Human versus equine intramuscular antitoxin, with or without human intrathecal antitoxin, for the treatment of adults with tetanus: a 2 × 2 factorial randomised controlled trial

Background

Intramuscular antitoxin is recommended in tetanus treatment, but there are few data comparing human and equine preparations. Tetanus toxin acts within the CNS, where there is limited penetration of peripherally administered antitoxin; thus, intrathecal antitoxin administration might improve clinical outcomes compared with intramuscular injection.

Methods

In a 2  × 2 factorial trial, all patients aged 16 years or older with a clinical diagnosis of generalised tetanus admitted to the intensive care unit of the Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam, were eligible for study entry. Participants were randomly assigned first to 3000 IU human or 21 000 U equine intramuscular antitoxin, then to either 500 IU intrathecal human antitoxin or sham procedure. Interventions were delivered by independent clinicians, with attending clinicians and study staff masked to treatment allocations. The primary outcome was requirement for mechanical ventilation. The analysis was done in the intention-to-treat population. The study is registered at ClinicalTrials.gov, NCT02999815; recruitment is completed.

Findings

272 adults were randomly assigned to interventions between Jan 8, 2017, and Sept 29, 2019, and followed up until May, 2020. In the intrathecal allocation, 136 individuals were randomly assigned to sham procedure and 136 to antitoxin; in the intramuscular allocation, 109 individuals were randomly assigned to equine antitoxin and 109 to human antitoxin. 54 patients received antitoxin at a previous hospital, excluding them from the intramuscular antitoxin groups. Mechanical ventilation was given to 56 (43%) of 130 patients allocated to intrathecal antitoxin and 65 (50%) of 131 allocated to sham procedure (relative risk [RR] 0·87, 95% CI 0·66–1·13; p=0·29). For the intramuscular allocation, 48 (45%) of 107 patients allocated to human antitoxin received mechanical ventilation compared with 48 (44%) of 108 patients allocated to equine antitoxin (RR 1·01, 95% CI 0·75–1·36, p=0·95). No clinically relevant difference in adverse events was reported. 22 (16%) of 136 individuals allocated to the intrathecal group and 22 (11%) of 136 allocated to the sham procedure experienced adverse events related or possibly related to the intervention. 16 (15%) of 108 individuals allocated to equine intramuscular antitoxin and 17 (16%) of 109 allocated to human antitoxin experienced adverse events related or possibly related to the intervention. There were no intervention-related deaths.

Interpretation

We found no advantage of intramuscular human antitoxin over intramuscular equine antitoxin in tetanus treatment. Intrathecal antitoxin administration was safe, but did not provide overall benefit in addition to intramuscular antitoxin administration.

Funding

The Wellcome Trust.

Antimicrobial use and resistance data in human and animal sectors in the Lao PDR: evidence to inform policy

OBJECTIVES

To review the scientific evidence base on antimicrobial use (AMU) and antimicrobial resistance (AMR) in human and animal sectors in the Lao PDR (Laos).

METHODS

We reviewed all publications from July 1994 (the first article describing AMR in Laos) to December 2020. Electronic searches were conducted using Google Scholar and PubMed with specific terms relating to AMR and AMU in Lao, French and English languages.

FINDINGS

We screened 1,357 peer-reviewed and grey reports by title and abstract and then full articles/reports. Of 80 included, 66 (83%) related to human health, nine (11%) to animal health, four (5%) to both animal and human health and one (1%) to the environment. Sixty-two (78%) were on AMR and 18 (22%) on AMU. Extended spectrum beta lactamase-producing Escherichia coli was the greatest concern identified; the proportion of isolates increased fivefold from 2004 to 2016 (2/28 (7%) to 27/78 (35%)) from blood cultures submitted to the Microbiology Laboratory, Mahosot Hospital, Vientiane. Carbapenem resistant Escherichia coli was first identified in 2015. Methicillin-resistant Staphylococcus aureus (MRSA) was uncommon, with 15 cases of MRSA from blood cultures between its first identification in 2017 and December 2020. AMR patterns of global antimicrobial resistance surveillance system (GLASS) target pathogens from livestock were less well documented. There were few data on AMU in human health and none on AMU in livestock. The first hospital AMU survey in Laos showed that 70% (1,386/1,981) of in-patients in five hospitals from 2017 to 2018 received antimicrobial(s). Antibiotic self-medication was common.

CONCLUSION

AMR in Laos is occurring at relatively low proportions for some GLASS pathogens, giving the country a window of opportunity to act quickly to implement strategies to protect the population from a worsening situation. Urgent interventions to roll out new guidelines with enhanced one-health antibiotic stewardship, reduce antibiotic use without prescriptions, enhance surveillance and improve understanding of AMU and AMR are needed.

Defining the burden of febrile illness in rural South and Southeast Asia: an open letter to announce the launch of the Rural Febrile Illness project

In rural areas of South and Southeast Asia malaria is declining but febrile illnesses still account for substantial morbidity and mortality. Village health workers (VHWs) are often the first point of contact with the formal health system, and for patients with febrile illnesses they can provide early diagnosis and treatment of malaria. However, for the majority of febrile patients, VHWs lack the training, support and resources to provide further care. Consequently, treatable bacterial illnesses are missed, antibiotics are overused and poorly targeted, and patient attendance wanes along with declining malaria. This Open Letter announces the start of a new initiative, the Rural Febrile Illness (RFI) project, the first in a series of projects to be implemented as part of the South and Southeast Asian Community-based Trials Network (SEACTN) research programme. This multi-country, multi-site project will begin in Bangladesh, Cambodia, Lao PDR, and Myanmar and will define the epidemiological baseline of febrile illness in five remote and underserved areas of Asia where malaria endemicity is declining and access to health services is limited. The RFI project aims to determine the incidence, causes and outcomes of febrile illness; understand the opportunities, barriers and appetite for adjustment of the role of VHWs to include management of non-malarial febrile illnesses; and establish a network of community healthcare providers and facilities capable of implementing interventions designed to triage, diagnose and treat patients presenting with febrile illnesses within these communities in the future.

Impact of low blood culture usage on rates of antimicrobial resistance

OBJECTIVES

The magnitude of impact caused by low blood culture utilization on estimates of the proportions and incidence rates of antimicrobial-resistant (AMR) bacterial infections is largely unknown.

METHODS

We used routine electronic databases of microbiology, hospital admission and drug prescription at Sunpasitthiprasong Hospital, Ubon Ratchathani, Thailand, from 2011 to 2015, and bootstrap simulations.

RESULTS

The proportions of Escherichia coli and Klebsiella pneumoniae bacteraemias caused by 3rd generation cephalosporin resistant isolates (3GCREC and 3GCRKP) were estimated to increase by 13 and 24 percentage points (from 44% to 57% and from 51% to 75%), respectively, if blood culture utilization rate was reduced from 82 to 26 blood culture specimens per 1,000 patient-days. Among patients with hospital-origin bloodstream infections, the proportion of 3GCREC and 3GCRKP whose first positive blood culture was taken within ±1 calendar day of the start of a parenteral antibiotic at the study hospital was substantially lower than those whose first positive blood culture was taken later into parenteral antibiotic treatment (30% versus 79%, p<0.001; and 37% versus 86%, p<0.001). Similar effects were observed for methicillin-resistant Staphylococcus aureus, carbapenem-resistant Acinetobacter spp. and carbapenem-resistant Pseudomonas aeruginosa.

CONCLUSION

Impacts of low blood culture utilization rate on the estimated proportions and incidence rates of AMR infections could be high. We recommend that AMR surveillance reports should additionally include blood culture utilization rate and stratification by exposure to a parenteral antibiotic at the hospital.

Automating the Generation of Antimicrobial Resistance Surveillance Reports: Proof-of-Concept Study Involving Seven Hospitals in Seven Countries

BACKGROUND

Reporting cumulative antimicrobial susceptibility testing data on a regular basis is crucial to inform antimicrobial resistance (AMR) action plans at local, national, and global levels. However, analyzing data and generating a report are time consuming and often require trained personnel.

OBJECTIVE

This study aimed to develop and test an application that can support a local hospital to analyze routinely collected electronic data independently and generate AMR surveillance reports rapidly.

METHODS

An offline application to generate standardized AMR surveillance reports from routinely available microbiology and hospital data files was written in the R programming language (R Project for Statistical Computing). The application can be run by double clicking on the application file without any further user input. The data analysis procedure and report content were developed based on the recommendations of the World Health Organization Global Antimicrobial Resistance Surveillance System (WHO GLASS). The application was tested on Microsoft Windows 10 and 7 using open access example data sets. We then independently tested the application in seven hospitals in Cambodia, Lao People's Democratic Republic, Myanmar, Nepal, Thailand, the United Kingdom, and Vietnam.

