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P Pfister

Publications and source records attributed to P Pfister.

At least 19 recordsLinked to original sources
PubMed2006

A genetic model to investigate drug-target interactions at the ribosomal decoding site.

Recent advances in X-ray crystallography have greatly contributed to the understanding of the structural interactions between aminoglycosides and the ribosomal decoding site. Efforts to genetically probe the functional relevance of proposed drug-nucleotide contacts have in part been hampered by the presence of multiple rRNA operons in most bacteria. A derivative of the Gram-positive Mycobacterium smegmatis was rendered single rRNA operon allelic by means of gene inactivation techniques. In this system, genetic manipulation of the single chromosomal rRNA operon results in cells carrying homogeneous populations of mutant ribosomes. An exhaustive mutagenesis study of the ribosomal A site has been performed to define the importance of individual drug-nucleotide contacts. Mutational alterations in the M. smegmatis decoding site are discussed here, comparing the results with those obtained in other organisms. Implications for the selectivity of antimicrobial agents and for the fitness cost of resistance mutations are addressed.

Anti-Bacterial Agents↗
PubMed2006

[Diagnosis of malaria in Antananarivo City: examination of the results obtained at the Institut Pasteur de Madagascar from 2001 to 2004].

Malaria diagnosis is part of the daily activities of the Clinical Biology Center (CBC) of the Institut Pasteur de Madagascar in Antananarivo. Over a period of four years (2001-2004), regardless the methods being used, out of 6537 blood samples examined, 159 (2.43%) tests were positive. All four species of Plasmodium infecting human. were detected with a high prevalence of P. falciparum (87.2%). 49/159 patients were foreigners, but their files did not allow us to distinguish imported from locally acquired malaria cases. Also, among Malagasy patients, there was no possibility to recognize introduced malaria cases (contracted in coastal areas). In Madagascar malaria remains a public health problem. But fever and recent history of fever are often considered and treated as malaria. Our results demonstrated that confirmed malaria rate was very low. Reporting malaria on the basis of clinical signs overestimates malaria cases at the national level. The importance of malaria biological diagnosis is discussed in this article.

Humans↗
PubMed2004

Mutagenesis of 16S rRNA C1409-G1491 base-pair differentiates between 6'OH and 6'NH3+ aminoglycosides.

Using a single rRNA allelic Gram-positive model system, we systematically mutagenized 16S rRNA positions 1409 and 1491 to probe the functional relevance of structural interactions between aminoglycoside antibiotics and the A-site rRNA that were suggested by X-ray crystallography. At the structural level, the interaction of the 2-deoxystreptamine aminoglycosides with the rRNA base-pair C1409-G1491 has been suggested to involve the following features: (i) ring I of the disubstituted 2-deoxystreptamines stacks upon G1491 and H-bonds to the Watson-Crick edge of A1408; (ii) ring III of the 4,5-disubstituted aminoglycosides shows hydrogen bonding to G1491. However, we found that mutants with altered 16S rRNA bases 1409 and 1491 discriminated poorly between 4,5-disubstituted and 4,6-disubstituted 2-deoxystreptamines, but differentially affected aminoglycosides with a hydroxyl group versus an ammonium group at position 6' of ring I, e.g. G1491U conferred high-level drug resistance to paromomycin and geneticin, but not to neomycin, tobramycin or gentamicin.

Aminoglycosides↗
PubMed2004

[Haemophilus influenzae, the second cause of bacterial meningitis in children in Madagascar].

The Haemophilus influenzae b is one of the main germs causing bacterial meningitis in children in countries where the vaccine anti-Haemophilus influenzae b is not widely used. In Madagascar, no epidemiological study on this germ has been carried out. The objective of this research is to assess the role of Haemophilus influenzae meningitis in Antananarivo and to determine its epidemiological aspects and evolution. A multicentric study coordinated by the Institut Pasteur de Madagascar included all children less than 15 years old with infectious syndromes associated to a syndrome of meningial irritation and/or convulsion and/or coma. These children were admitted in the pediatric service of the three main hospitals in Antananarivo from June 1998 and June 2000. A lumbar puncture was performed on each child; the cerebrospinal fluid was set aside for cytobacterial and biochemical controls completed with an antimicrobial sensitivity testing and a soluble antigens research. Out of 160 case studies, the Haemophilus influenzae b arrives at the second place among the agents causing bacterial meningitis in children. This type of bacteria is the source of 32% of meningitis after the Streptococcus pneumoniae (34%). It affects 96% of children less than two years old, with a maximal frequency before the age of one year. The lethality rate is 28.6% and the neurological sequelae were observed in 31.4% of patients. Haemophilus influenzae is sensitive to the third generation cephalosporins but shows high resistance to chloramphenicol (42%), amoxicillin (29%) and gentamicin (22%). The relatively high frequency as well as the high lethality rate caused by the Haemophilus influenzae b meningitis, affecting selectively the children under two years old, bring in the need to introduce the anti-Haemophilus influenzae b vaccine in the national vaccination program in Madagascar. This vaccine has proved to be efficient in many countries where it has been used. Furthermore, in the probabilistic treatment of bacterial meningitis in children, the third generation cephalosporins should be used in the first place.

