-
Volume 13,
Issue 2,
1980
Volume 13, Issue 2, 1980
- Short Articles
-
-
-
Experimental infection of athymic mice with Toxoplasma gondii (Plate XV)
More LessSummaryCongenitally athymic nude mice and their hirsute littermates with thymuses were infected with a normally avirulent cyst-producing strain of Toxoplasma gondii. The nude mice were much less able to cope with the infection. Unlike their hirsute littermates they failed to produce any detectable antibody and apparently allowed faster multiplication of cysts in the brain where the normal inflammatory response was absent. It was concluded that the thymus plays an essential role in the development of immunity to a cyst-producing strain of Toxoplasma in mice and in its absence neither humoral nor cellular protective mechanisms can develop.
-
-
- Articles
-
-
-
Ammonia production by intestinal bacteria: the effects of lactose, lactulose and glucose
More LessSummaryAmmonia production by eight groups of intestinal bacteria was measured, and the effect on ammonia production of lowered pH and ambient ammonia concentration was determined. Endogenous ammonia production from bacterial protoplasm was also examined.
To examine the mechanisms by which fermentable substrates reduce ammonia formation in a faecal incubation system, the effect of lactose, lactu-lose or glucose on ammonia release by pure cultures of intestinal bacteria was studied.
The largest amounts of ammonia were generated by gram-negative anaerobes, clostridia, enterobacteria, and Bacillus spp. Gram-positive non-sporing anaerobes, streptococci and micrococci formed modest amounts, and lactoba-cilli and yeasts formed very little ammonia. All groups of bacteria formed less ammonia at /?H 5 0 than at pH 70 and production of ammonia was not inhibited when 30 mmol ammonia/litre was included in the medium. Small amounts of ammonia were formed due to endogenous metabolism of bacterial cells.
Washed cell suspensions of four isolates of Bacteroides, one clostridial isolate and two streptococcal isolates formed less ammonia from alanine, methionine or histidine after growth in the presence of either lactose or lactulose. In contrast, the Bacteroides isolates formed more ammonia from aspartate than from either lactose or lactulose. Also, cultures of gram-negative anaerobes and enterobacteria, and to a lesser extent clostridia and streptococci, formed significantly less ammonia in nutrient broth when lactose, lactulose or glucose was included in the medium. This decrease in ammonia formation was not due to a fall in/?H of the medium. Ammonia production by gram-positive non-sporing anaerobes was not affected by carbohydrate fermentation.
These results suggest that gram-negative anaerobic bacteria make a major contribution to ammonia generated from peptides and amino acids in vivo, and that ammonia may be formed from bacterial cells in the colon. Fermentation of lactose and lactulose may repress the formation and inhibit the activity of enzymes responsible for ammonia release. In the human colon these substrate effects may decrease the amount of ammonia available to exert a toxic effect on the host, and thus contribute to the beneficial effects of lactulose when it is used in the treatment of portosystemic encephalopathy.
-
-
-
-
Partitioning of staphylococcal δ haemolysin
R. A. Murphy and R. HaqueSummaryThe behaviour of the biologically active components present in crude δ haemolysin was followed during various fractionation procedures utilised in the purification of δ haemolysin. Most chromatographic techniques yielded multiple peaks of δ haemolysin. None of the procedures completely separated δ haemolysin from the other components of crude culture filtrates. Efforts to purify δ haemolysin should be renewed.
-
-
-
Pseudomonas aeruginosa infection and vaccination in the rat
More LessSummaryA large molecular-weight fraction of Pseudomonas aeruginosa culture filtrate protected rats and mice against a lethal infection with a heterologous serotype, and to some extent against Escherichia coli and Listeria monocyto-genes. The active components were obtained from cultures grown for several days in a simple synthetic medium. Infection and vaccination with P. aeruginosa serotype 16 induced agglutinating and precipitating antibodies to the components of this serotype only; in rats infected or vaccinated with serotype 1, low titres of agglutinating antibody against type 16 were found. Vaccine prepared from type 1 or 16 increased, within 3 days of infection, the resistance of rats to type-16 organisms; within the same period agglutinins or precipitins were not produced. It is possible that the protection was based on opsonic and antitoxic activities.
