[Diffusion-weighted imaging characteristics of uterine leiomyomas with different pathological subtypes at 3.0 T]

OBJECTIVE

To investigate the imaging features of uterine leiomyomas with different pathological subtypes on DWI.

METHODS

Clinical records and MR images of pathologically confirmed uterine leiomyomas were retrospectively collected from the Second Affiliated Hospital of Wenzhou Medical University from June 2012 to April 2015. A total of 60 uterine leiomyomas were found and evaluated.All the patients were divided into three groups according to different pathological types, which included 17 cases of cellular leiomyomas, 10 cases of degenerated leiomyomas and 33 cases of ordinary leiomyomas.The DWI signal and ADC values in cellular portion of the lesions and adjacent normal myometrium (the control group) were measured.

RESULTS

(1) Most cellular leiomyomas showed hyperintensity on DWI (15/17), while degenerated leiomyomas manifested hypointensity, isointensity or hyperintensity signal on DWI, and most ordinary leiomyomas displayed isointensity signal on DWI (57.6%, 19/33). (2) The ADC values of cellular leiomyomas, degenerated leiomyomas and ordinary leiomyomas were (1.01±0.14)×10(-3) mm(2)/s, (1.73±0.49)×10(-3) mm(2)/s and (1.38±0.22)×10(-3) mm(2)/s respectively.The ADC values of adjacent normal myometrium (the control group) were (1.35±0.16)×10(-3) mm(2)/s.There were no significant statistical differences in the ADC values between ordinary leiomyomas and adjacent normal myometrium (P=0.623). There were significant statistical differences in the ADC values among other groups(all P<0.05). (3)The ROC curve showed that the diagnostic threshold for cellular leiomyomas was 1.11×10(-3) mm(2)/s, the sensitivity and specificity were 88.2%and 93.0% respectively.

CONCLUSION

The signal intensity on DWI and the ADC values are different in uterine leiomyomas with different pathological subtypes.Combination of these two parameters in clinical practice may be helpful to reflect the histopathological characteristics of uterine leiomyomas.

Identification and genetic mapping of the putative Thinopyrum intermedium-derived dominant powdery mildew resistance gene PmL962 on wheat chromosome arm 2BS

Powdery resistance putatively derived from Thinopyrum intermedium in the wheat line L962 is controlled by a single dominant gene designated PmL962 and mapped to chromosome arm 2BS. Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a destructive disease affecting the production of wheat (Triticum aestivum). Powdery mildew resistance was putatively transferred from Thinopyrum intermedium to the common wheat line L962, which conferred resistance to multiple Chinese Bgt isolates. Genetic analysis of the powdery mildew response was conducted by crossing the resistant line L962 with the susceptible line L983. Disease assessments of the F1, F2, and F2:3 populations from the cross L983/L962 indicated that resistance was controlled by a single dominant gene. A total of 373 F2:3 lines and 781 pairs of genomic simple sequence repeat (SSR) primers were employed to determine the chromosomal location of the resistance gene. The gene was linked to four publicly available and recently developed wheat genomic SSR markers and seven EST-STS markers. The resistance gene was mapped to chromosome arm 2BS based on the locations of the linked markers. Pedigree, molecular marker and resistance response data indicated that the powdery mildew resistance gene in L962 is novel. It was temporarily designated PmL962. It is flanked by Xwmc314 and BE443737at genetic distances of 2.09 and 3.74 cM, respectively, and located in a 20.77 cM interval that is co-linear with a 269.4 kb genomic region on chromosome 5 in Brachypodium distachyon and a 223.5 kb genomic region on rice (Oryza sativa) chromosome 4. The markers that are closely linked to this gene have potential applications in marker-assisted breeding.

A novel quantitative trait locus for Fusarium head blight resistance in chromosome 7A of wheat

A Chinese Spring-Sumai 3 chromosome 7A disomic substitution line (CS-Sumai 3-7ADSL) was reported to have a high level of Fusarium head blight (FHB) resistance for symptom spread within a spike (Type II) and low deoxynivalenol accumulation in infected kernels (Type III), but a quantitative trait locus (QTL) on chromosome 7A has never been identified from this source. To characterize QTL on chromosome 7A, we developed 191 7A chromosome recombinant inbred lines (7ACRIL) from a cross between Chinese Spring and CS-Sumai 3-7ADSL and evaluated both types of resistance in three greenhouse experiments. Two major QTL with Sumai 3 origin, conditioning both Type II and III resistance, were mapped in the short arm of chromosomes 3B (3BS) and near the centromere of chromosome 7A (7AC). The 3BS QTL corresponds to previously reported Fhb1 from Sumai 3, whereas 7AC QTL, designated as Fhb7AC, is a novel QTL identified from CS-Sumai 3-7ADSL in this study. Fhb7AC explains 22% phenotypic variation for Type II and 24% for Type III resistance. Marker Xwmc17 is the closest marker to Fhb7AC for both types of resistance. Fhb1 and Fhb7AC were additive, and together explained 56% variation for Type II and 41% for Type III resistance and resulted in 66% reduction in FHB severity and 84% reduction in deoxynivalenol (DON) content. Haplotype analysis of Sumai 3 parents revealed that Fhb7AC originated from Funo, an Italian cultivar. Fhb7AC has the potential to be used in improving wheat cultivars for both types of resistance.

