finally, even though B. pertussis expresses in vitro the Bvg(i) phase at the human nasal temperature, anti-BipA antibodies were undetectable in a large collection of sera from pertussis patients.