RESULTS

We developed the AutoMated tool for Antimicrobial resistance Surveillance System (AMASS), which can support clinical microbiology laboratories to analyze their microbiology and hospital data files (in CSV or Excel format) onsite and promptly generate AMR surveillance reports (in PDF and CSV formats). The data files could be those exported from WHONET or other laboratory information systems. The automatically generated reports contain only summary data without patient identifiers. The AMASS application is downloadable from https://www.amass.website/. The participating hospitals tested the application and deposited their AMR surveillance reports in an open access data repository.

CONCLUSIONS

The AMASS is a useful tool to support the generation and sharing of AMR surveillance reports.

The challenges of estimating the human global burden of disease of antimicrobial resistant bacteria

Estimating the contribution of antimicrobial resistance (AMR) to global mortality and healthcare costs enables evaluation of interventions, informs policy decisions on resource allocation, and drives research priorities. However assembling the high quality, patient-level data required for global estimates is challenging. Capacity for accurate microbiology culture and antimicrobial susceptibility testing is woefully neglected in low and middle-income countries, and further surveillance and research on community antimicrobial usage, bias in blood culture sampling, and the contribution of co-morbidities such as diabetes is essential. International collaboration between governments, policy makers, academics, microbiologists, front-line clinicians, veterinarians, the food and agriculture industry and the public is critical to understand and tackle AMR.

Determinants of dihydroartemisinin-piperaquine treatment failure in Plasmodium falciparum malaria in Cambodia, Thailand, and Vietnam: a prospective clinical, pharmacological, and genetic study

BACKGROUND

The emergence and spread of resistance in Plasmodium falciparum malaria to artemisinin combination therapies in the Greater Mekong subregion poses a major threat to malaria control and elimination. The current study is part of a multi-country, open-label, randomised clinical trial (TRACII, 2015-18) evaluating the efficacy, safety, and tolerability of triple artemisinin combination therapies. A very high rate of treatment failure after treatment with dihydroartemisinin-piperaquine was observed in Thailand, Cambodia, and Vietnam. The immediate public health importance of our findings prompted us to report the efficacy data on dihydroartemisinin-piperaquine and its determinants ahead of the results of the overall trial, which will be published later this year.

METHODS

Patients aged between 2 and 65 years presenting with uncomplicated P falciparum or mixed species malaria at seven sites in Thailand, Cambodia, and Vietnam were randomly assigned to receive dihydroartemisinin-piperaquine with or without mefloquine, as part of the TRACII trial. The primary outcome was the PCR-corrected efficacy at day 42. Next-generation sequencing was used to assess the prevalence of molecular markers associated with artemisinin resistance (kelch13 mutations, in particular Cys580Tyr) and piperaquine resistance (plasmepsin-2 and plasmepsin-3 amplifications and crt mutations). This study is registered with ClinicalTrials.gov, number NCT02453308.

FINDINGS

Between Sept 28, 2015, and Jan 18, 2018, 539 patients with acute P falciparum malaria were screened for eligibility, 292 were enrolled, and 140 received dihydroartemisinin-piperaquine. The overall Kaplan-Meier estimate of PCR-corrected efficacy of dihydroartemisinin-piperaquine at day 42 was 50·0% (95% CI 41·1-58·3). PCR-corrected efficacies for individual sites were 12·7% (2·2-33·0) in northeastern Thailand, 38·2% (15·9-60·5) in western Cambodia, 73·4% (57·0-84·3) in Ratanakiri (northeastern Cambodia), and 47·1% (33·5-59·6) in Binh Phuoc (southwestern Vietnam). Treatment failure was associated independently with plasmepsin2/3 amplification status and four mutations in the crt gene (Thr93Ser, His97Tyr, Phe145Ile, and Ile218Phe). Compared with the results of our previous TRACI trial in 2011-13, the prevalence of molecular markers of artemisinin resistance (kelch13 Cys580Tyr mutations) and piperaquine resistance (plasmepsin2/3 amplifications and crt mutations) has increased substantially in the Greater Mekong subregion in the past decade.

INTERPRETATION

Dihydroartemisinin-piperaquine is not treating malaria effectively across the eastern Greater Mekong subregion. A highly drug-resistant P falciparum co-lineage is evolving, acquiring new resistance mechanisms, and spreading. Accelerated elimination of P falciparum malaria in this region is needed urgently, to prevent further spread and avoid a potential global health emergency.

FUNDING

UK Department for International Development, Wellcome Trust, Bill & Melinda Gates Foundation, Medical Research Council, and National Institutes of Health.

Panton-Valentine leucocidin is the key determinant of Staphylococcus aureus pyomyositis in a bacterial GWAS

Pyomyositis is a severe bacterial infection of skeletal muscle, commonly affecting children in tropical regions, predominantly caused by Staphylococcus aureus. To understand the contribution of bacterial genomic factors to pyomyositis, we conducted a genome-wide association study of S. aureus cultured from 101 children with pyomyositis and 417 children with asymptomatic nasal carriage attending the Angkor Hospital for Children, Cambodia. We found a strong relationship between bacterial genetic variation and pyomyositis, with estimated heritability 63.8% (95% CI 49.2–78.4%). The presence of the Panton–Valentine leucocidin (PVL) locus increased the odds of pyomyositis 130-fold (p=10^-17.9). The signal of association mapped both to the PVL-coding sequence and to the sequence immediately upstream. Together these regions explained over 99.9% of heritability (95% CI 93.5–100%). Our results establish staphylococcal pyomyositis, like tetanus and diphtheria, as critically dependent on a single toxin and demonstrate the potential for association studies to identify specific bacterial genes promoting severe human disease.

Certain bacteria that normally live on the skin or in the nose without causing problems can sometimes lead to diseases elsewhere in the body. For example, the bacterium Staphylococcus aureus can cause blood infections or a severe and painful infection of the muscle called pyomyositis, which is very common in children who live in the tropics.

Scientists believe that pyomyositis happens when S. aureus bacteria in the blood stream infect the muscles. Some strains of this bacteria are more likely to cause such infections, but why is unclear. One potential cause is a toxin produced by some S. aureus bacteria called Panton-Valentine leucocidin (PVL). So far, studies looking at whether PVL-producing bacteria are more likely to cause pyomyositis have had conflicting results.

Now, Young et al. show that the gene for PVL is always present in S. aureus strains that cause pyomyosistis in Cambodian children, but is rarely found in S. aureus taken from the noses of their healthy counterparts. In the experiments, bacteria were collected from 101 children with pyomyositis and from the noses of 417 healthy children at the Angkor Hospital for Children in Cambodia over a 5-year period. The DNA in these bacteria were compared using very sensitive genetic techniques. The comparisons showed having the gene for PVL increased the odds of having pyomyositis 130-fold, showing that this one toxin likely accounts for much of the risk of developing this disease.

If more studies confirm the link between PVL and pyomyositis, developing vaccines that block the gene for PVL might be one way to protect children in the tropics from developing this infection. Treating children with pyomyositis with antibiotics that reduce the production of the PVL toxin may also be helpful.

Collider bias and the apparent protective effect of glucose-6-phosphate dehydrogenase deficiency on cerebral malaria

Case fatality rates in severe falciparum malaria depend on the pattern and degree of vital organ dysfunction. Recent large-scale case-control analyses of pooled severe malaria data reported that glucose-6-phosphate dehydrogenase deficiency (G6PDd) was protective against cerebral malaria but increased the risk of severe malarial anaemia. A novel formulation of the balancing selection hypothesis was proposed as an explanation for these findings, whereby the selective advantage is driven by the competing risks of death from cerebral malaria and death from severe malarial anaemia. We re-analysed these claims using causal diagrams and showed that they are subject to collider bias. A simulation based sensitivity analysis, varying the strength of the known effect of G6PDd on anaemia, showed that this bias is sufficient to explain all of the observed association. Future genetic epidemiology studies in severe malaria would benefit from the use of causal reasoning.

The persistence and oscillations of submicroscopic Plasmodium falciparum and Plasmodium vivax infections over time in Vietnam: an open cohort study

BACKGROUND

A substantial proportion of Plasmodium species infections are asymptomatic with densities too low to be detectable with standard diagnostic techniques. The importance of such asymptomatic plasmodium infections in malaria transmission is probably related to their duration and density. To explore the duration of asymptomatic plasmodium infections and changes in parasite densities over time, a cohort of participants who were infected with Plasmodium parasites was observed over a 2-year follow-up period.

METHODS

In this open cohort study, inhabitants of four villages in Vietnam were invited to participate in baseline and subsequent 3-monthly surveys up to 24 months, which included the collection of venous blood samples. Samples were batch-screened using ultra-sensitive (u)PCR (lower limit of detection of 22 parasites per mL). Participants found to be infected by uPCR during any of these surveys were invited to join a prospective cohort and provide monthly blood samples. We estimated the persistence of Plasmodium falciparum and Plasmodium vivax infections and changes in parasite densities over a study period of 24 months.