Adolescent↗
PubMed2003

Role of 16S rRNA Helix 44 in Ribosomal Resistance to Hygromycin B.

Hygromycin B is an aminoglycoside antibiotic active against prokaryotic and eukaryotic ribosomes. Ribosomal alterations in bacteria conferring resistance to hygromycin B have not been described, prompting us to use a single rRNA allelic derivative of the gram-positive bacterium Mycobacterium smegmatis for investigation of the molecular mechanisms involved in ribosomal resistance to hygromycin B in eubacteria. Resistance mutations were found to localize exclusively in 16S rRNA. The mutations observed, i.e., 16S rRNA U1406C, C1496U, and U1498C (E. coli numbering), are in close proximity to the hygromycin B binding site located in conserved helix 44 of 16S rRNA. The 16S rRNA positions involved in hygromycin B resistance are highly conserved in all three domains of life, explaining the lack of specificity and general toxicity of hygromycin B.

Anti-Bacterial Agents↗
PubMed2002

[Non-tubercular bacterial meningitis in children in Antananarivo, Madagascar].

OBJECTIVE: To determine the bacterial causal agents of meningitis and their pattern of resistance, in children more than one month to 14 years of age. METHODS: A 2 years, prospective study (June 1998 to June 2000) on bacterial meningitis in children was carried out in the main hospitals in Antananarivo. The enrollment criteria upon admission were fever with symptoms of meningitis and/or convulsions and/or coma. A lumbar puncture was systematically performed in each child. The aspect of the cerebrospinal fluid was described, the level of protein and glucose estimated, soluble antigens measured. Following the examination of a Gram straining, an aliquot of the fluid was cultured on specific medium. Antimicrobial sensitivity testing of isolated pathogens was performed. RESULTS: Bacterial meningitis was confirmed in 119 children: 95 (80%) and 111 (93%) were less than 12 and 24 months of age, respectively. The sex distribution was 1:1. Three predominant microorganisms were identified: Streptococcus pneumoniae (45%), Haemophilus influenzae b (43%) and Neisseria meningitidis (10%) of which ten of 12 cases were belonging to serogroup B. The other microorganisms isolated were E. coli (2%). S. pneumoniae were found to be sensitive to penicillin G and H. influenzae were found to be sensitive to the third generation cephalosporins. Seven percent of the S. pneumoniae strains were mildly resistant (R + I) to chloramphenicol and between 29 and 50% to aminoglucosides. A moderate resistance against gentamicin and amoxicillin was found in 22-29% of the H. influenzae strains. The mortality rate was high (31%) and among the surviving children 30% presented with neurosensitive disorders. CONCLUSION: According to these data we may recommend the inclusion of vaccination against H. influenzae in the children immunization program in Madagascar. The early diagnosis and treatment with appropriate antibiotics, such as third generation of cephalosporins, are other critical measures to be taken in order to reduce the risk of developing severe complications associated to bacterial meningitis.

Adolescent↗
PubMed2002

Ribosomal and non-ribosomal resistance to oxazolidinones: species-specific idiosyncrasy of ribosomal alterations.

