SUMMARYNotified cases of dengue infections in Singapore reached historical highs in 2004 (9459 cases) and 2005 (13 817 cases) and the reason for such an increase is still to be established. We apply a mathematical model for dengue infection that takes into account the seasonal variation in incidence, characteristic of dengue fever, and which mimics the 2004-2005 epidemics in Singapore. We simulated a set of possible control strategies and confirmed the intuitive belief that killing adult mosquitoes is the most effective strategy to control an ongoing epidemic. On the other hand, the control of immature forms was very efficient in preventing the resurgence of dengue epidemics. Since the control of immature forms allows the reduction of adulticide, it seems that the best strategy is to combine both adulticide and larvicide control measures during an outbreak, followed by the maintenance of larvicide methods after the epidemic has subsided. In addition, the model showed that the mixed strategy of adulticide and larvicide methods introduced by the government seems to be very effective in reducing the number of cases in the first weeks after the start of control.

Thirty-one patients with acute schistosomiasis were evaluated clinically and immunologically. Cytokine levels were determined in peripheral blood mononuclear cell (PBMC) supernatants. Levels of total and antigen-specific IgE, tumor necrosis factor (TNF)-alpha, and immune complexes were measured in serum samples. Clinical findings included general symptoms, liver damage, pulmonary involvement, and pericarditis. All patients had eosinophilia. Immune complexes were detected in 55% of the patients (mean+/-SD, 7.8+/-7.6 microg Eq/mL) and were associated with cough, dyspnea, and abnormal chest radiographic findings. Levels (mean +/- SD) of TNF-alpha (1349.3+/-767.6 pg/mL), interleukin (IL)-1 (2683+/-1270 pg/mL), and IL-6 (382 +/- 52.3 pg/mL) were elevated in PBMC. Serum TNF-alpha levels were elevated in 87% of the patients and were associated with abdominal pain. Higher interferon-gamma levels were detected in PBMC of patients with acute disease than in those of patients with chronic schistosomiasis; IL-5 levels were higher in those with chronic disease. Low IL-5 levels were associated with weight loss. Proinflammatory cytokines and immune complexes with low Th2 responses might explain the immunopathogenesis of acute schistosomiasis.

Yellow fever and dengue are viral infections that in urban centres are transmitted by the same arthropod vector, a mosquito of the genus Aedes. In order to estimate the risk of an epidemic of urban yellow fever in a dengue-infested area we calculated the threshold in the basic reproduction number, R0, of dengue, above which any single sylvatic yellow fever-infected individual will trigger an urban yellow fever epidemic. Specifically, we analysed the relationship between the extrinsic incubation period and the duration of viraemia, from which it is possible to define the R0 for dengue that would also suggest an outbreak potential for yellow fever. We also calculated the critical proportion of people to vaccinate against yellow fever in order to prevent an epidemic in a dengue-endemic area. The theory proposed is illustrated by the case of São Paulo State in southern Brazil, where dengue is endemic and the risk of urban yellow fever is already imminent.

INTRODUCTION:Imipenem‐resistant Pseudomonas aeruginosa resulting from metallo‐β‐lactamases has been reported to be an important cause of nosocomial infection and is a critical therapeutic problem worldwide, especially in the case of bacteremia.OBJECTIVES:To determine the frequency of metallo‐β‐lactamases among imipenem‐resistant Pseudomonas aeruginosa isolates and to compare methods of phenotypic and molecular detection.METHODS:During 2006, 69 imipenem‐resistant Pseudomonas aeruginosa samples were isolated from blood and tested for metallo‐β‐lactamase production using phenotypic methods. Minimal Inhibitory Concentratrions (MIC) (µg/mL) was determined with commercial microdilution panels. Pulsed Field Gel Electrophoresis (PFGE) was performed among metallo‐β‐lactamase producers.RESULTS:Of all the blood isolates, 34.5% were found to be imipenem‐resistant Pseudomonas aeruginosa. Positive phenotypic tests for metallo‐β‐lactamases ranged from 28%‐77%, and Polymerase Chain Reaction (PCR) were positive in 30% (of note, 81% of those samples were blaSPM‐1 and 19% were blaVIM‐2). Ethylenediamine tetracetic acid (EDTA) combinations for the detected enzymes had low kappa values; thus, care should be taken when use it as a phenotypic indicator of MBL. Despite a very resistant antibiogram, four isolates demonstrated the worrisome finding of a colistin MIC in the resistant range. PFGE showed a clonal pattern.CONCLUSION:Metallo‐β‐lactamases among imipenem‐resistant Pseudomonas aeruginosa were detected in 30.4% of imipenem‐resistant Pseudomonas aeruginosa isolates. This number might have been higher if other genes were included. SPM‐1 was the predominant enzyme found. Phenotypic tests with low kappa values could be misleading when testing for metallo‐β‐lactamases. Polymerase Chain Reaction detection remains the gold standard.

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