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Burkholderia pseudomallei Is Spatially Distributed in Soil in Northeast Thailand
Direk Limmathurotsakul ,Vanaporn Wuthiekanun,Narisara Chantratita,Gumphol Wongsuvan,Premjit Amornchai,Nicholas P. J. Day,Sharon J. Peacock
PLOS Neglected Tropical Diseases , 2010, DOI: 10.1371/journal.pntd.0000694
Abstract: Background Melioidosis is a frequently fatal infectious disease caused by the soil dwelling Gram-negative bacterium Burkholderia pseudomallei. Environmental sampling is important to identify geographical distribution of the organism and related risk of infection to humans and livestock. The aim of this study was to evaluate spatial distribution of B. pseudomallei in soil and consider the implications of this for soil sampling strategies. Methods and Findings A fixed-interval sampling strategy was used as the basis for detection and quantitation by culture of B. pseudomallei in soil in two environmental sites (disused land covered with low-lying scrub and rice field) in northeast Thailand. Semivariogram and indicator semivariogram were used to evaluate the distribution of B. pseudomallei and its relationship with range between sampling points. B. pseudomallei was present on culture of 80/100 sampling points taken from the disused land and 28/100 sampling points from the rice field. The median B. pseudomallei cfu/gram from positive sampling points was 378 and 700 for the disused land and the rice field, respectively (p = 0.17). Spatial autocorrelation of B. pseudomallei was present, in that samples taken from areas adjacent to sampling points that were culture positive (negative) for B. pseudomallei were also likely to be culture positive (negative), and samples taken from areas adjacent to sampling points with a high (low) B. pseudomallei count were also likely to yield a high (low) count. Ranges of spatial autocorrelation in quantitative B. pseudomallei count were 11.4 meters in the disused land and 7.6 meters in the rice field. Conclusions We discuss the implications of the uneven distribution of B. pseudomallei in soil for future environmental studies, and describe a range of established geostatistical sampling approaches that would be suitable for the study of B. pseudomallei that take account of our findings.
Molecular detection and speciation of pathogenic Leptospira spp. in blood from patients with culture-negative leptospirosis
Siriphan Boonsilp, Janjira Thaipadungpanit, Premjit Amornchai, Vanaporn Wuthiekanun, Wirongrong Chierakul, Direk Limmathurotsakul, Nicholas P Day, Sharon J Peacock
BMC Infectious Diseases , 2011, DOI: 10.1186/1471-2334-11-338
Abstract: We evaluated our hypothesis during a prospective study of 418 consecutive patients presenting to a hospital in northeast Thailand with an acute febrile illness. Admission blood samples were taken for Leptospira culture and PCR. A single tube nested PCR that amplified a region of the rrs gene was developed and applied, amplicons sequenced and a phylogenetic tree reconstructed.39/418 (9%) patients were culture-positive for Leptospira spp., and 81/418 (19%) patients were culture-negative but rrs PCR-positive. The species associated with culture-positive leptospirosis (37 L. interrogans and 2 L. borgpetersenii) were comparable to those associated with culture-negative, PCR-positive leptospirosis (76 L. interrogans, 4 L. borgpetersenii, 1 unidentified, possibly new species).Molecular speciation failed to identify a unique bacterial subset in patients with culture-negative, PCR-positive leptospirosis. The rate of false-negative culture was high, and we speculate that antibiotic pre-treatment is the most likely explanation for this.Leptospirosis is an acute febrile illness caused by pathogenic species belonging to the genus Leptospira [1,2]. This zoonotic disease has a worldwide distribution but is most common in tropical and subtropical regions and has the greatest impact on public health in developing countries [1-4]. Disease is maintained by chronic carrier hosts that excrete the organism into the environment, and infection in man results from direct contact with infected animals or indirect contact with a contaminated environment [1-3].Leptospira are present in the blood during the first week of infective symptoms [1,2]. Culture is rarely performed in routine clinical practice since this may take several months and requires considerable expertise, which places it within the domain of specialist reference centres. Culture continues to have an important role, however, in defining the global epidemiology of infection [4]. Identification of the serovar of infecting isolate
Diagnostic Accuracy of Real-Time PCR Assays Targeting 16S rRNA and lipl32 Genes for Human Leptospirosis in Thailand: A Case-Control Study
Janjira Thaipadunpanit,Wirongrong Chierakul,Vanaporn Wuthiekanun,Direk Limmathurotsakul,Premjit Amornchai,Siriphan Boonslip,Lee D. Smythe,Roongrueng Limpaiboon,Alex R. Hoffmaster,Nicholas P. J. Day,Sharon J. Peacock
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0016236
Abstract: Rapid PCR-based tests for the diagnosis of leptospirosis can provide information that contributes towards early patient management, but these have not been adopted in Thailand. Here, we compare the diagnostic sensitivity and specificity of two real-time PCR assays targeting rrs or lipL32 for the diagnosis of leptospirosis in northeast Thailand.