A derivative of Mycobacterium smegmatis, which carries only one functional rRNA (rrn) operon, was used to isolate mutants resistant to the ribosome-targeted antibiotic linezolid. Isolation and characterization of linezolid-resistant clones revealed two classes of mutants. Ribosomes from class I mutants are resistant to oxazolidinones in an in vitro peptidyl transferase assay, indicating that resistance maps to the ribosome component. In contrast, ribosomes from class II mutants show wild-type susceptibility to a linezolid derivative in vitro, pointing to a non-ribosomal mechanism of resistance. Introduction of a wild-type ribosomal RNA operon into linezolid-resistant strains restored linezolid sensitivity in class I mutants, indicating that resistance (i) maps to the rRNA and (ii) is recessive. Sequencing of the entire rrn operon identified a single nucleotide alteration in 23S rRNA of class I mutant strains, 2447G --> T (Escherichia coli numbering). Introduction of mutant rrl2447T into M. smegmatis rrn- resulted in a linezolid-resistant phenotype, demonstrating a cause-effect relationship of the 2447G --> T alteration. The 2447G --> T mutation, which renders M. smegmatis linezolid resistant, confers lethality in E. coli. This finding is strong evidence of structural and pos-sibly functional differences between the ribosomes of Gram-positive and Gram-negative bacteria. In agreement with the results of the in vitro assay, class II mutants show a wild-type sequence of the complete rRNA operon. The lack of cross-resistance of the class II mutants to other antibiotics suggests a resistance mechanism other than activation of a broad-spectrum multidrug transporter.

Acetamides↗
PubMed2001

The genome of archaeal prophage PsiM100 encodes the lytic enzyme responsible for autolysis of Methanothermobacter wolfeii.

Methanothermobacter wolfeii (formerly Methanobacterium wolfei), a thermophilic methanoarchaeon whose cultures lyse upon hydrogen starvation, carries a defective prophage called PsiM100 on its chromosome. The nucleotide sequence of PsiM100 and its flanking regions was established and compared to that of the previously sequenced phage PsiM2 of Methanothermobacter marburgensis (formerly Methanobacterium thermoautotrophicum Marburg). The PsiM100 genome extends over 28,798 bp, and its borders are defined by flanking 21-bp direct repeats of a pure-AT sequence, which very likely forms the core of the putative attachment site where the crossing over occurred during integration. A large fragment of 2,793 bp, IFa, apparently inserted into PsiM100 but is absent in the genome of PsiM2. The remaining part of the PsiM100 genome showed 70.8% nucleotide sequence identity to the whole genome of PsiM2. Thirty-four open reading frames (ORFs) on the forward strand and one ORF on the reverse strand were identified in the PsiM100 genome. Comparison of PsiM100-encoded ORFs to those encoded by phage PsiM2 and to other known protein sequences permitted the assignment of putative functions to some ORFs. The ORF28 protein of PsiM100 was identified as the previously known autolytic enzyme pseudomurein endoisopeptidase PeiW produced by M. wolfeii.

Bacteriophages↗
PubMed2001

Similar efficacy following four weeks treatment of asthmatics with formoterol 12 micrograms b.d. delivered by two different dry powder inhalers: differences in inhaler handling.

This randomised, multicentre, parallel-group study compared the clinical efficacy and ease of handling of two dry powder inhalers delivering the long-acting beta 2-agonist formoterol. After run-in, 200 asthmatics on treatment with inhaled corticosteroids and still presenting with suboptimal asthma control were randomised to receive 12 micrograms formoterol twice daily via either the Aerolizer inhaler (Foradil Aerolizer) or the Turbuhaler inhaler (Oxis Turbuhaler) for four weeks. Study variables included the mean morning pre-medication peak expiratory flow (PEF) during the last seven days of treatment and the correct inhaler handling according to inhaler-specific checklists. The mean difference in the effect on morning pre-medication PEF was 13.86 l/min in favour of formoterol via the Aerolizer inhaler (90% confidence interval 2.50, 25.21) in the intent-to-treat population. Eighty-six per cent of the patients under treatment with formoterol via the Turbuhaler inhaler performed correctly all the essential inhalation manoeuvres, whereas 98% of those on the Aerolizer inhaler did so. These results strongly suggest similar clinical efficacy with twice daily treatment of formoterol 12 micrograms metered dose delivered either by the Aerolizer, or the Turbuhaler device. They also suggest that handling the Aerolizer is easier than that of the Turbuhaler.

Administration, Inhalation↗
PubMed2001

[Vibrio cholerae in Madagascar: study of a multiresistant strain].

