Pro- and antiinflammatory cytokines were measured on admission in 287 consecutive Vietnamese adults with severe falciparum malaria. Plasma interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-alpha concentrations and the IL-6: IL-10 ratio were significantly higher in patients who died than in survivors (P<.001). On multivariate analysis, hyperparasitemia, jaundice, and shock were all associated independently with raised IL-6, IL-10, and interferon-gamma, and acute renal failure specifically with raised TNF-alpha levels. Cerebral malaria patients, particularly those without other vital organ dysfunction, had significantly lower levels of these cytokines (P=.006), reflecting a more localized pathology. Serial IL-6 and IL-10 measurements made on 43 patients who died and matched survivors indicated a relative deficiency in IL-10 production as death approached. Elevated plasma cytokines in severe malaria are associated with systemic pathologic abnormalities, not cerebral involvement. Both the overall magnitude of the cytokine responses and the eventual imbalance between the pro- and antiinflammatory responses are important determinants of mortality.
Tuberculosis remains a global health problem, with an estimated 10.4 million cases and 1.8 million deaths resulting from the disease in 2015. The most lethal and disabling form of tuberculosis is tuberculous meningitis (TBM), for which more than 100,000 new cases are estimated to occur per year. In patients who are co-infected with HIV-1, TBM has a mortality approaching 50%. Study of TBM pathogenesis is hampered by a lack of experimental models that recapitulate all the features of the human disease. Diagnosis of TBM is often delayed by the insensitive and lengthy culture technique required for disease confirmation. Antibiotic regimens for TBM are based on those used to treat pulmonary tuberculosis, which probably results in suboptimal drug levels in the cerebrospinal fluid, owing to poor blood-brain barrier penetrance. The role of adjunctive anti-inflammatory, host-directed therapies - including corticosteroids, aspirin and thalidomide - has not been extensively explored. To address this deficit, two expert meetings were held in 2009 and 2015 to share findings and define research priorities. This Review summarizes historical and current research into TBM and identifies important gaps in our knowledge. We will discuss advances in the understanding of inflammation in TBM and its potential modulation; vascular and hypoxia-mediated tissue injury; the role of intensified antibiotic treatment; and the importance of rapid and accurate diagnostics and supportive care in TBM.
Background
Streptococcus suis is a zoonotic pathogen that infects pigs and can occasionally cause serious infections in humans. S. suis infections occur sporadically in human Europe and North America, but a recent major outbreak has been described in China with high levels of mortality. The mechanisms of S. suis pathogenesis in humans and pigs are poorly understood.Methodology/Principal FindingsThe sequencing of whole genomes of S. suis isolates provides opportunities to investigate the genetic basis of infection. Here we describe whole genome sequences of three S. suis strains from the same lineage: one from European pigs, and two from human cases from China and Vietnam. Comparative genomic analysis was used to investigate the variability of these strains. S. suis is phylogenetically distinct from other Streptococcus species for which genome sequences are currently available. Accordingly, ∼40% of the ∼2 Mb genome is unique in comparison to other Streptococcus species. Finer genomic comparisons within the species showed a high level of sequence conservation; virtually all of the genome is common to the S. suis strains. The only exceptions are three ∼90 kb regions, present in the two isolates from humans, composed of integrative conjugative elements and transposons. Carried in these regions are coding sequences associated with drug resistance. In addition, small-scale sequence variation has generated pseudogenes in putative virulence and colonization factors.Conclusions/SignificanceThe genomic inventories of genetically related S. suis strains, isolated from distinct hosts and diseases, exhibit high levels of conservation. However, the genomes provide evidence that horizontal gene transfer has contributed to the evolution of drug resistance.
Tuberculous meningitis (TBM) is the most severe form of tuberculosis. Microbiological confirmation is rare, and treatment is often delayed, increasing mortality and morbidity. The GeneXpert MTB/RIF test was evaluated in a large cohort of patients with suspected tuberculous meningitis. Three hundred seventy-nine patients presenting with suspected tuberculous meningitis to the Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam, between 17 April 2011 and 31 December 2012 were included in the study. Cerebrospinal fluid samples were tested by Ziehl-Neelsen smear, mycobacterial growth indicator tube (MGIT) culture, and Xpert MTB/RIF. Rifampin (RIF) resistance results by Xpert were confirmed by an MTBDR-Plus line probe assay and all positive cultures were tested by phenotypic MGIT drug susceptibility testing. Overall, 182/379 included patients (48.0%) were diagnosed with tuberculous meningitis. Sensitivities of Xpert, smear, and MGIT culture among patients diagnosed with TBM were 59.3% (108/182 [95% confidence interval {CI}, 51.8 to 66.5%]), 78.6% (143/182 [95% CI, 71.9 to 84.3%]) and 66.5% (121/182 [95% CI, 59.1 to 73.3%]), respectively. There was one false-positive Xpert MTB/RIF test (99.5% specificity). Four cases of RIF resistance (4/109; 3.7%) were identified by Xpert, of which 3 were confirmed to be multidrug-resistant (MDR) TBM and one was culture negative. Xpert MTB/RIF is a rapid and specific test for the diagnosis of tuberculous meningitis. The addition of a vortexing step to sample processing increased sensitivity for confirmed TBM by 20% (P = 0.04). Meticulous examination of a smear from a large volume of cerebrospinal fluid (CSF) remains the most sensitive technique but is not practical in most laboratories. The Xpert MTB/RIF represents a significant advance in the early diagnosis of this devastating condition.
These results confirm the importance of acidosis in the pathophysiology of severe adult malaria and suggest a multifactorial origin involving tissue hypoxia, liver dysfunction, and impaired renal handling of bicarbonate.
S. suis serotype 2 is the most frequent cause of bacterial meningitis in adults in southern Vietnam and is associated with substantial morbidity attributable to hearing loss.
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