Diverse origins of aluminum-resistance sources in wheat

Aluminum (Al) toxicity is a major constraint for wheat production in acidic soils. Wheat producers now routinely use Al-resistant cultivars as one cost-effective means to reduce risks associated with acidic soils. To date, diverse Al-resistant materials have been identified, but their genetic relationship has not been well characterized. A total of 57 wheat accessions, including the majority of the parents of Al-resistant accessions we identified in a previous study, were evaluated for Al resistance and analyzed with 49 simple sequence repeat (SSR) markers and 4 markers for Al-activated malate transporter (ALMT1). Pedigree and principle coordinate analysis (PCA) both separated Al-resistant accessions into four groups labeled according to common ancestry or geographical origin: US-Fultz, Polyssu, Mexican and Chinese. Al resistance in the four groups may have three independent origins given their distinct geographic origins and gene pools. Fultz originated in the USA as a major ancestor to soft red winter wheat, Polyssu originated in Brazil as a major source of Al resistance used in most genetic studies worldwide, and the Chinese group originated in China. Based on ALMT1 marker haplotypes, the Al resistance in the Polyssu and Mexico groups was likely derived from Polyssu, while most Al-resistant cultivars developed in the USA most likely inherited most of Al resistance from Fultz. Fultz was released about 50 years earlier than Polyssu. Norin 10 likely played a pivotal role in passing Al-resistant gene(s) from Fultz to better adapted, semi-dwarf wheat cultivars developed in the USA. Further characterization of Al resistance in the three different sources could reveal multiple Al-resistant mechanisms in wheat.

[Single-strand conformational polymorphism markers associated with a major QTL for fusarium head blight resistance in wheat]

A major quantitative trait locus (QTL) associated with resistance to Fusarium head blight (FHB) was identified on chromosome 3BS between simple sequence repeat (SSR) markers Xgwm389 and Xgwm493 in wheat 'Ning 7840', a derivative from 'Sumai 3'. However, the marker density of SSR in the QTL region was much lower than that required for marker-assisted selection (MAS) and map-based cloning. The objective of this study was to exploit new markers to increase marker density in this QTL region by using single-strand conformational polymorphism (SSCP) markers developed from wheat expressed sequence tags (ESTs) on 3BS bin 8-0.78-1.0. Sixty-nine out of 85 SSCP primer pairs amplified PCR (polymerase chain reaction) products from the genomic DNA of 'Chinese Spring'. Thirty-four primer pairs amplified PCR products that could form clear ssDNA (single strand DNA) bands through denaturation treatment. Ten SSCP markers had polymorphisms between 'Ning 7840' and 'Clark'. Five of the ten polymorphic SSCP markers were located on chromosome 3B by nulli-tetrasomic analysis. Three SSCP markers (Xsscp6, Xsscp20, and Xsscp21) were mapped into the region between Xgwm493 and Xgwm533, and possessed higher coefficient of determination (R2) than Xgwm493 and Xgwm533. The SSCP markers, Xsscp6, Xsscp20, and Xsscp21, can be used for map-based cloning of the QTL and for marker-assisted selection in FHB resistance breeding.

Quantitative trait loci for aluminum resistance in Chinese wheat landrace FSW

Aluminum (Al) toxicity is a major constraint for wheat production in acid soils worldwide. Chinese landrace FSW demonstrates a high level of Al resistance. A population of recombinant inbred lines (RILs) was developed from a cross between FSW and an Al-sensitive Chinese line, ND35, using single seed descent, to map quantitative trait loci (QTLs) for Al resistance. Wheat reaction to Al stress was measured by net root growth (NRG) in a nutrient solution culture containing Al(3+) and hematoxylin staining score (HSS) of root after Al stress. After 1,437 simple sequence repeats (SSRs) were screened using bulk segregant analysis, three QTLs were identified to control Al resistance in FSW. One major QTL (Qalt.pser-4DL) was mapped on chromosome 4DL that co-segregated with Xups4, a marker for the promoter of the Al-activated malate transporter (ALMT1) gene. The other two QTLs (Qalt.pser-3BL, Qalt.pser-2A) were located on chromosomes 3BL and 2A, respectively. Together, the three QTLs accounted for up to 81.9% of the phenotypic variation for HSS and 78.3% of the variation for NRG. The physical positions of flanking markers for Qalt.pser-4DL and Qalt.pser-3BL were determined by analyzing these markers in corresponding nulli-tetrasomic, ditelosomic, and 3BL deletion lines of Chinese Spring. Qalt.pser-3BL is a novel QTL with a major effect on Al resistance discovered in this study. The two major QTLs on 4DL and 3BL demonstrated an additive effect. The SSR markers closely linked to the QTLs have potential to be used for marker-assisted selection (MAS) to improve Al resistance of wheat cultivars in breeding programs.

Deletion of a Chromosome Arm Altered Wheat Resistance to Fusarium Head Blight and Deoxynivalenol Accumulation in Chinese Spring

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe, is an important disease of wheat worldwide. Production of deoxynivalenol (DON) in infected wheat grain by F. graminearum is a major safety concern when considering use of the grain as feed for livestock or for human consumption. Determining chromosome locations of FHB-related genes may facilitate enhancement of wheat resistance to FHB and DON accumulation. In this study, a set of 30 ditelosomic lines derived from Chinese Spring, a moderately FHB-resistant landrace from China, were evaluated for proportion of scabbed spikelets per inoculated spike in the greenhouse and for DON contamination in harvested grain over 2 years. Significant variation in the proportion of scabbed spikelets was observed among ditelosomic lines, ranging from 13 to 95%. Seven ditelosomic lines exhibited a greater proportion of scabbed spikelets and three of these also had greater DON content than Chinese Spring (P = 0.01), suggesting that those missing chromosome arms may carry genes that contribute to resistance to FHB. Six ditelosomic lines had a reduction in proportion of scabbed spikelets, suggesting that susceptibility factors or resistance suppressors may be on these missing chromosomal arms. Selection for low proportion of scabbed spikelets in general will select for low DON content.

An Internet-based surveillance system for tuberculosis in Korea

SETTING

The Korea Tuberculosis Surveillance (KTBS) network includes 248 health centres throughout the country, as well as other public and private health institutions.

OBJECTIVE

To develop a web-based surveillance system for tuberculosis (TB) and to monitor implementation of the National TB Control Programme (NTP) on an ongoing basis.

DESIGN

A TB notification form was developed with new case definitions, and standardised to obtain uniform essential information of the cases with ease and speed. Data collection, compilation, analysis and feedback were made available at every level of the health authority via the Internet without restrictions of time and space.

