-
[show abstract]
[hide abstract]
ABSTRACT: The diagnostic utility of the Standard Diagnostics Leptospira IgM ELISA for detection of acute leptospirosis was assessed in febrile adults admitted in Vientiane, Laos. Using the cut-off suggested by the manufacturer [optical density (OD) ≥0.75], the assay demonstrated limited diagnostic capacity with a sensitivity of 95% and a specificity of 41% compared with the Leptospira microscopic agglutination test, which is the serological gold standard. However, re-evaluation of the diagnostic cut-off to an OD of 1.7 demonstrated improved diagnostic accuracy overall (sensitivity 70%; specificity 78%).
Transactions of the Royal Society of Tropical Medicine and Hygiene 07/2012; 106(9):563-6. · 2.16 Impact Factor
-
Daniel H Paris,
Rattanaphone Phetsouvanh,
Ampai Tanganuchitcharnchai,
Margaret Jones,
Kemajittra Jenjaroen, Manivanh Vongsouvath,
David P J Ferguson,
Stuart D Blacksell,
Paul N Newton,
Nicholas P J Day,
Gareth D H Turner
[show abstract]
[hide abstract]
ABSTRACT: Scrub typhus is a common and underdiagnosed cause of febrile illness in Southeast Asia, caused by infection with Orientia tsutsugamushi. Inoculation of the organism at a cutaneous mite bite site commonly results in formation of a localized pathological skin reaction termed an eschar. The site of development of the obligate intracellular bacteria within the eschar and the mechanisms of dissemination to cause systemic infection are unclear. Previous postmortem and in vitro reports demonstrated infection of endothelial cells, but recent pathophysiological investigations of typhus patients using surrogate markers of endothelial cell and leucocyte activation indicated a more prevalent host leucocyte than endothelial cell response in vivo. We therefore examined eschar skin biopsies from patients with scrub typhus to determine and characterize the phenotypes of host cells in vivo with intracellular infection by O. tsutsugamushi, using histology, immunohistochemistry, double immunofluorescence confocal laser scanning microscopy and electron microscopy. Immunophenotyping of host leucocytes infected with O. tsutsugamushi showed a tropism for host monocytes and dendritic cells, which were spatially related to different histological zones of the eschar. Infected leucocyte subsets were characterized by expression of HLADR+, with an "inflammatory" monocyte phenotype of CD14/LSP-1/CD68 positive or dendritic cell phenotype of CD1a/DCSIGN/S100/FXIIIa and CD163 positive staining, or occasional CD3 positive T-cells. Endothelial cell infection was rare, and histology did not indicate a widespread inflammatory vasculitis as the cause of the eschar. Infection of dendritic cells and activated inflammatory monocytes offers a potential route for dissemination of O. tsutsugamushi from the initial eschar site. This newly described cellular tropism for O. tsutsugamushi may influence its interaction with local host immune responses.
PLoS Neglected Tropical Diseases 01/2012; 6(1):e1466. · 4.69 Impact Factor
-
Manisone Khennavong,
Viengmon Davone, Manivanh Vongsouvath,
Rattanaphone Phetsouvanh,
Joy Silisouk,
Olay Rattana,
Mayfong Mayxay,
Josée Castonguay-Vanier,
Catrin E Moore,
Michel Strobel,
Paul N Newton
[show abstract]
[hide abstract]
ABSTRACT: Widespread use of antibiotics may be important in the spread of antimicrobial resistance. We estimated the proportion of Lao in- and outpatients who had taken antibiotics before medical consultation by detecting antibiotic activity in their urine added to lawns of Bacillus stearothermophilus, Escherichia coli, and Streptococcus pyogenes. In the retrospective (N = 2,058) and prospective studies (N = 1,153), 49.7% (95% confidence interval [CI] = 47.4-52.0) and 36.2% (95% CI = 33.4-38.9), respectively, of Vientiane patients had urinary antibiotic activity detected. The highest frequency of estimated antibiotic pre-treatment was found in patients recruited with suspected central nervous system infections and community-acquired septicemia (both 56.8%). In Vientiane, children had a higher frequency of estimated antibiotic pre-treatment than adults (60.0% versus 46.5%; P < 0.001). Antibiotic use based on patients histories was significantly less frequent than when estimated from urinary antibiotic activity (P < 0.0001).
