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W H Haas

Publications and source records attributed to W H Haas.

At least 19 recordsLinked to original sources
PubMed1999

Transmission dynamics of tuberculosis in a high-incidence country: prospective analysis by PCR DNA fingerprinting.

We have prospectively analyzed the DNA fingerprints of Mycobacterium tuberculosis strains from a random sample of patients with newly diagnosed tuberculosis in Windhoek, Namibia. Strains from 263 smear-positive patients in whom tuberculosis was diagnosed during 1 year were evaluated, and the results were correlated with selected epidemiological and clinical data. A total of 163 different IS6110 fingerprint patterns were observed among the 263 isolates. Isolates from a high percentage of patients (47%) were found in 29 separate clusters, with a cluster defined as isolates with 100% matching patterns. The largest cluster included isolates from 39 patients. One predominant strain of M. tuberculosis caused 15% of cases of smear-positive pulmonary tuberculosis in Windhoek. That strain was also prevalent in the north of the country, suggesting that in contrast to other African countries with isolates with high levels of diversity in their DNA fingerprint patterns, only a restricted number of different strains significantly contribute to the tuberculosis problem in Namibia.

Adult↗
PubMed1999

Identification of contaminating fungal DNA sequences in Zymolyase.

When different preparations of Zymolyase were included in the pretreatment protocol of a panfungal PCR assay using a primer system for the 18S rRNA gene, an amplification product occurred in negative controls. The amplified fragment showed 100.0% sequence identity to the Saccharomyces sensu stricto complex and Kluyveromyces lodderae. Lyticase, lysing enzymes, and proteinase K appeared to be free from fungal DNA.

DNA Primers↗
PubMed1999

Comparison of methods based on different molecular epidemiological markers for typing of Mycobacterium tuberculosis complex strains: interlaboratory study of discriminatory power and reproducibility.

In this study, the currently known typing methods for Mycobacterium tuberculosis isolates were evaluated with regard to reproducibility, discrimination, and specificity. Therefore, 90 M. tuberculosis complex strains, originating from 38 countries, were tested in five restriction fragment length polymorphism (RFLP) typing methods and in seven PCR-based assays. In all methods, one or more repetitive DNA elements were targeted. The strain typing and the DNA fingerprint analysis were performed in the laboratory most experienced in the respective method. To examine intralaboratory reproducibility, blinded duplicate samples were included. The specificities of the various methods were tested by inclusion of 10 non-M. tuberculosis complex strains. All five RFLP typing methods were highly reproducible. The reliability of the PCR-based methods was highest for the mixed-linker PCR, followed by variable numbers of tandem repeat (VNTR) typing and spoligotyping. In contrast, the double repetitive element PCR (DRE-PCR), IS6110 inverse PCR, IS6110 ampliprinting, and arbitrarily primed PCR (APPCR) typing were found to be poorly reproducible. The 90 strains were best discriminated by IS6110 RFLP typing, yielding 84 different banding patterns, followed by mixed-linker PCR (81 patterns), APPCR (71 patterns), RFLP using the polymorphic GC-rich sequence as a probe (70 patterns), DRE-PCR (63 patterns), spoligotyping (61 patterns), and VNTR typing (56 patterns). We conclude that for epidemiological investigations, strain differentiation by IS6110 RFLP or mixed-linker PCR are the methods of choice. A strong association was found between the results of different genetic markers, indicating a clonal population structure of M. tuberculosis strains. Several separate genotype families within the M. tuberculosis complex could be recognized on the basis of the genetic markers used.

Bacterial Typing Techniques↗
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↗
PubMed1998

Preoperative diagnosis of Mycobacterium avium lymphadenitis in two immunocompetent children by polymerase chain reaction of gastric aspirates.