RESULTS

The Internet-based surveillance system was successfully implemented across the country, providing real-time national figures of TB using different variables-patient, time, area, site and type of disease--and facilitating on-line evaluation of NTP implementation.

CONCLUSION

The web-based surveillance system has been well established within the existing health infrastructure, providing real-time figures on the TB burden. However, it requires continued improvement of the quality of information and of case reporting activities.

Marker-assisted characterization of Asian wheat lines for resistance to Fusarium head blight

The major quantitative trait locus (QTL) on 3BS from Sumai 3 and its derivatives has been used as a major source of resistance to Fusarium head blight (FHB) worldwide, but resistance genes from other sources are necessary to avoid complete dependence on a single source of resistance. Fifty-nine Asian wheat landraces and cultivars differing in the levels of FHB resistance were evaluated for type II FHB resistance and for genetic diversity on the basis of amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSRs). Genetic relationships among these wheat accessions estimated by cluster analysis of molecular marker data were consistent with their geographic distribution and pedigrees. Chinese resistant landraces had broader genetic diversity than that of accessions from southwestern Japan. The haplotype pattern of the SSR markers that linked to FHB resistance quantitative trait loci (QTLs) on chromosomes 3BS, 5AS and 6BS of Sumai 3 suggested that only a few lines derived from Sumai 3 may carry all the putative QTLs from Sumai 3. About half of the accessions might have one or two FHB resistance QTLs from Sumai 3. Some accessions with a high level of resistance, may carry different FHB resistance loci or alleles from those in Sumai 3, and are worth further investigation. SSR data also clearly suggested that FHB resistance QTLs on 3BS, 5AS, and 6BS of Sumai 3 were derived from Chinese landrace Taiwan Xiaomai.

Recovery rate of NTM from AFB smear-positive sputum specimens at a medical centre in South Korea

OBJECTIVE

To investigate the recovery rate of non-tuberculous mycobacteria (NTM) from acid-fast bacilli (AFB) smear-positive sputum specimens at a tertiary care medical centre in South Korea with a high pulmonary tuberculosis (PTB) burden.

DESIGN

Retrospective analysis of data from AFB smear- and culture-positive sputum specimens collected between January 1998 and December 2001.

RESULTS

Over 4 years, 1328 sputum specimens collected from 616 patients were AFB smear- and culture-positive. NTM were recovered from 9.1% (121/1328) of the smear-positive sputum specimens, and from 8.1% (50/616) of patients with smear-positive sputum. NTM were isolated at least twice in 94% (47/50) of the patients from whom NTM was recovered. The most common organism found was Mycobacterium avium complex, followed by M. abscessus.

CONCLUSION

These results suggest that a substantial proportion of patients at a tertiary care medical centre in South Korea with AFB smear-positive sputum specimens may have NTM lung disease rather than PTB.

AFLP analysis of Cynodon dactylon (L.) Pers. var. dactylon genetic variation

Cynodon dactylon (L.) Pers. var. dactylon (common bermudagrass) is geographically widely distributed between about lat 45°N and lat 45°S, penetrating to about lat 53°N in Europe. The extensive variation of morphological and adaptive characteristics of the taxon is substantially documented, but information is lacking on DNA molecular variation in geographically disparate forms. Accordingly, this study was conducted to assess molecular genetic variation and genetic relatedness among 28 C. dactylon var. dactylon accessions originating from 11 countries on 4 continents (Africa, Asia, Australia, and Europe). A fluorescence-labeled amplified fragment length polymorphism (AFLP) DNA profiling method was used to detect the genetic diversity and relatedness. On the basis of 443 polymorphic AFLP fragments from 8 primer combinations, the accessions were grouped into clusters and subclusters associating with their geographic origins. Genetic similarity coefficients (SC) for the 28 accessions ranged from 0.53 to 0.98. Accessions originating from Africa, Australia, Asia, and Europe formed major groupings as indicated by cluster and principal coordinate analysis. Accessions from Australia and Asia, though separately clustered, were relatively closely related and most distantly related to accessions of European origin. African accessions formed two distant clusters and had the greatest variation in genetic relatedness relative to accessions from other geographic regions. Sampling the full extent of genetic variation in C. dactylon var. dactylon would require extensive germplasm collection in the major geographic regions of its distributional range.Key words: common bermudagrass, AFLP marker, genetic relatedness.

Effect of individual Sumai 3 chromosomes on resistance to scab spread within spikes and deoxynivalenol accumulation within kernels in wheat

Two sets of substitution lines were developed by crossing individual monosomic lines of Chinese Spring (recipient) with scab (Fusarium graminearum) resistant cultivar Sumai 3 (donor) and then using the monosomics as the recurrent male parent for four backcrosses (without selfing after each backcross). The disomic substitution lines were separated from selfed BC4F2 plants. Chromosome specific SSR markers were analyzed for polymorphism between Sumai 3 and Chinese Spring. Polymorphic markers were used to identify substitution lines for specific chromosomes. Based on the specific SSR markers, chromosome substitutions occurred in thirty-six lines, and six lines segregated alleles from the two parents or were homozygous for the allele from Chinese Spring. These substitution lines were used to evaluate Type II (spread within the head) and Type V (deoxynivalenol accumulation within kernels) scab resistance. The objective was to use the substitution lines to evaluate the effect of individual chromosomes of Sumai 3 on Type 11 and Type V scab resistance in the greenhouse. Significant differences in Type II scab resistance and deoxynivalenol (DON) levels among different Chinese Spring (Sumai 3) substitution lines were detected. Positive chromosome substitution effects on Type II scab resistance were found on chromosomes 2B, 3B. 6B, and 7A from Sumai 3. Chromosomes 3B and 7A also reduced DON accumulation within the kernels, while chromosomes IB, 2D, and 4D from Sumai 3 increased DON concentration. Chromosome 7A from Sumai 3 had the largest effect on resistance to scab spread and DON accumulation. Additional research is in progress on the scab resistance conferred by chromosome 7A.