The American journal of tropical medicine and hygiene 08/2011; 85(2):295-302. · 2.59 Impact Factor
-
Mayfong Mayxay,
Rattanaphone Phetsouvanh,
Catrin E Moore,
Vilada Chansamouth, Manivanh Vongsouvath,
Syho Sisouphone,
Pankham Vongphachanh,
Thaksinaporn Thaojaikong,
Soulignasack Thongpaseuth,
Simmaly Phongmany,
Valy Keolouangkhot,
Michel Strobel,
Paul N Newton
[show abstract]
[hide abstract]
ABSTRACT: To examine the accuracy of the admission tourniquet test in the diagnosis of dengue infection among Lao adults.
Prospective assessment of the predictive diagnostic value of the tourniquet test for the diagnosis of dengue infection, as defined by IgM, IgG and NS1 ELISAs (Panbio Ltd, Australia), among Lao adult inpatients with clinically suspected dengue infection.
Of 234 patients with clinically suspected dengue infection on admission, 73% were serologically confirmed to have dengue, while 64 patients with negative dengue serology were diagnosed as having scrub typhus (39%), murine typhus (11%), undetermined typhus (12%), Japanese encephalitis virus (5%), undetermined flavivirus (5%) and typhoid fever (3%); 25% had no identifiable aetiology. The tourniquet test was positive in 29.1% (95% CI = 23.2-34.9%) of all patients and in 34.1% (95% CI = 27.0-41.2%) of dengue-seropositive patients, in 32.7% (95% CI = 23.5-41.8) of those with dengue fever and in 36.4% (95% CI = 24.7-48.0) of those with dengue haemorrhagic fever. Interobserver agreement for the tourniquet test was 90.2% (95% CI = 86.4-94.0) (Kappa = 0.76). Using ELISAs as the diagnostic gold standard, the sensitivity of the tourniquet test was 33.5-34%; its specificity was 84-91%. The positive and negative predictive values were 85-90% and 32.5-34%, respectively.
The admission tourniquet test has low sensitivity and adds relatively little value to the diagnosis of dengue among Lao adult inpatients with suspected dengue. Although a positive tourniquet test suggests dengue and that treatment of alternative diagnoses may not be needed, a negative test result does not exclude dengue.
Tropical Medicine & International Health 10/2010; 16(1):127-33. · 2.80 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Rotavirus is one of the most common causes of severe life-threatening diarrhoea in children leading to hospitalization especially in developing countries. At Mahosot Hospital in Vientiane, Lao PDR, children with diarrhoea underwent standard clinical evaluation and faecal specimen collection to estimate the burden of rotavirus hospitalizations and to determine rotavirus strain patterns among children aged less than 5 years old. From March 2005 to February 2007, a total of 1158 stool specimens were collected from children aged less than 5 years old hospitalized with acute diarrhoea. Rotavirus was identified in 624 (54%) of these patients. The G1P[8] strain was the most common genotype (35%), followed by G9P[8] (25%). These surveillance data suggest that improved prevention and control programs for rotavirus as well as other causes of diarrhoea are needed in Lao PDR.
Vaccine 11/2009; 27 Suppl 5:F85-8. · 3.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Chromobacterium violaceum is a Gram negative facultative anaerobic bacillus, found in soil and stagnant water, that usually has a violet pigmented appearance on agar culture. It is rarely described as a human pathogen, mostly from tropical and subtropical areas.
A 53 year-old farmer died with Chromobacterium violaceum septicemia in Laos. A modified oxidase method was used to demonstrate that this violacious organism was oxidase positive. Forensic analysis of the glucose-6-phosphate dehydrogenase genotypes of his family suggest that the deceased patient did not have this possible predisposing condition.
C. violaceum infection should be included in the differential diagnosis in patients presenting with community-acquired septicaemia in tropical and subtropical areas. The apparently neglected but simple modified oxidase test may be useful in the oxidase assessment of other violet-pigmented organisms or of those growing on violet coloured agar.
Annals of Clinical Microbiology and Antimicrobials 08/2009; 8:24. · 2.64 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Human infections with non-O1, non-O139 V. cholerae have been described from Laos. Elsewhere, non cholera-toxin producing, non-O1, non-O139 V. cholerae have been described from blood cultures and ascitic fluid, although they are exceedingly rare isolates.