BACKGROUND: Analysis of gastric aspirates is a routine procedure for detection of Mycobacterium tuberculosis in pediatric pulmonary tuberculosis. However, identification of nontuberculous mycobacteria in gastric aspirates of immunocompetent children is not thought to be clinically significant. METHODS: A PCR method was devised for the detection of M. avium in clinical specimens. The method is based on the amplification of a M. avium-specific DNA fragment present in the 3'-end of the repetitive element IS1245. Surgically removed lymphatic tissue was analyzed prospectively by microscopy, culture and PCR in 13 children admitted to our hospital with suspected mycobacterial lymphadenitis. In 4 of these children 1 to 4 gastric aspirates were obtained before surgical treatment and submitted to the same analysis. RESULTS: We report the detection of M. avium in the gastric aspirates of two children with cervical lymphadenitis before surgical intervention by a novel PCR method. The subsequently surgically removed lymph nodes were also positive by PCR and culture. In one child cultures of both sources grew M. avium. The isolates could be identified as the same strain by DNA fingerprinting. The PCR assay was almost twice as sensitive as culture in detecting M. avium. CONCLUSIONS: Our findings suggest the possibility for noninvasive diagnosis of cervical lymphadenitis caused by nontuberculous mycobacteria before surgery. In addition detection of M. avium in gastric aspirates without evidence of fistula formation provides new insights into the pathogenesis of mycobacterial infection and disease in immunocompetent children.

DNA Fingerprinting↗
PubMed1998

DNA fingerprinting of Mycobacterium tuberculosis complex culture isolates collected in Brazil and spotted onto filter paper.

The usefulness of filter paper for preservation of bacterial cells was shown by mixed-linker DNA fingerprint analysis of Mycobacterium tuberculosis isolates from 77 Brazilian patients. DNA fingerprints of samples spotted onto filter paper and conventional culture material were identical. Thus, filter paper specimens analyzed by an amplification-based typing method provide a new resource for epidemiological studies of infectious diseases.

Brazil↗
PubMed1998

[Molecular biology methods in epidemiology of tuberculosis].

The spread of tuberculosis often remains undetected and development of disease may occur years after the primary infection. However, tracing chains of transmission is an important task for prevention of new cases, especially for multi-drug-resistant tuberculosis. Today, molecular typing methods have become an important tool for identification and confirmation of epidemiological links between tuberculosis patients in an outbreak situation. Differentiation between strains of Mycobacterium tuberculosis also allows to decide between reactivation because of treatment failure and superinfection. A growing number of typing methods have been developed that differ mainly in their reproducibility and the ability to differentiate between isolates closely related at the molecular level. Based on further standardisation and automation, molecular typing techniques can provide pertinent information for tuberculosis control.

Contact Tracing↗
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

A new agent of mycobacterial lymphadenitis in children: Mycobacterium heidelbergense sp. nov.

Nontuberculous mycobacterial lymphadenitis presents an increasing clinical problem in immunocompetent young children. A slowly growing, nonphotochromogenic mycobacterium was recovered twice (isolates 2553/91 and 2554/91) from the lymphatic tissue of a child with recurrent cervical lymphadenitis. It could be differentiated biochemically from described Mycobacterium species, although it most closely resembled Mycobacterium malmoense by thin-layer chromatography and high-performance liquid chromatography of mycolic acids. A striking characteristic of the isolate was its high degree of susceptibility to antituberculous drugs in vitro, including isoniazid. Direct determination of the 16S rRNA gene sequence revealed a unique sequence and positioned the strain phylogenetically on a branch separate from M. malmoense within a group of slowly growing mycobacteria that show a high degree of similarity to M. simiae at the 16S rRNA gene level. Despite 99.6% sequence identity with M. simiae at the 16S rRNA gene level, DNA-DNA hybridization studies (hydroxyapatite method) demonstrated DNA relatedness of less than 40%. We conclude that this organism is a new species for which we propose the name M. heidelbergense. A culture of the type strain, strain 2554/91, has been deposited in the American Type Culture Collection as strain ATCC 51253.

