- Volume 44, Issue 2, 1996
Volume 44, Issue 2, 1996
- Editorial
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- Review Article
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Susceptibility of oral bacterial biofilms to antimicrobial agents
More LessThere is great interest in the use of antimicrobial agents for the prevention and treatment of plaque-related oral diseases and many publications have reported the results of studies in which the minimum inhibitory concentrations of agents for cariogenic and periodontopathogenic bacteria have been determined. However, such data are relevant only to situations where the organisms of interest are in aqueous suspension, whereas in caries and the inflammatory periodontal diseases the target organisms are in the form of biofilms. On the basis of studies with medically important bacteria, it has been established that bacteria in biofilms are invariably less susceptible to antimicrobial agents than their planktonic counterparts. Therefore, in the laboratory assessment of agents which may be suitable for treating plaque-related diseases, the target organisms should be in the form of biofilms. While laboratory evaluation of chemical agents for the prevention of plaque formation has usually employed biofilm-based models, the search for antimicrobial agents effective in the treatment of plaque-related diseases has not. Therefore, there are few data available regarding those characteristics of antimicrobial agents (e.g., their biofilm eliminating concentrations or biofilm killing concentrations) that could be used to judge their suitability for treating plaque-related diseases. In this review the limited information available concerning the antimicrobial susceptibility of oral bacteria in biofilms is presented.
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- Epidemiological Typing
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Investigation of outbreaks of Enterobacter aerogenes colonisation and infection in intensive care units by random amplification of polymorphic DNA
More LessDuring a 4-month period, 41 isolates of Enterobacter aerogenes were cultured from different specimens from a 14-bed intensive care unit (ICU1). These were obtained from 12 patients out of a total of 187 patients admitted to the ICU. Sixteen E. aerogenes isolates were cultured from another ICU (ICU2) 6 months later. Six non-outbreak-associated strains were included as controls and all the isolates were compared by random amplification of polymorphic DNA (RAPD), with three different 10-mer oligonucleotide primers. The six non-outbreak-associated strains were distinguishable by RAPD with two of the three primers. RAPD fingerprinting with primer AP12h was as discriminatory as the combined results from all three primers and defined 22 different patterns for the 41 isolates from the ICU1. In nine instances, isolates with indistinguishable RAPD patterns were detected in two-to-five patients over a 3–15-day period, suggesting patient-to-patient transmission. During their stay in ICU1, patients harboured one-to-12 distinguishable isolates. Isolates from ICU2 were indistinguishable by RAPD analysis with the three different primers. These findings suggest that the cluster of colonisations and infections in ICU1 was a “false outbreak”, consisting of successive patient-to-patient transmission of different E. aerogenes strains. In contrast, the outbreak on ICU2 probably involved the extensive spread of a single strain.
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- Technical Note
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Evaluation of verification assays in EIA specimens presumptively positive for Chlamydia trachomatis
More LessVerification of specimens positive for Chlamydia trachomatis by enzyme immunoassay (EIA) has been recommended when testing low prevalence populations. This study compared direct fluorescent antibody (DFA) and blocking antibody (BLA) verification assays in specimens presumptively positive for C. trachomatis by the Syva Microtrak II EIA. Of 1785 specimens originally tested by EIA, 96 were presumptively positive for C. trachomatis. Verification assays were concordant in 86 specimens (69 positive, 17 negative); nine of the remaining samples gave positive results in a second EIA and one was unresolved. Both verification assays gave some false-negative results. When initial EIA absorbance values were correlated with verified results, all EIA false positive results had absorbances in the low range (less than a three-fold increase over assay cutoff values). Verification of EIA results by both DFA and BLA was effective in detecting false positive results, but confining verification to low-value positive specimens could be considered for cost-effective C. trachomatis testing.
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Enterovirus typing by immune electronmicroscopy
More LessA simple method of typing enteroviruses by immune electronmicroscopy (IEM) is given. Forty-four of 50 picornavirus strains typed by both IEM and neutralisation in cell culture gave identical results. Four strains could not be typed by one or other method. Two rhinovirus isolates were untypable by both methods. There were no discrepant results. The IEM method is convenient and has considerable savings in time and reagents.
