- Volume 35, Issue 5, 1991
Volume 35, Issue 5, 1991
- Articles
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Expression in vivo of additional plasmid-mediated proteins during intestinal infection with Yersinia enterocolitica serotype 08
More LessSummaryThe decisive aspect of Yersinia enterocolitica virulence in vivo is the ability of the plasmid-bearing bacteria to resist the immune response within the host tissue. The expression of plasmid-mediated virulence proteins was investigated in the intestinal lumen and in the Peyer’s patches of infected mice. Three novel plasmid-mediated outer-membrane proteins have been identified with antisera raised against bacteria grown in vivo. When the bacteria were grown in the intestinal lumen, all plasmid-coded proteins known to be expressed in vitro, except the 26-Kda protein were expressed. Additionally, a novel outer-membrane protein of 23 Kda was synthesised. After penetration into the Peyer’s patches, two further proteins of 240 and 210 Kda were expressed. None of these three proteins was detected in the outer membrane of bacteria grown in vitro. By contrast, plasmid-coded released proteins, which are abundantly synthesised in Ca2+-deficient media in vitro, were not detectable in the ileal lumen nor in the tissue of infected Peyer’s patches, which suggests that they are not required for Y. enterocolitica pathogenesis.
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Plasmid associated virulence properties of environmental isolates of Aeromonas hydrophila
SummaryThe plasmid profiles, and their association with antimicrobial resistance, of 60 strains of Aeromonas hydrophila isolated from fish, shellfish and water were investigated. Only two strains were susceptible to all the antimicrobial agents tested; the highest incidences of resistance were to tetracycline (96.7%), prystanamycin (93.3%), ampicillin (91.7%) and cephalothin (91.7%). Forty strains harboured one or more plasmids and the plasmid profile most frequently detected (15%) was the association of three small plasmids of 4.2, 3.2 and 2.8 Mda. Curing experiments indicated that the plasmid-free derivative strains simultaneously lost their resistance determinants to tobramycin, neomycin, gentamicin and kanamycin. More than 90% of the strains tested produced siderophores and displayed haemolytic activity. However, the relationship between these virulence characters and the presence of plasmids was different; in 74.5% of the strains there was siderophore production and plasmids were detectable, whereas only 60% of the strains simultaneously possessed plasmids and haemolytic activity.
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Biochemical phenotypes of enteropathogenic Escherichia coli common to Iran and Sweden
M. Katouli, I. KÜhn and R. MÖllbySummaryA collection of 143 strains of enteropathogenic Escherichia coli (EPEC) of 11 different serogroups isolated from children with diarrhoea, 71 in Sweden and 72 in Iran, was tested for similarity with a computerised biochemical fingerprinting method. From Sweden, there were 54 different phenotypes, 42 consisting of a single strain and 12 (common phenotypes) containing more than one isolate. From Iran, there were 48 different phenotypes, 38 with only one strain and 10 with more than one. Many of the strains which were biochemically similar, in both countries, also had similar virulence factors. Nine Swedish and 20 Iranian isolates showed biochemical identity to at least one of the strains of the other country, most of them belonging to serogroups O55, O119, O126, O127 and O128. The value of the biochemical fingerprinting method as an epidemiological tool and its ability to evaluate clonal relations among E. coli strains in different geographical areas is discussed.
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Identification of enteropathogenic Escherichia coli isolated in Britain as enteroaggregative or as members of a subclass of attaching-and-effacing E. coli not hybridising with the EPEC adherence-factor probe
More LessSummaryStrains of Escherichia coli from sporadic cases of diarrhoea and belonging to serotypes O44:H18, O55:H7, O111ab:H21 O111ab:H25 or O126:H25 or O126:H27 were examined for virulence properties. With the exception of O111ab:H25 these are considered to be classical enteropathogenic E. coli (EPEC) serotypes. The strains had been isolated in Britain from the faeces of children <3 years old. Of the serotypes examined, 7 of 13 O44:H18 strains, all of 10 O111ab:H21 strains and 13 of 21 O126:H27 strains belonged to the enteroaggregative class of E. coli (EAggEC) that attached to HEp-2 cells in the characteristic aggregative pattern and hybridised with the EAggEC probe. They also caused mannose-resistant haemagglutination of rat erythrocytes, a property which may be a useful marker for their identification. Strains of O44:H18 with similar properties were also isolated from three small outbreaks in Britain, one of which involved elderly patients. EAggEC have not been considered previously as aetiological agents of diarrhoea in developed countries and have rarely been reported as belonging to EPEC serotypes. All 15 O55:H7 strains and seven of eight O111ab:H25 strains were also considered to be potentially diarrhoeagenic as they gave localised attachment (LA) to HEp-2 cells that resulted in a positive fluorescence actinstaining test. This test is considered to correlate with the attaching-and-effacing virulence mechanisms of EPEC in vivo. None of the strains in this study hybridised with the EPEC adherence-factor (EAF) probe. Neither the aggregative EPEC nor the LA-positive EAF-negative EPEC described here would be identified in epidemiological surveys when the EAF probe is used in the absence of cell tests.
