Showing papers by "Martin Antonio published in 2010"
TL;DR: A review of the phenotypic differences described thus far between M. africanum and M. tuberculosis sensu stricto in animals and within the Mycobacterium tuberculosis complex is summarized.
Abstract: Mycobacterium africanum consists of two phylogenetically distinct lineages within the Mycobacterium tuberculosis complex, known as M. africanum West African 1 and M. africanum West African 2. These lineages are restricted to West Africa, where they cause up to half of human pulmonary tuberculosis. In this review we discuss the definition of M. africanum, describe the prevalence and restricted geographical distribution of M. africanum West African 1 and 2, review the occurrence of M. africanum in animals, and summarize the phenotypic differences described thus far between M. africanum and M. tuberculosis sensu stricto.
251 citations
TL;DR: This longitudinal carriage study in Gambian villages provides unique information on the pattern of spread of S. pneumoniae in rural Africa and a baseline for evaluating the impact of the introduction of pneumococcal conjugate vaccine into the region.
Abstract: BACKGROUND. To prepare for national introduction of a pneumococcal vaccine of restricted valency, we studied the pattern of nasopharyngeal carriage of Streptococcus pneumoniae and its transmission in Gambian villages over time. METHODS. We collected nasopharyngeal swab specimens every 2 weeks from 158 villagers in 19 households in 2 villages over 1 year. We studied the prevalence and duration of S. pneumoniae carriage, the effect of household size and composition on carriage, and sequence type-specific carriage within and between households. RESULTS. Ninety-seven percent of children and 85% of adults carried S. pneumoniae at some time. Fifty-three serotypes were represented among 1522 isolates. Carriage was more common among children than adults for all serotypes studied except 9V. There was an overall trend toward shorter carriage with increasing age (P = .043) and significant differences in carriage duration between serotypes. For most serotypes, the odds of being a carrier were greater if there were other carriers in the household. The prevalence of carriage varied by serotype. Most notably, serotype 5 carriage occurred in only 1 village and was transient. Multilocus sequence typing of serotype 6B isolates from 1 village revealed 8 different sequence types and strong evidence of nonrandom distribution among households (P < .001). Study by sequence type suggested household spread starting most commonly in children, followed by spread to adults. CONCLUSIONS. This longitudinal carriage study in Gambian villages provides unique information on the pattern of spread of S. pneumoniae in rural Africa and a baseline for evaluating the impact of the introduction of pneumococcal conjugate vaccine into the region.
87 citations
TL;DR: P phenotypic differences between MAF and Mycobacterium tuberculosis (MTB) among 692 tuberculosis patients infected with the two most common lineages within the MTB complex found in the Gambia, namely MAF West African type 2 and Euro-American MTB are identified.
Abstract: Mycobacterium africanum (MAF) is a common cause of human pulmonary tuberculosis in West Africa. We previously described phenotypic differences between MAF and Mycobacterium tuberculosis (MTB) among 290 patients. In the present analysis, we compared 692 tuberculosis patients infected with the two most common lineages within the (MTB) complex found in the Gambia, namely MAF West African type 2 (39% prevalence) and Euro-American MTB (55% prevalence). We identified additional phenotypic differences between infections with these two organisms. MAF patients were more likely to be older and HIV infected. In addition, they had worse disease on chest X-ray, despite complaining of cough for an equal duration, and were more likely severely malnourished. In this cohort, the prevalence of MAF did not change significantly over a 7-year period.
54 citations
TL;DR: Sensitivity to C3 deposition and opsonophagocytosis was associated with serotype-specific mortality of invasive pneumococcal disease, suggesting that the primary pathogens, such as serotypes 1 and 5, are more resistant to complement and require a higher concentration of capsule antibodies for opsonphagocytic killing than the opportunistic serotypes such as 6B and 23F, which are associated with a more severe disease outcome.
Abstract: The polysaccharide capsule is a major virulence factor of Streptococcus pneumoniae; it affects complement resistance and shields the bacterium from phagocytes. Certain capsular serotypes appear to be better able to cause invasive disease than others. Serotypes 1 and 5 are common causes of invasive disease but are rarely isolated from healthy carriers, whereas serotypes 6B and 23F are more frequently isolated from carriage than invasive disease. We have recently shown that serotypes 6B and 19F differ in resistance to complement C3 deposition and opsonophagocytic killing. In this study we assessed the complement resistance and susceptibility to opsonophagocytosis of several other serotypes targeted by the pneumococcal conjugate vaccines. Clinical isolates of serotypes 1, 4, 5, 14, 18C, and 23F were tested along reference strains of corresponding capsular types. The concentration of anticapsular antibodies required for opsonophagocytic killing correlated inversely with C3 deposition on the serotype. Serotype 1 was the most resistant of the clinical isolates to C3 deposition and, along with serotypes 5 and 19F, required the highest concentration of capsule antibodies for opsonophagocytic killing, whereas serotype 23F was the most sensitive to opsonophagocytosis. Sensitivity to C3 deposition and opsonophagocytosis was associated with serotype-specific mortality of invasive pneumococcal disease, suggesting that the primary pathogens, such as serotypes 1 and 5, are more resistant to complement and require a higher concentration of capsule antibodies for opsonophagocytic killing than the opportunistic serotypes such as 6B and 23F, which are associated with a more severe disease outcome.
51 citations
TL;DR: Antigens from the TbD1 region induced IFNγ responses in only 35% patients and did not discriminate between patients infected with M. africanum vs. M. tuberculosis, while PPD induced universally high responses.
Abstract: Currently available tools cannot be used to distinguish between sub-species of the M. tuberculosis complex causing latent tuberculosis (TB) infection. M. africanum causes up to half of TB in West- Africa and its relatively lower progression to disease suggests the presence of a large reservoir of latent infection relative to M. tuberculosis. We assessed the immunogenicity of the TbD1 region, present in M. africanum and absent from "modern" M. tuberculosis, in an ELISPOT assay using cells from confirmed M. africanum or M. tuberculosis infected TB patients without HIV infection in the Gambia. Antigens from the TbD1 region induced IFNγ responses in only 35% patients and did not discriminate between patients infected with M. africanum vs. M. tuberculosis, while PPD induced universally high responses. Further studies will need to assess other antigens unique to M. africanum that may induce discriminatory immune responses.
7 citations