We describe a farmer who died with Vibrio cholerae O21 bacteremia and peritonitis in Vientiane, Laos, after eating partially cooked apple snails (Pomacea canaliculata) and mussels (Ligumia species). The cultured V. cholerae were non-motile. PCR detected ompW and toxR gene regions but not the ctxA, ompU, omp K and TCP gene regions. Although the organisms lacked flagellae on scanning electron microscopy, they possessed the Vibrio flagellin flaA gene.
Severe bacteremic non-O1, non-O139 V. cholerae is reported from Laos. The organisms were unusual in being non-motile. They possessed the Vibrio flagellin flaA gene. Further research to determine the reasons for the non-motility and virulence is required.
Annals of Clinical Microbiology and Antimicrobials 02/2008; 7:10. · 2.64 Impact Factor
-
Stuart D Blacksell,
David Bell,
James Kelley,
Mammen P Mammen,
Robert V Gibbons,
Richard G Jarman,
David W Vaughn,
Kemajittra Jenjaroen,
Ananda Nisalak,
Soulignasack Thongpaseuth, Manivanh Vongsouvath,
Viengmone Davong,
Phonelavanh Phouminh,
Rattanaphone Phetsouvanh,
Nicholas P J Day,
Paul N Newton
[show abstract]
[hide abstract]
ABSTRACT: There is an urgent need for accurate and simple dengue virus infection diagnostic assays in limited-resource settings of dengue endemicity, to assist patient management. Using a panel of reference samples (S. D. Blacksell, P. N. Newton, D. Bell, J. Kelley, M. P. Mammen, D. W. Vaughn, V. Wuthiekanun, A. Sungkakum, A. Nisalak, and N. P. Day, Clin. Infect. Dis. 42:1127-1134, 2006), we recently evaluated eihgt commercially available immunochromatographic rapid diagnostic tests (RDTs) designed to detect dengue virus-specific immunoglobulin M (IgM) and/or IgG. We found that 6/8 RDTs had sensitivities of less than 50% (range, 6 to 65%), but specificities were generally high. Here, in conjuction with dengue virus serotyping by reverse transcriptase PCR and in the limited-resource setting of Laos, where dengue virus is endemic, we evaluated the same eight RDTs against a previously validated dengue IgM/IgG enzyme-linked immunosorbent assay for diagnosis of acute dengue virus infection. Paired serum samples were collected from 87 patients, of whom 38 had confirmed dengue virus infections (4 had primary infections, 33 had secondary infections, and 1 had an infection of indeterminate status). RDT sensitivity was low, with 7/8 RDTs having admission sample sensitivities of less than 20% (range, 4 to 26%). The majority (6/8) of the RDTs, demonstrated high specificity (>95%). Kappa statistic values ranged from 6 to 54% for the RDTs, demonstrating poor to moderate variation between three operators. No RDT adequately differentiated between primary and secondary dengue virus infections. The findings of this study suggest that currently available RDTs based on the detection of IgM antibodies for the diagnosis of acute dengue virus infections are unlikely to be useful for patient management.
Clinical and Vaccine Immunology 12/2007; 14(11):1458-64. · 2.55 Impact Factor
-
Stuart D Blacksell,
Lee Smythe,
Rattanaphone Phetsouvanh,
Michael Dohnt,
Rudy Hartskeerl,
Meegan Symonds,
Andrew Slack, Manivanh Vongsouvath,
Viengmone Davong,
Olay Lattana,
Simmaly Phongmany,
Valy Keolouangkot,
Nicholas J White,
Nicholas P J Day,
Paul N Newton
[show abstract]
[hide abstract]
ABSTRACT: The diagnostic utility of immunochromatographic (Leptotek) and enzyme-linked immunosorbent assay (ELISA; Panbio) tests for the detection of Leptospira immunoglobulin M antibodies was assessed in febrile adults admitted in Vientiane, Laos. Both tests demonstrated poor diagnostic accuracy using admission serum (Leptotek sensitivity of 47.3% and specificity of 75.5%: ELISA sensitivity of 60.9% and specificity of 65.6%) compared to the Leptospira "gold standard" microscopic agglutination test.
Clinical and Vaccine Immunology 11/2006; 13(10):1166-9. · 2.55 Impact Factor