FINDINGS

Between Dec 1, 2013, and Jan 8, 2016, 356 villagers participated in between one and 22 surveys. These study participants underwent 4248 uPCR evaluations (11·9 tests per participant). 1874 (32%) of 4248 uPCR tests indicated a plasmodium infection; 679 (36%) of 1874 tests were P falciparum monoinfections, 507 (27%) were P vivax monoinfections, 463 (25%) were co-infections with P falciparum and P vivax, and 225 (12%) were indeterminate species of Plasmodium. The median duration of P falciparum infection was 2 months (IQR 1-3); after accounting for censoring, participants had a 20% chance of having parasitaemia for 4 months or longer. The median duration of P vivax infection was 6 months (3-9), and participants had a 59% chance of having parasitaemia for 4 months or longer. The parasite densities of persistent infections oscillated; following ultralow-density infections, high-density infections developed frequently.

INTERPRETATION

Persistent largely asymptomatic P vivax and P falciparum infections are common in this area of low seasonal malaria transmission. Infections with low-density parasitaemias can develop into much higher density infections at a later time, which are likely to sustain malaria endemicity.

FUNDING

The Wellcome Trust, Bill & Melinda Gates Foundation.

Antibiotic use in poultry: a survey of eight farms in Thailand

Objective

To investigate antibiotic use in poultry farms in Thailand and estimate the total amount of antibiotics used annually in Thai production of chicken meat.

Methods

In a single province, we surveyed eight farms in which chickens were raised for meat and interviewed the farms’ owners in 2016. The antibiotic use for each chicken was defined as the amount of antibiotic given to the chicken over its entire lifetime divided by the target weight of the chicken at the time of its slaughter. Assuming that the results were nationally representative, we estimated annual antibiotic use on all Thai chickens raised for meat.

Findings

No use of antibiotics for growth promotion was reported. Five farms raised 1-kg chickens for company A and reportedly used no antibiotics unless the chickens were sick. The other three farms raised 3-kg chickens for company B and reported routine use of antibiotics for prophylaxis. Per kg final weight, each chicken raised for company B was reportedly routinely given a mean of 101 mg of antibiotics – that is, 33 mg of amoxicillin, 29 mg colistin, 19 mg oxytetracycline, 18 mg doxycycline and 2 mg tilmicosin. The total amount of antibiotic used on all Thai chickens raised for meat in 2016 was estimated to be 161 tonnes.

Conclusion

Each year in Thailand, many tonnes of antibiotics are probably routinely used in raising chickens for meat. Labels on retail packs of meat should include data on antibiotic use in the production of the meat.

Epidemiology and burden of multidrug-resistant bacterial infection in a developing country

Little is known about the excess mortality caused by multidrug-resistant (MDR) bacterial infection in low- and middle-income countries (LMICs). We retrospectively obtained microbiology laboratory and hospital databases of nine public hospitals in northeast Thailand from 2004 to 2010, and linked these with the national death registry to obtain the 30-day mortality outcome. The 30-day mortality in those with MDR community-acquired bacteraemia, healthcare-associated bacteraemia, and hospital-acquired bacteraemia were 35% (549/1555), 49% (247/500), and 53% (640/1198), respectively. We estimate that 19,122 of 45,209 (43%) deaths in patients with hospital-acquired infection due to MDR bacteria in Thailand in 2010 represented excess mortality caused by MDR. We demonstrate that national statistics on the epidemiology and burden of MDR in LMICs could be improved by integrating information from readily available databases. The prevalence and mortality attributable to MDR in Thailand are high. This is likely to reflect the situation in other LMICs.

DOI:http://dx.doi.org/10.7554/eLife.18082.001

Antimicrobial resistance is a global problem. Each year, an estimated 23,000 deaths in the United States and 25,000 deaths in the European Union are extra deaths caused by bacteria resistant to antibiotics. People in low- and middle-income countries are also using more antibiotics, in part because of rising incomes, lower costs of antibiotics, and a lack of control of antimicrobial usage in the hospitals and over-the-counter sales of the drugs. These factors are thought to be driving the development and spread of bacteria that are resistant to multiple antibiotics in countries such as China, India, Indonesia and Thailand. However, a lack of information makes it difficult to estimate the size of the problem and, then, to track how antimicrobial resistance and multi-drug resistance is changing over time in these and other low- and middle-income countries.

Now, by integrating routinely collected data from a range of databases, Lim, Takahashi et al. estimate that around an extra 19,000 deaths are caused by multi-drug resistant bacteria in Thailand each year. Thailand has a population of about 70 million, and so, per capita, this estimate is about 3 to 5 times larger than those for the United States and European Union (which have a populations of about 300 million and 500 million, respectively). Lim, Takahashi et al. also show that more of the bacteria collected from patients are resistant to multiple antimicrobial drugs and that the burden of antimicrobial resistance in Thailand is worsening over time.

These findings suggest that more studies with a systematic approach need to be done in other low- and middle-income countries, especially in countries where microbiological laboratories are readily available and routinely used. Further work is also needed to identify where resources and attentions are most needed to effectively fight against antimicrobial resistance in low- and middle-income countries.

DOI:http://dx.doi.org/10.7554/eLife.18082.002

Predicted global distribution of Burkholderia pseudomallei and burden of melioidosis

Burkholderia pseudomallei, a highly pathogenic bacterium that causes melioidosis, is commonly found in soil in Southeast Asia and Northern Australia1,2. Melioidosis can be difficult to diagnose due to its diverse clinical manifestations and the inadequacy of conventional bacterial identification methods3. The bacterium is intrinsically resistant to a wide range of antimicrobials, and treatment with ineffective antimicrobials may result in case fatality rates (CFRs) exceeding 70%4,5. The importation of infected animals has, in the past, spread melioidosis to non-endemic areas6,7. The global distribution of B. pseudomallei and burden of melioidosis, however, remain poorly understood. Here, we map documented human and animal cases, and the presence of environmental B. pseudomallei, and combine this in a formal modelling framework8-10 to estimate the global burden of melioidosis. We estimate there to be 165,000 (95% credible interval 68,000-412,000) human melioidosis cases per year worldwide, of which 89,000 (36,000-227,000) die. Our estimates suggest that melioidosis is severely underreported in the 45 countries in which it is known to be endemic and that melioidosis is likely endemic in a further 34 countries which have never reported the disease. The large numbers of estimated cases and fatalities emphasise that the disease warrants renewed attention from public health officials and policy makers.

Serum antibody responses to pneumococcal colonization in the first 2 years of life: results from an SE Asian longitudinal cohort study

Assessment of antibody responses to pneumococcal colonization in early childhood may aid our understanding of protection and inform vaccine antigen selection. Serum samples were collected from mother-infant pairs during a longitudinal pneumococcal colonization study in Burmese refugees. Maternal and cord sera were collected at birth and infants were bled monthly (1–24 months of age). Nasopharyngeal swabs were taken monthly to detect colonization. Serum IgG titres to 27 pneumococcal protein antigens were measured in 2624 sera and IgG to dominant serotypes (6B, 14, 19F, 19A and 23F) were quantified in 864 infant sera. Antibodies to all protein antigens were detectable in maternal sera. Titres to four proteins (LytB, PcpA, PhtD and PhtE) were significantly higher in mothers colonized by pneumococci at delivery. Maternally-derived antibodies to PiuA and Spr0096 were associated with delayed pneumococcal acquisition in infants in univariate, but not multivariate models. Controlling for infant age and previous homologous serotype exposure, nasopharyngeal acquisition of serotypes 19A, 23F, 14 or 19F was associated significantly with a ≥2-fold antibody response to the homologous capsule (OR 12.84, 7.52, 6.52, 5.33; p <0.05). Acquisition of pneumococcal serotypes in the nasopharynx of infants was not significantly associated with a ≥2-fold rise in antibodies to any of the protein antigens studied. In conclusion, nasopharyngeal colonization in young children resulted in demonstrable serum IgG responses to pneumococcal capsules and surface/virulence proteins. However, the relationship between serum IgG and the prevention of, or response to, pneumococcal nasopharyngeal colonization remains complex. Mechanisms other than serum IgG are likely to have a role but are currently poorly understood.

