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Volume 9,
Issue 3,
1976
Volume 9, Issue 3, 1976
- Short Articles
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The Detection and Avoidance of False-Positive Reactions in Tests for Rubella-Specific IgM
More LessSummarySerum specimens tested for rubella-specific IgM by the haemagglutination-inhibition technique may give false-positive results due to (a) storage at — 20°C, (b) bacterial contamination, or (c) inactivation at 56°C. These false-positive reactions can be distinguished from rubella-specific IgM activity by their resistance to 2-ME.
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A Transmissible Plasmid Determining Lactose Fermentation and Multiple Antibiotic Resistance in a Strain of Klebsiella Pneumoniae
More LessSummaryIn a wild strain of Klebsiella pneumoniae the plasmid that determined lactose fermentation also determined resistance to chloramphenicol, ampicillin, tetracyclines, streptomycin, spectinomycin, and sulphonamides. The plasmid transferred at a very low rate to Escherichia coli K12 and Salmonella typhi. By implanting other transfer factors in the strain the rate of transfer and the recipient range were increased. Plasmid transfer from the modified strain to Salm. typhimurium and Salm. gallinarum was detected in the alimentary tract of experimentally infected chicks fed diets containing ampicillin.
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The Presence of a Variant of Type-Iiia β-Lactamase in a Series of Strains Isolated in a Burns Unit
More LessSummaryAn outbreak of carbenicillin-resistant Pseudomonas aeruginosa infection in a Burns Unit in 1968-69 occurred in two phases separated by a period when no resistant pseudomonas were detected. Nevertheless, strains of Klebsiella aerogenes carrying R factors similar to those in the pseudomonas strains were encountered in the intervening period. The similarity of the plasmids occurring in all stages of this outbreak has been confirmed by the fact that each specifies a novel variant of type-IIIa β-lactamase.
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- Articles
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A New Practical Classification of the Mycobacteria
More LessSummaryA new classification is presented for mycobacteria cultured from clinical specimens. Five categories were defined on temperature requirement, and these were subdivided into 14 groups by pigmentation, oxygen preference and Tween hydrolysis. Support for some of the groups and for the recognition of certain important species within others was provided by drug-sensitivity tests. Less than 1-0% of the opportunist mycobacteria met in Britain eluded classification by these means.
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The Adherence of Pilate and Non-pilate Strains of Neisseria Gonorrhoeae to Human and Guinea-pig Epithelial Tissues
More LessSummaryStrains of Neisseria gonorrhoeae adhered to pieces of human endocervix and appeared to be embedded in the surface mucus. Although a pilate strain adhered better than a non-pilate strain, the difference was small and pilation did not appear to be exclusively responsible for adherence. The pilate strain showed better adherence to pieces of human ectocervix and fallopian tube, but both strains were similarly adsorbed to human bronchus and guinea-pig uterus, cervix, male urethra and bladder, although to different degrees for different tissues.
Since gonococci adhered to all tissues examined, their ability to infect human endocervix and fallopian tube and their failure to infect human ectocervix or guinea-pig urogenital tract mucosae are determined by factors other than a capacity for primary adherence to the tissue.
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Streptococci and Aerococci Associated With Systemic Infection in Man
More LessSummaryA collection of 820 isolates of streptococci and aerococci from human blood or internal organs was classified by means of a set of cultural and biochemical tests. Of these, 719 (712 streptococci and 7 aerococci) were from patients believed to be suffering from a systemic infection: endocarditis 317; a purulent lesion in an internal organ (“ purulent disease ”) 152; bacteriaemia 250.
The endocarditis streptococci included members of all recognisable taxa, but only certain of these were common: Streptococcus sanguis, 16-4%; dextran- positive and usually mannitol-fermenting strains of S. bovis (S. bovis I), 15·1 %; S. mutans, 14·2%; S. mitior, 13·2%. Streptococci of the “ α-haemolytic ” taxa (S. sanguis, S. mitior and related strains) formed only 44-8% of the total. When the percentage frequency of streptococcal taxa among the endocarditis and “ non-endocarditis ” isolates was compared, the dextran-forming taxa (S. mutans, S. bovis I, S. sanguis, and dextran-positive streptococci otherwise resembling S. mitior) all had higher “ endocarditis : non-endocarditis ’’ratios than did any of the non-dextran-producing taxa.
Endocarditis increased in frequency with age, and showed an excess of males over females up to the age of 65 years. In young patients (<35 years), “α-haemolytic” streptococci predominated; with increasing age, the proportion of other streptococci increased progressively but the absolute numbers of isolations of “ α-haemolytic ” streptococci did not fall. Infections with S. mutans were prominent in the age-group 35-54 years and with S. bovis I at ages ⋝55 years. A history of previous heart disease was more often obtained in endocarditis due to “ α-haemolytic ” streptococci than in other streptococcal endocarditis.
The streptococcus most often isolated from purulent lesions in internal organs was S. milleri (29·3 %). It was associated with brain abscess, meningitis, pleural empyema and a variety of intra-abdominal abscesses.
The only common predisposing factor in endocarditis was previous heart damage. In other systemic streptococcal diseases, other general or local predisposing causes could be observed, mainly in infections with the “ pyogenic ” groupable streptococci, the enterococci and S. milleri.