Madagascar was cholera free until March 1999. The first case was reported in Mahajanga, a north west coast harbor. Ten months later and despite a massive use of tetracycline as prophylactic drug, cholera had reached every region of the island. All suspected cholera samples were analysed at the Pasteur Institute of Madagascar where susceptibility to tetracycline was systematically performed. On February 2000, a multidrug resistant strain of V. cholerae was isolated. We studied this strain by performing Minimal Inhibitory Concentration (MIC) and by plasmidic and conjugative assay. As the original strain, this multiresistant V. cholerae showed a resistance to cotrimoxazole, to streptomycin and chloramphenicol but, in addition to, appeared strongly resistant to ampicillin and tetracycline. This strain harboured a 26 kb self-transmissible plasmid. Conjugation tests showed the possibility of plasmidic segregates or acquisition of two different plasmids. The weak transfer rate could explain why we have isolated only one multiresistant strain. The emergence of a such multiresistant strain should encourage the medical authorities to reinforce the epidemic survey in every medical Malagasy district and to carry out new antimicrobial surveys to describe the mechanisms of the spread of these resistances.

Cholera↗
PubMed2000

Phylogenetic analysis of 18 thermophilic Methanobacterium isolates supports the proposals to create a new genus, Methanothermobacter gen. nov., and to reclassify several isolates in three species, Methanothermobacter thermautotrophicus comb. nov., Methanothermobacter wolfeii comb. nov., and Methanothermobacter marburgensis sp. nov.

Using a combination of 16S rRNA analysis and antigenic fingerprinting consisting of new and published data, the phylogenetic position of 18 thermophilic isolates currently classified as Methanobacterium species was reinvestigated. The results were verified by independent methods, including, where applicable, plasmid and phage typing. Comparative analysis of 16S rRNA data for 30 strains belonging to the order Methanobacteriales strongly suggested that mesophilic and thermophilic Methanobacterium isolates are distantly related and should be assigned to separate genera. For the thermophilic strains the genus Methanothermobacter was initially proposed by Boone, Whitman and Rouvière. Furthermore, the results support a reclassification of 15 isolates in three species within the proposed genus: (i) Methanothermobacter thermautotrophicus comb. nov., containing eight isolates, six of which are able to utilize formate (type strain deltaHT); (ii) Methanothermobacter wolfeii comb. nov., containing four formate-utilizing isolates (type strain DSM 2970T); (iii) Methanothermobacter marburgensis sp. nov., containing three obligately autotrophic isolates (type strain MarburgT). Of the nine isolates formerly referred to as Methanobacterium thermoformicicum, six were reclassified as Methanothermobacter thermautotrophicus and three as Methanothermobacter wolfeii.

Antigens, Archaeal↗
PubMed2000

[Estimation of normal hemogram values in Madagascar].

In Madagascar, as in several african countries, haematological normal values has not been established. To assess the haematological normal values in the laboratory of the Institut Pasteur de Madagascar, blood cell counts among 67 adults healthy malagasy volunteers, living in highlands of Madagascar, was performed. Blood was analysed with a Coulter STKS haematological autoanalyzer. A significant difference was noted between both sexes for the count of red blood cells, leukocytes, platelets, neutrophile polynuclears, eosinophile polynuclears, lymphocytes and for haemoglobin and haematocrit values. Our data were compared to those of different african and caucasian populations.

Adolescent↗
PubMed1999

Formoterol and beclomethasone versus higher dose beclomethasone as maintenance therapy in adult asthma.

A total of 132 adult asthmatics who were symptomatic on 500 microg x day(-1) inhaled beclomethasone dipropionate (BDP) were studied in an open-label randomized, parallel group, 12 week, clinical trial. The addition of 12 microg formoterol fumarate solution aerosol (pressurized metered dose inhaler) b.i.d. to BDP at a dose of 500 microg x day(-1) was compared with a higher dose of 1,000 microg x day(-1) BDP. Mean morning premedication peak expiratory flow rate (PEF) during the final week of treatment (primary end-point) increased in both groups compared to baseline. The estimated treatment difference of 20.4 L x min(-1) (95% confidence interval 3.2-37.6) after 12 weeks of treatment was statistically significant (p<0.05) in favour of the formoterol/BDP group. The overall mean morning premedication PEF for the entire treatment period was higher in the formotero/BDP group (p=0.002). The overall number of puffs of rescue medication and asthma symptom scores were less in the formotero/BDP group (p<0.01). Safety and tolerability evaluations were satisfactory in both groups. In conclusion, the results suggest that the addition of formoterol fumarate to the existing dose of an inhaled corticosteroid should be considered as an alternative to increasing the dose of inhaled corticosteroid in the inadequately controlled asthmatic.

