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Volume 40,
Issue 3,
1994
Volume 40, Issue 3, 1994
- Articles
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Support of Paracoccidioides brasiliensis multiplication by human monocytes or macrophages: inhibition by activated phagocytes
More LessSUMMARYThe interaction of human monocytes or monocyte-derived macrophages and yeast-form Paracoccidioides brasiliensis was studied in vitro. Yeast cells were readily ingested by adherent monocytes or macrophages. Multiplication of P. brasiliensis, measured by growth as colony forming units (cfu) on a supplemented medium with good plating efficiency, was greater in monocyte co-cultures compared to the number of cfu obtained from complete tissue-culture medium (CTCM). Multiplication increased with time in macrophage co-cultures, e.g., from two-six-fold in 24 h to nine-fold in 72 h. Microscopic observations indicated that ingested yeast cells multiplied inside macrophages. When monocytes were treated with supernate cytokines (CK) from concanavalin-A-stimulated mononuclear cells, then co-cultured with P. brasiliensis, multiplication was significantly inhibited compared with control monocyte co-cultures. Treatment of macrophages—derived from monocytes by culture in vitro for 3 days—for a further 3 days with CK resulted in maximal inhibition of multiplication over the subsequent 72 h. Similarly, when monocyte-derived macrophages (after culture for 7 days) were treated for 3 days with recombinant human y-interferon (IFN; 300 U/ml) or CK they restricted multiplication of P. brasiliensis by 65% and 95%, respectively, compared with control macrophages. Antibody to IFN abrogated the effect of IFN or CK treatment. These findings show that ingested P. brasiliensis can multiply in human monocytes or macrophages and that this multiplication can be restricted by activated monocytes or macrophages.
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Pyrolysis typing of isolates from a recurrence of systemic cryptococcosis
More LessSummaryCryptococcal meningitis was diagnosed in a 71-year-old male diabetic patient with underlying ischaemic heart disease, asthma and bilateral axillo-femoral vascular grafts. After treatment with fluconazole for 2 months, the patient appeared to be cured. Two years later he presented with an aneurysm of the right graft that was resected and replaced with a new graft segment. Cryptococcus neoformans var. neoformans was grown from post-operative blood cultures and samples of the excised graft. The patient was treated with fluconazole and discharged after 6 weeks. Multiple isolates from both episodes had been preserved, and these, together with isolates from other UK patients, were cultured in duplicate, blind coded and characterised by pyrolysis mass spectrometry (PMS). Duplicate culture and re-isolate sets formed tight clusters, with each patient set clearly distinct. Sets of isolates from the two episodes in this patient formed a single tight cluster and were indistinguishable by PMS. These results support the contention that C. neoformans infection can be reactivated after being dormant for a prolonged period.
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Rapid identification of species within the Mycobacterium tuberculosis complex by artificial neural network analysis of pyrolysis mass spectra
More LessSUMMARYAn artificial neural network (ANN) was trained to distinguish between Mycobacterium tuberculosis and M. bovis with averaged pyrolysis mass spectra from duplicate subcultures of four strains of each of these species, each pyrolysed in triplicate. Once trained, the ANN was interrogated with spectrum data from the original organisms (the “training set” and from 26 other mycobacterial isolates (the “ challenge set ”) of the M. tuberculosis complex (MTBC). Eight strains of M. bovis and 13 of M. tuberculosis, whether sensitive or variously resistant to antituberculosis drugs, were identified in agreement with conventional identification. Four strains of “M. africanum ” were identified as M. bovis. Of two atypical M. tuberculosis strains from South India, one was identified as M. tuberculosis and the other as M. bovis. Six strains of BCG proved heterogeneous; two gave equivocal identifications, three were identified as M. bovis and one was identified as M. tuberculosis.
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Removal of LPS from a Brucella cytoplasmic fraction by affinity chromatography with an anti-LPS monoclonal antibody as immunosorbent
More LessSUMMARYAffinity chromatography on polymyxin B-Sepharose 4B is one of the most commonly used methods for the removal of contaminating lipopolysaccharides (LPS). However, the LPS of Brucella spp. do not bind to polymyxin B. An affinity chromatography method with an anti-O antigen of Brucella LPS monoclonal antibody as immunosorbent was developed. The method produced a 1000-fold reduction in the LPS content of the cytoplasmic fraction of B. abortus. The eluted proteins retained their antigenicity. The method, which uses mild physiological conditions, is simple, effective and reproducible.