Serum antibody responses to pneumococcal colonization in the first 2 years of life: results from an SE Asian longitudinal cohort study

Assessment of antibody responses to pneumococcal colonization in early childhood may aid our understanding of protection and inform vaccine antigen selection. Serum samples were collected from mother-infant pairs during a longitudinal pneumococcal colonization study in Burmese refugees. Maternal and cord sera were collected at birth and infants were bled monthly (1–24 months of age). Nasopharyngeal swabs were taken monthly to detect colonization. Serum IgG titres to 27 pneumococcal protein antigens were measured in 2624 sera and IgG to dominant serotypes (6B, 14, 19F, 19A and 23F) were quantified in 864 infant sera. Antibodies to all protein antigens were detect ablein maternal sera. Titres to four proteins (LytB, PcpA, PhtD and PhtE) were significantly higher in mothers colonized by pneumococci at delivery. Maternally-derived antibodies to PiuA and Spr0096 were associated with delayed pneumococcal acquisition in infants in univariate,but not multivariate models. Controlling for infant age and previous homologous serotype exposure, nasopharyngeal acquisition of serotypes 19A, 23F, 14 or 19F was associated significantly with a ≥2-fold antibody response to the homologous capsule (OR 12.84, 7.52,6.52, 5.33; p <0.05). Acquisition of pneumococcal serotypes in the nasopharynx of infants was not significantly associated with a ≥2-fold rise in antibodies to any of the protein antigens studied. In conclusion, nasopharyngeal colonization in young children resulted in demonstrable serum IgG responses to pneumococcal capsules and surface/virulence proteins. However, the relationship between serum IgG and the prevention of, or response to, pneumococcal nasopharyngeal colonization remains complex. Mechanisms other than serum IgG are likely to have a role but are currently poorly understood.

Prevalence of antifolate resistance mutations in Plasmodium falciparum isolates in Afghanistan

Background

Artesunate plus sulphadoxine-pyrimethamine (AS+SP) is now first-line treatment for Plasmodium falciparum infection in several south Asian countries, including Afghanistan. Molecular studies provide a sensitive means to investigate the current state of drug susceptibility to the SP component, and can also provide information on the likely efficacy of other potential forms of artemisinin-combination therapy.

Methods

During the years 2007 to 2010, 120 blood spots from patients with P. falciparum malaria were obtained in four provinces of Afghanistan. PCR-based methods were used to detect drug-resistance mutations in dhfr, dhps, pfcrt and pfmdr1, as well as to determine copy number of pfmdr1.

Results

The majority (95.5%) of infections had a double mutation in the dhfr gene (C59R, S108N); no mutations at dhfr positions 16, 51 or 164 were seen. Most isolates were wild type across the dhps gene, but five isolates from the provinces of Kunar and Nangarhar in eastern Afghanistan had the triple mutation A437G / K540E / A581G; all five cases were successfully treated with three receiving AS+SP and two receiving dihydroartemisinin-piperaquine. All isolates showed the pfcrt SVNMT chloroquine resistance haplotype. Five of 79 isolates had the pfmdr1 N86Y mutation, while 52 had pfmdr1 Y184F; positions 1034, 1042 and 1246 were wild type in all isolates. The pfmdr1 gene was not amplified in any sample.

Conclusions

This study indicates that shortly after the adoption of AS+SP as first-line treatment in Afghanistan, most parasites had a double mutation haplotype in dhfr, and a small number of isolates from eastern Afghanistan harboured a triple mutation haplotype in dhps. The impact of these mutations on the efficacy of AS+SP remains to be assessed in significant numbers of patients, but these results are clearly concerning since they suggest a higher degree of SP resistance than previously detected. Further focused molecular and clinical studies in this region are urgently required.

Central venous catheter use in severe malaria: time to reconsider the World Health Organization guidelines?

BACKGROUND

To optimize the fluid status of adult patients with severe malaria, World Health Organization (WHO) guidelines recommend the insertion of a central venous catheter (CVC) and a target central venous pressure (CVP) of 0-5 cmH2O. However there are few data from clinical trials to support this recommendation.

METHODS

Twenty-eight adult Indian and Bangladeshi patients admitted to the intensive care unit with severe falciparum malaria were enrolled in the study. All patients had a CVC inserted and had regular CVP measurements recorded. The CVP measurements were compared with markers of disease severity, clinical endpoints and volumetric measures derived from transpulmonary thermodilution.

RESULTS

There was no correlation between the admission CVP and patient outcome (p = 0.67) or disease severity (p = 0.33). There was no correlation between the baseline CVP and the concomitant extravascular lung water (p = 0.62), global end diastolic volume (p = 0.88) or cardiac index (p = 0.44). There was no correlation between the baseline CVP and the likelihood of a patient being fluid responsive (p = 0.37). On the occasions when the CVP was in the WHO target range patients were usually hypovolaemic and often had pulmonary oedema by volumetric measures. Seven of 28 patients suffered a complication of the CVC insertion, although none were fatal.

CONCLUSION

The WHO recommendation for the routine insertion of a CVC, and the maintenance of a CVP of 0-5 cmH2O in adults with severe malaria, should be reconsidered.

Effect of colony morphology variation of Burkholderia pseudomallei on intracellular survival and resistance to antimicrobial environments in human macrophages in vitro

Background

Primary diagnostic cultures from patients with melioidosis demonstrate variation in colony morphology of the causative organism, Burkholderia pseudomallei. Variable morphology is associated with changes in the expression of a range of putative virulence factors. This study investigated the effect of B. pseudomallei colony variation on survival in the human macrophage cell line U937 and under laboratory conditions simulating conditions within the macrophage milieu. Isogenic colony morphology types II and III were generated from 5 parental type I B. pseudomallei isolates using nutritional limitation. Survival of types II and III were compared with type I for all assays.

Results

Morphotype was associated with survival in the presence of H₂O₂ and antimicrobial peptide LL-37, but not with susceptibility to acid, acidified sodium nitrite, or resistance to lysozyme, lactoferrin, human neutrophil peptide-1 or human beta defensin-2. Incubation under anaerobic conditions was a strong driver for switching of type III to an alternative morphotype. Differences were noted in the survival and replication of the three types following uptake by human macrophages, but marked strain-to strain-variability was observed. Uptake of type III alone was associated with colony morphology switching.

Conclusions

Morphotype is associated with phenotypes that alter the ability of B. pseudomallei to survive in adverse environmental conditions.

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

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').

Rheumatological manifestations in patients with melioidosis

Melioidosis, an infection caused by the bacterium Burkholderia pseudomallei, has a wide range of clinical manifestations. Here, we describe rheumatological melioidosis (involving one or more of joint, bone or muscle), and compare features and outcome with patients without rheumatological involvement. A retrospective study of patients with culture-confirmed melioidosis admitted to Sappasithiprasong Hospital, Ubon Ratchathani during 2002 and 2005 identified 679 patients with melioidosis, of whom 98 (14.4%) had rheumatological melioidosis involving joint (n=52), bone (n = 5), or muscle (n = 12), or a combination of these (n=29). Females were over-represented in the rheumatological group, and diabetes and thalassemia were independent risk factors for rheumatological involvement (OR; 2.49 and 9.56, respectively). Patients with rheumatological involvement had a more chronic course, as reflected by a longer fever clearance time (13 vs 7 days, p = 0.06) and hospitalization (22 vs 14 days, p < 0.001), but lower mortality (28% vs 44%, p = 0.005). Patients with signs and symptoms of septic arthritis for longer than 2 weeks were more likely to have extensive infection of adjacent bone and muscle, particularly in diabetic patients. Surgical intervention was associated with a survival benefit, bur not a shortening of the course of infection.

Activation of coagulation with concurrent impairment of anticoagulant mechanisms correlates with a poor outcome in severe melioidosis

BACKGROUND

Melioidosis, which is caused by infection with the Gram-negative bacterium Burkholderia pseudomallei, is an important cause of sepsis in South-East Asia with a mortality of up to 40%. Knowledge of the involvement of coagulation and fibrinolysis in the pathogenesis of melioidosis is highly limited.

OBJECTIVE

To define the involvement of the coagulation and fibrinolytic systems in patients with severe melioidosis.

METHODS

Parameters of coagulation and fibrinolysis were measured in 34 patients with culture proven septic melioidosis and 32 healthy controls.

RESULTS

Patients demonstrated strong activation of the coagulation system, as reflected by high plasma levels of soluble tissue factor, the prothrombin fragment F(1+2) and thrombin-antithrombin complexes (TATc), and consumption of coagulation factors resulting in a prolonged prothrombin time and activated partial thromboplastin time. Concurrently, anticoagulant pathways were downregulated in patients: protein C, protein S, and antithrombin levels were all decreased when compared to controls. Patients also demonstrated evidence of activation and inhibition of fibrinolysis, as reflected by elevated concentrations of tissue-type plasminogen activator (tPA), plasminogen activator inhibitor type 1, plasmin-alpha2-antiplasmin complexes (PAPc) and D-dimer. High TATc/PAPc ratios in patients pointed to a predominance of the prothrombotic pathway in melioidosis. Furthermore, soluble thrombomodulin levels were increased. The extent of coagulation activation correlated with mortality; patients who went on to die had higher TATc, F(1+2), tPA and PAPc and lower protein C and antithrombin levels on admission than patients who survived.

CONCLUSIONS

The coagulation system is strongly activated during melioidosis. A high degree of activation of the coagulation system is an indicator of poor outcome in patients with melioidosis.