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- Bacterial Pathogenicity
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Effect of growth condition on in-vitro susceptibility of Shigella dysenteriae type 1 to killing by murine peritoneal macrophages
More LessThe intracellular fate of Shigella dysenteriae type 1 strains grown in casamino acid-yeast extract (CYE) broth and nutrient broth (NB) was studied in casein-elicited mouse peritoneal macrophages. Virulent strains 14731 and W30864 cultured in NB and opsonised with normal mouse serum were susceptible to killing by peritoneal macrophages (66 SEM 1.7% killing by 2 h). In contrast, both strains grown in CYE broth and opsonised with normal mouse serum showed resistance to killing by peritoneal macrophages (76 SEM 1.4% survival by 2 h). Electronmicroscopy demonstrated that the bacteria escaped from the phagosome compartment by lysing the phagocytic vacuole and remained within the cytoplasm. Lipopolysaccharide (LPS) stimulated peritoneal macrophages to kill the opsonised strains 14731 and W30864 grown in CYE broth (85.4 SEM 1.6% killing by 2 h). Recombinant murine gamma interferon (rIFN-γ) also stimulated macrophages to kill CYE-grown bacteria (52.1 SEM 1.3% killing by 2 h). However, an avirulent rough mutant strain W30864-22 grown in either NB or CYE broth showed marked susceptibility to killing by peritoneal macrophages, which was similar to that of NB-grown strain 14731 or W30864. The results of the present study suggest that in-vitro growth conditions may modulate the susceptibility of S. dysenteriae type 1 to killing by phagocytes.
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Experimental infection of Wistar rats with ‘Gastrospirillum suis’
In order to develop a model for the study of gastric spiral bacteria, and based on the observation that Wistar rats do not carry urease-positive spiral bacteria in their gastric mucosa, mucus from a pig naturally colonised by “Gastrospirillum suis” (an organism with 16S rDNA 99.5% similar to that of “G. hominis” type 1), was inoculated into 35 Wistar rats (test group). Fourteen rats were given mucus taken from “G. suis”-negative swine (control group). Five test animals and two controls were killed 1, 2, 4, 8, 12, 26 and 52 weeks after inoculation. ‘G-suis‘ was observed in the antral mucosa of all test rats but not in the gastric mucosa of any control animal. The number of organisms was high from the beginning of the infection and increased over the period of observation. The bacteria were seen deep in the gastric antral glands, especially in the advanced stages of infection. Histological study of two test rats killed 1 week after inoculation and of all rats killed from the second week after infection revealed the presence of a mild inflammatory response characterised by the infiltration of small numbers of mononuclear cells and scarce polymorphonuclear cells in the subglandular region of the antral mucosa. Lymphoid aggregates were observed in the antral mucosa of rats killed from 1 month onwards, and increased in size and number over the period of infection. Control animals did not have any histological changes in the gastric mucosa. The natural transmission of the bacterium from rat to rat was also investigated. Five non-inoculated animals (contact group) and rats of the test group were maintained in the same cage and killed after 12 weeks. Two animals of the contact group showed slight infiltration of mononuclear cells in the antral mucosa, although they were not colonised by “G. suis”, a finding that supports the hypothesis of faecal-oral transmission of gastric Helicobacter spp. This animal model could be used not only to understand different aspects of the relationship between spiral bacteria and the gastric mucosa but also to obtain large numbers of the organism, free from other spiral bacteria to study some of its properties.
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Enhancement of Clostridium difficile toxin production in biotin-limited conditions
More LessThe effect of biotin on toxin production by Clostridium difficile was examined in a defined medium. When toxin production by strain KZ 1647, which was isolated from a healthy adult, was examined in relation to its biotin requirement, it was found that with decreasing concentrations of biotin, bacterial growth was decreased, but production of both toxins A and B were remarkably increased, particularly with 0.05 nM biotin. The time course of production of both toxins in biotin-limited conditions was similar to that in biotin-enriched conditions. The biotin effect on toxin production was also observed in 15 other strains, suggesting that the effect occurs frequently amongst toxigenic C. difficile strains. The biotin effect is discussed in relation to the pathogenesis of C. difficile colitis.
