Evidence of clonal dissemination of multidrug-resistant Streptococcus pneumoniae in Hong Kong.
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The relationship between the phenotypic and genotypic characteristics of 105 penicillin-intermediate or -resistant Streptococcus pneumoniae isolates saved during 1994 to 1997 at the Prince of Wales Hospital and Pamela Youde Nethersole Eastern Hospital, Hong Kong, was studied. The pbp genes for penicillin-binding proteins 1a, 2b, and 2x for each isolate were amplified by PCR, and the products were digested with restriction enzymes HinfI and AluI. A combination of the pulsed-field gel electrophoresis (PFGE) profiles, pbp fingerprints, and phenotypic characteristics of capsular types and antibiograms enabled these isolates to be divided into four major groups. Seventy-four percent (78 of 105) of the strains, belonging to serotypes 23F, 19F, and 14, showed indistinguishable pbp fingerprint patterns (group A1, 1-1-1, 1-1-1), with PFGE patterns belonging to group A and its subtypes, suggesting that these strains were closely related. Eighty-three percent (65 of 78) of these isolates were also resistant to tetracycline, erythromycin, chloramphenicol, and trimethoprim. The type 23F isolates were indistinguishable from representative strains of the Spanish 23F clone by these molecular methods, indicating that these strains may be variants of the Spanish 23F clone. Serotype 6B accounted for 19% (20 of 105) of the isolates with reduced penicillin susceptibility and was made up of variants belonging to four different pbp fingerprint groups with the PFGE pattern group B, the predominant group being indistinguishable from that of the Spanish 6B clone. Other PFGE and fingerprint groups were mainly obtained from penicillin-susceptible strains of various serotypes. The results suggest that the rapid emergence of drug-resistant S. pneumoniae in Hong Kong has been due to the rapid dissemination of several successful clones. (+info)
Discrimination of multidrug-resistant Mycobacterium tuberculosis IS6110 fingerprint subclusters by rpoB gene mutation analysis.
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The rpoB gene mutations in a 69-bp region of the gene, resulting in resistance to rifampin, were used to discriminate between Mycobacterium tuberculosis IS6110 fingerprint subclusters. These subclusters exhibited identical IS6110 fragments or had one or two additional fragments. In the two major subclusters all the analyzed strains have the same variant rpoB allele but are different from each other, suggesting the occurrence of independent outbreaks. (+info)
Molecular characterization and antibiotic susceptibilities of ocular isolates of Staphylococcus epidermidis.
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Nineteen isolates of Staphylococcus epidermidis from patients with ocular infections were analyzed. Patients were selected in retrospect, by choosing cases in which S. epidermidis was the sole isolate. Twelve different patterns were obtained after hybridization with a probe with high-level homology to insertion sequences found in S. epidermidis. Susceptibilities to penicillin, methicillin, gentamicin, tetracycline, erythromycin, ciprofloxacin, vancomycin, and teicoplanin were determined. Six strains were resistant to three or more antibiotics. (+info)
Sequence-tagged connectors: a sequence approach to mapping and scanning the human genome.
(60/3442)
The sequence-tagged connector (STC) strategy proposes to generate sequence tags densely scattered (every 3.3 kilobases) across the human genome by arraying 450,000 bacterial artificial chromosomes (BACs) with randomly cleaved inserts, sequencing both ends of each, and preparing a restriction enzyme fingerprint of each. The STC resource, containing end sequences, fingerprints, and arrayed BACs, creates a map where the interrelationships of the individual BAC clones are resolved through their STCs as overlapping BAC clones are sequenced. Once a seed or initiation BAC clone is sequenced, the minimum overlapping 5' and 3' BAC clones can be identified computationally and sequenced. By reiterating this "sequence-then-map by computer analysis against the STC database" strategy, a minimum tiling path of clones can be sequenced at a rate that is primarily limited by the sequencing throughput of individual genome centers. As of February 1999, we had deposited, together with The Institute for Genomic Research (TIGR), into GenBank 314,000 STCs ( approximately 135 megabases), or 4.5% of human genomic DNA. This genome survey reveals numerous genes, genome-wide repeats, simple sequence repeats (potential genetic markers), and CpG islands (potential gene initiation sites). It also illustrates the power of the STC strategy for creating minimum tiling paths of BAC clones for large-scale genomic sequencing. Because the STC resource permits the easy integration of genetic, physical, gene, and sequence maps for chromosomes, it will be a powerful tool for the initial analysis of the human genome and other complex genomes. (+info)
Molecular fingerprinting of Porphyromonas gingivalis by PCR of repetitive extragenic palindromic (REP) sequences and comparison with other fingerprinting methods.