Cerebral calpain in fatal falciparum malaria

Disruption of axonal transport may represent a final common pathway leading to neurological dysfunction in cerebral malaria (CM). Calpains are calcium (Ca2+)-activated cysteine proteases which have been implicated in axonal injury in neurological diseases of various aetiologies. In this study we examined the association between mu- and m-calpain, the specific inhibitor calpastatin, and axonal injury in post mortem brain tissue from patients who died from severe malaria. Calpains were associated with axons labelled for the beta-amyloid precursor protein that detects impaired axonal transport. Elevated levels of calpastatin were rarely observed in injured axons. There were increased numbers of neurones with mu-calpain in the nuclear compartment in severe malaria cases compared with non-neurological controls, and increased numbers of glia with nuclear mu-calpain in CM patients compared with non-CM malaria cases and non-neurological controls. There was marked redistribution of calpastatin in the sequestered Plasmodium falciparum-infected erythrocytes. Responses specific to malaria infection were ascertained following analysis of brain samples from fatal cases with acute axonal injury, HIV encephalitis, and progressive multifocal leucoencephalopathy. Our findings implicate a role for calpains in the modulation of disease progression in CM.

Characterization of human urinary metabolites of the antimalarial piperaquine

Five metabolites of the antimalarial piperaquine (PQ) (1,3-bis-[4-(7-chloroquinolyl-4)-piperazinyl-1]-propane) have been identified and their molecular structures characterized. After a p.o. dose of dihydroartemisinin-piperaquine, urine collected over 16 h from two healthy subjects was analyzed using liquid chromatography (LC)/UV, LC/tandem mass spectrometry (MS/MS), Fourier transform ion cyclotron resonance (FTICR)/MS, and H NMR. Five different peaks were recognized as possible metabolites [M1, 320 m/z; M2, M3, and M4, 551 m/z (PQ + 16 m/z); and M5, 567 m/z (PQ + 32 m/z)] using LC/MS/MS with gradient elution. The proposed carboxylic M1 has a theoretical monoisotopic molecular mass of 320.1166 m/z, which is in accordance with the FTICR/MS (320.1168 m/z) findings. The LC/MS/MS results also showed a 551 m/z metabolite (M2) with a distinct difference both in polarity and fragmentation pattern compared with PQ, 7-hydroxypiperaquine, and the other 551 m/z metabolites. We suggest that this is caused by N-oxidation of PQ. The results showed two metabolites (M3 and M4) with a molecular ion at 551 m/z and similar fragmentation pattern as both PQ and 7-hydroxypiperaquine; therefore, they are likely to be hydroxylated PQ metabolites. The molecular structures of M1 and M2 were also confirmed using H NMR. Urinary excretion rate in one subject suggested a terminal elimination half-life of about 53 days for M1. Assuming formation rate-limiting kinetics, this would support recent findings that the terminal elimination half-life of PQ has been underestimated previously.

Strong HLA class I--restricted T cell responses in dengue hemorrhagic fever: a double-edged sword?

Dengue is an increasingly important cause of morbidity and mortality in the tropics, but vaccine development has been impeded by a poor understanding of disease pathogenesis and, in particular, of immunologic enhancement. In a large case-control study of Vietnamese patients with dengue hemorrhagic fever (DHF), variation at the HLA-A locus was significantly associated with susceptibility to DHF (P=.02), and specific HLA-A susceptibility and resistance alleles were identified. HLA-A-specific epitopes were predicted from binding motifs, and ELISPOT analyses of patients with DHF revealed high frequencies of circulating CD8 T lymphocytes that recognized both serotype-specific and -cross-reactive dengue virus epitopes. Thus, strong CD8 T cell responses are induced by natural dengue virus infection, and HLA class I genetic variation is a risk factor for DHF. These genetic and immunologic data support both protective and pathogenic roles for dengue virus-specific CD8 T cell responses in severe disease. The potentially pathogenic role of serotype-cross-reactive CD8 T cells poses yet another obstacle to successful dengue vaccine development.

Cellular stress and injury responses in the brains of adult Vietnamese patients with fatal Plasmodium falciparum malaria

Immunohistochemical techniques have been used to investigate specific patterns of potentially reversible cellular injury, DNA damage, and apoptosis in the brainstems of Vietnamese patients who died of severe Plasmodium falciparum malaria. The degree and pattern of neuronal and glial stress responses were compared between patients with cerebral and non-cerebral malaria (CM), and appropriate non-malaria infected controls. The following markers were examined: (i) heat shock protein 70 (HSP70), for reversible injury; (ii) heme oxygenase-1, for oxidative stress; (iii & iv) two DNA-repair proteins, poly(ADP) ribose polymerase (PARP) and DNA-dependent protein kinase catalytic subunit; (v) poly(ADP) ribose, an end-product of PARP activity; and (vi) caspase-3-active, for apoptosis. Stress responses were found in a range of cell types as reflected by the widespread expression of HSP70. Oxidative stress predominated in the vicinity of vessels and haemorrhages. Some degree of DNA damage was found in the majority of malaria patients, but the distribution and frequency of the damage was much less than that observed in controls with irreversible neuronal injury. Similarly, caspase-3-active expression, as a measure of apoptosis, was no higher in the majority of malaria patients than the negative control cases, although 40% of CM cases expressed caspase-3-active in a small number of neurones of the pontine nuclei or within swollen axons of the pontocerebellar and corticospinal tracts. In conclusion, cells within the brainstem of all patients who died from severe malaria showed staining patterns indicative of considerable stress response and reversible neuronal injury. There was no evidence for a specific pattern of widespread irreversible cell damage in those patients with cerebral malaria.

Fibronectin-binding protein A of Staphylococcus aureus has multiple, substituting, binding regions that mediate adherence to fibronectin and invasion of endothelial cells

Invasive Staphylococcus aureus infection frequently involves bacterial seeding from the bloodstream to other body tissues, a process necessarily involving interactions between circulating bacteria and vascular endothelial cells. Staphylococcus aureus fibronectin-binding protein is central to the invasion of endothelium, fibronectin forming a bridge between bacterial fibronectin-binding proteins and host cell receptors. To dissect further the mechanisms of invasion of endothelial cells by S. aureus, a series of truncated FnBPA proteins that lacked one or more of the A, B, C or D regions were expressed on the surface of S. aureus and tested in fibronectin adhesion, endothelial cell adhesion and invasion assays. We found that this protein has multiple, substituting, fibronectin-binding regions, each capable of conferring both adherence to fibronectin and endothelial cells, and endothelial cell invasion. By expressing S. aureus FnBPA on the surface of the non-invasive Gram-positive organism Lactococcus lactis, we have found that no other bacterial factor is required for invasion. Furthermore, we have demonstrated that, as with other cell types, invasion of endothelial cells is mediated by integrin alpha5beta1. These findings may be of relevance to the development of preventive measures against systemic infection, and bacterial spread in the bacteraemic patient.

Genetic population structure of coagulase-negative staphylococci associated with carriage and disease in preterm infants

Coagulase-negative staphylococci (CoNS) are a leading cause of sepsis in the neonatal intensive care unit (NICU) setting. To evaluate the hypothesis that isolates of CoNS associated with disease belong to hypervirulent clones, as opposed to being drawn randomly from the neonatal unit carriage flora, we conducted a prospective, case-controlled study in a busy NICU. Using pulsed-field gel electrophoresis (PFGE), we compared the population structures of CoNS isolates associated with bacteremia with isolates from the skin of healthy and infected neonates and with blood culture contaminants. Endemic clones of CoNS were identified, but there was no difference in the distribution of the 6 species or 73 PFGE types between the carriage and disease isolate groups; this suggests that hypervirulent clones with an enhanced ability to cause disease were not present in this NICU setting.

A link between virulence and ecological abundance in natural populations of Staphylococcus aureus

Staphylococcus aureus is a major cause of severe infection in humans and yet is carried without symptoms by a large proportion of the population. We used multilocus sequence typing to characterize isolates of S. aureus recovered from asymptomatic nasal carriage and from episodes of severe disease within a defined population. We identified a number of frequently carried genotypes that were disproportionately common as causes of disease, even taking into account their relative abundance among carriage isolates. The existence of these ecologically abundant hypervirulent clones suggests that factors promoting the ecological fitness of this important pathogen also increase its virulence.