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The 16Sribosomal RNA of Mycobacterium leprae contains a unique sequence which can be used for identification by the polymerase chain reaction
More LessSummaryNucleotide sequence data for bacterial 16S ribosomal RNA was used to identify oligodeoxyribonucleotide primers suitable for probing the rRNA gene of mycobacteria and related organisms, with the polymerase chain reaction. The method enabled us to distinguish mycobacteria from other closely related genera, and to differentiate between slow- and fastgrowing mycobacteria. Mycobacterium leprae fell within the slow-growing group of mycobacteria but there are significant differences between the sequence of the M. leprae 16S rRNA gene and that of other slow-growing mycobacteria. These differences were used to devise a rapid, non-radioactive method for detecting M. leprae in infected tissue.
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Comparison of ultracentrifugation and polyethylene glycol precipitation for concentration of hepatitis B virus (HBV) DNA for molecular hybridisation tests and the relationship of HBV-DNA to HBe antigen and anti-HBe status
More LessSummaryA 32P-labelled DNA probe was used to examine 50 hepatitis B surface antigen (HBsAg)-positive sera for the presence of hepatitis B virus (HBV) DNA. HBV-DNA was detected in all 21 HBeAg-positive samples, in one out of 21 anti-HBe-positive samples and in three out of eight HBeAg- and anti-HBe-negative samples. The results of this DNA hybridisation test correlated well with HBeAg status and could be used to determine infectivity in HBeAg- and anti-HBe-negative samples. Ultracentrifugation was marginally superior to polyethylene glycol precipitation for concentrating HBV-DNA from serum.
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Bacteroides ureolyticus (NTU) medium for the selective recovery of Bacteroides gracilis
More LessSummaryBacteroides gracilis is a gram-negative anaerobic bacillus which requires formate and fumarate for growth; it has been implicated in periodontal disease and serious infections of the head and neck. In this study, Bacteroides ureolyticus (NTU) medium was tested for its ability to allow the growth of B. gracilis and other formate-fumarate requiring gram-negative anaerobes and to enable the recovery of these organisms from clinical specimens. All reference strains grew on NTU medium with the exception of Wolinella recta and formate-fumarate requiring organisms were isolated from 18 of 20 samples of subgingival dental plaque from patients with chronic periodontitis. B. gracilis was the commonest species isolated (14 of the 29 isolates); B. ureolyticus was not found.
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Restriction endonuclease digest patterns of chromosomal DNA from group B β-haemolytic streptococci
More LessSummaryScanning densitometry and computer-assisted numerical analysis were used to examine restriction endonuclease digest patterns (RDPs) of chromosomal DNA from 26 infecting strains and 44 vaginal isolates of group B β-haemolytic streptococci (GBS). At the 95% similarity level, HindIII RDPs of serotype Ia and III strains clustered into four and three RDP types, respectively. Nine of 10 strains from neonates with early-onset septicaemia belonged to two particular RDP types (Ia-3 and III-3). In contrast, serotype III GBS strains from meningitis cases were not characterised by particular RDP types. Associations between RDPs and certain phenotypic characteristics were also found.
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Typing of Streptococcus pyogenes by pyrolysis mass spectrometry
More LessSummaryStrains of Streptococcus pyogenes from an outbreak in an oncology ward (13) and routine isolates from sporadic cases (6) were examined blind by pyrolysis mass spectrometry (Py-MS), extending previous work on epidemiological typing. This outbreak appeared more complex than one reported previously, but Py-MS and conventional typing results were in complete agreement. The results confirm the potential of Py-MS as a rapid method for identification at strain level in studies of cross infection.
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