The treatment of tuberculosis in South Korea

South Korea's complex system of tuberculosis control has never been fully described. The prevalence of tuberculosis has dropped dramatically since 1965, partly because of farsighted governmental policy that provided low-cost, accessible tuberculosis treatment to the entire population. Within the tuberculosis control system, public and private sector entities provide a wide variety of treatment options. The National Tuberculosis Program focuses on improving cure rates for new cases, while the private sector has taken more of a role in the treatment of drug-resistant tuberculosis and other types of complicated cases. There has been a decrease in drug-resistant tuberculosis since 1980 for multiple reasons, including increased cure rates from the introduction of rifampin-based regimens, improved nutrition and living standards, and the treatment of drug-resistant cases in the private sector. Multidrug-resistant tuberculosis, however, still poses a significant threat to public health. The limited outcomes data that exist in South Korea for multidrug-resistant tuberculosis treatment suggest that cure rates are low and failure and abandonment rates are high. New public health measures are needed to improve the control of multidrug-resistant tuberculosis.

[Analysis of major QTL for Fusarium head blight resistance on the short arm of chromosome 3B in wheat]

Three recombinant inbred populations, Ning894037/Alondra, Wangshuibai/Alondra and Sumai3/Alondra, were analyzed for QTLs associated with Fusarium head blight resistance by interval mapping and composite interval mapping in this study. The result showed that the major QTLs were detected on the short arm of chromosome 3B of all three resistant parents using the data of FHB resistance evaluated in greenhouse or field. They were located in the interval of 5.0 cM between BARC133 and Xgwm493 in Ning894037, 11.5 cM between BARC147 and Xgwm493 in Wangshuibai, and 13.0 cM between Xgwm533a and Xgwm493 in Sumai3, explaining 42.8%, 15.1% and 10.6% of the phenotypic variance for Type II resistance (spread within the spike), respectively. Some of the SSR markers linking to the major QTLs tightly can be used directly in marker-assisted breeding to improve FHB resistance in wheat.

Deoxynivalenol-nonproducing fusarium graminearum causes initial infection, but does not cause disease spread in wheat spikes

Fusarium graminearum is a major pathogen that causes fusarium head blight (FHB) in wheat and produces deoxynivalenol (DON) in infected grain. In previous studies, the trichodiene synthase gene (Tri5) in the fungal strain GZ3639 was disrupted to produce the DON-nonproducing strain GZT40. In this report, the virulence of strains GZ3639 and GZT40 was tested on wheat cultivars with various resistance levels by using methods of spray inoculation and injection inoculation with fungal conidia. Under field and greenhouse conditions, strain GZ3639 produced significantly more disease symptoms and reduced more yield than strain GZT40 in all wheat cultivars tested. Conidia of strain GZT40 germinated and infected inoculated spikelets, but disease symptoms were limited to inoculated spikelets without spread to uninoculated spikelets. When strain GZT40 was inoculated using the spray method, multiple initial infection sites in a spike resulted in higher levels of disease symptoms than in spikes inoculated by a single injection. Greenhouse tests confirmed that strain GZT40 did not produce DON in the infected kernels following either inoculation method. The results confirm that DON production plays a significant role in the spread of FHB within a spike, and are the first report that DON production is not necessary for initial infection by the fungus.

Cross-resistance between rifampicin and KRM-1648 is associated with specific rpoB alleles in Mycobacterium tuberculosis

KRM-1648 resistant Mycobacterium tuberculosis strains were identified from a collection of rifampicin-resistant strains. Several strains had novel rpoB gene mutations in codons 512, 529 and 533 of the rpoB gene. The strains with mutations in codons 526 or 531, major mutation sites in rifampicin-resistant M. tuberculosis, were resistant to KRM-1648. Also, the strains with other mutations in the rpoB gene that were initially susceptible to KRM-1648 were prone to developing KRM-1648 resistance after further mutation. Thus, KRM-1648 is unlikely to be useful for the treatment of rifampicin-resistant tuberculosis.

Long-term results of Charnley low-friction arthroplasty in tuberculosis of the hip

We reported 8 to 13 years of follow-up of cases of tuberculosis of the hip previously. Now we report on 60 cases of hip tuberculosis treated with total hip arthroplasty. The results have been reasonably acceptable, with the longest follow-up >28 years. Prosthetic life was limited to at most 20 years in our longest cases mainly because of loss of fixation of the acetabular component. There were recurrences of tuberculosis in 5 hips. We confirmed that antituberculous chemotherapy is crucial in total hip arthroplasty reconstruction. Detection of Mycobacterium tuberculosis using polymerase chain reaction may provide rapid diagnosis and follow-up for treatment response.

Transmission of Mycobacterium tuberculosis among high school students in Korea

SETTING

Screening of pulmonary tuberculosis (PTB) patients from high school students by chest radiography and sputum examination.

OBJECTIVE

To investigate transmission of Mycobacterium tuberculosis among high school students.

DESIGN

The restriction fragment length polymorphism (RFLP) profiles of M. tuberculosis isolated from PTB patients of high school students were analysed.

RESULTS

Clustering cases were found in PTB patients screened among high school students. During this study, a single strain with a particular RFLP profile was found most frequently. This particular strain was also the one that was found to be most prevalent among Korean clinical isolates of M. tuberculosis during a nationwide TB prevalence survey previously done in 1995. This strain seems to be the most widely distributed one in Korea, and has thus been designated K1. In addition, by close examination of the RFLP profiles, it was also found that there existed 34 isolates that had RFLP profiles that were similar to the K1 strain. Therefore, K1 and K1-related strains (18.4% of strains, designated as the K family) seem to comprise the most dominant M. tuberculosis strains present in Korea.

CONCLUSION

Clustering cases were found in PTB patients screened among high school students in Korea. The K family was found to be most prevalent among the clinical isolates of M. tuberculosis found.