Quantitation of bacteria in bone marrow from patients with typhoid fever: relationship between counts and clinical features

Enteric fever is the only bacterial infection of humans for which bone marrow examination is routinely recommended. A prospective study of the concentrations of bacteria in the bone marrow and their relationship to clinical features was conducted with 120 Vietnamese patients with suspected enteric fever, of whom 89 had confirmed typhoid fever. Ninety-three percent of the Salmonella enterica serovar Typhi samples isolated were resistant to ampicillin, chloramphenicol, and co-trimoxazole. For 81 patients with uncomplicated typhoid and satisfactory bone marrow aspirates, the number of serovar Typhi CFU in bone marrow aspirates was a median value of 9 (interquartile range [IQR], 1 to 85; range, 0.1 to 1,580) compared to 0.3 (IQR, 0.1 to 10; range, 0.1 to 399) CFU/ml in simultaneously sampled blood. The ratio of individual blood counts to bone marrow counts was 10 (IQR, 2.3 to 97.5). The number of bacteria in blood but not bone marrow was correlated inversely with the duration of preceding fever. Thus, with increasing duration of illness the ratio of bone marrow-to-blood bacterial concentrations increased; the median ratio was 4.8 (IQR, 1 to 27.5) during the first week compared with 158 (IQR, 60 to 397) during the third week. After lysing the host cells, the median ratio of viable bone marrow to blood increased, reflecting the higher concentration of intracellular serovar Typhi in the bone marrow. Effective antibiotic pretreatment had a significantly greater effect in reducing blood counts compared to bone marrow counts (P < 0.001). Thus, bacteria in the bone marrow of typhoid patients are less affected by antibiotic treatment than bacteria in the blood. The numbers of bacteria in bone marrow correlated negatively with the white blood cell (R = -0.3, P = 0.006) and platelet counts (R = -0.32, P = 0.01) and positively with fever clearance time after treatment (R = 0.4, P < 0.001). The bacterial load in bone marrow therefore may reflect the clinical course of the infection, and high levels may suppress neutrophil proliferation.

Noninvasive measurement of microvascular leakage in patients with dengue hemorrhagic fever

Dengue shock syndrome (DSS) is a potentially lethal complication of dengue virus infection associated with hypotension and leakage of plasma water into the extravascular space. To determine whether the underlying pathophysiology of DSS is distinct from that in milder forms of the disease, we assessed microvascular permeability, by use of strain gauge plethysmography, in Vietnamese children with DSS (n=19), or dengue hemorrhagic fever (DHF) without shock (n=16), and in healthy control children (n=15). At admission and after fluid resuscitation, the mean coefficient of microvascular permeability (K(f)) for the patients with dengue was approximately 50% higher than that for the control patients (P=.02). There was no significant difference in K(f) between the 2 groups of patients with dengue; this suggests the same underlying pathophysiology. We hypothesize that in patients with DSS, the fluctuations in K(f) are larger than those in patients with DHF, which leads to short-lived peaks of markedly increased microvascular permeability and consequent hemodynamic shock.

Recombination within natural populations of pathogenic bacteria: short-term empirical estimates and long-term phylogenetic consequences

The identification of clones within bacterial populations is often taken as evidence for a low rate of recombination, but the validity of this inference is rarely examined. We have used statistical tests of congruence between gene trees to examine the extent and significance of recombination in six bacterial pathogens. For Neisseria meningitidis, Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus, the congruence between the maximum likelihood trees reconstructed using seven house-keeping genes was in most cases no better than that between each tree and trees of random topology. The lack of congruence between gene trees in these four species, which include both naturally transformable and nontransformable species, is in three cases supported by high ratios of recombination to point mutation during clonal diversification (estimates of this parameter were not possible for Strep. pyogenes). In contrast, gene trees constructed for Hemophilus influenzae and pathogenic isolates of Escherichia coli showed a higher degree of congruence, suggesting lower rates of recombination. The impact of recombination therefore varies between bacterial species but in many species is sufficient to obliterate the phylogenetic signal in gene trees.

Blood-brain barrier function in cerebral malaria and CNS infections in Vietnam

BACKGROUND

The intraerythrocytic parasite Plasmodium falciparum induces the life-threatening neurologic syndrome of cerebral malaria (CM) from within cerebral blood vessels, without entering the brain parenchyma.

OBJECTIVES

1) To assess the use of CSF as an indicator of specific pathologic processes occurring in the brain during CM; 2) to compare this with other neurologic and infectious diseases to understand the distinct pathogenic features of CM; 3) to test the hypothesis that CM involves a specific functional breakdown of the blood-brain barrier (BBB).

METHODS

1) Radial immunodiffusion assays to detect albumin and IgG in matched plasma and CSF samples as indicators of BBB integrity and intrathecal IgG production; and 2) ELISA for soluble intracellular adhesion molecule-1 and sE-selectin, the cytokines tumor necrosis factor-alpha and transforming growth factor-beta1, and the matrix metalloproteinase MMP-9, to detect cellular activation and inflammatory responses within the brain.

RESULTS

Albumin and IgG indices implied only minimal degree of BBB breakdown in a few cases of CM, with most remaining within the normal range. In contrast, cryptococcal, tubercular, and acute bacterial meningitis produced detectable changes in the composition of the CSF and evidence of BBB breakdown.

CONCLUSIONS

CM appears to involve only subtle functional changes in BBB integrity with minimal intraparenchymal inflammatory responses compared with other neurologic infections. This focuses attention on local events within and around the cerebral microvasculature in CM, rather than indicating widespread parenchymal disease.

Clinical isolates of Staphylococcus aureus exhibit diversity in fnb genes and adhesion to human fibronectin

OBJECTIVES

The fibronectin-binding proteins (FnBPs) of Staphylococcus aureus are involved in the pathogenesis of infection, but their characteristics in clinical isolates are incompletely defined. The aim of this study was to evaluate phenotypic and genotypic characteristics of the FnBPs of a large collection of recent isolates.

METHODS

The adherence of 163 S. aureus isolates to immobilized fibronectin was compared with that of S. aureus 8325-4 using a microtitre assay. The presence of the genes encoding the fibronectin-binding proteins FnBPA and FnBPB was evaluated by Southern dot blot using probes specific for region A of fnbA or fnbB.

RESULTS

The adherence of clinical isolates to fibronectin (expressed as a percentage of the mean adherence of S. aureus 8325-4) was 56%-125% for 155 isolates (95%), and less than 20% for eight isolates (5%). Adherence of the bacterial group associated with orthopaedic implant-associated infection was significantly greater than that for isolates associated with nasal carriage, endocarditis, or septic arthritis/osteomyelitis. Southern dot blot demonstrated that 126/163 isolates had two genes (77%) and 37/163 had one detectable gene (23%). There was no difference in adherence between isolates with one or two fnb, but isolates associated with invasive disease (endocarditis or primary septic arthritis and/or osteomyelitis) were more likely to have two genes.

CONCLUSIONS

These data demonstrate diversity in the FnBPs of clinical isolates of S. aureus. The findings suggest that the interplay between pathogenesis and a single virulence determinant is unlikely to be a uniform process across a spectrum of infections. This confirms the need to extend the study of staphylococcal pathogenesis from the laboratory to non-uniform populations of clinically relevant isolates.

The pathophysiologic and prognostic significance of acidosis in severe adult malaria

OBJECTIVE

To investigate the pathophysiology and prognostic significance of acidosis in severe adult malaria.

DESIGN

Cohort study.

SETTING

The intensive care unit of an infectious diseases hospital in southern Vietnam.

PATIENTS

Three hundred forty-six consecutive adult patients with severe falciparum malaria.

INTERVENTIONS

Measurements of baseline venous lactate and pyruvate concentrations and an extensive range of clinical and laboratory variables were made, and patients were followed up carefully until death or discharge from the hospital. Admission arterial blood pH and gas tensions were recorded in 296 patients, and hepatic venous sampling was done in 12 patients.

MEASUREMENTS AND MAIN RESULTS

Overall, 198 (67%) patients were acidotic (standard base deficit [SBD], >3.3 mmol/L [n = 196], or arterial Pco2, >45 torr [6 kPa] [n = 3]). Hyperlactatemia (plasma lactate, >4 mmol/L) occurred in 120 (35%) of the 346 patients and was associated significantly with acidosis (p < .0001). The hepatosplanchnic lactate extraction ratio was negatively correlated with mixed venous plasma lactate (r2 = .50; p = .006). Hyperlactatemia, metabolic acidosis (SBD, >3.3), and acidemia (pH <7.35) were strongly positively associated with a fatal outcome (relative risks [95% confidence interval], 4.3 [range, 1.8-10.6], 5.0 [range, 3.0-8.1], and 2.7 [range, 1.8-4.1], respectively). The SBD was the single best clinical or laboratory predictor of fatal outcome. The overall median lactate/pyruvate ratio was raised at 30.6 (range, 20.6-62.3; normal range, <15), suggesting hypoxia and anaerobic glycolysis, and was significantly higher in fatal cases (p < .0001). In an additive multivariate model, the two main independent contributors to metabolic acidosis were plasma creatinine, as a measure of renal dysfunction, and venous plasma lactate, together accounting for 63% of the variance in SBD. In univariate analyses, they contributed 29% and 38%, respectively.

CONCLUSIONS

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.

Effects of dopamine and epinephrine infusions on renal hemodynamics in severe malaria and severe sepsis

OBJECTIVE

To describe and compare the effects of dopamine and epinephrine in various doses on renal hemodynamics and oxygen transport in patients with severe malaria and severe sepsis.

