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Biomedical subjects

P Berche

Publications and source records attributed to P Berche.

At least 163 records · Page 9Linked to original sources
PubMed1987

Purification, characterization, and toxicity of the sulfhydryl-activated hemolysin listeriolysin O from Listeria monocytogenes.

We purified and characterized an extracellular hemolysin produced by Listeria monocytogenes. Hemolysin production was greatly enhanced by growing bacteria in resin (Chelex)-treated medium. This hemolysin was separated as a homogeneous protein of 60,000 daltons by using thiol-disulfide exchange affinity chromatography. This protein was a sulfhydryl-activated toxin, termed listeriolysin O, which shared the classical properties of other bacterial sulfhydryl-activated toxins: inhibition by very low amounts of cholesterol; activation by reducing agents and suppression of the lytic activity by oxidation; antigenic cross-reactivity with streptolysin O. However, listeriolysin O differed remarkably from the other sulfhydryl-activated toxins in that its cytolytic activity towards erythrocytes from various animal species was maximum at low pH (approximately 5.5) and was undetectable at pH 7.0. This suggests that the lytic activity of the toxin in host tissues might be better expressed in the acidic microenvironment, including macrophage phagosomes where bacteria presumably replicate. Listeriolysin O was lethal to mice (50% lethal dose of ca. 0.8 microgram) and induced a rapid inflammatory reaction when injected intradermally. These results favor the view that listeriolysin O might play a major role during intracellular replication of L. monocytogenes, ultimately promoting death of infected macrophages.

Animals↗
PubMed1987

[Complications of infections attributed to cytomegalovirus in a group of 52 kidney transplant patients].

Cytomegalovirus (CMV) infection after renal transplantation was studied over a one year period in 52 patients receiving immunosuppressive drugs. During the infectious episodes, viral shedding was systematically detected in the blood and urines by culture on MRC5 cells and CMV antibodies were titrated in the serum by ELISA (IgG: M. A. Bioproducts, IgM: immunocapture Wellcome) and compared to the initial antibody titer determined the day of transplantation. Primary CMV infection was observed in 6 of 22 seronegative patients, attested by CMV shedding from urine and/or blood and by the emergence of CMV IgM antibodies. This primary infection was severe, including at least 4 of the following features: fever greater than 38 degrees C, neutropenia, thrombocytopenia, cytolytic hepatitis, pneumonia, impaired renal function, neurological syndrome, usually occurring about 6 weeks after transplantation. Reactivation was found in 12 of 30 seropositive patients, as shown by excretion of CMV in the urine and significant rise of specific antibodies. This reactivation occurring about 9 weeks after surgery was symptomatic in 5 patients with severe illness and associated with the presence of IgM antibodies in 2 cases. Rise of CMV antibodies was observed in 10 seropositive patients without excretion of virus. It coincided with symptomatic infection in only three patients who displayed severe symptoms, with presence of CMV IgM antibodies in one case. As previously reported, we confirm that CMV infection is a frequent complication of organ transplantation. It may be clinically silent in renal transplant patients or cause problems ranging from fever to pneumonia or retinitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Transposon mutagenesis as a tool to study the role of hemolysin in the virulence of Listeria monocytogenes.

The role of hemolysin in the virulence of Listeria monocytogenes was studied by using transposon mutagenesis. The 26-kilobase conjugative transposon Tn1545, originally found in Streptococcus pneumoniae, was transferred to a hemolytic virulent strain of L. monocytogenes. The frequency of transfer was estimated to be about 10(-8) per recipient. This allowed us to isolate a nonhemolytic mutant which most likely harbors a single copy of Tn1545. Loss of hemolysin production was associated with loss of virulence. The 50% lethal dose of the mutant was assessed to about 10(9.6) bacteria per mouse after intravenous challenge. Nonhemolytic bacteria were unable to grow in host tissues and were rapidly eliminated from the spleen and liver of infected mice. Virulence was restored in hemolysin-producing revertant obtained by spontaneous loss of transposon Tn1545. These results strongly suggest that hemolysin is a major virulence factor implicated in the intracellular growth of L. monocytogenes.

Animals↗
PubMed1986

[In vitro activity of cefotaxime, latamoxef and ceftriaxone on hospital strains of Enterobacteriaceae resistant to cefalotine and cefoxitine].

An in vitro study of the sensitivity of three cephalosporins of the third generation was performed on 119 wild strains of enterobacteriae selected because of their resistance to cefalotine and cefoxitine. Cefotaxime, latamoxef and cetriaxone remain very active on such strains since almost all of the strains were inhibited by a dose of 4 micrograms/ml and CI 50 p. cent was below 0.20 micrograms/ml. The activity of these three cephalosporins was comparable on groups E. coli, Klebsiella-Enterobacter-Serratia and C. freudii. Ceftriaxone appeared clearly more active than latamoxef and cefotaxime on Proteus stains.

Cefotaxime↗
PubMed1985

Protection against Yersinia infection induced by non-virulence-plasmid-encoded antigens.