Differentiation of mycobacterial species by PCR-restriction analysis of DNA (342 base pairs) of the RNA polymerase gene (rpoB)

PCR amplification-restriction analysis (PRA) of rpoB DNA (342 bp), which comprises the Rif(r) region, was used for the differential identification of 49 mycobacteria. The DNA had been used previously for the identification of mycobacterial species by comparative sequence analysis (B. J. Kim et al., J. Clin. Microbiol. 37:1714-1720, 1999). Digestion with four restriction enzymes (HaeIII, HindII, MvaI, and AccII), which were selected on the basis of rpoB DNA sequences, generated distinctive PRA patterns that allowed not only the reference strains but also the clinical isolates of mycobacteria to be distinguished. Both rapidly and slowly growing mycobacteria were distinctly differentiated by HaeIII digestion of the amplified rpoB DNA. By HindII digestion the Mycobacterium tuberculosis complex was distinguished from the other mycobacteria. Furthermore, six subspecies of Mycobacterium kansasii (subspecies I to VI) as well as the closely related Mycobacterium gastri, and other closely related species, were distinguished by simultaneous digestion of MvaI and AccII. According to the rpoB PRA scheme, 240 strains of clinical isolates could be identified. It was also possible to detect and identify M. tuberculosis directly from sputa and bronchoalveolar lavage specimens. These results suggest that PRA of rpoB DNA is a simple and feasible method not only for the differentiation of culture isolates but also for the rapid detection and identification of pathogenic mycobacteria in primary clinical specimens.

Detection of rifampin-resistant Mycobacterium tuberculosis in sputa by nested PCR-linked single-strand conformation polymorphism and DNA sequencing

Either PCR-mediated single strand conformation polymorphism (SSCP) analysis or DNA sequencing of rpoB DNA (157 bp) can be used as a rapid screening method for the detection of mutations related to the rifampin resistance of Mycobacterium tuberculosis. However, due to the nonspecific amplification of rpoB DNA from nontuberculous mycobacteria these methods cannot be directly applied to clinical specimens such as sputa. We developed a nested PCR method that can specifically amplify the rpoB DNA of M. tuberculosis on the basis of rpoB DNA sequences of 44 mycobacteria. Nested PCR-linked SSCP analysis and the DNA sequencing method were applied directly in order to detect M. tuberculosis and determine its rifampin susceptibility in 56 sputa. The results obtained by nested PCR-SSCP and DNA sequencing were concordant with those of conventional drug susceptibility testing and DNA sequencing performed with culture isolates.

Incidence of pulmonary tuberculosis in Korean civil servants: second study, 1992-1994

SETTING

A survey based on biennial medical examinations for civil servants, including school teachers.

OBJECTIVE

To estimate the incidence of pulmonary tuberculosis (PTB) for the general population from a sample survey, and to compare it with the previous results from 1988-1990.

DESIGN

A retrospective follow-up study which started in April 1996 and ended in December 1997. Development of PTB among all South Korean civil servants who were tuberculosis-free in the 1992 biennial medical examination was followed up to the 1994 medical examination. The survey was based on newly-developed cases by 1) the findings of the biennial medical examination, 2) scrutiny of the medical records of all those claiming health insurance for tuberculosis, and 3) checking of the TB registers in all health centres during the period. Civil servants constituted 2.6% of the Korean population aged 20 to 64.

RESULTS

Of 958137 subjects who were found to be TB-free in the 1992 medical examination, 957216 were eligible for the study. Radiologically active PTB was found in 4146 cases over the 2-year period of the study. Bacteriological examinations were performed in 3306 patients: there were 1551 bacteriologically proven cases (46.9%), including 1049 smear-positives (31.7%) and 502 smear-negative culture-positives (15.2%). The age-sex adjusted incidence rate for the general population was 202/100000 in radiologically active PTB, 81/100000 in bacteriologically proven PTB, and 54/100000 in smear-positive PTB. Overall PTB incidence rates were higher in males (240/100000) than in females (163/100000), and in the age group 20-24 years (280/ 100 000) than in the other age groups.

CONCLUSION

Comparing the 1992-1994 PTB incidence with that observed in the 1988-1990 survey, the highest incidence was observed among young adults in both surveys, and it had not changed over time.

Prevention of encephalomyocarditis virus-induced diabetes by live recombinant Mycobacterium bovis bacillus Calmette-Guérin in susceptible mice

The D variant of encephalomyocarditis (EMC-D) virus causes diabetes in susceptible mice by direct cytolysis of pancreatic beta-cells. cDNA covering the major outer capsid protein (VP1) of the EMC-D virus was cloned into Mycobacterium bovis bacillus Calmette-Guerin (BCG). None of the SJL/J mice immunized with live recombinant BCG-VP1 (rBCG-VP1) became diabetic when challenged with the highly diabetogenic EMC-D virus, but the control mice inoculated with normal BCG developed diabetes during the same challenge. VP1-specific antibodies (including neutralizing antibodies) were markedly increased over time and reached the maximum titer at week 10 after a single immunization. The plateau of the titer lasted longer than 4 weeks. Mice and guinea pigs immunized with live rBCG-VP1 showed strong delayed-type hypersensitivity to the VP1 of the EMC-D virus. The preventive immunity still worked effectively 10 months after the primary immunization. At that time, the VP1-specific antibody was almost undetectable in the bloodstream, but a large number of VP1-specific lymphocytes was found in the spleen of the immunized mice. Our results show that live rBCG-VP1 elicits effective humoral and long-lasting cellular immune responses against EMC-D virus infection that results in the prevention of virus-induced diabetes in susceptible mice.

Species identification of mycobacteria by PCR-restriction fragment length polymorphism of the rpoB gene

PCR-restriction fragment length polymorphism analysis (PRA) using the novel region of the rpoB gene was developed for rapid and precise identification of mycobacteria to the species level. A total of 50 mycobacterial reference strains and 3 related bacterial strains were used to amplify the 360-bp region of rpoB, and the amplified DNAs were subsequently digested with restriction enzymes such as MspI and HaeIII. The results from this study clearly show that most of the mycobacterial species were easily differentiated at the species level by this PRA method. In addition, species with several subtypes, such as Mycobacterium gordonae, M. kansasii, M. celatum, and M. fortuitum, were also differentiated by this PRA method. Subsequently, an algorithm was constructed based on the results, and a blinded test was carried out with more than 260 clinical isolates that had been identified on the basis of conventional tests. Comparison of these two sets of results clearly indicates that this new PRA method based on the rpoB gene is more simple, more rapid, and more accurate than conventional procedures for differentiating mycobacterial species.

