Molecular epidemiology of multidrug-resistant Shigella dysenteriae type 1 causing dysentery outbreaks in Central African Republic, 2003-2004.

Shigella dysenteriae type 1 (Sd1) represents a particular threat in developing countries because of the severity of the infection and its epidemic potential. Antimicrobial susceptibility testing and molecular subtyping by pulsed-field gel electrophoresis (PFGE) and plasmid profiling (PP) of Sd1 isolates collected during two dysentery outbreaks (2013 and 445 cases of bloody diarrhoea) in Central African Republic (CAR) during the period 2003-2004 were reported. Eleven Sd1 comparison strains (CS) acquired by travellers or residents of Africa (n=10) or Asia (n=1) between 1993 and 2003 were also analysed. The 19 Sd1 isolates recovered from CAR outbreaks were multidrug resistant, although susceptible to quinolones and fluoroquinolones. Molecular subtyping by PFGE was more discriminatory than PP. The PFGE using XbaI and NotI restriction enzymes indicated that the two outbreaks were due to two different clones and also revealed a genetic diversity among the CS recovered from outbreak or sporadic cases between 1993 and 2003. This study was the result of a fruitful collaboration between field physicians and microbiologists. The data collected will serve as the basis for establishing long-term monitoring of Sd1 in CAR

The complete genome and proteome of laribacter hongkongensis reveal potential mechanisms for adaptations to different temperatures and habitats

Laribacter hongkongensis is a newly discovered Gram-negative bacillus of the Neisseriaceae family associated with freshwater fish-borne gastroenteritis and traveler's diarrhea. The complete genome sequence of L. hongkongensis HLHK9, recovered from an immunocompetent patient with severe gastroenteritis, consists of a 3,169-kb chromosome with G+C content of 62.35%. Genome analysis reveals different mechanisms potentially important for its adaptation to diverse habitats of human and freshwater fish intestines and freshwater environments. The gene contents support its phenotypic properties and suggest that amino acids and fatty acids can be used as carbon sources. The extensive variety of transporters, including multidrug efflux and heavy metal transporters as well as genes involved in chemotaxis, may enable L. hongkongensis to survive in different environmental niches. Genes encoding urease, bile salts efflux pump, adhesin, catalase, superoxide dismutase, and other putative virulence factors-such as hemolysins, RTX toxins, patatin-like proteins, phospholipase A1, and collagenases-are present. Proteomes of L. hongkongensis HLHK9 cultured at 37°C (human body temperature) and 20°C (freshwater habitat temperature) showed differential gene expression, including two homologous copies of argB, argB-20, and argB-37, which encode two isoenzymes of N-acetyl-L-glutamate kinase (NAGK)-NAGK-20 and NAGK-37-in the arginine biosynthesis pathway. NAGK-20 showed higher expression at 20°C, whereas NAGK-37 showed higher expression at 37°C. NAGK-20 also had a lower optimal temperature for enzymatic activities and was inhibited by arginine probably as negative-feedback control. Similar duplicated copies of argB are also observed in bacteria from hot springs such as Thermus thermophilus, Deinococcus geothermalis, Deinococcus radiodurans, and Roseiflexus castenholzii, suggesting that similar mechanisms for temperature adaptation may be employed by other bacteria. Genome and proteome analysis of L. hongkongensis revealed novel mechanisms for adaptations to survival at different temperatures and habitats. Copyright: © 2009 Woo et al.published_or_final_versio

Recent Increase in Meningitis Caused by Neisseria meningitidis Serogroups A and W135, Yaoundé, Cameroon

From 1991 to 1998, Neisseria meningitidis serogroups A, B, and C represented 2%-10% of strains isolated from cases of bacterial meningitis in Yaoundé. During 1999 to 2000, the percentage of meningococci reached 17%, a proportion never reported since recordkeeping began in 1984. The increase of serogroup A meningococci and the emergence of W135 strains highlight the need for increased surveillance for better diagnosis and prevention

Réalisation et caractérisation d'une caméra à balayage de fente synchroscan à résolution temporelle proche de la picoseconde

Les caméras à balayage de fente sont les instruments de détection optique résolue en temps les plus performants en terme de résolution temporelle. Le mode synchroscan accumule plu-sieurs événements lumineux récurrents à un taux de répétition élevé (environ 100 MHz) et augmente le rapport signal à bruit de la mesure. La caméra est alors associée à une source de lumière impulsionnelle, généralement un laser à modes bloqués et à un déclencheur qui syn-chronise la caméra avec cette source. Seule une bonne mise en œuvre du tube permet d'approcher sa résolution temporelle intrinsèque, limite ultime du système de mesure. La gi-gue de synchronisation de la tension de déflexion avec le train d'impulsions laser constitue la détérioration majeure de la résolution temporelle lorsqu'elle s'approche de la picoseconde. De plus, une bonne résolution temporelle entraîne une sensibilité importante de la caméra vis-à-vis des perturbations internes et externes. Une dérive de plus de 200 ps est généralement constatée durant la première heure de fonctionnement d'une caméra standard. Une technique permettant de mesurer électriquement la gigue de synchronisation d'un déclencheur est dé-crite. Un système de déclenchement à base de boucle à verrouillage de phase a été réalisé afin de limiter cette gigue à celle d'une photodiode tout en filtrant efficacement le bruit d'amplitude du laser. Un système de stabilisation électrique de la caméra a été développé. Il réduit la dérive de la caméra à moins de 12 ps durant la première heure et il permet d'atténuer la gigue de synchronisation induite par la caméra à moins de 200 fs efficace. Les dérives rési-duelles sont complètement annulées à l'aide d'un système logiciel complémentaire dont les instabilités résiduelles sont de 200 fs efficace. La résolution temporelle de la caméra fonc-tionnant avec ces systèmes n'est plus limitée que par celle du tube et par la gigue de synchro-nisation du déclencheur et cela, quelque soit la durée de l'acquisition.Streak camera have the best temporal resolution achievable of the time resolved fast optical detection device. Synchroscan mode accumulates recurrent optical events at high repetition rate (about 100 MHz) and increases the signal to noise ratio. The camera is then coupled with a impulsion light source, generally a mode locked laser, and with a trigger which synchronies the camera with this source. Just a good use of the tube allows reaching its intrinsic temporal resolution, ultimate limit of the measurement system.Synchronization jitter of the deflection voltage with the laser beam is the major degradation of the temporal resolution when ap-proaching the picoseconds or subpicoseconds range. Moreover, a good temporal resolution induces a high sensibility to external and internal perturbations. A more than 200 ps is gener-ally observed with standard synchroscan streak camera durring theirs warm up time (about 1 hour). A technique allowing measuring the electrically the synchronization jitter is de-scribed. A trigger system with phase locked loop has been realized to limit this jitter down to a photodiode jitter while filtering the laser amplitude noise. A stabilization system for the camera has been realized. It reduces the camera drift to 12 ps during the warm up time and decreases the jitter induced by the camera to less than 200 fs rms. The residual drifts can be completely annihilated by a complementary software system which has just 200 fs rms tem-poral instabilities. The temporal resolution of a streak camera working with those systems is then only limited by the tube one and the trigger's synchronization jitter, whatever is the ac-cumulation time.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF