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G Bretzel

Publications and source records attributed to G Bretzel.

At least 19 recordsLinked to original sources
PubMed2007

A stepwise approach to the laboratory diagnosis of Buruli ulcer disease.

OBJECTIVE: In view of technical and financial limitations in areas of endemicity, the current practice and recommendations for the laboratory diagnosis of Buruli ulcer disease (BUD) may have to be reconsidered. We reviewed diagnostic results in order to explore options for a modified, more practicable, cost-effective and timely approach to the laboratory diagnosis of BUD. METHODS: Diagnostic specimens from 161 clinically diagnosed BUD patients from four different treatment centres in Ghana were subjected to laboratory analysis. The positivity rates of the laboratory assays were compared. RESULTS: The number of laboratory-confirmed clinically diagnosed BUD cases with one positive confirmative test was 20% higher than that with two positive confirmative tests. The specificity of microscopy (MIC) and PCR was 96.6% and 100%, respectively. Subsequent analysis of specimens from surgically excised pre-ulcerative tissue-by-tissue MIC and tissue PCR rendered 65% laboratory-confirmed BUD cases. Subsequent analysis of diagnostic swabs from ulcerative lesions by swab smear MIC and swab PCR rendered 70% of laboratory-confirmed BUD cases. CONCLUSIONS: The specificity of the diagnostic tests used in this study suggests that one positive diagnostic test may be considered sufficient for the laboratory confirmation of BUD. Subsequent application of different diagnostic tests rendered a laboratory confirmation of 65% pre-ulcerative and of 70% ulcerative lesions. Implementation of a stepwise, subsequent analysis of diagnostic specimens will result in considerable cost saving compared with simultaneous testing of specimens by several diagnostic assays.

Cost-Benefit Analysis↗
PubMed2006

External quality assurance for the laboratory diagnosis of Buruli ulcer disease in Ghana.

OBJECTIVE: To assure the quality of the laboratory diagnosis of Buruli ulcer disease; microscopy and PCR were subjected to external quality assurance (EQA). METHODS: Slides were read by test laboratory staff, followed by blinded re-reading by the controller. Parallel testing of PCR specimens was carried out at the local and external reference laboratory. Slides and PCR specimens with discordant results were subjected to a second reading/testing by the controller to determine the final result. For training purposes, slides and PCR specimens with discrepant results were subsequently re-read/re-tested under supervision at the test laboratory. RESULTS: Microscopy. First reading: concordance rate 82.9%, discordance rate 17.1%, percentage false negatives 27.1% (sensitivity 72.9%), percentage false positives 10.1% (specificity 89.9%). Second reading: concordance rate 97.9%, discordance rate 2.1%, percentage false negatives 4.2% (sensitivity 95.8%), percentage false positives 0.6% (specificity 99.4%). PCR. First testing: concordance rate 87.9%, discordance rate 12.1%, percentage false negatives 8.2% (sensitivity 91.8%), percentage false positives 19.1% (specificity 80.9%). Second testing: concordance rate 96.2%, discordance rate 3.8%, percentage false negatives 4.7% (sensitivity 95.3%), percentage false-positives 2.1% (specificity 97.9%). CONCLUSIONS: EQA identified deficiencies in the laboratory performance. Corrective action consisted in on-site training and reduced the number of false-negative and false-positive microscopy and PCR results.

Clinical Laboratory Techniques↗
PubMed2005

Post-surgical assessment of excised tissue from patients with Buruli ulcer disease: progression of infection in macroscopically healthy tissue.

OBJECTIVE: The current standard of treatment of Buruli ulcer disease (BUD) is surgical excision of lesions. Excision size is determined macroscopically assuming the complete removal of all infected tissue. However, dissemination of infection beyond the excision margins into apparently healthy tissue, possibly associated with recurrences, cannot be excluded in this way. To assess the central to peripheral progression of Mycobacterium ulcerans infection and the mycobacterial infiltration of excision margins, excised tissue was examined for signs of infection. METHODS: 20 BUD lesions were excised in general anaesthesia including all necrotic and subcutaneous adipose tissue down to the fascia and at an average of 40 mm into the macroscopically unaffected tissue beyond the border of the lesion. Tissue samples were subjected to PCR and histopathology. RESULTS: Although the bacillary load decreased from central to peripheral, M. ulcerans infection was detected throughout all examined tissue specimens including the peripheral segments as well as excision margins of all patients. During the post-operative hospitalization period (averaging 2 months) no local recurrences were observed. CONCLUSION: Available data suggest a correlation of surgical techniques with local recurrences. The results of this study indicate the unnoticed early progression of mycobacterial infection into macroscopically healthy tissue. Thus, the removal of all infected tissue cannot always be verified visually by the surgeon. Provided that long-term follow up of patients with positive excision margins will establish the clinical relevance of these findings, on-site laboratory assessment of excised tissue in combination with follow up may contribute to reduce recurrence rates.

Adolescent↗
PubMed2005

Dry-reagent-based PCR as a novel tool for laboratory confirmation of clinically diagnosed Mycobacterium ulcerans-associated disease in areas in the tropics where M. ulcerans is endemic.

After tuberculosis and leprosy, Buruli ulcer (BU), caused by Mycobacterium ulcerans, is the third most common mycobacterial disease in immunocompetent humans. The disease occurs in tropical countries, with foci in West Africa, Central Africa, and the western Pacific. BU is defined as an infectious disease involving the skin and the subcutaneous adipose tissue characterized by a painless nodule, papule, plaque, or edema, evolving into a painless ulcer with undermined edges and often leading to invalidating sequelae. Due to the fundamental lack of understanding of modes of transmission, disease control in endemic countries is limited to early case detection through improved active surveillance and surgical treatment. The laboratory confirmation of BU is complicated by the absence of a diagnostic "gold standard." Therefore, misclassification and delayed diagnosis of BU may occur frequently, causing a considerable socioeconomic impact in terms of treatment costs due to prolonged hospitalization. In order to respond to the urgent need to develop reliable tools for early case detection and to overcome technical difficulties accompanying the implementation of diagnostic PCR procedures in tropical countries, a dry-reagent-based PCR formulation for the detection of M. ulcerans in diagnostic specimens has been developed at the Bernhard Nocht Institute for Tropical Medicine. Following technical and clinical validation, the assay has been successfully installed and field tested at the Kumasi Centre for Collaborative Research in Tropical Medicine, Kumasi, Ghana. Preliminary results show an excellent diagnostic sensitivity of >95%.

Endemic Diseases↗
PubMed2002

Use of a standardised checklist to assess peripheral sputum smear microscopy laboratories for tuberculosis diagnosis in Uganda.

SETTING: TB diagnostic units in Uganda. OBJECTIVES: To assess and improve the supervision and performance of sputum smear microscopy in the peripheral diagnostic units in Uganda using a standardised laboratory checklist. DESIGN: A standardised checklist was developed and used during the quarterly supervisory visits of the District TB and Leprosy Supervisors for five quarters from the fourth quarter of 1997 until the last quarter of 1998. Individual peripheral laboratory performance was monitored during the study period. RESULTS: Forty-eight of 304 TB diagnostic units in six of the 45 Ugandan Districts were supervised using the checklist. A total of 208 checklists were analysed. The situational analysis of the peripheral diagnostic units at the beginning and at the end of the study showed a marked improvement in laboratory performance in all aspects related to sputum smear microscopy. Individual laboratory performance was monitored over five quarters, and timely response to shortcomings was provided. CONCLUSION: The systematic use of a standardised laboratory checklist can be considered an important step forward in improving the performance of the peripheral laboratories in Uganda through on-the-spot correction of any identified shortcomings.

Bacteriological Techniques↗
PubMed1999

Phenotypic and genotypic characterization of Mycobacterium africanum isolates from West Africa.

