- Volume 26, Issue 3, 1988
Volume 26, Issue 3, 1988
- Article
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Evaluation of electrophoretic methods for typing methicillin-resistant Staphylococcus aureus
SUMMARYThree electrophoretic methods of typing methicillin-resistant Staphylococcus aureus (MRSA) strains–plasmid profiles (PP), whole-cell protein profiles (WCPP) and immunoblotting profiles (IP)–were evaluated and compared with phage typing. The results obtained with isolates from 12 outbreaks were compared both within the outbreaks, to determine the consistency of results, and between outbreaks. There was generally good agreement between the typing methods but in only six outbreaks did all four methods indicate the same relationship between isolates. WCPP comprised more than 50 bands; when differences occurred, they were seen in only a few bands. In contrast, IP comprised only one or two major bands and the differences were much easier to interpret. The PPs of many of the isolates were similar; many isolates contained a plasmid of mol. wt (18–25) × 106. In several outbreaks both WCPP and IP showed minor differences between isolates that were not apparent with phage typing. When comparisons were made between the 12 index strains and an isolate representing the London epidemic MRSA strain, phage typing and WCPP were the most discriminatory methods; both gave nine distinct patterns, whereas there were eight IPs and only six PPs amongst the 13 strains. It was concluded that both WCPP and IP could provide valuable epidemiological data on MRSA and that IP was the easiest of the three methods to interpret.
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Site of action of a gonococcal growth inhibitor produced by Staphylococcus haemolyticus
More LessSUMMARYThe inhibitory substance produced by Staphylococcus haemolyticus strain no. 7 acts on growing as well as resting gonococcal cells, as shown by reductions in viable counts. The optical density of these cell suspensions was only slightly reduced. The inhibitor caused lysis of gonococcal spheroplasts at 24°C and 37°C, but was much less active at 4°C. Acting on intact gonococcal cells, the inhibitor caused a temperature-dependent release of radioactive cytoplasmic material. Electronmicros-copy showed that treated suspensions contained ghost cells with the cell envelope relatively intact. Our results suggest that the inhibitor may act on the cytoplasmic membrane of the gonococcal cell causing cytoplasmic leakage and, eventually, death.
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Bovine erythrocyte-agglutinin as a possible adhesin of Bordetella bronchiseptica responsible for binding to porcine nasal epithelium
More LessSUMMARYThe bovine erythrocyte-agglutinin (BEA) of Bordetella bronchiseptica, located on the cell surface in non-fimbrial form, has been identified as a possible adhesin responsible for binding to porcine nasal epithelium in studies with BEA-negative (BEA−) mutants and in competitive studies with bovine erythrocytes.
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Characteristics of cysteine-requiring strains of Klebsiella isolated from urinary tract infections
More LessSUMMARYClinical and bacteriological findings in seven cases of urinary tract infection with cysteine-requiring strains of Klebsiella are described. The organisms were isolated from patients with long-standing urinary tract abnormalities and grew as small (c. 1 mm) colonies on MacConkey agar. The organisms failed to grow in a minimal medium supplemented with sodium sulphate but grew when the medium was supplemented with cysteine sulphinic acid, sodium sulphide or L-cysteine. The smallest amount of cysteine required for optimal growth in a chemically denned medium was 20 mg/L. Cysteine-requiring strains of Escherichia coli had previously been shown to require a similar amount of cysteine and to be unable to reduce sulphate to sulphite; this suggests a common influence in the selection of cysteine auxotrophs in vivo. However, the amino acid inhibited the growth of E. coli at concentrations which only slightly altered growth of the Klebsiella strains. Problems with the isolation, identification and sensitivity testing of cysteine-requiring Klebsiella were also observed and methods by which these may be minimised are suggested.
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Immunochemical characterisation of antigens and growth inhibition of Fonsecaea pedrosoi by species-specific IgG
More LessSUMMARYAntigens of Fonsecaea pedrosoi, the most common agent of chromomycosis, were characterised by immunoprecipitation with a rabbit antiserum raised against the cell-protein extract and serum from an infected patient. Thirteen antigens were commonly detected and, as some of these antigens could be iodinated, they may be present in the fungal cell wall. Purified IgG from the rabbit antiserum was shown to produce a 50-60% inhibition of fungal growth. Some of the antigens characterised may be important in relation to the stimulation of protective immunity against chromomycosis.
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Ribosomal-RNA patterns of Escherichia coli, Salmonella typhimurium and related Enterobacteriaceae
More LessSUMMARYrRNA sequences are usually highly conserved among species. In Enterobacteriaceae we have shown that Salmonella typhimurium does not have an equivalent to the 23S rRNA of Escherichia coli but its 23S rRNA is cleaved in vivo into two smaller species. This cleavage appears to be a result of a difference between the S. typhimurium and E. coli rRNA sequences rather than to differences in ribonuclease activity. We have surveyed a wide range of Enterobacteriaceae for the presence or absence of 23S rRNA and found this rRNA species to be present in all strains of E. coli, Shigella and Citrobacter and all salmonellae examined except S. typhimurium. All S. typhimurium cultures, isolated at different times and from several different countries, lack an intact 23S rRNA. Thus, the presence or absence of this rRNA species is an excellent diagnostic characteristic for S. typhimurium.
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The effect of antibiotics on bacterial colonisation of vascular cannulae in a novel in-vitro model
More LessSUMMARYAn in-vitro model for studying semi-quantitatively the bacterial colonisation of the external and internàl surfaces of peripheral intravascular cannulae is described. Using this model, we studied the effect of ciprofloxacin, teicoplanin and fusidic acid on cannula colonisation by Staphylococcus epidermidis. Exposure of colonised cannulae to sub-MICs of ciprofloxacin and fusidic acid reduced bacterial attachment, whereas sub-MIC levels of teicoplanin had little effect. Pre-exposure of S. epidermidis to sub-MICs of ciprofloxacin and fusidic acid also reduced slime production and colonisation. In comparison, pre-exposure of S. epidermidis to teicoplanin 1.0mg/L did not influence colonisation, whereas at 0.1 mg/L it was reduced. The model allowed investigation of bacterial colonisation of cannulae and offers a screening system for the assessment of potential agents for the prophylaxis and treatment of these infections.
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A study of the evolution of specific and non-specific immune complexes in acute hepatitis B and chronic hepatitis
More LessSUMMARYCirculating immune complexes (ICs) containing IgG and HBsAg, and IgG and HBeAg, in sera from groups of patients with various liver diseases were sought by ELISA and immunodiffusion. A correlation was found between the absence of ICs and the disappearance of HBsAg in patients who had recovered from acute hepatitis B, but complexes containing HBsAg were always found in chronic hepatitis.
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