- Volume 42, Issue 6, 1995
Volume 42, Issue 6, 1995
- Editorial
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- Antimicrobial Agents
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Electronmicroscopic investigation of the effects of biocides on Pseudomonas aeruginosa PAO bacteriophage F116
More LessSurmmaryElectronmicroscopy was used to observe morphological changes of the Pseudomonas aeruginosa PA0 bacteriophage F116 when treated with various biocides commonly used as antibacterial and antifungal agents. Because of its large size (145 nm) and its organised structure (an isometric head and a tail), it was possible to classify structural damage into eight categories. The morphological changes induced depended on the type of biocide used and its concentration. Glutaraldehyde increased the number of phages with empty heads. Peracetic acid and phenol altered the appearance of the viral genome packaged inside the head, produced fractured heads, and damaged the tail. Peracetic acid also induced folding of the phage heads. The alcohols tested also altered the head structure. Cetylpyridinium chloride induced mainly fractured head damage. Chlorhexidine had little effect on the structure of F116.
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Antibiotic susceptibility of Mycoplasma fermentans strains from various sources and the development of resistance to aminoglycosides in vitro
More LessSurmmaryMycoplasma fermentans strains reputedly from human infections or tissue culture cells were much more susceptible to azithromycin than to clarithromycin or erythromycin. Lincomycin, clindamycin and several tetracyclines also exhibited good mycoplasmastatic activity but mycoplasmacidal concentrations were substantially greater than the MICs. Ciprofloxacin was the most active of three fluoroquinolones tested and was mycoplasmacidal at concentrations close to the MIC. Tiamulin and mupirocin were also very active. Synergy with specific M. fermentans antiserum plus guinea-pig complement was not observed with any class of antibiotic although the number of viable mycoplasmas was markedly reduced by the combined immunological components. Marked differences in susceptibility to various aminoglycosides were observed. Human strains isolated in cell-free media up to 1967 were aminoglycoside susceptible (MIC range 0.5–25 mg/L) but recent human isolates and strains isolated from tissue culture cells often showed either single or multiple aminoglycoside resistance (MIC > 500 mg/L). Two aminoglycoside-susceptible strains developed resistance to streptomycin or neomycin (> 500 mg/L) within five passages in broth containing streptomycin or neomycin, respectively. Resistance to tobramycin, kanamycin or gentamicin emerged after seven, eight and 14 cycles of exposure to the respective antibiotic. Streptomycin resistance was associated with a five-fold increase in resistance to tobramycin. Neomycin-, kanamycin-, gentamicin- and tobramycin-resistant variants showed mutual cross-resistance but remained susceptible to streptomycin. Induced resistance persisted for at least 17 passages in aminoglycoside-free broth. The use of aminoglycosides in human medicine and the frequent inclusion of some of these drugs in tissue cell cultures to combat bacterial and mycoplasmal contamination might account for the aminoglycoside resistance of recent M. fermentans isolates.
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Back mutations to the TEM-1 β-lactamase from TRC-1 lead to restored sensitivity to clavulanic acid
More LessSurmmaryBack mutations from the TRC-1 β-lactamase to the TEM-1 enzyme were selected in vitro. The revertant β-lactamase was obtained from Escherichia coli strain J62.2 carrying plasmid pUK901 which encodes the TRC-1 β-lactamase. The revertant was obtained after repeated subculture of E. coli J62.2 (pUK901) in amoxycillin 512 mg/L for 5 days. The revertant β-lactamase had the same pI as TEM-1 (5.4) and had restored inhibition by clavulanic acid (ID50 reduced from 4.2 μ m to 0.15 μ m). The prevalence of these β-lactamases in the clinical population may be the result of a two-way flux, with mutations in both forward and backward directions.
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- Epidemiological Typing
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Identification and typing of pyogenic streptococci by enzyme electrophoretic polymorphism
More LessSurmmaryPolyacrylamide-agarose gel electrophoresis was used to study polymorphism of lactate dehydrogenase (LDH), nucleoside phosphorylase (NSP), phosphoglucose isomerase (PGI), hydroxybutyrate dehydrogenase (HBD), adenylate kinase (ADK) and esterases of 44 strains of Streptococcus pyogenes, 25 group G streptococcal strains, 11 “S. equisimilis” strains, seven S. dysgalactiae strains, four S. canis strains, three S. equi strains and seven S. zooepidemicus strains. Analysis of LDH, NSP, PGI, HBD and ADK provided valuable interspecies differentiation, by showing that four groups of strains corresponded to the four known DNA homology groups. Esterases showed greater intraspecies variation than the other enzymes. The combined analysis of the six enzymes indicated 31 zymotypes among S. pyogenes, 14 in group G streptococci and 11 in “S. equisimilis” strains. This was shown to be an effective technique for typing pyogenic streptococci.
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- Models Of Infection
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Experimental Legionnaires’ disease in SCID-Beige mice reconstituted with human leucocytes
More LessSurmmaryA new small animal model of experimental Legionnaires′ disease is described in which the reconstitution of SCID-Beige mice with human peripheral blood leucocytes permits the in-vivo growth of Legionella pneumophila in the lungs of aerosol-challenged mice. Following infection, viable bacterial counts within the lungs of mice increased from 105 cfu/lung at the time of inoculation to a maximum of 1010 cfu/lung by 48 h post-inoculation. Two types of disease were detected in the lungs of infected SCID-Beige mice. An acute exudative bronchiolitis and bronchopneumonia were seen in the most severely affected mice and, in the less severely affected mice, lesions of subacute or chronic disease were seen with thickening of alveolar walls and consolidation of lung tissue. Human cells did not appear to be involved directly in the pathology but were required for the establishment of infection. Immunohistological staining of lung tissue revealed substantial amounts of bacterial antigen distributed in a pattern similar to that seen in human Legionnaires’ disease.