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Growth inhibition of Clostridium difficile by intestinal flora of infant faeces in continuous flow culture
More LessSummaryGrowth of Clostridium difficile was inhibited more strongly in continuous flow (CF) culture with C. difficile-negative faeces of infants than with C. difficile-positive faeces. Culture of faecal flora of infants yielded a greater variety of bacterial species in C. difficile-negative than in C. difficile-positive faeces. In the mixed CF culture of C. difficile with Enterococcus avium, Bacteroides distasonis, Eubacterium lentum, C. ramosum, C. perfringens and either Escherichia coli or Klebsiella pneumoniae isolated from C. difficile-negative faeces, inhibition of growth of C. difficile was demonstrated when the pH of the culture medium was decreased. Amino-acid analysis of CF cultures showed considerable utilisation of aspartic acid, serine, threonine, arginine and asparagine. A marked increase in concentrations of citrulline and ornithine was found in the culture that inhibited growth of C. difficile. The addition of citrulline and ornithine into a Gifu anaerobic medium (GAM) broth produced no inhibition of growth of C. difficile. The addition of the mixture of the depleted amino acids (aspartic acid, serine, threonine, arginine and asparagine) to the culture filrate or adjustment of the pH of the culture filtrate induced considerable growth of C. difficile. These results suggest that the inhibition of growth of C. difficile may be due to consumption of amino acids by intestinal flora, and not to the presence of inhibitors produced by the intestinal flora.
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Cytotoxic and haemagglutinating activities of motile Aeromonas species
More LessSUMMARYCytotoxic and haemagglutinating properties were determined in 114 Aeromonas strains isolated from various sites in slaughtered lambs and from processed lamb meat. Cytotoxic activity on Vero cells was observed in 48 (42%) of the strains. It was more common in A. sobria and A. hydrophila isolates than with A. caviae isolates. Haemagglutination (HA) activity was found frequently in motile aeromonads irrespective of species; it was present in 50% of A. sobria strains, 51% of A. hydrophila strains and 48% of A. caviae strains. HA was inhibited by fucose, galactose and mannose at low concentration and, in most cases, two or three of these sugars were inhibitory. A significant association was found between certain HA-inhibition patterns and the production of cytotoxin by Aeromonas spp.
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Vibrio mimicus with multiple toxin types isolated from human and environmental sources
SummaryA collection of 13 strains of Vibrio mimicus, including both clinical and environmental isolates from different geographic regions, was examined for various toxins. One strain of environmental origin produced cholera-like toxin (CT) which was completely absorbed with anti-CT immunoglobulin G, five strains produced a haemolysin that cross-reacted with the thermostable direct haemolysin of V. parahaemolyticus and DNA from two strains hybridised with a DNA probe specific for the heat-stable enterotoxin of V. cholerae non-O1. Culture supernates of all strains produced a factor that was cytotoxic to Vero and Chinese hamster ovary cells. In this study, we were able to identify strains of V. mimicus that produced, or had the genetic potential to produce, several toxin types simultaneously. The role of these strains as genetic reservoirs is discussed.
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Protection of mice against vaginal colonisation by Mycoplasma pulmonis
More LessSUMMARYResistance against vaginal colonisation by Mycoplasma pulmonis in strain TO mice after exposure to the mycoplasma was investigated. Eighteen mice from which M. pulmonis had been eliminated from the vagina, either naturally or by antibiotic therapy, were resistant to vaginal recolonisation. Specific antibody was measured by an indirect micro-immunofluorescence technique and the geometric mean titre (GMT) for each group of mice is presented. Almost all of 31 mice that had developed circulating antibody (GMT 83) or local antibody (GMT 40), or both, after vaginal exposure were resistant to re-colonisation, as were those in which antibodies could not be detected. Seven other mice which had been colonised only in the oropharynx previously and which possessed antibody—circulating (GMT 64) or local (GMT30), or both—were resistant to vaginal colonisation, but 13 mice with little or no antibody after lack of colonisation at either anatomical site were susceptible. All of 15 mice given killed M. pulmonis organisms intravenously, despite developing circulating antibody in high titre (GMT 122), were susceptible to vaginal colonisation, as were 14 of 15 mice that developed circulating (GMT 15) and local antibodies after being given killed organisms intravaginally. However, 25 mice with high titres of circulating (GMT 154–170) or local (GMT 20) antibody, or both, after receiving live organisms intravenously, were less susceptible to vaginal colonisation (17 becoming colonised) than were 21 non-immunised mice (all becoming colonised) and the organisms were eradicated more rapidly from the former. Despite this, the mice that were colonised following intravenous inoculation of live organisms had pre-challenge antibody titres that were as great as those that were not colonised. The results indicate that vaginal protection is likely to be mediated by factors other than, or in addition to, antibody, presumably by a cell-mediated means, and that concurrent respiratory infections are likely to contribute to vaginal immunity.