-
-
-
Immunogenicity and molecular characterisation of staphylococcal δ haemolysin (Plate XIII)
More LessSummaryIn rabbit antisera to staphylococcal δ haemolysin the haemolysin-neutra-lising activity was associated with the IgG fraction as well as with the α and β lipoproteins. On an equal-weight basis, the neutralising capacity of specific antibody was not significantly greater than that of serum α or β lipoproteins. Anti-α haemolysin was not detected in any of the anti-δ-haemolysin antisera. Amino-acid analysis of δ haemolysin showed that lysine, aspartic acid, threonine and isoleucine were the predominant amino acids present; histidine, arginine, proline, cysteine and tyrosine were absent. The molecular weight of δ-haemolysin in phosphate-buffered saline was approximately 210 000.
-
-
-
The action of formaldehyde on staphylococcal δ haemolysin
More LessSummaryNative staphylococcal δ haemolysin was poorly immunogenic in the mouse. After treatment with formaldehyde at pH 5 or pH 7.5, haemolytic activity was rapidly lost but antigenic reactivity retained and, at pH 5, im-munogenicity was enhanced. Treatment of the haemolysin with formaldehyde at pH 9.5 reduced haemolytic activity by 97% but did not enhance immunogenicity. There was no evidence of polymerisation of formaldehyde-treated δ haemolysin, and the enhanced immunogenicity was considered to be partly due to a reduced affinity for phospholipids.
-
-
-
A scheme for the identification of clinical isolates of gram-negative anaerobic bacilli by conventional bacteriological tests
More LessSummaryMore than 1000 strains of gram-negative anaerobic bacilli, including reference strains, clinical isolates, and members of the normal flora of the mouth, lower gastro-intestinal tract and vagina of healthy human subjects, were studied by conventional bacteriological methods and by gas-liquid chromato-graphic analysis of metabolic products in a series of investigations. A short combined set of tests with particular discriminant value was selected, and a scheme for the identification of the species and subspecies encountered in the diagnostic bacteriological laboratory was based upon our composite results. The tests are: antibiotic-disk resistance tests with neomycin 1000 μg, kanamy-cin 1000 μg, penicillin 2 units and rifampicin 15μg per disk; tolerance tests with sodium taurocholate, Victoria blue 4R and gentian violet; and tests for pigment production, indole production, aesculin hydrolysis and the fermentation of glucose, lactose, sucrose, rhamnose, trehalose, mannitol and xylose. Gram-negative anaerobic bacilli are divided into four groups: (1) the fragilis group with nine species, which include the five subgroups previously classified as subspecies of B. fragilis; (2) the melaninogenicus-oralis group, which includes the three saccharolytic subspecies (ss.) of B. melaninogenicus-ss. melanino-genicus, ss. intermedius and ss. levii-and four non-pigmented species; (3) the asaccharolytic group, which comprises B. asaccharolyticus (formerly B. melaninogenicus ss. asaccharolyticus), B. corrodens and other non-pigmented non-saccharolytic strains, and (4) the fusobacteria.
-
-
-
Bacterial flora of the jejunum: a comparison of luminal aspirate and mucosal biopsy
More LessSummaryThe aerobic and anaerobic bacterial flora grown from 40 human jejunal aspirates were compared with the flora grown from an intestinal mucosal biopsy obtained simultaneously from the same level. In four paired samples the flora was identical; in nine the flora differed by only one organism. In six pairs the flora differed by two organisms, and in 11 pairs by three or more organisms. In nine pairs the jejunal aspirate grew only one organism or was sterile, but the biopsy showed considerable numbers of organisms. In one pair the jejunal aspirate grew organisms, but there was no growth from the biopsy. It is apparent that for adequate bacteriological study of the intestine, the flora at both sites should be investigated.
-
-
-
Prolonged primary incubation in the isolation of anaerobic bacteria from clinical specimens *
More LessSummaryThe value of prolonged primary anaerobic incubation for the isolation of anaerobic bacteria from clinical material was assessed by comparison of two incubation systems. Continuous incubation of primary anaerobic plates for 48 h was superior to conventional methods in that more anaerobes were isolated. The results indicate that in some cases prolonged incubation may be the only method of achieving the correct bacteriological diagnosis, particularly when relatively oxygen-sensitive strains are involved or when organisms may be damaged by exposure to oxygen during transport.