The Mycobacterium tuberculosis complex includes M. tuberculosis, M. bovis, M. africanum, and M. microti. Most clinical isolates are M. tuberculosis or M. bovis. These species can be distinguished by phenotypes and genotypes. However, there is no simple definition of M. africanum, and some authors question the validity of this species. We analyzed 17 human isolates from Sierra Leone, identified as M. africanum by biochemical and growth characteristics. We sequenced polymorphic genes and intergenic regions. We amplified DNA from six loci with variable numbers of tandem repeats (VNTRs) and determined the exact number of repeats at each locus in each strain. All M. africanum isolates had the ancestral CTG Leu at katG codon 463. Drug-resistant M. africanum isolates had katG and rpoB mutations similar to those found in drug-resistant M. bovis and M. tuberculosis. Fourteen Sierra Leone M. africanum isolates (designated group A) had katG codon 203 ACC Thr, also found in M. africanumT (the T indicates type strain) from Senegal. Group A isolates clustered with M. africanumT by VNTR analysis. Three M. africanum isolates (group B) had katG codon 203 ACT Thr, found in M. tuberculosisT, and clustered with M. tuberculosisT by VNTR analysis. Phenotypic identification of M. africanum yielded a heterogeneous collection of strains. Genotypic analyses identified a cluster (M. africanum group A) which included M. africanumT and was distinct from the rest of the M. tuberculosis complex. Future studies of M. africanum should include both phenotypic and genotypic analyses.

Codon↗
PubMed1999

Universal pattern of RpoB gene mutations among multidrug-resistant isolates of Mycobacterium tuberculosis complex from Africa.

SETTING: Multidrug-resistant tuberculosis (MDR-TB) presents an increasing burden in Southern Africa. Rapid diagnostic tests for drug resistance to rifampicin have been developed based on mutation analysis of the rpoB gene. However, geographic differences of underlying mutations have recently been suggested. OBJECTIVE: Drug-resistant strains of Mycobacterium tuberculosis complex from Africa were analysed for geographic differences in frequency and location of rpoB mutations. DESIGN: A random sample of rifampicin-resistant strains was collected from 87 patients with pulmonary MDR-TB treated in 12 hospitals from six different regions of South Africa. In addition, 18 isolates of M. tuberculosis complex from Namibia, Sierra Leone, and Uganda, including 13 isolates of M. africanum, were analyzed. Point mutations were detected by direct sequence analysis of the rpoB gene. RESULTS: Missense mutations were identified for 91 isolates (87%). Double mutations were present in eight (8%) MDR-TB isolates, two of which carried one mutation outside a previously described diagnostic region. We found no geographic differences regarding the frequency and pattern of single rpoB gene mutations. CONCLUSION: Our results confirm that molecular genetic analysis of rifampicin resistance based on a core region within the rpoB gene is universally applicable to strains of M. tuberculosis complex from different geographic regions.

Africa↗
PubMed1999

Anti-tuberculosis drug resistance surveillance in Uganda 1996-1997.

SETTING: Drug resistance surveillance conducted by the National Tuberculosis and Leprosy Control Programme (NTLP) Uganda from 1996-1997 in collaboration with the Armauer Hansen Institute/German Leprosy Relief Association (GLRA), Germany, for the WHO/IUATLD Global Project on Anti-Tuberculosis Drug Resistance Surveillance. OBJECTIVE: To determine the prevalence of primary and acquired anti-tuberculosis drug resistance in Uganda. DESIGN: The survey area covered three GLRA-supported operational NTLP zones, corresponding to 50% of the Ugandan population. A representative random sampling of individual patients was chosen as sampling procedure. Altogether 586 smear-positive TB patients (537 new cases and 49 previously treated cases) were included in the survey. RESULTS: For primary resistance the results were as follows: isoniazid (H) 6.7%, rifampicin (R) 0.8%, ethambutol (E) 6.1%, streptomycin (S) 13.4%, thioacetazone (T) 3.2%, pyrazinamide (Z) 0%, multidrug resistance (MDR) 0.5%; for acquired resistance they were: H 37.8%, R 4.4%, S 22.2%, E 11.1%, T 20.0%, Z 0%, and MDR 4.4%. CONCLUSION: According to these data the NTLP Uganda has been effective in preventing high levels of primary drug resistance. If it is assumed that the sampling process reflects the distribution of new patients and previously treated patients in the study areas, the amount of acquired resistance (any resistance) in the community of smear-positive patients is approximately 5%. To further monitor programme performance the NTLP will embark on a nationwide survey in 1998/1999.