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Cell surface properties of Clostridium difficile: haemagglutination, relative hydrophobicity and charge
More LessFive well characterised strains of Clostridium difficile of differing virulence and two Escherichia coli strains, a verotoxigenic O157:H7 isolate and a urinary isolate, were examined for cell surface hydrophobicity and charge, and haemagglutinating ability. Phase partition in hexadecane or octan-1-ol was similar for C. difficile and E. coli, as was retention by hydrophobic interaction chromatography (HIC), indicating moderate hydrophobicity. The salt agglutination test showed E. coli to be hydrophobic and C. difficile to be hydrophilic. Relative hydrophobicity determined by HIC when charge effects were not nullified, i.e., to reflect more closely conditions in vivo, showed C. difficile to bind less well. Growth of C. difficile in caecal emulsions to simulate conditions in vivo did not alter the cell surface hydrophobicity. The phase partition method for charge determination indicated that E. coli and C. difficile had a net negative charge, although this was weaker for C. difficile than E. coli. However, although E. coli exhibited a net negative charge as determined by immuno-gold electronmicroscopy (IGEM), in keeping with the results of the phase partition method, C. difficile was shown to be predominantly positively charged by IGEM, and by movement in a charged field as determined by paper electrophoresis and a novel method based on light microscope observation. A cell-wall deficient mutant of C. difficile was weakly positively charged, showing that most of the charge resides in the cell wall.
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Genetic regulation of fatty acid modifying enzyme from Staphylococcus aureus
More LessFatty acid modifying enzyme (FAME) is an extracellular enzyme that inactivates staphylocidal lipids by catalysing the esterification of these lipids to cholesterol. In-vitro expression of FAME began at the start of the stationary phase. This expression of FAME was very similar to other staphylococcal extracellular proteins controlled by the global regulators Agr and Sar. A Staphylococcus aureus strain ISP546 (Agr−) produced c. 80% less FAME than an isogenic Agr+ strain ISP479C. Similar results were obtained with the isogenic Agr+/Agr− strain pair RN6390 and RN6911. A S. aureus strain R (Sar−) produced c. 86% less FAME than an isogenic Sar+ strain RN6390. However, lipase assays on the same culture filtrates from the Sar+/Sar− strains did not demonstrate any affect on lipase production by the sar mutation.
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- Immune Response To Infection
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Immune response to Fusobacterium nucleatum and Prevotella intermedia in patients with infectious mononucleosis
I. Brook and F. De LeyvaThe role of four oral flora organisms (Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans) was investigated in 22 patients with infectious mononucleosis. Immunoglobulin-G class antibody titres to these organisms were measured by enzyme-linked immunosorbent assay. Serum levels in the patients were determined at day 1 and 42–56 days later. Significantly higher antibody levels to F. nucleatum and Pr. intermedia were found in the second serum sample of patients as compared to their first sample. The elevated antibody levels to F. nucleatum and Pr. intermedia, known oral pathogens, suggest a potential pathogenic role for these organisms in the pharyngo-tonsillitis associated with infectious mononucleosis.
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Increased expression of Fcγ receptors on neutrophils and monocytes may reflect ongoing bacterial infection
More LessThe FcγR receptors for IgG, FcγRI, FcγRII and FcγRIII were measured on neutrophils and monocytes from 36 patients suspected of systemic infection. These results were compared with 30 blood donor controls to assess the level of expression as an early indicator of bacterial infection. FcγRI expression on neutrophils was found to be significantly increased from patients with systemic or localised infections, when compared to the non-infected patient group, i.e., patients with no cultural evidence of bacterial infections, (p = 0.02, p = 0.04) or normal controls (p < 0.0001, p = 0.0005). FcγRI expression on monocytes was also significantly increased in both of the infected groups compared to normal controls (p < 0.0001, p = 0.001); however, no significant difference could be seen when compared with the non-infected patients. FcγRIII was found to be significantly increased on a subset of monocytes in patients with systemic or localised infections compared to the non-infected group (p = 0.009, p = 0.006) and compared to the normal controls (p = 0.009, p = 0.003). Infections caused by gram-negative bacilli induced a higher FcγR response than infection with either streptococci or staphylococci. These data suggest that the measurement of FcγRI on neutrophils and FcγRIII on monocytes may be a useful rapid indicator of bacterial infection.