Specific immunity against Yersinia was induced by plasmid-encoded antigens not associated with virulence. Mice were immunised with viable bacteria from a virulence-plasmid-cured strain of Y. pseudotuberculosis. This antigenic stimulation generated specific protection against virulence-plasmid-harbouring strains of Y. pseudotuberculosis and Y. pestis, demonstrating that protection can be generated by organisms lacking plasmid-encoded virulence antigens.

Animals↗
PubMed1984

Growth of Yersinia pseudotuberculosis in mouse spleen despite loss of a virulence plasmid of mol. wt 47 X 10(6).

A highly virulent strain of Yersinia pseudotuberculosis (LD50 c. 10(2) bacteria/mouse) harboured two plasmids with mol. wt of 47 X 10(6) and 61 X 10(6). The role of these plasmids in virulence was studied in mice with derived strains cured of plasmids. It was confirmed that the plasmid of mol. wt 47 X 10(6) played a major function in virulence. This was shown both by the increase of the LD50 and the lower rate of multiplication in the spleen obtained with strains cured of the plasmid of mol. wt 47 X 10(6). The plasmid of mol. wt 61 X 10(6) did not play any role in virulence. This work also demonstrates that the strain cured of the plasmid of mol. wt 47 X 10(6) and the plasmid-free strain were able to multiply in the spleens of infected mice during a 7-day period. This suggests that virulence factors not associated with plasmids are also responsible for the bacterial growth in tissues in vivo.

Animals↗
PubMed1984

Impaired resistance to Listeria monocytogenes in mice chronically exposed to cadmium.

It is shown in this work that resistance to Listeria monocytogenes is greatly impaired in C57BL/6 mice chronically exposed to cadmium (Cd) chloride. Animals received 0.5 mg/kg Cd by an intraperitoneal route three times a week during a 4-week period and were then infected with L. monocytogenes. Susceptibility to this pathogenic bacteria was not due to a defect of the specific immune response, since mice developed normal levels of anti-Listeria T cell-mediated immunity and did not show any impairment of macrophage activation. In fact, bacterial growth in organs was rapid in Cd-exposed mice during the early phase of infection, suggesting an impairment of non-specific defence mechanisms. Experimental data indicate that the susceptibility to L. monocytogenes might be due to a defect of macrophage recruitment in sites of infection during the early phase of the host response.

Animals↗
PubMed1980

Fulminant meningococcemia in a child with hereditary deficiency of the seventh component of complement and proteinuria.

A previously healthy 14-year-old boy presented with fulminant meningococcemia. He was found to have a total deficiency of C7. His serum totally lacked bactericidal activity against Neisseria meningitidis. Addition of purified C7 restored the serum hemolytic and bactericidal activity. Susceptibility to disseminated Neisseria infections has previously been reported in 3 patients with C7 deficiency, as well as in a few patients with deficiency of C5, C6 and C8. These findings emphasize the importance of intact complement mediated bactericidal activity in host defense against disseminated Neisseria infections. Evaluation of the complement system in individuals with Neisseria infections appears mandatory.

Adolescent↗
PubMed1980

[Search for homologous antibodies during urinary infections in patients with or without renal allografts (author's transl)].

We studied the immune response during urinary infections, firstly in 20 patients with a renal allograft and receiving immunosuppressive agents, secondly in 55 patients consulting on a renal unit. Homologous antibodies were sought in the urine (test for antibodies fixed on urinary bacteria AFBU) and in the serum (seroagglutination, indirect immunofluorescence) using an antigens strains isolated from patients' urine. Comparative statistical analysis of the results given by the 3 methods reveals a good correlation between these tests in non-transplanted patients. On the other hand, there is no statistical link between seroagglutination and the AFBU test in transplanted patients, whereas the results of indirect immunofluorescence and the AFBU test remain strongly correlated. The interest of the 3 methods is discussed.

Antibodies, Bacterial↗
PubMed1979

[Bacterial infections in renal homotransplant recipients. Results of regular bacteriological controls (author's transl)].

Bacterial infections were studied in 51 immunosuppression kidney transplant recipients. Eighty infectious episodes occured in the first six post-transplantation months. Forty percent of these episodes were nonfebrile, detected during the routine bacteriological follow-up examination. Out of these 80 bacterial infections, 59 were localized (47 in the urinary tract, nine in the surgical wound and three in the lungs) and 21 had spread. Neutopenia occured in 13 patients, in association with septicaemia in eight of them. Usually septicaemia appeared before neutropenia. In 12 cases, infectious episodes (10 septicaemias and two localized infections) and transplant failure were closely related. The bacterial strains responsible for these infections were essentially: Staphylococcus spp (39), Streptococcus spp (14), Klebsiella pneumoniae (9), Escherichia coli (9). Most of the localized infections cleared up when treated with a specific antibiotic. Seven failures of antibiotic treatment were observed in 21 cases of generalized infections. The importance of regular post-transplantation bacteriological check-up in detecting and treating infectious complications in graft recipients must be emphasized.