Use of extended primary incubation provides a clearer picture of the microbial flora of the original lesion and reveals that some anaerobic genera may be more commonly involved than is at present recognised.
-
-
-
Passive protection of lambs against enteropathogenic Escherichia coli: role of antibodies in serum and colostrum of dams vaccinated with K99 antigen
More LessSummaryLambs from suckling ewes vaccinated with the K99 antigen were resistant to challenge with K99-positive enteropathogenic Escherichia coli. Serum and colostrum from these ewes were compared with samples from control ewes to establish methods for monitoring vaccination and to determine the mechanism of protection.
Vaccination stimulated production of K99 antibodies. These could be detected by an indirect haemagglutination test and a haemagglutination-inhi-bition test. Antiglobulin and gel-diffusion tests were less reliable. Experiments with brush-border cells from calf intestine showed that the antibodies were associated with anti-adhesive activity. The antibodies were predominantly IgG and did not neutralise the activity of heat-stable enterotoxin. It was concluded that neutralisation of the adhesive properties of the K99-posi-tive E. coli by colostral antibodies significantly contributed to the resistance of the lambs from vaccinated ewes.
-
-
-
Maternal factors that enhance the acquisition of group-B streptococci by newborn infants
More LessSummaryBacteriological and clinical data in respect of 113 mothers who were vaginal carriers of group-B streptococci at the time of labour, and of their 113 infants, were examined for factors that contributed to mother-infant transmission of these micro-organisms. A semi-quantitative system (1 + = 1-10, 2 + = 11-50, and 3 + = > 50 colonies) was used to record the heaviness of growth in all positive primary cultures.
Positive cultures at birth or at the time of discharge from hospital (or both) were obtained from 44/66 of the infants of mothers with 3 + vaginal cultures (67%), but from only 17/47 of the infants of mothers with 2 + or 1 + cultures (36%; p < 0-005). Of 38 infants who gave positive cultures at birth, 32 (84%) were born to mothers with 3 + vaginal cultures. At birth, infants born to heavily colonised mothers were more often positive at multiple sites and were more heavily contaminated than infants born to lightly colonised mothers. However, nearly one-half of the infants whose swabs were first positive on discharge were born to mothers with 2 + or 1 + swabs.
When the mothers had been in labour for > 6 h after rupture of the membranes, the proportion of infants yielding positive cultures at birth was higher (47%) than the proportion for infants of mothers in labour for a lesser time after membrane rupture (27%; p<0-05), but there was no difference between the two groups in the eventual isolation rate (at birth-I-at discharge).
Although the distribution of group-B streptococcal serotypes was similar for mothers and infants, mothers carrying serotype-III strains delivered infants positive at birth more frequently than did mothers carrying all other serotypes.
The most important predictive factor determining neonatal acquisition of group-B streptococci appeared to be the number of group-B streptococci in the maternal vagina at the time of labour.
-
-
-
Experimental staphylococcal infections in newborn mice: inhibition of weight gain as an index of virulence
More LessSummaryWe attempted to evaluate the neonatal mouse model as an indicator of the virulence of staphylococcal strains freshly isolated from human patients in hospital. In preliminary studies with two previously characterised clinical isolates of Staphylococcus aureus and one of S. epidermidis, three indices of infection were studied. These were: mortality rate, multiplication of organisms in the skin, and the effect on weight gain. Of these, inhibition of normal weight gain by mice given subcutaneous injections when 3 days old was the most convenient and easily applied test. At a challenge dose of 106 c.f.u., the multiplication of organisms in the skin was correlated with the inhibition of normal weight gain. Weight gain was used to compare the virulence of a small series of clinical isolates from different types of staphylococcal infection. Strains isolated from severe infections caused a greater inhibition of weight gain than did strains from milder infections or environmental sources.
-
-
-
Identification of pathogenic neisseriae by genetic transformation
More LessSummaryThe detection of pathogenic neisseriae by genetic transformation of a naturally occurring proline auxotroph of Neisseria gonorrhoeae strain F62 is described. Of 169 clinical isolates of N. gonorrhoeae, approximately 90% gave a positive transformation assay. Twelve clinical isolates of N. meningitidis and stock cultures of the various meningococcal serogroups also gave a positive result. However, the sensitivity of the assay was found to be approximately 1000-fold lower with N. meningitidis as test organism. Eleven other members of the family Neisseriaceae failed to transform the recipient organism.