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Knowledge of the genetic structure of populations of potentially pathogenic bacteria is important in understanding the epidemiology of diseases. Porphyromonas gingivalis is thought to be an important aetiological agent in periodontal diseases and several methods have been used for typing strains of this species. Here, PCR with primers to repetitive extragenic palindromic sequences (REP-PCR) was compared with three other widely used molecular fingerprinting techniques -- restriction endonuclease analysis (REA), ribotyping and PCR with arbitrary primers (AP-PCR) -- to type P. gingivalis isolates from healthy and diseased periodontal sites. The data obtained with all four methods were in broad agreement and, with one exception, each subject harboured a single unique genotype of P. gingivalis. REP-PCR of P. gingivalis resulted in the production of 5-10 amplicons, which gave unique electrophoretic patterns in each individual (10 REP-PCR types in 10 patients) and similar results were obtained with AP-PCR. Two isolates from one subject appeared identical by REP-PCR and AP-PCR, but could be differentiated by ribotyping, although there was only minor polymorphism. Thus, ribotyping and REA were the most discriminating methods; however, these are time-consuming and expensive relative to the PCR-based techniques. REP-PCR has the advantage that the same pair of primers is used for all species, whereas AP-PCR needs to be optimised by screening a range of primers. These results show that REP-PCR is a useful and rapid technique for typing P. gingivalis. (+info)
Typing Listeria monocytogenes by random amplified polymorphic DNA (RAPD) fingerprinting.
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Twenty epidemiologically unrelated Listeria monocytogenes strains isolated from different animals, locations and on different dates in Japan were classified into 18 types by the random amplified polymorphic DNA (RAPD) fingerprinting technique with four primers. Further, seven epidemiologically related L. monocytogenes strains isolated from raw milk and a bulk tank on a dairy farm represented the same RAPD type suggesting that they were all of the same origin. Therefore, RAPD-polymerase chain reaction (PCR) analysis, which is rapid, simple and inexpensive to perform, can be used in surveys as a convenient epidemiological technique. (+info)
Discrimination between endemic and feedborne Salmonella Infantis infection in cattle by molecular typing.
(63/3442)
Salmonella enterica serovar Infantis is endemic in Finnish cattle. Feed contaminated with S. Infantis was distributed to cattle farms in May 1995. Following increased sampling, S. Infantis was detected on 242 farms in 1995. Molecular typing was used to differentiate the farms that were infected by the feed-related Infantis from those infected by other endemic strains. Twenty-three isolates from feed in 1995 and 413 from cattle (72 from 19924, 324 from 1995, 17 from 1996-7) were analysed. The feed-related Infantis was clonally related to the endemic infection by the ribotype, IS200-type and XbaI-profile. The feed isolates had a distinctive plasmid that appeared in pulsed-field gel electrophoresis as a 60 kb band when cleaved with XbaI or linearized by S1-nuclease. This plasmid appeared in cattle only since the outbreak and seemed stable on the follow-up farms. In addition to contact farms, the feedborne strain was found on 19% of the farms infected with S. Infantis in 1995 but not having bought suspected feedstuffs, possibly as secondary infections. (+info)
Antigenic variants in Bordetella pertussis strains isolated from vaccinated and unvaccinated children.
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Bordetella pertussis shows polymorphism in two proteins, pertactin (Prn) and the pertussis toxin (PT) S1 subunit, which are important for immunity. A previous study has shown antigenic shifts in these proteins in the Dutch B. pertussis population, and it was suggested that these shifts were driven by vaccination. The recent Italian clinical trial provided the opportunity to compare the frequencies of Prn and PT S1 subunit variants in strains isolated from unvaccinated children, and from children vaccinated with two acellular and one whole-cell pertussis vaccine. Four Prn variants (Prn1, Prn2, Prn3 and Prn5) were found in the 129 strains analysed. Prn1, Prn2 and Prn3 have been described previously, whereas Prn5 is a novel variant. Prn1, Prn2, Prn3 and Prn5 were found in, respectively, 6, 41, 51 and 2% of the strains. The B. pertussis strains used to produce the vaccines administered in the clinical trial were found to produce Prn1, or a type which differed from Prn1 in one amino acid. The frequency of the Prn1 variant was found to be lowest in the strains isolated from vaccinated groups, suggesting that Prn1 strains are more affected by vaccine-induced immunity than Prn2 and Prn3 strains. Only one PT S1 type (S1A) was observed in the examined strains, which was distinct from the types produced by the vaccine strains (S1B and S1D). The S1A type also predominates in the Dutch B. pertussis population. The genetic relationship among B. pertussis strains analysed by IS1002-based DNA fingerprinting revealed that three fingerprint types predominate, representing more than 70% of the strains. Prn2 strains showed a greater variety of fingerprint types compared to Prn3, suggesting that Prn3 has emerged more recently. The results are discussed in the light of vaccine-driven evolution. (+info)