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Serosurvey on household contacts of Marburg hemorrhagic fever patients
No full textThe first major outbreak of Marburg hemorrhagic fever (MHF) outside a laboratory environment occurred in the subdistrict of Watsa, Democratic Republic of Congo, from October 1998 to August 2000. We performed a serosurvey of household contacts of MHF patients to identify undetected cases, ascertain the frequency of asymptomatic Marburg infection, and estimate secondary attack risk and postintervention reproduction number. Contacts were interviewed about their exposure and symptoms consistent with MHF. Blood samples were tested for anti-Marburg immunoglobulin G (IgG). One hundred twenty-one (51%) of 237 identified contacts participated; 72 (60%) were not known to the health authorities. Two participating contacts were seropositive and reported becoming ill after the contact; no serologic evidence for asymptomatic or mild Marburg infection was found. The secondary attack risk was 21%; the postintervention reproduction number was 0.9, consistent with an outbreak sustained by repeated primary transmission, rather than large-scale secondary transmission
A new rapid and simple colorimetric method to detect pyrazinamide resistance in Mycobacterium tuberculosis using nicotinamide
No full textOBJECTIVES: The purpose of this study was to develop and assess a rapid method for pyrazinamide resistance detection in Mycobacterium tuberculosis using nicotinamide in a colorimetric resazurin assay. METHODS: We have tested M. tuberculosis isolates using nicotinamide in a 96-well format with the redox indicator resazurin (REMA) and compared results using the BACTEC 460-TB system with two concentrations of pyrazinamide (100 and 300 mg/L), as well as the Wayne method for detecting pyrazinamidase activity. Mutations in the pncA gene were detected by DNA sequencing of the pyrazinamide-resistant strains. RESULTS: Out of 95 clinical isolates of M. tuberculosis tested, 25 were determined to be resistant by the Wayne, BACTEC (300 mg/L), and the REMA nicotinamide methods. Using a nicotinamide MIC>250 mg/L as the cut-off for defining resistance, only one strain was falsely labelled as resistant. The REMA nicotinamide assay demonstrated a sensitivity of 100% and a specificity of 98%. The BACTEC (100 mg/L) falsely classified 8 strains as resistant. DNA sequencing detected mutations in 18/22 of the pncA genes from pyrazinamide-resistant strains. CONCLUSIONS: The REMA plate using nicotinamide to detect resistance to pyrazinamide is a simple and rapid method that could be useful in limited-resource countries
Clinical evaluation of a 16S ribosomal RNA polymerase chain reaction test for the diagnosis of lymph node tuberculosis
No full textReports on the sensitivity of polymerase chain reaction (PCR) for the diagnosis of lymph node tuberculosis (TB) show divergent results. We evaluated the accuracy of the Roche Amplicor Mycobacterium tuberculosis PCR test with lymph node aspirate and biopsy samples. METHODS: The study was conducted at a public reference hospital in Lima, Peru. From the period of January 2003 to January 2004, we included patients who had lymphadenopathy and in whom the attending physician suspected TB. Aspirate and biopsy samples were submitted for culturing in Lowenstein-Jensen medium, for histopathologic testing, and for PCR. The sensitivity and specificity of PCR were calculated against a reference standard based on histopathologic findings and culture. RESULTS: Our study included 154 patients. Median age was 29 years (interquartile range, 21-40 years); 97 patients (62.9%) were men. Twenty-nine patients (18.8%) had acid fast bacilli-positive histopathologic findings, and 44 (28.6%) had a positive culture result. Using the combination of histopathologic findings and culture as reference standard, 55 patients (35.7%) had a diagnosis of tuberculous lymphadenitis. The sensitivity of the PCR test was 58.2%, and the specificity was 93.9%. For biopsy tissue only, the sensitivity of PCR was 52.7%, and the specificity was 97.0%. For aspirate samples only, the sensitivity of PCR was 47.3%, and the specificity was 96.0%. CONCLUSION: The Amplicor PCR test revealed low sensitivity and high specificity for the diagnosis of lymph node TB. The sensitivity was higher in cases in which the bacillary load was high--in acid fast bacilli-positive samples and among HIV-infected patients. Considering the results of microbiological and PCR tests together, there was still a patient group in whom no final diagnosis could be established
Heterogeneity among Mycobacterium ulcerans isolates from Africa
