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  • Pediatric bloodstream infections in Cambodia, 2007 to 2011.

    17 July 2018

    Pediatric bacterial bloodstream infections (BSIs) are a major cause of morbidity and mortality worldwide. Epidemiological data from resource-limited settings in southeast Asia, such as Cambodia, are sparse but have important implications for treatment and public health strategies.We retrospectively investigated BSI in children at a pediatric hospital and its satellite clinic in Siem Reap, Cambodia, from January 1, 2007, to July 31, 2011. The range of bacterial pathogens and their antimicrobial susceptibility patterns were analyzed in conjunction with demographic, clinical and outcome data.Of 7682 blood cultures with results (99.9% of cultures taken), 606 (7.9%) episodes of BSI were identified in 588 children. The incidence of BSI increased from 14 to 50/1000 admissions (P < 0.001); this was associated with an increased sampling rate. Most BSI were community acquired (89.1%). Common pathogens included Salmonella Typhi (22.8% of all isolates), Staphylococcus aureus (12.2%), Streptococcus pneumoniae (10.0%), Klebsiella pneumoniae (6.4%) and Escherichia coli (6.3%). 21.5% of BSI were caused by a diverse group of uncommon organisms, the majority of which were environmental Gram-negative species. No Listeria monocytogenes or Group B streptococcal BSI were identified. Antimicrobial resistance, particularly among the Enterobacteriaceae, was common. Overall mortality was substantial (19.0%), higher in neonates (36.9%) and independently associated with meningitis/meningoencephalitis and K. pneumoniae infection.BSI is a common problem in Cambodian children attending hospital and associated with significant mortality. Further studies are needed to clarify the epidemiology of neonatal sepsis, the contribution of atypical organisms and the epidemiology of pneumococcal disease before the introduction of vaccine.

  • Causes of non-malarial fever in Laos: a prospective study.

    17 July 2018

    Because of reductions in the incidence of Plasmodium falciparum malaria in Laos, identification of the causes of fever in people without malaria, and discussion of the best empirical treatment options, are urgently needed. We aimed to identify the causes of non-malarial acute fever in patients in rural Laos.For this prospective study, we recruited 1938 febrile patients, between May, 2008, and December, 2010, at Luang Namtha provincial hospital in northwest Laos (n=1390), and between September, 2008, and December, 2010, at Salavan provincial hospital in southern Laos (n=548). Eligible participants were aged 5-49 years with fever (≥38°C) lasting 8 days or less and were eligible for malaria testing by national guidelines.With conservative definitions of cause, we assigned 799 (41%) patients a diagnosis. With exclusion of influenza, the top five diagnoses when only one aetiological agent per patient was identified were dengue (156 [8%] of 1927 patients), scrub typhus (122 [7%] of 1871), Japanese encephalitis virus (112 [6%] of 1924), leptospirosis (109 [6%] of 1934), and bacteraemia (43 [2%] of 1938). 115 (32%) of 358 patients at Luang Namtha hospital tested influenza PCR-positive between June and December, 2010, of which influenza B was the most frequently detected strain (n=121 [87%]). Disease frequency differed significantly between the two sites: Japanese encephalitis virus infection (p=0·04), typhoid (p=0·006), and leptospirosis (p=0·001) were more common at Luang Namtha, whereas dengue and malaria were more common at Salavan (all p<0·0001). With use of evidence from southeast Asia when possible, we estimated that azithromycin, doxycycline, ceftriaxone, and ofloxacin would have had significant efficacy for 258 (13%), 240 (12%), 154 (8%), and 41 (2%) of patients, respectively.Our findings suggest that a wide range of treatable or preventable pathogens are implicated in non-malarial febrile illness in Laos. Empirical treatment with doxycycline for patients with undifferentiated fever and negative rapid diagnostic tests for malaria and dengue could be an appropriate strategy for rural health workers in Laos.Wellcome Trust, WHO-Western Pacific Region, Foundation for Innovative New Diagnostics, US Centers for Disease Control and Prevention

  • A prospective assessment of the accuracy of commercial IgM ELISAs in diagnosis of Japanese encephalitis virus infections in patients with suspected central nervous system infections in Laos.