Analysis of aberrant virulence of Gibberella zeae following transformation-mediated complementation of a trichothecene-deficient (Tri5) mutant

Gibberella zeae causes wheat ear blight and produces trichothecene toxins in infected grain. In previous studies, trichothecene production in this fungus was disabled by specific disruption of the trichodiene synthase gene (Tri5) and was restored by two methods: gene reversion and transformation-mediated mutant complementation. In previous field tests of wheat ear blight, trichothecene-nonproducing mutants were less virulent than the wild-type progenitor strain from which they were derived. Trichothecene-producing revertants also were restored to wild-type levels of virulence. In contrast, in the field test of wheat ear blight reported here, trichothecene-producing strains obtained by Tri5 mutant complementation were not restored to wild-type levels of virulence. The complemented mutants showed a slightly reduced radial growth compared to the wild-type strain, but otherwise appeared normal in morphology, pigmentation and sexual fertility. Genetic analysis indicated that the aberrant virulence of a complemented mutant was likely due to non-target effects that occurred during the process of transforming the trichothecene-nonproducing mutant with Tri5. These results confirm previous findings that trichothecenes contribute to the virulence of G. zeae, but also demonstrate that manipulating this fungus in the laboratory may cause it to undergo subtle changes that reduce its virulence.

3'UTR polymorphisms in the NRAMP1 gene are associated with susceptibility to tuberculosis in Koreans

SETTING

Korea University and the Korean Institute of Tuberculosis, Seoul, Korea.

OBJECTIVE

To determine whether polymorphisms in the 3' untranslated region (UTR) of the NRAMP1 gene are associated with susceptibility to tuberculosis in Koreans.

DESIGN

A case-control study design was used to compare the frequency of 3'UTR of NRAMP1 among 192 tuberculosis patients and 192 healthy individuals. All of the samples were diagnosed by X-ray, smear and culture tests between 1998 and 1999 in the Cross of Lorraine Clinic at the Korean Institute of Tuberculosis.

RESULTS

A significant association was found between the Korean tuberculosis patients and polymorphisms in the 3'UTR of the NRAMP1 gene (odds ratio [OR] 1.845; 95% confidence interval [CI] 1.097-3.104; chi2 = 5.424; P = 0.020).

CONCLUSION

This study showed that genetic variations in the human NRAMP1 gene are associated with susceptibility to smear-positive tuberculosis in Korean patients. The 3'UTR variant allele associated with susceptibility to tuberculosis is very uncommon in Caucasians, but is present in Koreans and West Africans. These observations may explain in part why African Americans and Koreans have greater susceptibility to tuberculosis than Caucasians.

Exclusive mutations related to isoniazid and ethionamide resistance among Mycobacterium tuberculosis isolates from Korea

SETTING

The single base change at the 94th codon of inhA has been referred to as the event that confers resistance on the drugs isoniazid (INH) and ethionamide (ETH) in Mycobacterium smegmatis and M. bovis. From this observation, it has been anticipated that some of the INH-resistant clinical isolates of M. tuberculosis would carry missense mutations in the same region of the gene. However, few polymorphisms have been identified in this region among INH-resistant isolates.

OBJECTIVE

To understand the molecular basis for M. tuberculosis resistance to INH and ETH.

DESIGN

The sequence polymorphism at the 94th codon of inhA among M. tuberculosis isolates from Korea was analyzed by polymerase chain reaction (PCR) cloning and sequence analysis.

RESULTS

No nucleotide change at the 94th codon of inhA was detected in any of the 24 INH-resistant isolates analyzed in this study. On the other hand, a point mutation was found exclusively at the regulatory region flanking a putative ribosome-binding site of the inhA locus in 14 isolates. Interestingly, all the mutations were of the same kind, which substitutes C to T. Among 14 isolates, 12 were resistant to INH as well as to ETH, while two were resistant to INH only.

DISCUSSION

It seems that mutations previously found at the 94th codon of inhA have no particular relationship with the mechanism involved in the resistance of M. tuberculosis to INH and/or ETH. On the other hand, the resistance mechanism of M. tuberculosis to INH/ETH may involve an altered level of InhA, an expression which may have been influenced by the sequence change in the regulatory region of the inhA locus.

Restriction fragment length polymorphism analysis of Mycobacterium tuberculosis isolated from countries in the western pacific region

A total of 422 Mycobacterium tuberculosis isolates from eight countries were subjected to IS6110 and IS1081 DNA fingerprinting by means of restriction fragment analysis to characterize M. tuberculosis strains from each country. Chinese, Mongolian, Hong Kong, Filipino, and Korean isolates had comparatively more copies of IS6110 (proportion with eight or more copies; 95% +/- 5%), while Thai, Malaysian, and Vietnamese isolates had fewer copies (proportion with eight or more copies, 60% +/- 4%). We found a number of novel IS1081 types in this study. One IS1081 type was present in 56% of Filipino isolates, had a specific 6.6-kb PvuII fragment in its IS6110 DNA fingerprint, and was termed the "Filipino family." The IS1081 types of Thai isolates had interposing characteristics between the characteristics of northeastern Asian and southeastern Asian IS1081 types. A 1.3-kb single-copy IS6110 fragment was found only in Vietnamese M. tuberculosis isolates. Although M. tuberculosis isolates from each country had comparatively similar characteristics depending on the classification factor, each country's isolates showed characteristic DNA fingerprints and differed slightly from the isolates from the other countries in either the mode number of IS6110 copies or the distribution of IS1081 types.