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- Parasitology
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Reactivity of various leishmanial antigens in a direct agglutination test and their value in differentiating post-kala azar dermal leishmaniasis from leprosy and other skin conditions
A direct agglutination test (DAT) for the detection of post-kala azar dermal leishmaniasis (PKDL) was evaluated in conditions that simulate the disease clinically or immunologically. A reference strain of Leishmania donovani (LEM 1399), and antigen preparations from two Leishmania isolates from Bangladeshi patients with post-kala azar dermal leishmaniasis or visceral leismaniasis were used. A titre of at least 51200 was obtained in tests of patients with PKDL with all three antigens, whereas a maximum titre of 1600 was recorded in patients with cutaneous leishmaniasis, mucocutaneous leishmaniasis or leprosy. Antigens from dermal isolates of L. tropica (LV 140) and L. braziliensis (LV 65) yielded titres of 1600-6400 in patients with PKDL. The lowest titre recorded in 70 patients tested with the homologous PKDL antigen was 409600. In patients with leprosy, cutaneous leishmaniasis, syphilis, onchocerciasis, tuberculosis, blastomycosis or vitiligo, titres ranged from 100 to 1600. The DAT is better than current parasitological and histopathological methods for the diagnosis of PKDL in areas in which leprosy is co-endemic.
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Volumes and issues
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Volume 73 (2024)
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Volume 72 (2023 - 2024)
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Volume 71 (2022)
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Volume 70 (2021)
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Volume 69 (2020)
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Volume 68 (2019)
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Volume 67 (2018)
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Volume 66 (2017)
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Volume 65 (2016)
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Volume 64 (2015)
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Volume 63 (2014)
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Volume 62 (2013)
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Volume 61 (2012)
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Volume 60 (2011)
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Volume 59 (2010)
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Volume 58 (2009)
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Volume 57 (2008)
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Volume 56 (2007)
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Volume 55 (2006)
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Volume 54 (2005)
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Volume 53 (2004)
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Volume 52 (2003)
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Volume 51 (2002)
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Volume 50 (2001)
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Volume 49 (2000)
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Volume 48 (1999)
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Volume 47 (1998)
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Volume 46 (1997)
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Volume 45 (1996)
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Volume 44 (1996)
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Volume 43 (1995)
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Volume 42 (1995)
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Volume 41 (1994)
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Volume 40 (1994)
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Volume 39 (1993)
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Volume 38 (1993)
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Volume 37 (1992)
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Volume 36 (1992)
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Volume 35 (1991)
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Volume 34 (1991)
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Volume 33 (1990)
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Volume 32 (1990)
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Volume 31 (1990)
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Volume 30 (1989)
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Volume 29 (1989)
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Volume 28 (1989)
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Volume 27 (1988)
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Volume 26 (1988)
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Volume 25 (1988)
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Volume 24 (1987)
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Volume 23 (1987)
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Volume 22 (1986)
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Volume 21 (1986)
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Volume 20 (1985)
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Volume 19 (1985)
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Volume 18 (1984)
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Volume 17 (1984)
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Volume 16 (1983)
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Volume 15 (1982)
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Volume 14 (1981)
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Volume 13 (1980)
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Volume 12 (1979)
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Volume 11 (1978)
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Volume 10 (1977)
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Volume 9 (1976)
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Volume 8 (1975)
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Volume 7 (1974)
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Volume 6 (1973)
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Volume 5 (1972)
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Volume 4 (1971)
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Volume 3 (1970)
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Volume 2 (1969)
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Volume 1 (1968)