Genetic Diversity and Microevolution of Burkholderia pseudomallei in the Environment
Narisara Chantratita equal contributor,Vanaporn Wuthiekanun equal contributor,Direk Limmathurotsakul,Mongkol Vesaratchavest,Aunchalee Thanwisai,Premjit Amornchai,Sarinna Tumapa,Edward J. Feil,Nicholas P. Day,Sharon J. Peacock
PLOS Neglected Tropical Diseases , 2008, DOI: 10.1371/journal.pntd.0000182
Abstract: Background The soil dwelling Gram-negative pathogen Burkholderia pseudomallei is the cause of melioidosis. The diversity and population structure of this organism in the environment is poorly defined. Methods and Findings We undertook a study of B. pseudomallei in soil sampled from 100 equally spaced points within 237.5 m2 of disused land in northeast Thailand. B. pseudomallei was present on direct culture of 77/100 sampling points. Genotyping of 200 primary plate colonies from three independent sampling points was performed using a combination of pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Twelve PFGE types and nine sequence types (STs) were identified, the majority of which were present at only a single sampling point. Two sampling points contained four STs and the third point contained three STs. Although the distance between the three sampling points was low (7.6, 7.9, and 13.3 meters, respectively), only two STs were present in more than one sampling point. Each of the three samples was characterized by the localized expansion of a single B. pseudomallei clone (corresponding to STs 185, 163, and 93). Comparison of PFGE and MLST results demonstrated that two STs contained strains with variable PFGE banding pattern types, indicating geographic structuring even within a single MLST-defined clone. Conclusions We discuss the implications of this extreme structuring of genotype and genotypic frequency in terms of micro-evolutionary dynamics and ecology, and how our results may inform future sampling strategies.
Emergence of Community-Associated Methicillin-Resistant Staphylococcus aureus Associated with Pediatric Infection in Cambodia
Kheng Chheng, Sarah Tarquinio, Vanaporn Wuthiekanun, Lina Sin, Janjira Thaipadungpanit, Premjit Amornchai, Ngoun Chanpheaktra, Sarinna Tumapa, Hor Putchhat, Nicholas P. J. Day, Sharon J. Peacock
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006630
Abstract: Background The incidence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection is rising in the developed world but appears to be rare in developing countries. One explanation for this difference is that resource poor countries lack the diagnostic microbiology facilities necessary to detect the presence of CA-MRSA carriage and infection. Methodology and Principal Findings We developed diagnostic microbiology capabilities at the Angkor Hospital for Children, Siem Reap, western Cambodia in January 2006 and in the same month identified a child with severe community-acquired impetigo caused by CA-MRSA. A study was undertaken to identify and describe additional cases presenting between January 2006 and December 2007. Bacterial isolates underwent molecular characterization using multilocus sequence typing, staphylococcal cassette chromosome mec (SCCmec) typing, and PCR for the presence of the genes encoding Panton-Valentine Leukocidin (PVL). Seventeen children were identified with CA-MRSA infection, of which 11 had skin and soft tissue infection and 6 had invasive disease. The majority of cases were unrelated in time or place. Molecular characterization identified two independent MRSA clones; fifteen isolates were sequence type (ST) 834, SCCmec type IV, PVL gene-negative, and two isolates were ST 121, SCCmec type V, PVL gene-positive. Conclusions This represents the first ever report of MRSA in Cambodia, spread of which would pose a significant threat to public health. The finding that cases were mostly unrelated in time or place suggests that these were sporadic infections in persons who were CA-MRSA carriers or contacts of carriers, rather than arising in the context of an outbreak.