Adolescent↗
PubMed1999

Tuberculosis chemotherapy and sputum conversion among HIV-seropositive and HIV-seronegative patients in south-eastern Uganda.

OBJECTIVE: To investigate if there is a difference in response to tuberculosis treatment between HIV seronegative and HIV seropositive patients following two months of intensive phase tuberculosis treatment. DESIGN: Prospective cohort study. SETTING: St. Francis Leprosy Centre, south-east Uganda. SUBJECTS: Four hundred fifty seven patients with never previously treated sputum smear-positive tuberculosis admitted during a two-year period in 1991/1993. INTERVENTION: Intensive phase treatment with streptomycin, isoniazid, rifampicin and pyrazinamide. MAIN OUTCOME MEASURES: Sputum conversion from a positive to a negative smear at eight weeks of treatment. RESULTS: HIV seropositivity prevalence was 28%. Among HIV seronegative patients, conversion to a negative smear status occurred in 76% persons compared to 78% in HIV seropositive patients. This difference was not statistically significant (OR = 0.9; 95% CI, 0.6-1.5). HIV seropositive patients, however, were more likely to die (p = 0.017). A high prevalence of resistance to isoniazid and streptomycin was found. Isoniazid resistance was more likely in HIV seronegative patients with M. tuberculosis strains compared to HIV seropositive persons (p < 0.005). Initial resistance to antituberculosis drugs did not have a significant effect on smear conversion. CONCLUSION: This study demonstrates that HIV-seropositive status is not a principal factor in delaying sputum conversion among patients receiving intensive phase tuberculosis treatment.

AIDS-Related Opportunistic Infections↗
PubMed1998

Significance of ahpC promoter mutations for the prediction of isoniazid resistance in Mycobacterium tuberculosis.

To determine the value of ahpC promoter mutations for the rapid prediction of isoniazid resistance, this genomic region was characterized in 50 isoniazid-resistant and 12 isoniazid-sensitive Mycobacterium tuberculosis isolates. Of the resistant isolates, 12 had ahpC promoter mutations, but only one possessed both an ahpC promoter mutation and a katG codon 315 substitution, although the latter was found in the majority (54%) of the isoniazid-resistant isolates investigated. This investigation presents empirical evidence that the central portion of the ahpC promoter is the most valuable genetic locus to complement katG codon 315 characterizations in order to increase the sensitivity of molecular tests for the prediction of isoniazid resistance.

Antitubercular Agents↗
PubMed1997

Geographic variation of the predictive values of genomic mutations associated with streptomycin resistance in Mycobacterium tuberculosis.

Specific mutations associated with resistance to streptomycin (SM) in Mycobacterium tuberculosis suggest themselves for its rapid prediction. However, as with any diagnostic test, their predictive values are dependent on their prevalences. In this report, SM resistance associated mutations in the rrs and rpsL genes of 25 SM resistant isolates from Germany and 25 SM resistant isolates from Sierra Leone were characterized and compared. Mutations in the rrs gene were infrequent in isolates from both localities (20% and 12%, respectively) and thus of limited predictive values. In contrast, rpsL mutations were found in 48% of the German isolates but only in 24% of the isolates from Sierra Leone. It is concluded that the predictive values of mutations in this gene may vary significantly with the origin of the samples under investigation.

Antibiotics, Antitubercular↗
PubMed1997

[Current aspects of leprosy].

About 95% of individuals who come in contact with M. leprae do not develop overt disease. The clinical form of the disease correlates with the T-cell mediated immune response of the host rather the direct damage caused by bacilli. We review the current aspects of epidemiology, transmission, bacteriology, clinical features, reactions, diagnosis, chemotherapy and treatment of reactions.

Animals↗
PubMed1997

Disequilibria in the distribution of rpoB alleles in rifampicin-resistant M. tuberculosis isolates from Germany and Sierra Leone.