Antitubercular Agents↗
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↗
PubMed1996

DNA fingerprinting by infrequent-restriction-site amplification.

Identification of bacterial strains by DNA fingerprinting facilitates epidemiologic studies and improves disease control. For some species of organisms, no typing method is available; for others, typing methods are tedious. We developed a method of amplifying DNA sequences flanking infrequent restriction sites by PCR and used the method to produce strain-specific electrophoretic patterns from crude bacterial lysates. This method of fingerprinting is rapid, sensitive, and widely applicable. Identical enzymes, adaptors, primers, and PCR conditions were used to characterize 32 Mycobacterium avium-M. intracellulare isolates, 4 Pseudomonas aeruginosa isolates, and 4 Staphylococcus aureus isolates.

DNA Fingerprinting↗
PubMed1996

Automated DNA fingerprinting analysis of Mycobacterium tuberculosis using fluorescent detection of PCR products.

DNA fingerprints of Mycobacterium tuberculosis are produced by restriction fragment length polymorphism analysis of the insertion element IS6110. We modified a PCR-based subtyping method, mixed-linker PCR with fluorescent-labeled IS6110-specific oligonucleotides, to demonstrate rapid, automated, and unattended electrophoretic analysis. Variation in band sizing (normally occurring with fragment mobility), an artifact of lane-to-lane and gel-to-gel differences, was controlled with an internal lane standard, resulting in accurate and precise DNA sizing. By using this method, fingerprint analysis can be performed using actual fragment length rather than estimated position analysis.

Base Sequence↗
PubMed1996

Hearing and the development of language and speech.

The criticality of hearing is discussed in relation to language and speech development in children. The fundamentals for such development, the significant milestones in normal language and speech acquisition, and a delineation of the deleterious effects of significant hearing loss on the development of expressive and receptive oral communication are presented.

Child↗
PubMed1995

Nosocomial transmission of Mycobacterium tuberculosis: role of health care workers in outbreak propagation.

To investigate an outbreak of tuberculosis (TB) among health care workers (HCWs) at a county hospital, all patients with culture-confirmed TB on wards A and B and all HCWs working at least one shift on these wards from January 1991 through March 1992 were studied. Tuberculin skin test conversions occurred in 30% (ward A) and 48% (ward B) of HCWs; 8 developed active TB. Workers exposed for at least one shift to workers or patients with active TB were more likely to have skin test conversion than were workers who were not exposed (ward A exposure relative risk [RR] for workers = 2.8, P = .005, and for patients = 2.2, P > .5; ward B exposure RR for workers = 2.8, P < .001, and for patients = 5.3, P < .001). Underlying conditions and performing charting activities in the nurses' work room were associated with progression to active TB among infected workers. Transmission was facilitated by delays of < or = 2.5 months in treatment of workers with skin test conversion or TB symptoms.

Cross Infection↗
PubMed1993

Amenity retirement migration process: a model and preliminary evidence.

A heuristic model of the retirement migration process was developed and explored using survey data from 586 migrants to western North Carolina. Five distinct subgroups were investigated: those who went from part- to full-time residency; those who thought about not migrating; individuals who migrated, remained in the labor force for a short period, and then retired; people who made two retirement migrations; and destination-selecting versus destination-specific migrants.

Adult↗
PubMed1993

Cervical lymphadenitis in a child caused by a previously unknown mycobacterium.

Acid-fast bacilli were isolated from lymph nodes of an immunocompetent child presenting with unilateral cervical lymphadenitis. The slowly growing mycobacterium could not be identified by traditional methods. Direct sequencing of the enzymatically amplified 16S rRNA gene revealed a unique sequence belonging to a previously unrecognized mycobacterium. Direct 16S rDNA sequencing enables definitive identification of mycobacterial isolates. The method is useful for rapid recognition of previously unrecognized pathogens.

Base Sequence↗