Identification of mycobacterial species by comparative sequence analysis of the RNA polymerase gene (rpoB)

For the differentiation and identification of mycobacterial species, the rpoB gene, encoding the beta subunit of RNA polymerase, was investigated. rpoB DNAs (342 bp) were amplified from 44 reference strains of mycobacteria and clinical isolates (107 strains) by PCR. The nucleotide sequences were directly determined (306 bp) and aligned by using the multiple alignment algorithm in the MegAlign package (DNASTAR) and the MEGA program. A phylogenetic tree was constructed by the neighbor-joining method. Comparative sequence analysis of rpoB DNAs provided the basis for species differentiation within the genus Mycobacterium. Slowly and rapidly growing groups of mycobacteria were clearly separated, and each mycobacterial species was differentiated as a distinct entity in the phylogenetic tree. Pathogenic Mycobacterium kansasii was easily differentiated from nonpathogenic M. gastri; this differentiation cannot be achieved by using 16S rRNA gene (rDNA) sequences. By being grouped into species-specific clusters with low-level sequence divergence among strains of the same species, all of the clinical isolates could be easily identified. These results suggest that comparative sequence analysis of amplified rpoB DNAs can be used efficiently to identify clinical isolates of mycobacteria in parallel with traditional culture methods and as a supplement to 16S rDNA gene analysis. Furthermore, in the case of M. tuberculosis, rifampin resistance can be simultaneously determined.

Tuberculin PPD RT23: has it lost some of its potency?

PPD RT23 is a tuberculin that is used worldwide. Korea has been using 1TU RT23 for its nationwide tuberculosis prevalence surveys at five-yearly intervals since 1965, and found a drop in its potency after the 1975 survey. This finding draws attention to the interpretation of tuberculin survey data observed with RT23 at different time periods.

Differential expression of ferritin heavy chain in THP-1 cells infected with Mycobacterium bovis BCG

To identify the host genes induced or suppressed by infection of mycobacteria, the reverse transcriptase polymerase chain reaction (RT-PCR) and the differential display reverse transcriptase polymerase chain reaction (DD RT-PCR) methods were used. In this study, cDNAs complement to mRNA extracted from human peripheral monocyte derived naive THP-1 cells, THP-1 cells infected with live Mycobacterium bovis BCG, THP-1 cells treated with heat-killed BCG, and THP-1 cells incubated with IgG-coated glass-beads were compared on the sequencing gel. One (TG2-1) of the clones selected by DD RT-PCR is 446 bp long and is identical to human ferritin heavy (H) chain gene. Northern blot analysis confirmed that ferritin H chain gene has been markedly over-expressed in monocytic THP-1 cells incubated with live and dead M. bovis BCG. Differential display techniques of host genes whose expression levels were varied by infection of mycobacteria could provide information about the response of macrophages to mycobacterial infection.

Cloning and sequencing of the secY gene homolog from Mycobacterium bovis BCG

The complete nucleotide sequence of a 1,513 bp fragment of Mycobacterium bovis BCG containing the secY gene homolog and partial adk gene that encodes an adenylate kinase has been determined. The secY gene of BCG has an open reading frame of 441 amino acids with homology to the SecY protein family. Comparative analyses of the deduced amino acid sequence of additional partial ORF revealed strong similarity to the known adenylate kinases.

Drug-resistant tuberculosis in Korea, 1994

SETTING

Sample survey based on pulmonary tuberculosis (TB) patients registered in 264 health centres in Korea, compared with data obtained from nationwide TB prevalence surveys conducted since 1965.

OBJECTIVE

To determine the level of antituberculosis drug resistance (DR) and to assess its impact on treatment outcome and its relationship with cure rates in the National TB Programme (NTP).

DESIGN

Mycobacterium tuberculosis isolates from 2,486 new patients and 189 previously treated patients were subjected to susceptibility testing against 10 antituberculosis drugs. Treatment outcome was assessed. The DR levels were compared with those observed in the national TB prevalence surveys, and the trend was correlated with the cure rate of patients treated in the NTP.

RESULTS

Resistance to any drug was 11.3% in new cases and 54.0% in previously treated cases. Initial resistance to isoniazid (INH) or rifampicin (RMP) was 7.7% or 2.2%, and to INH and RMP (+/- other drugs) 1.6%. Compared with previous data, initial drug resistance (IDR) has decreased significantly and is inversely related to improvement of cure rates in the NTP. The treatment outcome of patients with single drug resistance was satisfactory.

CONCLUSION

Drug-resistant TB has decreased remarkably during the last decades in Korea as a result of improved efficiency in the treatment programme of the NTP.

Complete sequence of the UPP gene encoding uracil phosphoribosyltransferase from Mycobacterium bovis BCG

The nucleotide sequence of a 799 bp fragment of Mycobacterium bovis BCG containing the putative upp gene that encodes a uracil phosphoribosyltransferase (UPRTase [EC 2.4.2.9]) has been determined. The upp gene of BCG has an open reading frame (ORF) of 621 bp (207 amino acids) starting with GTG (position 112) and ending with TGA (position 733), and its molecular mass was calculated to be 21,864 Da. Comparative analyses of the deduced amino acid sequence of BCG UPRTase with the UPRTase of six bacterial genera revealed that 24% (50/211) of the residues are perfectly conserved and 32% (67/211) of the residues are well conserved.

Mutations in the rpoB gene of Mycobacterium tuberculosis that interfere with PCR-single-strand conformation polymorphism analysis for rifampin susceptibility testing

Rifampin susceptibility of 32 rifampin-resistant and 26 rifampin-susceptible Mycobacterium tuberculosis strains was analyzed by PCR-single-strand conformation polymorphism (SSCP) and DNA sequencing within the 157-bp region of the rpoB gene (Ala500 to Val550). Two false-positive PCR-SSCP results were observed among the susceptible strains due to the silent mutation Gln513 (CAA-->CAG) and the deletion mutation Thr508 and Ser509. Another silent mutation [Leu511 (CTG-->CTA)], combined with the mutation Ser531-->Leu, was observed in a resistant strain. These results suggest that to rule out false-positive PCR-SSCP results, sequencing of the target DNA is required.