Although proline requirement did not appear to limit the value of the assay greatly, it probably was the main reason for negative results. The sensitivity of the assay and its ability to detect non-viable gonococci suggests that this method merits further investigation as a possible aid to diagnosis of gonococ-cal infection in special circumstances.
-
-
-
Influenza virus infection of newborn rats: virulence of recombinant strains prepared from influenza virus strain A/Okuda/57
More LessSummaryInfant rats were infected intranasally with wild influenza virus strains, attenuated strain A/Okuda/57 or recombinants prepared from these parents. The growth of viruses in the turbinates or lungs, and the ability of virus infections to potentiate subsequent bacterial infection by Haemophilus influen-zae (HIb) were measured. The two wild strains of virus and a recombinant strain WRL105, known to be virulent for man, reached titres of 105·1 − 106·5 EBID50/ml in the turbinates of infant rats 48 h after infection; infection by these viruses was followed by HIb bacteraemia in 77-92% and meningitis in 58-75% of animals. In contrast, virus strains known to be attenuated for man grew to lower titres in infant-rat turbinates and promoted a lower incidence of systemic infection by HIb than the virulent strains. A comparison of the various results of infection of infant rats with influenza virus strains of known pathogenicity for man indicated that the subsequent incidence of HIb bacteraemia was the most discriminating measurement of virus virulence; the range of yields of attenuated virus in rat turbinates overlapped that of virulent strains. These results, together with those of previous studies, indicate that the behaviour of influenza viruses in infant rats is an indication of virus virulence for man, and could provide a test of virulence that would facilitate the development of live attenuated virus vaccines for human use.
-
-
-
Immunosuppression in toxoplasmosis: further studies on mice infected with louping-ill virus
More LessSummaryMice were infected with an avirulent cyst-producing strain of Toxoplasma gondii and given injections of louping-ill virus 7 days later; control mice were given virus but not Toxoplasma. Test and control mice were then killed, in groups, 2, 4, 6, 8 and 10 days later. In the dually infected mice viraemia was later, greater and more prolonged; titres of virus recovered from brain and spleen were greater; production of haemagglutinating antibody to louping-ill virus was later and less, and inflammation in the brain was more severe, than in mice given virus alone. We suggest that T. gondii suppressed the immunity of mice, making them more susceptible to the virus, and that a significant proportion of the increased number of inflammatory cells observed in the brain could have been toxoplasma specific and not virus-specific and hence contributed to the increased susceptibility of the dually infected mice to louping-ill virus.
-
-
-
Increased susceptibility of rabbits to intravenous challenge with Mycobacterium avium after mild hepatitis produced by carbon tetrachloride
More LessSUMMARYA mild grade of liver damage in rabbits was produced by giving 23 subcutaneous injections of carbon tetrachloride (CCl4). The CCl4-treated rabbits and untreated controls were subsequently challenged with the mildly virulent strain of Mycobacterium avium Kirschberg (TMC 801). In two successive experiments it has been found that liver damage increased the susceptibility of rabbits to infection with this organism.
-
-
-
The role of glycoprotein carbohydrate in the immunological reactivity of antistreptococcal cell-membrane and antiglomerular basement-membrane antisera
More LessSUMMARYRabbit antisera to “carbohydrate-rich” antigens prepared from group-A, type-12 strepto-coccal cell-membrane and human glomerular basement-membrane were found to react by an indirect fluorescent-antibody test with the glomerular basement membrane of adult human kidney. This activity was absent or diminished in neonatal tissue. Removal of the carbohydrate epitopes from the adult tissue by means of carbohydrases removed the immunological activity. Antisera against the “carbohydrate-rich” antigens showed immunological reactivities distinctly different from those against the parent native immunogens-streptococcal cell membrane or glomerular basement membrane-which proved to be directed towards the protein epitopes.