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- Character Isation Of Bacteria
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Presence of lysogenic phage in the outbreak strains of Vibrio cholerae O139
S. N. Mitra, S. Kar, R. K. Ghosh, S. Pajn and A. GhoshSurmmaryFour outbreak strains of Vibrio cholerae O139 from endemic areas of India and Bangladesh were found to carry lysogenic phage(s). All of these phage(s) produced turbid plaques characteristic of lysogeny on V. cholerae MAK 757 (El Tor, Ogawa) cells as well as on their VcA-1 lysogens but were unable to infect V. cholerae 154 (classical) cells, the universal host for all classical phages. Colonies in the turbid plaques were O139 lysogens and these developed an auxotrophic requirement, mainly for purines suggesting the integration of the prophage into the host chromosome. The immunity profile of the O139 phage(s) was similar to that of phage α but differed in the sensitivity of the phage lysogen of V. cholerae MAK 757 to subsequent infection by phage β.
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- Characterisation Of Bacteria
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Genotyping of Shiga-like toxin genes in non-O157 Escherichia coli strains associated with haemolytic uraemic syndrome
More LessSurmmaryThe pheno- and genotypes of Shiga-like toxins (SLTs) in non-O157 Escherichia coli strains from patients with haemolytic uraemic syndrome were determined. The clinical isolates investigated were from Italy and Germany and belonged to serotypes O22:H8, O26:H−, O26:H11, O91:H−, O111:H− and O128:H−; one isolate was non-typable. SLT genotypes were analysed by complete nucleotide sequence analysis of the B-subunit genes. The results showed that 14 strains possessed slt-I alone, two contained slt-II alone and five isolates harboured both slt-I and slt-II genes. In only two strains were slt-II-related genes found, together with either slt-I or slt-II. These findings indicate that variants of SLT-II are rarely found in non-O157 E. coli isolates from patients with haemolytic uraemic syndrome. Polymerase chain reaction (PCR) with Taq cycle sequencing was found to be a suitable method for classification of slt genotypes.
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- Microbial Pathogenicity
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Modulatory action of Helicobacter pylori on histamine release from mast cells and basophils in vitro
More LessSurmmaryHelicobacter pylori is important in the aetiology of peptic ulceration. Despite inducing an inflammatory response in the mucosa, the organism persists, suggesting that it has efficient protective mechanisms. Some bacterial and viral products modulate histamine secretion from inflammatory cells. Therefore, this study examined the modulatory effects of H. pylori preparations on histamine release from rat peritoneal mast cells and human basophils. Eleven clinical isolates of H. pylori were prepared in different ways: As whole washed bacteria, washed sonicated bacteria, and formalin-killed bacteria, and as outermembrane and lipopolysaccharide (LPS) extracts. Histamine release from mast cells or basophils was not elicited by any of these bacterial preparations alone. However, when mixed with various secretory stimulants, the bacterial preparations caused inhibition of histamine release from rat mast cells (calcium ionophore A23187, compound 48/80, concanavalin A, anti-rat IgE) and human basophils (A23187, N-formyl Met-Leu-Phe). The degree of inhibition ranged from 48% to 97%. These results indicate that H. pylori exerts an inhibitory effect on cells of the immune system that contributes to its persistence within the gastric mucosa.
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Evidence of Pneumocystis carinii in cell line cultures infected with peripheral blood mononuclear cells isolated from AIDS patients with P. carinii pneumonia
More LessSurmmaryThe detection of Pneumocystis carinii was investigated in an in-vitro system consisting of a human lung epithelial cell line (A-549) inoculated with infected peripheral blood mononuclear cells (PMBC) from HIV-infected patients with proven or suspected P. carinii pneumonia (PCP), and from HIV-negative patients with other lung infections. Supernates from cultures were sampled daily and evaluated for the presence of P. carinii by Giemsa and immunofluorescence staining. P. carinii was isolated from 98 (95.1%) of 103 culture supernate samples from patients with proven pneumocystosis and 45 rvival in vitro for up to 3 weeks was observed. Recovery of P. carinii from infected PBMC strongly supports previous observations about its ability to disseminate haematogenously and could represent a further advance in understanding the pathogenesis and diagnosis of PCP.
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- Virology
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Human immunodeficiency virus type-1 can be detected in monocytes by polymerase chain reaction
SurmmaryLymphocytes and monocytes from 25 patients infected with human immunodeficiency virus type-1 (HIV-1)—13 asymptomatic, seven with the AIDS-related complex (ARC) and five with the acquired immunodeficiency syndrome (AIDS)—were lysed and subjected to PCR with three primer pairs: SK38/SK39 (gag), SK68/SK69 (env) and SK29/SK30 (LTR). Amplified DNA was solution-hybridised with 32P-labelled probes (SK19, SK70 and SK31, respectively) and detected by PAGE-autoradiography. HIV-1 DNA was detected as follows. Asymptomatic patients: Monocytes—gag 61.5%, env 100%, LTR 0%; lymphocytes—gag 100%, env 92.3%, LTR 53.84%. ARC patients: Monocytes—gag 71.4%, env 57.1%, LTR 0%; lymphocytes—gag 100%, env 71.4%, LTR 71.4%. AIDS patients: Monocytes—gag 80.0%, env 100%, LTR0%; lymphocytes—gag 100%, env 60%, LTR 60%. The presence of HIV-1 DNA was confirmed in the monocyte fraction. In this cell subset, the env gene-directed primers were the most effective for amplification, whereas the LTR gene-directed primers failed to amplify HIV-1 DNA. The different pattern of amplification found in monocytes may suggest that these cells could be infected by a genetic variant of the virus.
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- Announcement
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- Books Received
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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)