DESIGN

Prospective, controlled, crossover trial.

SETTING

The intensive care unit of an infectious diseases hospital in Viet Nam.

PATIENTS

Fourteen patients with severe falciparum malaria and five with severe sepsis.

INTERVENTIONS

In an open, crossover design, we observed the effects on renal and systemic hemodynamics and oxygen transport of separate stepped infusions of epinephrine and dopamine. We measured renal blood flow (RBF) and cardiac output by the thermodilution method using fluoroscopically guided catheters. Creatinine clearance at each time point was calculated from the renal plasma flow and the renal arteriovenous difference in plasma creatinine.

MEASUREMENTS AND MAIN RESULTS

Dopamine at a "renal" dose (2.5 microg/kg/min) was associated with a mean (95% confidence interval) fractional increase in the absolute renal blood flow index (RBFI) of 37% (13% to 61%) and in RBF as a fraction of cardiac output (RBF/CO) of 35% (10% to 59%; p = .007 and p = .014, respectively). The consequent 39% (14% to 64%) increase in renal oxygen supply (p = .002) was accompanied by a 32% (20% to 44%) decrease in the renal oxygen extraction ratio (p = .0003), leading to no net change in renal oxygen consumption. At higher doses (10 microg/kg/min), both RBF and RBF/CO were not significantly different from baseline values and decreased further as the dose was reduced again. There was no obvious explanation for this hysteresis. There was no change in renal oxygen consumption throughout the study. Because lactic acidosis developed, epinephrine was only given to eight of the 19 patients, and the full stepped epinephrine infusion was given to four patients. Epinephrine infusion was associated, both in absolute terms and when compared with dopamine, with a significant increase in renal vascular resistance (p = .0008 and .0005, respectively), a decrease in RBF/CO (p = .002 and .03), and a compensatory increase in the renal oxygen extraction ratio (p = .005 and .0001). RBFI and renal oxygen consumption remained constant throughout the epinephrine infusion profile. Neither epinephrine nor dopamine significantly affected creatinine clearance or urine output. Twelve patients (63%) were in established renal failure (plasma creatinine, >3 mg/dL) at the time of the study, although the presence or absence of renal failure did not significantly influence the effects of the study drugs. However, overall, the presence of renal failure was associated with a lower mean renal oxygen consumption, a lower mean renal oxygen consumption as a fraction of systemic oxygen consumption, and a higher mean renal vascular resistance.

CONCLUSION

Although dopamine increased and epinephrine decreased fractional renal blood flow, there was no evidence that either drug produced either a beneficial or a deleterious effect on renal oxygen metabolism or function at any of the doses investigated.

Neurological manifestations of dengue infection

BACKGROUND

Severe forms of dengue, the most important arboviral infection of man, are associated with haemorrhagic disease and a generalised vascular leak syndrome. The importance of dengue as a cause of neurological disease is uncertain.

METHODS

During 1995, all patients with suspected CNS infections admitted to a referral hospital in southern Vietnam were investigated by culture, PCR, and antibody measurement in serum and CSF for dengue and other viruses.

FINDINGS

Of 378 patients, 16 (4.2%) were infected with dengue viruses, compared with four (1.4%) of 286 hospital controls (odds ratio [95% CI] 3.1 [1.7-5.8]). Five additional dengue positive patients with CNS abnormalities were studied subsequently. No other cause of CNS infection was identified. Seven infections were primary dengue, 13 secondary, and one was not classified. Ten patients had dengue viruses isolated or detected by PCR, and three had dengue antibody in the CSF. 12 of the 21 had no characteristic features of dengue on admission. The most frequent neurological manifestations were reduced consciousness and convulsions. Nine patients had encephalitis. No patient died, but six had neurological sequelae at discharge. Phylogenetic analysis of the four DEN-2 strains isolated mapped them with a DEN-2 strain isolated from a patient with dengue haemorrhagic fever, and with other strains previously isolated in southern Vietnam.

INTERPRETATION

In dengue endemic areas patients with encephalitis and encephalopathy should be investigated for this infection, whether or not they have other features of the disease.

Outcome following staphylococcal peritonitis

OBJECTIVE

Staphylococcus spp predominate as the causative pathogen of continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis.This study evaluated the difference in morbidity and mortality between peritonitis caused by S. aureus and coagulase-negative staphylococci (CoNS).

DESIGN

Prospective observational study.

SETTING

A single regional dialysis unit in a teaching hospital.

PATIENTS

Thirty-seven patients had S. aureus peritonitis and 65 patients had CoNS peritonitis between July 1990 and November 1995.

MAIN OUTCOME MEASURES

Using the first recorded episode of peritonitis, survival analysis was performed for time to (1) death, (2) removal of peritoneal dialysis catheter, and (3) change to hemodialysis. Abdominal complications were recorded for the first and subsequent episodes.

RESULTS

No difference in time to death was demonstrated for the two groups (p = 0.79), although two deaths that occurred during therapy for peritonitis were attributable to S. aureus infection. In addition, 5 patients developed serious abdominal complications related to an episode of S. aureus peritonitis. Patients with S. aureus peritonitis had a shorter time to both peritoneal dialysis catheter removal (p = 0.004) and change to hemodialysis (p = 0.014). The change in mode of dialysis was independent of catheter loss.

CONCLUSION

This study highlights the serious nature of S. aureus peritonitis and confirms the need for effective preventive measures against infection by this pathogen.

Multilocus sequence typing for characterization of methicillin-resistant and methicillin-susceptible clones of Staphylococcus aureus

A multilocus sequence typing (MLST) scheme has been developed for Staphylococcus aureus. The sequences of internal fragments of seven housekeeping genes were obtained for 155 S. aureus isolates from patients with community-acquired and hospital-acquired invasive disease in the Oxford, United Kingdom, area. Fifty-three different allelic profiles were identified, and 17 of these were represented by at least two isolates. The MLST scheme was highly discriminatory and was validated by showing that pairs of isolates with the same allelic profile produced very similar SmaI restriction fragment patterns by pulsed-field gel electrophoresis. All 22 isolates with the most prevalent allelic profile were methicillin-resistant S. aureus (MRSA) isolates and had allelic profiles identical to that of a reference strain of the epidemic MRSA clone 16 (EMRSA-16). Four MRSA isolates that were identical in allelic profile to the other major epidemic MRSA clone prevalent in British hospitals (clone EMRSA-15) were also identified. The majority of isolates (81%) were methicillin-susceptible S. aureus (MSSA) isolates, and seven MSSA clones included five or more isolates. Three of the MSSA clones included at least five isolates from patients with community-acquired invasive disease and may represent virulent clones with an increased ability to cause disease in otherwise healthy individuals. The most prevalent MSSA clone (17 isolates) was very closely related to EMRSA-16, and the success of the latter clone at causing disease in hospitals may be due to its emergence from a virulent MSSA clone that was already a major cause of invasive disease in both the community and hospital settings. MLST provides an unambiguous method for assigning MRSA and MSSA isolates to known clones or assigning them as novel clones via the Internet.

Epidemic typhoid in vietnam: molecular typing of multiple-antibiotic-resistant Salmonella enterica serotype typhi from four outbreaks

Multidrug-resistant Salmonella enterica serotype Typhi isolates from four outbreaks of typhoid fever in southern Vietnam between 1993 and 1997 were compared. Pulsed-field gel electrophoresis, bacteriophage and plasmid typing, and antibiotic susceptibilities showed that independent outbreaks of multidrug-resistant typhoid fever in southern Vietnam are caused by single bacterial strains. However, different outbreaks do not derive from the clonal expansion of a single multidrug-resistant serotype Typhi strain.

Age-related changes in microvascular permeability: a significant factor in the susceptibility of children to shock?

During studies of the pathogenesis of dengue shock syndrome, a condition largely confined to childhood and characterized by a systemic increase in vascular permeability, we observed that healthy controls, age-matched to children with dengue shock syndrome, gave high values of filtration capacity (K(f)), a factor describing vascular permeability. We hypothesized that K(f) might be age dependent. Calf K(f) was studied in 89 healthy Vietnamese subjects aged 5 to 77 years. The K(f) was highest in the youngest children [7. 53 (1.96-15.46) K(f)U; median (range); where the units of K(f), K(f)U=ml.min(-1).100 ml(-1).mmHg(-1)]. Values were 3- to 4-fold lower towards the end of the second decade [4.69 (1.91-7.06) K(f)U]. Young mammals are known to have a larger microvascular surface area per unit volume of skeletal muscle than adults. During development the proportion of developing vessels is greater. Moreover, the novel microvessels are known to be more permeable to water and plasma proteins than when mature. These factors may explain why children more readily develop hypovolaemic shock than adults in dengue haemorrhagic fever and other conditions characterized by increased microvascular permeability.