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Identification of viridans streptococci associated with bacteraemia in neutropenic cancer patients
More LessSummaryTwenty-three viridans streptococcal isolates from pyrexial neutropenic patients with various malignant diseases were studied in a comprehensive identification scheme. Fourteen isolates were identified as Streptococcus oralis, five as S. mitis and two as S. salivarius but the remaining two could not be identified reliably. The virulence mechanisms associated with the ability of these species to survive and grow in vivo require further investigation but may involve the production of specific glycosidase and proteolytic enzyme activities.
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Cough production, leucocytosis and serology of rats infected intrabronchially with Bordetella pertussis
More LessSummaryAdult Sprague-Dawley rats infected intrabronchially with Bordetella pertussis strain 18-323 encased in agarose beads (BP-beads), developed a paroxysmal cough and leucocytosis, both of which peaked at around day 10. When animals were exposed to ether for 2 min after delivery of the beads, there was an enhancement of the number of subsequent coughing episodes. Inclusion of carrageenan in the beads also enhanced coughing. Control rats, given sterile beads or left untreated, showed only a low level of coughing or no coughing, depending upon their source. Rats challenged by the same route with heat-killed B. pertussis in beads, or with live organisms in suspension (without beads) showed no cough induction or leucocytosis. However, intranasal delivery of B. pertussis suspension gave rise to a moderate amount of coughing and leucocytosis. Serum IgG responses to B. pertussis antigens were greatest in rats infected with BP-beads and antibodies against both pertussis toxin and filamentous haemagglutinin were detected. Since the rat is the only conveniently accessible laboratory animal species in which B. pertussis induces an intermittent paroxysmal cough, as in man, it merits further study for determining the mechanisms of pathogenesis and immunity in pertussis.
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Multidrug resistance to antiseptics and disinfectants in coagulase-negative staphylococci
More LessSUMMARYThe occurrence of resistance to antiseptics and disinfectants in clinical isolates of coagulase-negative staphylococci (CNS) was examined. Of 164 clinical strains of CNS isolated in the early 1980s, 65 were resistant to cationic antimicrobial compounds such as cetyltrimethylammonium bromide. Further characterisation of 40 resistant isolates by DNA-DNA hybridisation analysis and phenotypic resistance studies revealed that this resistance was mediated by the multidrug export genes qacA and qacC, characterised previously in Staphylococcus aureus. Of the resistant CNS isolates, 50% contained only qacA, 10% contained only qacC, and the remaining 40% contained both qacA and qacC. Both qacA and qacC genes resided on plasmids in all cases, with qacA located on plasmids of > 10 kb, whereas qacC was located primarily on plasmids of 2–3 kb. Representative qacA and qacC plasmids were characterised by restriction endonuclease mapping, and were found to be similar in some cases, but different in others, to those plasmids on which these genes are found in S. aureus.
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Gentamicin resistance in clinical isolates of Escherichia coli encoded by genes of veterinary origin
More LessSummarySeven (27%) of 26 gentamicin-resistant human clinical isolates of Escherichia coli were resistant to the veterinary aminoglycoside antibiotic apramycin. A gentamicin-resistant Klebsiella pneumoniae isolate from a patient infected with gentamicin/apramycin-resistant E. coli was also resistant to apramycin. DNA hybridisation studies showed that all gentamicin/ apramycin-resistant isolates contained a gene encoding the enzyme 3-N-aminoglycoside acetyltransferase type IV (AAC[3]IV) that mediates resistance to gentamicin and apramycin in bacteria isolated from animals. Seven of the eight gentamicin/apramycin-resistant isolates were also resistant to the veterinary antihelminthic agent hygromycin B, a phenomenon observed previously in gentamicin/apramycin-resistant Enterobacteriaceae isolated from animals. Resistance to gentamicin/apramycin and hygromycin B was co-transferable in six of the isolates. Restriction enzyme analysis of plasmids in apramycin-resistant transconjugants derived from E. coli and K. pneumoniae isolates from the same patient were virtually identical, suggesting that inter-generic transfer of plasmids encoding apramycin resistance had occurred in vivo. These findings support the view that resistance to gentamicin and apramycin in clinical isolates of E. coli results from the spread of resistant organisms from animals to man, with subsequent inter-strain or inter-species spread, or both, of resistance genes on transferable plasmids.
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- Editorial
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Volumes and issues
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Volume 74 (2025)
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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 57 (2008)
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Volume 55 (2006)
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Volume 52 (2003)
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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)
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