The effectiveness of culture-independent resistance predictions by molecular techniques is dependent on the number and the frequency of accessible resistance-associated genomic mutations. We have characterized an rpoB gene region involved in rifampicin resistance in 49 Mycobacterium tuberculosis isolates resistant to rifampicin from Germany and Sierra Leone. The determined frequencies of mutations differed between both countries of origins as well as with respect to previously reported distributions of resistance mutations. It is concluded that at least for some isolates the acquisition of mutations leading to rifampicin resistance in clinical samples of M. tuberculosis is a non-random process which may lead to a geographical and temporal dependence of the sensitivities of molecular typing techniques for rifampicin resistance predictions.

Alleles↗
PubMed1997

Molecular analysis of katG gene mutations in strains of Mycobacterium tuberculosis complex from Africa.

A sample of 124 isoniazid (INH)-resistant and 88 susceptible strains of Mycobacterium tuberculosis complex from south, central, and west Africa was analyzed by direct sequence analysis and PCR-restriction fragment length polymorphism analysis of their catalase-peroxidase (katG) genes. Point mutations at codon 315 were found in the genomes of 64% of INH-resistant strains, but no complete deletions were identified. Mutations at codon 463 were independent of INH resistance and were linked to the geographic origins of the strains.

Africa↗
PubMed1997

Comparison of DNA fingerprint patterns of isolates of Mycobacterium africanum from east and west Africa.

Mycobacterium africanum is a pathogen found in tuberculosis patients in certain parts of Africa and is a member of the Mycobacterium tuberculosis complex. Biochemically, strains of M. africanum exhibit a high degree of variability, with some tendency to cluster according to their geographical origin. To investigate whether this phenotypic variability is reflected at the genetic level, we performed DNA fingerprint analysis of strains isolated from patients with pulmonary tuberculosis in Uganda and Sierra Leone. IS6110 DNA fingerprinting was carried out by the mixed-linker PCR method. A total of 138 strains of M. africanum were analyzed: 42 isolates from Uganda and 96 isolates from Sierra Leone. With few exceptions, the resulting DNA fingerprint patterns grouped together according to their country of origin. A striking lack of variability of DNA fingerprints was found for strains from Sierra Leone, where 70 of 96 isolates (61.5%) fell into clusters. The two largest clusters accounted for 41.7% of all isolates and differed by only one band, as confirmed by standard DNA fingerprinting. In contrast, only two clusters (7.1%) with two and three isolates, respectively, were found for M. africanum isolates collected in Uganda, and three of the DNA fingerprints contained fewer than seven bands. Strains of M. tuberculosis collected and processed during the same time period were highly variable in both countries. Our results support the concept of geographically defined subtypes of M. africanum. In addition, they demonstrate that natural geographic differences in the variability of IS6110 DNA fingerprints within the M. tuberculosis complex must be considered if this technique is used for epidemiologic studies.

Africa, Eastern↗
PubMed1997

Usefulness of Mycobacterium tuberculosis genomic mutations in the genes katG and inhA for the prediction of isoniazid resistance.

SETTING: Mutations in two genes of Mycobacterium tuberculosis, inhA and katG, are known to correlate with resistance to isoniazid (INH). OBJECTIVE: To determine which mutation or mutations are the most predictive for INH resistance and the most frequent ones in such isolates. Further, to propose a simple and generally applicable method for their detection. DESIGN: Codons 94 and 95 in the inhA gene and codons 315 and 463 in the katG gene were characterized in 50 INH-resistant and 12 INH-sensitive isolates from Germany and Sierra Leone. RESULTS: Mutations in codon 315 of the katG gene were detected in 27 of the INH-resistant and none of the INH-sensitive isolates. All mutations in this codon altered an AciI restriction enzyme site. No mutations were found in the investigated codons of the inhA gene. CONCLUSION: We propose that most INH resistances can be rapidly predicted by a simple AciI restriction enzyme digest of a polymerase chain reaction (PCR)-amplified katG fragment.

Antitubercular Agents↗