Administration, Inhalation↗
PubMed1999

Intermittent short courses of cyclosporin (Neoral(R)) for psoriasis unresponsive to topical therapy: a 1-year multicentre, randomized study. The PISCES Study Group.

We performed a 1-year study to determine whether intermittent short courses of the microemulsion formulation of cyclosporin (Neoral) could effectively control plaque psoriasis and whether tapering or abrupt cessation of cyclosporin therapy would influence time to relapse. Four hundred patients with plaque psoriasis were included in this open, multicentre, randomized study. All patients commenced cyclosporin at a dose of 2.5 mg/kg daily. Cyclosporin dosage could be increased to a maximum of 5 mg/kg daily. Treatment was continued until clearance of psoriasis or for a maximum of 12 weeks. Patients were then randomly assigned either to stop cyclosporin abruptly or to have the dose reduced by 1 mg/kg daily each week until cessation. On relapse, patients were given another course of cyclosporin. Patients were followed for at least 1 year, during which they could receive as many treatment courses as necessary. The number of patients who required one, two, three and four treatment courses was 400, 259, 117 and 26, respectively. The median time to relapse after the end of the first treatment period was 109 days in the group of patients randomized to stop cyclosporin abruptly and 113 days in patients randomized to taper off cyclosporin (P = 0.038). More than 30% of patients had not relapsed 6 months after having stopped treatment. After each treatment course, the Kaplan-Meier probability of achieving 75% or more reduction in disease area by day 84 of treatment was 83%, 76%, 73% and 66%, respectively. Mean serum creatinine concentration and blood pressure did not show any clinically significant changes over time. Our results show that intermittent short-course therapy with Neoral, when used in conjunction with topical therapy, is well tolerated and provides effective control of plaque psoriasis for 1 year. Tapering off cyclosporin on treatment cessation induces a slight delay in psoriasis relapse.

Adolescent↗
PubMed1999

[Acquired antibiotic resistance in Madagascar: first evaluation].

The purpose of this study was to evaluate the incidence of acquired resistance to antibiotics in Madagascar. Testing was carried out on total of 1267 strains of medically significant bacteria isolated from specimens sent to the Pasteur Institute of Madagascar in Antananarivo between October 1997 and October 1998. Antibiograms were performed using the diffusion technique on gel media with antibiotic disks. Results were read according to the criteria of the Antibiogram Committee of the French Society of Microbiology. Preliminary findings documented a high incidence of resistance to widely available, low-price antibiotics including penicillin G and tetracycline for which 84 p. 100 and 65 p. 100 of Staphylococcus aureus respectively demonstrated resistance; tetracyclin to which 80 p. 100 of streptococcus were resistant; and ampicillin, cotrimoxazole, and phenicoles to which 60 p. 100, 60 p. 100 and 28 p. 100 of Escherichia coli respectively and 77 p. 100, 83 p. 100, and 71 p. 100 of Shigella sp. respectively were resistant. Second-line antibiotics including penicillin M, macrolides, nalidixic acid, and nitrofuranes were still relatively active, thus providing an effective alternative. Newly developed antibiotics such as fluoroquinolones and third-generation cephalosporines were highly effective but a few resistant strains were observed. Although not representative of Madagascar as a whole, the findings of this preliminary study indicate that acquired resistance must be taken into account in designing simplified decision charts for front-line laboratories, that appropriate information must be made available to health care workers, and that further testing is needed to monitor the evolution of antibiotic resistance.

Bacterial Infections↗
PubMed1999

[First cases of cholera observed in children at the Befelatanana General Hospital--Antananarivo University Hospital Center (Madagascar)].

Ravages caused by cholera among children are well known. The disease invaded Madagascar in 1999 May. This retrospective study reported the first childhood cholera cases. The survey was carried out at the Befelatanana Hospital during the period of cholera outbreak from April 23th to July 31st. The purpose of the study was to specify clinical, epidemiological and bacteriological characteristics of the disease. 5 out of 178 suspected cholera cases were less than 15 years old. 2 young girls out these 5 children, inhabitants of Antananarivo-City were hospitalized for acute diarrhoea with serious dehydratation. Their disease was confirmed by bacteriology. Vibrio cholera O1 strain, serovar Ogawa was identified. Epidemiological investigation allowed to identify the contamination modal in the file no 1. The authors conclude that cholera is an important problem of public health in developing country like Madagascar. Disease control needs environmental sanitation and good individual hygiene practices.

Age Distribution↗