Factors Predicting and Reducing Mortality in Patients with Invasive Staphylococcus aureus Disease in a Developing Country
Emma K. Nickerson, Vanaporn Wuthiekanun, Gumphol Wongsuvan, Direk Limmathurosakul, Pramot Srisamang, Weera Mahavanakul, Janjira Thaipadungpanit, Krupal R. Shah, Arkhom Arayawichanont, Premjit Amornchai, Aunchalee Thanwisai, Nicholas P. Day, Sharon J. Peacock
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006512
Abstract: Background Invasive Staphylococcus aureus infection is increasingly recognised as an important cause of serious sepsis across the developing world, with mortality rates higher than those in the developed world. The factors determining mortality in developing countries have not been identified. Methods A prospective, observational study of invasive S. aureus disease was conducted at a provincial hospital in northeast Thailand over a 1-year period. All-cause and S. aureus-attributable mortality rates were determined, and the relationship was assessed between death and patient characteristics, clinical presentations, antibiotic therapy and resistance, drainage of pus and carriage of genes encoding Panton-Valentine Leukocidin (PVL). Principal Findings A total of 270 patients with invasive S. aureus infection were recruited. The range of clinical manifestations was broad and comparable to that described in developed countries. All-cause and S. aureus-attributable mortality rates were 26% and 20%, respectively. Early antibiotic therapy and drainage of pus were associated with a survival advantage (both p<0.001) on univariate analysis. Patients infected by a PVL gene-positive isolate (122/248 tested, 49%) had a strong survival advantage compared with patients infected by a PVL gene-negative isolate (all-cause mortality 11% versus 39% respectively, p<0.001). Multiple logistic regression analysis using all variables significant on univariate analysis revealed that age, underlying cardiac disease and respiratory infection were risk factors for all-cause and S. aureus-attributable mortality, while one or more abscesses as the presenting clinical feature and procedures for infectious source control were associated with survival. Conclusions Drainage of pus and timely antibiotic therapy are key to the successful management of S. aureus infection in the developing world. Defining the presence of genes encoding PVL provides no practical bedside information and draws attention away from identifying verified clinical risk factors and those interventions that save lives.
A Single Multilocus Sequence Typing (MLST) Scheme for Seven Pathogenic Leptospira Species
Siriphan Boonsilp equal contributor,Janjira Thaipadungpanit equal contributor ,Premjit Amornchai,Vanaporn Wuthiekanun,Mark S. Bailey,Matthew T. G. Holden,Cuicai Zhang,Xiugao Jiang,Nobuo Koizumi,Kyle Taylor,Renee Galloway,Alex R. Hoffmaster,Scott Craig,Lee D. Smythe,Rudy A. Hartskeerl,Nicholas P. Day,Narisara Chantratita,Edward J. Feil,David M. Aanensen,Brian G. Spratt,Sharon J. Peacock
PLOS Neglected Tropical Diseases , 2013, DOI: 10.1371/journal.pntd.0001954
Abstract: Background The available Leptospira multilocus sequence typing (MLST) scheme supported by a MLST website is limited to L. interrogans and L. kirschneri. Our aim was to broaden the utility of this scheme to incorporate a total of seven pathogenic species. Methodology and Findings We modified the existing scheme by replacing one of the seven MLST loci (fadD was changed to caiB), as the former gene did not appear to be present in some pathogenic species. Comparison of the original and modified schemes using data for L. interrogans and L. kirschneri demonstrated that the discriminatory power of the two schemes was not significantly different. The modified scheme was used to further characterize 325 isolates (L. alexanderi [n = 5], L. borgpetersenii [n = 34], L. interrogans [n = 222], L. kirschneri [n = 29], L. noguchii [n = 9], L. santarosai [n = 10], and L. weilii [n = 16]). Phylogenetic analysis using concatenated sequences of the 7 loci demonstrated that each species corresponded to a discrete clade, and that no strains were misclassified at the species level. Comparison between genotype and serovar was possible for 254 isolates. Of the 31 sequence types (STs) represented by at least two isolates, 18 STs included isolates assigned to two or three different serovars. Conversely, 14 serovars were identified that contained between 2 to 10 different STs. New observations were made on the global phylogeography of Leptospira spp., and the utility of MLST in making associations between human disease and specific maintenance hosts was demonstrated. Conclusion The new MLST scheme, supported by an updated MLST website, allows the characterization and species assignment of isolates of the seven major pathogenic species associated with leptospirosis.