-
-
-
Carriage of inhibitor-producing organisms on human skin
More LessSummaryThe carriage on skin lesions, on healthy skin and in the nose, of micro-organisms that produce antibiotics active against Staphylococcus aureus has been studied. About 5% of sites (10% of all patients) yielded such organisms. No evidence could be found that the presence of producer organisms in skin lesions had a protective effect against colonisation by S. aureus.
-
-
-
Distribution of Serratia marcescens serotypes in cancer patients
More LessSummaryA study of 1314 patients with malignancies was made to determine the prevalence ofSerratia marcescens in surveillance, diagnostic, and environmental cultures. Sera obtained from a commercial source were used to determine serotypic distributions of the S. marcescens strains isolated during a 51-month period. S. marcescens was isolated from 19% of patients with haematological neoplasms, from 5% of patients with lymphoma, and from 6% of those with solid tumours. Among carriers, rectal cultures were the commonest source in patients with lymphoma (32%); rectal and gingival cultures in patients with leukaemia (43% and 39%, respectively), and gingival cultures in patients with solid tumours (30%). Bacteraemias (07%) were infrequent sources. Although seldom isolated from environmental or food samples, S. marcescens may occasionally be abundant in fresh fruit and vegetables. Serotyping of 220 strains of S. marcescens demonstrated 38 distinct antigenic types. The predominant serotype, 014: H12, was present in the upper respiratory tract of half of the persons who carried this serotype. Serotyping is a readily reproducible method of subspeciating S. marcescens; it can be satisfactorily used as an epidemiological tool.
-
-
-
Phase variation in the genus Serratia
More LessSUMMARYDuring an investigation of the serotypes of Serratia marcescens present in a cancer centre, it was found that 8-7% of 241 strains had more than one H antigen. There were 19 diphasic and two triphasic strains. Antigen H1 was a component of the phases in approximately half of the strains with multiple phases. This is the first report of such phases in the genus Serratia.
-
Volumes and issues
-
Volume 74 (2025)
-
Volume 73 (2024)
-
Volume 72 (2023 - 2024)
-
Volume 71 (2022)
-
Volume 70 (2021)
-
Volume 69 (2020)
-
Volume 68 (2019)
-
Volume 67 (2018)
-
Volume 66 (2017)
-
Volume 65 (2016)
-
Volume 64 (2015)
-
Volume 63 (2014)
-
Volume 62 (2013)
-
Volume 61 (2012)
-
Volume 60 (2011)
-
Volume 59 (2010)
-
Volume 58 (2009)
-
Volume 57 (2008)
-
Volume 56 (2007)
-
Volume 55 (2006)
-
Volume 54 (2005)
-
Volume 53 (2004)
-
Volume 52 (2003)
-
Volume 51 (2002)
-
Volume 50 (2001)
-
Volume 49 (2000)
-
Volume 48 (1999)
-
Volume 47 (1998)
-
Volume 46 (1997)
-
Volume 45 (1996)
-
Volume 44 (1996)
-
Volume 43 (1995)
-
Volume 42 (1995)
-
Volume 41 (1994)
-
Volume 40 (1994)
-
Volume 39 (1993)
-
Volume 38 (1993)
-
Volume 37 (1992)
-
Volume 36 (1992)
-
Volume 35 (1991)
-
Volume 34 (1991)
-
Volume 33 (1990)
-
Volume 32 (1990)
-
Volume 31 (1990)
-
Volume 30 (1989)
-
Volume 29 (1989)
-
Volume 28 (1989)
-
Volume 27 (1988)
-
Volume 26 (1988)
-
Volume 25 (1988)
-
Volume 24 (1987)
-
Volume 23 (1987)
-
Volume 22 (1986)
-
Volume 21 (1986)
-
Volume 20 (1985)
-
Volume 19 (1985)
-
Volume 18 (1984)
-
Volume 17 (1984)
-
Volume 16 (1983)
-
Volume 15 (1982)
-
Volume 14 (1981)
-
Volume 13 (1980)
-
Volume 12 (1979)
-
Volume 11 (1978)
-
Volume 10 (1977)
-
Volume 9 (1976)
-
Volume 8 (1975)
-
Volume 7 (1974)
-
Volume 6 (1973)
-
Volume 5 (1972)
-
Volume 4 (1971)
-
Volume 3 (1970)
-
Volume 2 (1969)
-
Volume 1 (1968)
Most Read This Month