Fluid replacement in dengue shock syndrome: a randomized, double-blind comparison of four intravenous-fluid regimens

Dengue hemorrhagic fever and dengue shock syndrome (DSS) are major causes of childhood morbidity and mortality in many tropical countries. Increased intravascular permeability leading to shock is the cardinal feature of DSS. Fluid resuscitation to counteract massive plasma leakage is the mainstay of treatment. A double-blind, randomized trial comparing four intravenous-fluid regimens for acute resuscitation of 50 children with DSS was conducted. Colloids (dextran 70 or the protein digest gelafundin 35,000) restored cardiac index and blood pressure and normalized hematocrit more rapidly than crystalloids (Ringer's lactate or 0.9%-weight/volume saline). Dextran 70 provided the most rapid normalization of the hematocrit and restoration of the cardiac index, without adverse effects, and may be the preferred solution for acute resuscitation in DSS. Further large-scale double-blind trials are required to provide an evidence-based approach to the management of DSS.

The prognostic and pathophysiologic role of pro- and antiinflammatory cytokines in severe malaria

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.

Penicillin vs. erythromycin in the treatment of diphtheria

In an open-label, randomized trial, 44 Vietnamese children with diphtheria were given penicillin therapy (intramuscular benzylpenicillin, 50,000 U/[kg.d] for 5 days and then oral penicillin, 50 mg/[kg.d] for 5 days), and 42 were given erythromycin therapy (50 mg/[kg.d] orally for 10 days). There were no differences in times to membrane clearance or bacteriologic clearance, but median times to fever clearance were 27 hours (95% confidence interval [CI], 19-30; range, 0-124 hours) for penicillin recipients and 46 hours (95% CI, 34-54; range, 0-148 hours) for erythromycin recipients (P = .0004). In the penicillin group, acute treatment failed for one patient, and one patient relapsed. Three patients in the penicillin group developed diphtheritic myocarditis as evidenced by abnormal electrocardiograms. Erythromycin did not cause prolongation of the QT interval corrected for heart rate. Cultures of specimens from 15 patients (17.4%) were positive for toxigenic Corynebacterium diphtheriae. All isolates were susceptible to penicillin, but for isolates (27%), all of which were from patients who received penicillin treatment, were resistant to erythromycin (minimum inhibitory concentrations, > 64 mg/L). Penicillin is recommended as first-line treatment for diphtheria in Vietnam.

Systemic endothelial activation occurs in both mild and severe malaria. Correlating dermal microvascular endothelial cell phenotype and soluble cell adhesion molecules with disease severity

Fatal Plasmodium falciparum malaria is accompanied by systemic endothelial activation. To study endothelial activation directly during malaria and sepsis in vivo, the expression of cell adhesion molecules on dermal microvascular endothelium was examined in skin biopsies and correlated with plasma levels of soluble (circulating) ICAM-1, E-selectin, and VCAM-1 and the cytokine tumor necrosis factor (TNF)-alpha. Skin biopsies were obtained from 61 cases of severe malaria, 42 cases of uncomplicated malaria, 10 cases of severe systemic sepsis, and 17 uninfected controls. Systemic endothelial activation, represented by the up-regulation of inducible cell adhesion molecules (CAMs) on endothelium and increased levels of soluble CAMs (sCAMs), were seen in both severe and uncomplicated malaria and sepsis when compared with uninfected controls. Plasma levels of sICAM-1, sVCAM-1, and sE-selectin correlated positively with the severity of malaria whereas TNF-alpha was raised nonspecifically in malaria and sepsis. Immunohistochemical evidence of endothelial activation in skin biopsies did not correlate with sCAM levels or disease severity. This indicates a background of systemic endothelial activation, which occurs in both mild and severe malaria and sepsis. The levels of sCAMs in malaria are thus not an accurate reflection of endothelial cell expression of CAMs in a particular vascular bed, and other factors must influence their levels during disease.

Poliomyelitis-like illness due to Japanese encephalitis virus

BACKGROUND

Acute flaccid paralysis remains common among Vietnamese children despite a pronounced fall in the incidence of poliomyelitis.

METHODS

During 1995, all 22 children presenting with acute flaccid paralysis to a referral centre in Ho Chi Minh City, Vietnam, had virological cultures and antibody measurements done on serum, cerebrospinal fluid, and faeces. A year later the children were reassessed and electrophysiological studies were done.

FINDINGS

Wild poliovirus type 1 was isolated from the faeces of only one patient, and non-polio enteroviruses from three patients. 12 (55%) of the 22 children with acute flaccid paralysis had evidence of acute Japanese encephalitis virus (JEV) infection, compared with only one (1%) of 88 age-matched hospital controls (children with diphtheria; p<0.0001). Compared with JEV-negative patients, weakness in JEV-infected children was more rapid in onset, tended to be asymmetrical, but was less likely to involve the arms. All 12 children with JEV infection were febrile at the onset of weakness, seven had acute retention of urine, and ten had CSF pleiocytosis. Seven of eight JEV-negative patients met the case-definition of Guillain-Barré syndrome, compared with only one of 12 JEV-positive children. At follow-up, patients with JEV infection had greater disability and were more likely to have muscle wasting than were JEV-negative children. Nerve conduction and electromyographic studies indicated damage to the anterior horn cells.

INTERPRETATION

JEV causes an acute flaccid paralysis in children that has similar clinical and pathological features to poliomyelitis. In endemic areas, children with acute flaccid paralysis should be investigated for evidence of JEV infection.

Pathophysiologic and prognostic role of cytokines in dengue hemorrhagic fever

Dengue shock syndrome is a severe complication of dengue hemorrhagic fever (DHF), characterized by a massive increase in vascular permeability. Plasma cytokine concentrations were prospectively studied in 443 Vietnamese children with DHF, of whom 6 died. Shock was present in 188 children on admission to hospital, and in 71 children it developed later. Contrary to expectations, certain inflammatory markers (interleukin-6 and soluble intercellular adhesion molecule-1) were lower in the group with shock, and this may reflect the general loss of protein from the circulation due to capillary leakage. Only soluble tumor necrosis factor receptor (TNFR) levels showed a consistent positive relationship with disease severity. In patients with suspected DHF without shock, admission levels of sTNFR-75 in excess of 55 pg/mL predicted the subsequent development of shock, with a relative risk of 5.5 (95% confidence interval, 2.3-13.2). Large-scale release of soluble TNFR may be an early and specific marker of the endothelial changes that cause dengue shock syndrome.

Reactive nitrogen intermediates and outcome in severe adult malaria

The role of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) in the pathophysiology of severe falciparum malaria remains unclear. We conducted a retrospective case-control study of Vietnamese adults with severe malaria to determine the relationship between outcome and admission plasma reactive nitrogen intermediates (RNI), the stable metabolites of NO. The study was designed to take into account the potential confounders of recent dietary nitrogen intake and renal function. Seventy-six patients who died from severe malaria were matched for age and sex with 76 survivors from a prospectively studied series of 560 patients. Median untransformed unadjusted plasma RNI levels were slightly higher in fatal cases (45 mumol/L, range 0-482) than in survivors (24.1 mumol/L, range 1.4-466) (P = 0.031, Wilcoxon signed-rank). There was a significant positive correlation between RNI levels and plasma creatinine (Spearman's rho = 0.35, P < 0.0001), and the addition of plasma creatinine as a covariate in a multivariate analysis abolished the trend towards higher RNI levels in fatal cases (P for the coefficient for RNI = 0.96). There was no association between RNI levels and either depth of coma on admission or time to regain consciousness. These findings do not support a pivotal role for systemic generation of NO in the pathogenesis of severe malaria in general, or cerebral malaria in particular.

Quinolone-resistant Salmonella typhi in Viet Nam: molecular basis of resistance and clinical response to treatment

Nalidixic acid-resistant Salmonella typhi (NARST) was first isolated in Viet Nam in 1993. Analysis of the quinolone resistance-determining region of gyrA in 20 NARST isolates by polymerase chain reaction and single-stranded conformational polymorphism yielded two novel patterns: pattern II corresponding to a point mutation at nucleotide 87 Asp-->Gly (n = 17), and pattern III corresponding to a point mutation at nucleotide 83 Ser-->Phe (n = 3). In trials of short-course ofloxacin therapy for uncomplicated typhoid, 117 (78%) of 150 patients were infected with multidrug-resistant S. typhi, 18 (15%) of which were NARST. The median time to fever clearance was 156 hours (range, 30-366 hours) for patients infected with NARST and 84 hours (range, 12-378 hours) for those infected with nalidixic acid-susceptible strains (P < .001). Six (33.3%) of 18 NARST infections required retreatment, whereas 1 (0.8%) of 132 infections due to susceptible strains required retreatment (relative risk = 44; 95% confidence interval = 5.6-345; P < .0001). We recommend that short courses of quinolones not be used in patients infected with NARST.