Rapid detection of Mycobacterium avium in stool samples from AIDS patients by immunomagnetic PCR

Direct PCR detection of bacteria in clinical samples is often hindered by the presence of compounds that inhibit the PCR. To improve and accelerate the diagnosis of Mycobacterium avium-M. intracellulare complex infections, an immunomagnetic PCR (IM-PCR) assay was developed. This IM-PCR procedure combines the separation of mycobacteria by antimycobacterial monoclonal antibody coupled to magnetic beads with an M. avium-M. intracellulare complex-specific PCR protocol based on 16S rRNA gene sequences. As few as 10 M. avium bacilli were detected in spiked human stool samples, a clinical specimen usually refractory to conventional PCR analysis, by the IM-PCR method. Moreover, M. avium organisms were detected in about 24 h in 18 of 22 culture-confirmed fecal samples from AIDS patients. This IM-PCR protocol should allow for the rapid and sensitive detection of M. avium isolates in clinical specimens.

Characterization of the katG and inhA genes of isoniazid-resistant clinical isolates of Mycobacterium tuberculosis

Resistance to isoniazid in Mycobacterium tuberculosis has been associated with mutations in genes encoding the mycobacterial catalase-peroxidase (katG) and the InhA protein (inhA). Among the 26 isoniazid-resistant clinical isolates evaluated in this study, mutations in putative inhA regulatory sequences were identified in 2 catalase-positive isolates, katG gene alterations were detected in 20 strains, and 4 isolates had wild-type katG and inhA genes. Mutations in the katG gene were detected in all 11 catalase-negative isolates: one frameshift insertion, two partial gene deletions, and nine different missense mutations were identified. An arginine-to-leucine substitution at position 463 was detected in nine catalase-positive isolates. However, site-directed mutagenesis experiments demonstrated that the presence of a leucine at codon 463 did not alter the activity of the M. tuberculosis catalase-peroxidase and did not affect the capacity of this enzyme to restore isoniazid susceptibility to isoniazid-resistant, KatG-defective Mycobacterium smegmatis BH1 cells. These studies further support the association between katG and inhA gene mutations and isoniazid resistance in M. tuberculosis, while also suggesting that other undefined mechanisms of isoniazid resistance exist.

Mycobacterium tuberculosis infection in an orangutan (Pongo pygmaeus)

A respiratory disorder was noted in a 5-year-old female orangutan kept in the Yongin Farmland. Radiographically, multiple radiodense foci ranging from 2 to 6 mm diameter were seen throughout the lung lobes. Grossly, the thoracic cavity revealed a firm texture and grayish-pink discoloration of the left apical lung lobe. Histopathologically, multifocal areas of granulomatous pneumonia present the right and left apical lung lobes. Both primers from IS1081 and IS6110 targeting 196 bp and 245 bp respectively were used in polymerase chain reaction, Mycobacterium tuberculosis was isolated from liver and confirmed by polymerase chain reaction.

Molecular mechanisms of multiple drug resistance in clinical isolates of Mycobacterium tuberculosis

The molecular mechanisms of resistance to streptomycin, rifampin, and isoniazid in 53 Mycobacterium tuberculosis clinical isolates were examined. Twenty-five of 44 streptomycin-resistant strains had mutations in the rpsL gene and 5 of these had rrs gene perturbations. The region of the rpoB gene that is associated with resistance to rifampin was altered in 28 of 29 rifampin-resistant strains. Mutations in known genetic markers of isoniazid resistance were detected in 25 of 42 isoniazid-resistant isolates: 20 strains had katG gene alterations and 5 had perturbations in the inhA operon. Of the 20 multiply resistant strains with reduced sensitivity to streptomycin, rifampin, and isoniazid, 11 had mutations in genetic markers associated with resistance to each of these three drugs. These studies suggest that the primary mechanism of multiple drug resistance in tuberculosis is the accumulation of mutations in individual drug target genes.

The rpsL gene and streptomycin resistance in single and multiple drug-resistant strains of Mycobacterium tuberculosis

The recent emergence of indolent and rapidly fatal drug-resistant strains of Mycobacterium tuberculosis has renewed interest in defining the molecular mechanisms of drug resistance in the tubercle bacilli. In this report, we have examined the mechanism of resistance to streptomycin (Sm) in M. tuberculosis through the cloning and nucleotide sequence analysis of the gene encoding the ribosomal S12 protein (rpsL gene) from streptomycin-resistant strains and their streptomycin-sensitive parental strains. We have demonstrated that five singly SmR M. tuberculosis strains and an SmR isolate that has reduced sensitivity to multiple antibiotics have identical point mutations at codon 43 of the rpsL gene. Mutations at this same site confer SmR in Escherichia coli. In contrast, two other multiple drug-resistant M. tuberculosis strains that are resistant to Sm have rpsL genes that have the same nucleotide sequence as their drug-sensitive parent strains, suggesting that different resistance mechanisms are involved in these strains.

A comparison of the T cell delayed-type hypersensitivity epitopes of the 19-kD antigens from Mycobacterium tuberculosis and Myco. intracellulare using overlapping synthetic peptides

Mycobacterial disease remains a serious international public health concern. Improved methods to rapidly and specifically detect mycobacterial infections would greatly enhance clinical management of these diseases. To define species-specific T cell epitopes that may be useful for the immunodiagnosis of mycobacterial infections, polymerized synthetic peptides from the 19-kD Mycobacterium tuberculosis and Myco. intracellulare protein homologues were tested in guinea pig DTH assays. Five Myco. tuberculosis and eight Myco. intracellulare peptides evoked skin test responses. Although all of the active Myco. tuberculosis and seven of the Myco. intracellulare peptides elicited non-specific DTH reactions, the peptide IN13 induced a Myco. intracellulare-specific skin test reaction, and thus represents a specific Myco. intracellulare T cell DTH epitope. This result suggests that the development of monospecific peptide-based immunodiagnostic reagents may be feasible for future clinical use.