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Antibodies to Candida After Operations on the Heart
More LessSummaryThe occurrence of yeasts and antibodies to yeasts was studied in patients undergoing open-heart surgery without antifungal prophylaxis, and in a similar group receiving antifungal prophylaxis. An association was demonstrated between the occurrence of commensal yeasts and the appearance of antibodies. None of the patients developed overt systemic or superficial yeast infection. The antigenic stimulus for the post-operative production of antibodies appeared to be the increase in the yeast flora that occurred shortly after operation. When the commensal yeast population was suppressed by antifungal antibiotics, the antibody response was also reduced. The implications of these findings in the interpretation of serological tests for diagnosis of systemic yeast infections are discussed.
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The Infection of Rat Tongue Mucosa in vitro With Five Species of Candida
More LessSummaryOrthokeratinised mucosa from the dorsal surface of neonatal rat tongue was maintained in culture and then infected with Candida albicans, C. tropicalis C. kmsei, C. parapsilosis or C. guilliermondii for up to 45 h. The five species showed varying abilities to invade the tissues, which appeared to reflect their different pathogenicities. C. albicans was the only species able to invade all the tissues present, including the stratum corneum. C. tropicalis and C. krusei were able to invade connective tissue and the deeper nucleated cells of the epithelium but failed to penetrate the keratin layer, while C. parapsilosis and C. guilliermondii showed only slight invasion of the connective tissue. The keratin layer of rat tongue mucosa thus appeared to act as a barrier to invasion of the epithelium by anything but virulent species of candidal fungi.
The results suggest that oral mucosa in vitro retains its structural integrity and that the tissues do not act solely as a passive growth medium through which any fungal strain might proliferate. It seems that this in-vitro system is representative of the in-vivo situation and forms a useful experimental model in which to investigate the host-fungal relationship in mucosal candidiasis.
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The Relevance of Growth Rates in Urine to the Pathogenesis of Urinary-tract Infections Due to Micrococcus Subgroup 3 (Staphylococcus Saprophyticus Biotype 3)
More LessSummaryA novobiocin-resistant “ biotype ” of Micrococcus subgroup 3 (Staphylococcus saprophyticus) is known to be a primary pathogen of the female urinary tract and to cause infections as severe as those produced by Escherichia coli. The growth characteristics of this virulent biotype were compared in vitro with those of other Micrococcaceae and of E. coli to determine whether rapid growth explains the virulence of the biotype.
Nutrient broth was shown to have growth-supporting qualities that differed from those of urine and it was therefore unsuitable for these studies. In urine, the virulent biotype grew more slowly, had a longer lag period, and reached much lower final viable counts than did Escherichia coli. Surprisingly, the virulent biotype also grew more slowly and reached a lower final viable count than did several other Micrococcaceae isolated from the urinary tract of healthy women. Urine from women who had suffered a recent infection with the virulent biotype had growth-supporting properties similar to those of urine from healthy women.
Experiments with filtered forestream urine suggested that urethral secretions do not contain a factor determining growth rates of this organism in urine. The possibility that virulent strains adapt to rapid growth in urine was excluded. No evidence was obtained that the virulent biotype inhibits the growth of other Micrococcaceae in urine.
Ability to grow rapidly in urine does not therefore explain the virulence of novobiocin-resistant strains of subgroup-3 micrococci.
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Bifidobacteria in the Intestinal Tract of Infants: an In-vivo Study
More LessSummaryWeekly faecal specimens from 18 babies were examined during the first 8 weeks of life. Eight infants were breast fed, ten were bottle-fed. All suckling infants received supplementary feeds for the first 8 days.
A buffer consisting of acetic acid and acetate was demonstrated in the faeces of all the breast-fed infants at some time during the period of examination. This buffer was rarely detected during the 1st week of life when supplementary feeds were given, and buffer already present gradually disappeared with the introduction of mixed feeding. In contrast, at no time was an acetate buffer demonstrated in the faeces of bottle-fed infants. Babies receiving breast milk produced faeces with low pH, high counts of saccharolytic organisms including bifidobacteria and Streptococcus faecium, and low counts of Escherichia coli, bacteroides and clostridia. Bottle-fed infants on the other hand produced faeces with a high pH and high counts of E. coli and putrefactive bacteria, but with low counts of bifidobacteria.
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Bifidobacteria in the Intestinal Tract of Infants: an In-Vitro Study
More LessSummaryIn-vitro studies showed that a number of factors are likely to influence the production and maintenance of a bifidobacillary flora and low pH in the faeces of newborn infants. Considerable importance is attached to the nature of the end products of bacterial metabolism in the large intestine. Thus, there is evidence to suggest that acetic acid and other metabolites of intraluminal bacterial growth suppress the growth of gram-negative organisms, but are without effect upon that of bifidobacteria. This mechanism in turn is controlled by the nature of the feed; important factors in breast milk include high lactose, low protein and low phosphate content.
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Acinetobacter and Similar Organisms in Ear Infections
More LessSummaryFifty-seven strains of acinetobacter-like organisms were isolated over a period of 26 months from the ears of 55 patients with acute or chronic otitis media, or otitis externa, and one strain was isolated in a survey of 50 normal ears. After comparison with eight reference strains, 32 of the isolates were identified as Acinetobacter anitratus, 22 as Acinetobacter Iwoffii, three as Moraxella spp. and one as Achromobacter sp.
Analysis of the clinical findings suggests that although most of these organisms played little part in the disease process, a few strains were probably pathogenic in this situation.
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- Books Received
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