Implication of embB Gene Mutation in Ethambutol-Susceptible Clinical Isolates of Mycobacterium tuberculosis / 결핵및호흡기질환

BACKGROUND: Ethambutol(EMB) is one of the first-line drugs included in short-course anti-tuberculosis therapy. The point mutations in embB gene have been speculated to be associated EMB resistance. However, detection of embB mutations at these positions have been observed in both EMB-susceptible isolates; thus, it remains controversial whether these mutations are associated with EMB resistance METHODS: The 36 M. tuberculosis isolates were selected from clinical isolates which tested susceptible to EMB and resistant to at least one drug. DNA extracted from the isolates was analyzed by amplifying embB gene. The PCR products were purified and directly sequenced. We reviewed the history of past drug susceptibility test results. RESULTS: Out of 36 EMB-susceptible strains, 3 strains (8.3%) had a mutation in codon 306 or 406 of the embB gene. These three strains had at least isoniazid resistance. They grew at 1.0 mcg/ml of EMB in Lowenstein-Jensen media. The patients of the strains were continuously smear-positive for over 3 years despite taking TB therapy. One strain had been EMB-resistant in past drug susceptibility tests. CONCLUSION: EMB-susceptible strains containing embB mutation may be caused by decreased viability in vitro test not by itself.

Multidrug-resistant Salmonella typhimurium and Salmonella enteritidis identified by multiplex PCR from animals

Antibiotic resistance in Salmonella enteritidis and S. typhimurium, one of most frequent etiologic pathogens of food-borne bacterial gastroenteritidis in humans, is a serious health problem worldwide. Fifteen and 22 each of S. enteritidis and S. typhimurium were isolated from animals from 1983 to 1999 in Korea and tested for their antibiotic resistance patterns and phage types. S. enteritides isolates were highly resistant to sulfonamides (86.7%) and four of them (26.6%) showed multiple antibiotic resistance. The most frequent phage type (PT) of S. enteritids was PT1 (33.3%) even though none of them had multiple antibiotic resistance. S. typhimurium isolates were highly resistant to streptomycin, sulfonamides, and tetracycline, 100%, 95.5%, and 86.4% respectively. The incidence of multiple antibiotic resistance of S. typhimurium isolates was extremely high (100%) comparing to S. enteritidis isolates (26.7%). Two of the five ACSSuT type S. typhimurium isolates, resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline, were phage type DT104. All S. typhimurium isolates were sensitive to florfenicol. For the rapid detection of multiple antibiotic resistant S. enteritidis and S. typhimurium isolates, particularly ACSSuT type S. typhimurium DT104, antibiotic resistance genes, cmlA/tetR, PSE-1, and TEM, and Salmonella spp. Specific gene, SipB/C, were amplified using four pairs of primers in hot-started multiplex polymerase chain reaction. Two Korean isolates of S. typhimurium DT104 showed TEM amplicons instead of PSE-1 for the ampicillin resistance. The multiplex PCR used in this study was useful in rapid detection of ACSSuT type S. typhimurium and identification of b-lactamase gene distribution among Salmonella isolates.

Multidrug-resistant Salmonella typhimurium and Salmonella enteritidis Identified by Multiplex PCR in Korea

No Abstract Available.

Pulmonary infection with Mycobacterium celatum in immunocompetent host: The first case report in Korea / 결핵

Mycobacterium celatum is a recently described nontuberculous mycobacterium. Even though pulmonary or lymphatic infection cases were reported previously in human, the clinical significance of the infection with M.celatum is not yet understood completely. Most infections with this species occurred in the patients with suppressed cell-mediated immunity such as AIDS, and there are only a few cases of pulmonary infection with M.celatum in immunocompetent adults or infants in the world. In Korea, mycobacterial pulmonary infection is a major problem of respiratory disease but, there has been no pulmonary infection with M. celatum reported. We report, to our knowledge, the first Korean case of pulmonary infection with M. celatum, which was identified by gamma poB genomic sequencing.

rpoB Gene Analysis of helicobacter pylori

rpoB, which encodes the B subunit of RNA polymerase, is related to rifampin resistance of Mycobacterium tuberculosis and Escherichia coli. We determined the nucleotide sequences (346 bp) of rpoB gene from 25 Korean isolates of Helicobacter pylori. These nucleotide sequences were aligned and compared with H. pylori 26695 strain. No insertions or deletions were observed in all H. pylori strains. In the phylogenetic tree constructed by UPGMA method, 26 strains of H. pylori were separated into four clusters. Deduced amino acid sequences of amplified rpoB DNA comprised 115 amino acid residues. Twenty six H. pylori strains could be divided into 5 groups by the signature amino acid sequences. Two strains isolated from the same patient showed different nucleotide sequences. These results suggest that the sequences of rpoB are also highly divergent in H. pylori isolates and are useful for the epidemiologic study.