    17 July 2018

    Japanese encephalitis virus (JEV) is a major cause of encephalitis in Asia. We estimated the diagnostic accuracy of two anti-JEV immunoglobulin M (IgM) enzyme-linked immunosorbent assays (ELISAs) (Panbio and XCyton JEVCheX) compared with a reference standard (AFRIMS JEV MAC ELISA) in a prospective study of the causes of central nervous system infections in Laos. Cerebrospinal fluid (CSF; 515 patients) and serum samples (182 patients) from those admitted to Mahosot Hospital, Vientiane, were tested. The CSF from 14.5% of acute encephalitis syndrome (AES) patients and 10.1% from those with AES and meningitis were positive for anti-JEV IgM in the reference ELISA. The sensitivities for CSF were 65.4% (95% confidence interval [CI] = 51-78) (Xcyton), 69.2% (95% CI = 55-81) (Panbio), however 96.2% (95% CI = 87-100) with Panbio Ravi criteria. Specificities were 89-100%. For admission sera from AES patients, sensitivities and specificities of the Panbio ELISA were 85.7% (95% CI = 42-100%) and 92.9% (95% CI = 83-98%), respectively.

  • Paediatric Chromobacterium violaceum in Cambodia: the first documented case.

    17 July 2018

    Chromobacterium violaceum infection is rarely described in Southeast Asian children, which may be due partly to the lack of access to adequate microbiology facilities in many areas. This case report describes the first documented case to occur in a Cambodian child. An awareness of the disease and its manifestations is important as treatment can be difficult and may require prolonged courses of antimicrobials and surgery.

  • IkappaB genetic polymorphisms and invasive pneumococcal disease.

    17 July 2018

    Increasing evidence supports a key role for the transcription factor nuclear factor (NF)-kappaB in the host response to pneumococcal infection. Control of NF-kappaB activity is achieved through interactions with the IkappaB family of inhibitors, encoded by the genes NFKBIA, NFKBIB, and NFKBIE. Rare NFKBIA mutations cause immunodeficiency with severe bacterial infection, raising the possibility that common IkappaB gene polymorphisms confer susceptibility to common bacterial disease.To determine whether polymorphisms in NFKBIA, NFKBIB, and NFKBIE associate with susceptibility to invasive pneumococcal disease (IPD) and thoracic empyema.We studied the frequencies of 62 single-nucleotide polymorphisms (SNPs) across NFKBIA, NFKBIB, and NFKBIE in individuals with IPD and control subjects (n=1,060). Significantly associated SNPs were then studied in a group of individuals with thoracic empyema and a second control group (n=632).Two SNPs in the NFKBIA promoter region were associated with protection from IPD in both the initial study group and the pneumococcal empyema subgroup. Significant protection from IPD was observed for carriage of mutant alleles at these two loci on combining the groups (SNP rs3138053: Mantel-Haenszel 2x2 chi2=13.030, p=0.0003; odds ratio [OR], 0.60; 95% confidence interval [CI], 0.45-0.79; rs2233406: Mantel-Haenszel 2x2 chi2=18.927, p=0.00001; OR, 0.55; 95% CI, 0.42-0.72). An NFKBIE SNP associated with susceptibility to IPD but not pneumococcal empyema. None of the NFKBIB SNPs associated with IPD susceptibility.NFKBIA polymorphisms associate with susceptibility to IPD. Genetic variation in an inhibitor of NF-kappaB therefore not only causes a very rare immunodeficiency state but may also influence the development of common infectious disease.

  • Exonic single nucleotide polymorphisms within TLR3 associated with infant responses to serogroup C meningococcal conjugate vaccine.

