SalK/SalR, a Two-Component Signal Transduction System, Is Essential for Full Virulence of Highly Invasive Streptococcus suis Serotype 2

BACKGROUND: Streptococcus suis serotype 2 (S. suis 2, SS2) has evolved into a highly infectious entity, which caused the two recent large-scale outbreaks of human SS2 epidemic in China, and is characterized by a toxic shock-like syndrome. However, the molecular pathogenesis of this new emerging pathogen is still poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: 89K is a newly predicted pathogenicity island (PAI) which is specific to Chinese epidemic strains isolated from these two SS2 outbreaks. Further bioinformatics analysis revealed a unique two-component signal transduction system (TCSTS) located in the candidate 89K PAI, which is orthologous to the SalK/SalR regulatory system of Streptococcus salivarius. Knockout of salKR eliminated the lethality of SS2 in experimental infection of piglets. Functional complementation of salKR into the isogenic mutant DeltasalKR restored its soaring pathogenicity. Colonization experiments showed that the DeltasalKR mutant could not colonize any susceptible tissue of piglets when administered alone. Bactericidal assays demonstrated that resistance of the mutant to polymorphonuclear leukocyte (PMN)-mediated killing was greatly decreased. Expression microarray analysis exhibited a transcription profile alteration of 26 various genes down-regulated in the DeltasalKR mutant. CONCLUSIONS/SIGNIFICANCE: These findings suggest that SalK/SalR is requisite for the full virulence of ethnic Chinese isolates of highly pathogenic SS2, thus providing experimental evidence for the validity of this bioinformatically predicted PAI

The politics of control in Kenya : understanding the bureaucratic-executive state, 1952–78

Colonial rule in Kenya witnessed the emergence of a profoundly unbalanced institutional landscape. With all capacity resided in a strong prefectural provincial administration, political parties remained underdeveloped. The co-option of sympathetic African elites during the colonial twilight into the bureaucracy, the legislature and the private property-based economy meant that the allies of colonialism and representatives of transnational capital were able to reap the benefits of independence. In the late colonial period these elites not only attained the means of production, they also assumed the political and institutional capacity to reproduce their dominance. The post-colonial state must therefore be seen as a representation of the interests protected and promoted during the latter years of colonial rule. Under Jomo Kenyatta, the post-colonial state represented a ‘pact-of-domination’ between transnational capital, the elite and the executive. The ability of this coalition to reproduce itself over time lay in its capacity to demobilise popular forces, especially those elements of the nationalist movement that questioned both the social and economic cleavages of the post-colonial state. Whilst Kenya may have experienced changes to both the executive and legislature, the structure of the state itself has demonstrated remarkable continuity

Violence and exodus in Kenya's Rift Valley, 2008: predictable and preventable?

This article offers a preliminary analysis of the outbreak of violence in the Rift Valley Province of Kenya, over January and February 2008, following the national elections of December 2007. Maps of the earliest phase of the violence are reproduced to illustrate the sequencing and location of conflict. The causes of the violence are explored through discussion of historical patterns of land settlement in the Rift Valley, the impact of political violence in key constituencies since the early 1990s, and more recent political contingencies around the question of constitutional reform and regionalism (majimboism). The violence of 2008 bore strong similarities to earlier episodes of conflict in the Rift Valley, and in that sense was predictable and might have been prevented. Though the December 2007 poll was the catalyst for this violence, its causes are to be found in deeper-rooted historical and political conflicts