No full textMycobacterium ulcerans causes Buruli ulcer, an ulcerative skin disease in tropical and subtropical areas. Despite restricted genetic diversity, mycobacterial interspersed repetitive unit-variable-number tandem repeat analysis on M. ulcerans revealed 3 genotypes from different African countries. It is the first time this typing method succeeded directly on patient samples
Detection of the East and West African kdr mutation in Anopheles gambiae and Anopheles arabiensis from Uganda using a new assay based on FRET/Melt curve analysis
No full textBACKGROUND: Appropriate monitoring of vector resistance to insecticides is an integral component of planning and evaluation of insecticide use in malaria control programmes. The malaria vectors Anopheles gambiae s.s. and Anopheles arabiensis have developed resistance to pyrethroid insecticides as a result of a mechanism conferring reduced nervous system sensitivity, better known as knockdown resistance (kdr). In An. gambiae s.s. and An. arabiensis, two different substitutions in the para-type sodium channel, a L1014F substitution common in West Africa and a L1014S replacement found in Kenya, are linked with kdr. Two different allele-specific polymerase chain reactions (AS-PCR) are needed to detect these known kdr mutations. However, these AS-PCR assays rely on a single nucleotide polymorphism mismatch, which can result in unreliable results. METHODS: Here, a new assay for the detection of knockdown resistance in An. gambiae s.s. and An. arabiensis based on Fluorescence Resonance Energy Transfer/Melt Curve analysis (FRET/MCA) is presented and compared with the existing assays. RESULTS: The new FRET/MCA method has the important advantage of detecting both kdr alleles in one assay. Moreover, results show that the FRET/MCA is more reliable and more sensitive than the existing AS-PCR assays and is able to detect new genotypes. By using this technique, the presence of the East African kdr mutation (L1014S) is shown for the first time in An. arabiensis specimens from Uganda. In addition, a new kdr genotype is reported in An. gambiae s.s. from Uganda, where four An. gambiae s.s. mosquitoes possess both, the West (L1014F) and East (L1014S) African kdr allele, simultaneously. CONCLUSION: The presence of both kdr mutations in the same geographical region shows the necessity of a reliable assay that enables to detect both mutations in one single assay. Hence, this new assay based on FRET/MCA will improve the screening of the kdr frequencies in An. gambiae s.s. and An. arabiensis
Protective netting, an additional method for the integrated control of livestock trypanosomosis in KwaZulu-Natal province, South Africa
No full textStudies were conducted in KwaZulu-Natal, South Africa, to evaluate the effectiveness of netting in preventing Glossina austeni and Glossina brevipalpis from entering H-traps. Results indicated that a net of 1.5 m in height was effective in reducing catches of G. austeni by 59.6% and catches of G. brevipalpis by 80.9%. Increasing the net height to 2.5 m, reduced catches by 96.6% and 100% for G. brevipalpis and G. austeni, respectively. Nets of this height also reduced catches of horse flies by 55%. Although the potential use of protective netting has limitations in tsetse-infested areas of rural northern KwaZulu-Natal, it is a low-technology method that can be used as part of integrated disease management strategies
Evaluation sur le terrain et sur souris de la résistance des trypanosomes des bovins du plateau de l'Adamaoua au Cameroun à l'acéturate de diminazène et au chlorure d'isométamidium
No full textA modified AFLP for Trypanosoma congolense isolate characterisation
No full textThe amplified fragment length polymorphism (AFLP) technique is a reliable and powerful DNA fingerprint tool for genetic characterisation and analysis. In this paper, we described a modified AFLP with high resolution for Trypanosoma congolense using one enzyme and agarose or Elchrom gel electrophoresis. Eleven allopatric and fourteen sympatric isolates of T. congolense savannah were used to assess the resolution of the method and its ability to characterise T. congolense isolates. Two enzymes (Eco RI or Bgl II) and corresponding non-selective and selective primers were used to identify the most appropriate combination. Patterns generated by Bgl II enzyme and a single selective primer A, C, G or T produced clear profiles. Each of the four selective primers produced different profiles for all the 25 T. congolense isolates. Due to the reduction in the number of bands, profiles could be analysed using agarose or Elchrom gels. Although comparison of a great number of samples could benefit from software help, this technique did not require flurochrome detection methods. The results of the present study demonstrated that this modified AFLP makes the characterisation of T. congolense easier while maintaining high resolution