A Prospective Study of the Causes of Febrile Illness Requiring Hospitalization in Children in Cambodia
Kheng Chheng, Michael J. Carter, Kate Emary, Ngoun Chanpheaktra, Catrin E. Moore, Nicole Stoesser, Hor Putchhat, Soeng Sona, Sin Reaksmey, Paul Kitsutani, Borann Sar, H. Rogier van Doorn, Nguyen Hanh Uyen, Le Van Tan, Daniel Paris, Stuart D. Blacksell, Premjit Amornchai, Vanaporn Wuthiekanun, Christopher M. Parry, Nicholas P. J. Day, Varun Kumar
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0060634
Abstract: Background Febrile illnesses are pre-eminent contributors to morbidity and mortality among children in South-East Asia but the causes are poorly understood. We determined the causes of fever in children hospitalised in Siem Reap province, Cambodia. Methods and Findings A one-year prospective study of febrile children admitted to Angkor Hospital for Children, Siem Reap. Demographic, clinical, laboratory and outcome data were comprehensively analysed. Between October 12th 2009 and October 12th 2010 there were 1225 episodes of febrile illness in 1180 children. Median (IQR) age was 2.0 (0.8–6.4) years, with 850 (69%) episodes in children <5 years. Common microbiological diagnoses were dengue virus (16.2%), scrub typhus (7.8%), and Japanese encephalitis virus (5.8%). 76 (6.3%) episodes had culture-proven bloodstream infection, including Salmonella enterica serovar Typhi (22 isolates, 1.8%), Streptococcus pneumoniae (13, 1.1%), Escherichia coli (8, 0.7%), Haemophilus influenzae (7, 0.6%), Staphylococcus aureus (6, 0.5%) and Burkholderia pseudomallei (6, 0.5%). There were 69 deaths (5.6%), including those due to clinically diagnosed pneumonia (19), dengue virus (5), and melioidosis (4). 10 of 69 (14.5%) deaths were associated with culture-proven bloodstream infection in logistic regression analyses (odds ratio for mortality 3.4, 95% CI 1.6–6.9). Antimicrobial resistance was prevalent, particularly in S. enterica Typhi, (where 90% of isolates were resistant to ciprofloxacin, and 86% were multi-drug resistant). Comorbid undernutrition was present in 44% of episodes and a major risk factor for acute mortality (OR 2.1, 95% CI 1.1–4.2), as were HIV infection and cardiac disease. Conclusion We identified a microbiological cause of fever in almost 50% of episodes in this large study of community-acquired febrile illness in hospitalized children in Cambodia. The range of pathogens, antimicrobial susceptibility, and co-morbidities associated with mortality described will be of use in the development of rational guidelines for infectious disease treatment and control in Cambodia and South-East Asia.
Tennis Winner Prediction based on Time-Series History with Neural Modeling
Amornchai Somboonphokkaphan,Suphakant Phimoltares,Chidchanok Lursinsap
Lecture Notes in Engineering and Computer Science , 2009,
Fuel Processing Technologies for Hydrogen Production from Methane
Suttichai Assabumrungrat,Janewit Phromprasit,Amornchai Arpornwichanop
Engineering Journal , 2012, DOI: 10.4186/ej.2012.16.2.1
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