    17 July 2018

    The introduction of the serogroup C meningococcal (MenC) conjugate vaccination has successfully controlled the burden of disease associated with this serogroup in many countries. However, considerable inter-individual variation is observed in immune responses to MenC vaccine, and little is understood of the determinants of this variability. Previously, we reported an association between single nucleotide polymorphisms (SNPs) in TLR3 and CD44 and the persistence of MenC vaccine immunity. Here we further examine polymorphisms within these two candidate genes and immune responses to MenC vaccine. MenC-specific IgG concentrations and serum bactericidal assay (SBA) titres were measured one month after a primary course of MenC vaccination in 318 human infants. Tagging SNPs (TagSNPs) within TLR3 and CD44 were genotyped and regional imputations carried out to screen these genes for variations associated with immunological responses to MenC vaccine. This study reports an association between an exonic variant (rs3775290, P=0.025) in TLR3 and MenC IgG concentrations, as well as an association between three SNPs in CD44 (rs3794109, P=0.021; rs3794110, P=0.022; rs112762, P=0.049) and MenC SBA titres. These data support our previous findings of an association between SNPs in TLR3 and CD44, and present novel findings implicating exonic variants in these genes with MenC vaccine responses.

  • NFKBIZ polymorphisms and susceptibility to pneumococcal disease in European and African populations.

    17 July 2018

    The proinflammatory transcription factor nuclear factor-kappaB (NF-kappaB) has a central role in host defence against pneumococcal disease. Both rare mutations and common polymorphisms in the NFKBIA gene encoding the NF-kappaB inhibitor, IkappaB-alpha, associate with susceptibility to bacterial disease, but the possible role of polymorphisms within the related IkappaB-zeta gene NFKBIZ in the development of invasive pneumococcal disease (IPD) has not been reported previously. To investigate this further, we examined the frequencies of 22 single-nucleotide polymorphisms spanning NFKBIZ in two case-control studies, comprising UK Caucasian (n=1008) and Kenyan (n=723) individuals. Nine polymorphisms within a single UK linkage disequilibrium (LD) block and all four polymorphisms within the equivalent, shorter Kenyan LD block displayed either a significant association with IPD or a trend towards association. For each polymorphism, heterozygosity was associated with protection from IPD when compared with the combined homozygous states (for example, for rs600718, Mantel-Haenszel 2 x 2 chi(2)=7.576, P=0.006, odds ratio (OR)=0.67, 95% confidence interval (95% CI) for OR: 0.51-0.88; for rs616597, Mantel-Haenszel 2 x 2 chi(2)=8.715, P=0.003, OR=0.65, 95% CI: 0.49-0.86). We conclude that multiple NFKBIZ polymorphisms associate with susceptibility to IPD in humans. The study of multiple populations may aid in fine mapping of associations within extensive regions of strong LD ('transethnic mapping').

  • How clonal is Staphylococcus aureus?

    17 July 2018

    Staphylococcus aureus is an important human pathogen and represents a growing public health burden owing to the emergence and spread of antibiotic-resistant clones, particularly within the hospital environment. Despite this, basic questions about the evolution and population biology of the species, particularly with regard to the extent and impact of homologous recombination, remain unanswered. We address these issues through an analysis of sequence data obtained from the characterization by multilocus sequence typing (MLST) of 334 isolates of S. aureus, recovered from a well-defined population, over a limited time span. We find no significant differences in the distribution of multilocus genotypes between strains isolated from carriers and those from patients with invasive disease; there is, therefore, no evidence from MLST data, which index variation within the stable "core" genome, for the existence of hypervirulent clones of this pathogen. Examination of the sequence changes at MLST loci during clonal diversification shows that point mutations give rise to new alleles at least 15-fold more frequently than does recombination. This contrasts with the naturally transformable species Neisseria meningitidis and Streptococcus pneumoniae, in which alleles change between 5- and 10-fold more frequently by recombination than by mutation. However, phylogenetic analysis suggests that homologous recombination does contribute toward the evolution of this species over the long term. Finally, we note a striking excess of nonsynonymous substitutions in comparisons between isolates belonging to the same clonal complex compared to isolates belonging to different clonal complexes, suggesting that the removal of deleterious mutations by purifying selection may be relatively slow.