Adolescent↗
PubMed1979

Effect of antibiotics on mucoid strains of Pseudomonas aeruginosa.

A study of the susceptibility to 18 antibiotics has been performed on 47 mucoid strains comparatively to 71 fried-egg strains of Pseudomonas aeruginosa. The minimal inhibitory concentration was determinated by agar dilution method. On the whole, the mucoid strains were more sensitive to antibiotics than the fried-egg strains. The more effective antibiotics were carbenicillins, aminosids, colistin and tetracyclines. However, this drug susceptibility of mucoid strains were heterogeneous. The results of a statistical analysis demonstrated that the strains of P. aeruginosa were distributed into two classes: a first class clustered very sensitive strains to most antibiotics and a second class clustered more resistant strains. The mucoid strains were included almost equally into the two classes (respectively 45% and 55%). The fried-egg strains were more homogeneous, since 89% of these strains were in the resistant class. The antibiotics which distinguished the best between the two classes were: tobramycin, netilmicin, amikacin, colistin and tetracyclines. A study of the phenotypes and associations of resistances has been equally performed.

Anti-Bacterial Agents↗
PubMed1978

[Bacteriological aspects in the diagnosis and treatment of endocarditis (author's transl)].

The role of the laboratory is capital in ensuring the diagnosis of bacterial endocarditis. At the present time, the circumstance surrounding the onset of endocarditis have become broadened. The bacteria responsible may belong to various species, certain requiring the use of special techniques in their culture. If blood cultures are performed under suitable conditions, they should lead to isolation of the organism in more than 90 per cent of cases of endocarditis. Precise identification of the pathogenic organism forms the basis for rational antibiotic therapy. The bactericidal activity of treatment must nevertheless be confirmed in vitro, firstly by study of the reaction of the strain to antibiotics, and secondly by study of the bactericidal activity of the serum.

Anti-Bacterial Agents↗
PubMed1978

[Quantitative study of bacterial flora in operating room air].

A comparative study of two air-bacteria counting machines, MK II (Casella, London) and R.B. (Joubert, Lyon) was carried out. Pre-operation air samples from operating rooms were drawn by the two machines working simultaneously. The results from the two machines are similar, however the RB machine is more sensitive of the two machines. Moreover, an old operating room without filtrated air had a significantly higher air bacteria contamination (m = 199 +/- 173 bacteria/m3) than a new one with filtrated air (m = 40 +/- 36 bacteria/m3). Samples from laminar air flow (m = 1,3 +/- 1,5 bacteria/m3) were examined as test studies. Working methods and results of air bacteria counts are studied.

Air Microbiology↗
PubMed1978

[Clinical, bacteriological and pharmacokinetic study of Sisomicin in the newborn infant].

A study of the efficiency and tolerance of sisomicin in 19 children with severe bacterial infections led to the following conclusions: -sisomicin was efficient, particularly in association with beta-lactamin; -the local and systemic tolerance was good. The susceptibility of various bacterial strains was studied. The half-life of sisomicin given intramuscularly was : 4,0 +/- 1,8 hours in the new-borns under 10 days and 2,0 +/- 0,3 hours in older infants, when creatininemia was below 10 mg/l. No accumulation was found. The recommended daily dose of sisomicin by intramuscular route is 3 to 6 mg/kg, i.e. 1 to 2 mg every 8 hours in infants an 1,5 to 3 mg every 12 hours in new-borns.

Bacterial Infections↗
PubMed1978

[Quantitative study of the bacterial flora of air in operating theatres (author's transl)].

A comparative study of two air-bacteria counting machines, MK II (Casella, London) and R.B. (Joubert, Lyon) was carried out. Pre-operation air samples from operating rooms were drawn by the two machines working simultaneously. The results from the two machines are similar, however the RB machine is the more sensitive of the two machines. Moreover, an old operating room without filtrated air had a significantly higher air bacteria contamination (m = 199 +/- 173 bacteria/m3) than a new one with filtrated air (m = 40 +/- 36 bacteria/m3). Samples from laminar air flow (m = 1,3 +/- 1,5 bacteria/m3) were examined as test studies. Working methods and results of air bacteria counts are studied.

Air Microbiology↗
PubMed1978

[Bronchial brushing in severe lung diseases in children].

A distal bronchial brushing was performed in 25 children having severe lung diseases. The age of the patients ranged from 7 days to 14 years. Seventeen children were immuno-depressed. Bacteria were isolated five times (2 Staphylococcus aureus, 1 Streptococcus pneumoniae, 1 Serratia marcenscens, 1 Acinetobacter lwoffi), viruses twice (cytomegalovirus, syncytial respiratory virus), Pneumocystis carinii, four times. Cytologic study revealed malignant cells, and cells with intranuclear inclusions, evoking a viral infection. This procedure appears to be harmless in children over 2 years of age. In younger children there is a risk of pneumothorax. the principal indication for distal bronchial brushing is lung disease in immuno-depressed children. It may, however, also be useful in prolonged, treatment-resistant, severe lung diseases.

Adolescent↗