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Biomedical subjects

V Jarlier

Publications and source records attributed to V Jarlier.

At least 55 records · Page 3Linked to original sources
PubMed2000

Comparative potency of mecillinam and other beta-lactam antibiotics against Escherichia coli strains producing different beta-lactamases.

The activity of mecillinam, a beta-lactam antibiotic with high affinity for Gram-negative penicillin-binding protein 2 (PBP2), was assessed against ampicillin-resistant Escherichia coli strains producing beta-lactamases representing the three molecular classes, A (TEM-1 and -3, SHV-3 and IRT-5), C (AmpC) and D (OXA-3). The antimicrobial activity of mecillinam and other beta-lactam antibiotics was evaluated by determining their MICs on Mueller-Hinton agar. The time course of hydrolysis in crude extracts prepared from the various beta-lactamase-producing strains was also measured and was used to determine the relative rate of hydrolysis and the apparent affinity for ampicillin, cephalothin and mecillinam. When compared with the other beta-lactam antibiotics, mecillinam demonstrated significantly greater antibacterial potency and higher stability to beta-lactamase hydrolysis in TEM-, IRT- and AmpC-producing isolates. These findings confirm that the antimicrobial potency of mecillinam compares favourably with those of the other penicillins included in the present study, suggesting that mecillinam use in the treatment of infections caused by Gram-negative bacteria should be re-evaluated.

Journal Article↗
PubMed2000

[Mycobacterium ulcerans infection].

Mycobacterium ulcerans infection, or Buruli ulcer, is the third most common mycobacterial disease of the immunocompetent host in the tropical areas. M. ulcerans reservoir is aquatic. Infection occurs in children and young adults. The lesion begins with an indolent subcutaneous nodule, principally located on the limbs, that progressively changes into a deep indolent extensive ulcer. M. ulcerans produces a lipidic necrotic and immunosuppressive toxin, named mycolactone, that causes the clinical lesions. In endemic areas, clinical diagnosis is confirmed by microscopic examination. Spontaneous healing occurs after several months or years, causing retractile scars. Surgical excision and grafting is the treatment of choice. Antibiotic therapy is of limited value.

Adult↗
PubMed2000

Comparative potency of mecillinam and other beta-lactam antibiotics against Escherichia coli strains producing different beta-lactamases.

The activity of mecillinam, a beta-lactam antibiotic with high affinity for gram-negative penicillin-binding protein 2 (PBP2), was assessed against ampicillin-resistant Escherichia coli strains producing beta-lactamases representing the three molecular classes, A (TEM-1 and -3, SHV-3 and IRT-5), C (AmpC) and D (OXA-3). The antimicrobial activity of mecillinam and other beta-lactam antibiotics was evaluated by determining their MICs on Mueller-Hinton agar. The time course of hydrolysis in crude extracts prepared from the various beta-lactamase-producing strains was also measured and was used to determine the relative rate of hydrolysis and the apparent affinity for ampicillin, cephalothin and mecillinam. When compared with the other beta-lactam antibiotics, mecillinam demonstrated significantly greater antibacterial potency and higher stability to beta-lactamase hydrolysis in TEM-, IRT- and AmpC-producing isolates. These findings confirm that the antimicrobial potency of mecillinam compares favourably with those of the other penicillins included in the present study, suggesting that mecillinam use in the treatment of infections caused by gram-negative bacteria should be re-evaluated.

Amdinocillin↗
PubMed1999

Role of ser-237 in the substrate specificity of the carbapenem-hydrolyzing class A beta-lactamase Sme-1.

The role of the serine residue found at position 237 in the carbapenemase Sme-1 has been investigated by constructing a mutant in which Ser-237 was replaced by an alanine. The S237A mutant showed a catalytic behavior against penicillins and aztreonam very similar to that of Sme-1. By contrast, S237A was characterized by a reduced catalytic efficiency against cephems, such as cephalothin and cephaloridine. In addition, the weak activity of Sme-1 against the cephamycin cefoxitin was hardly detectable with the mutant enzyme. Finally, the Ser-237-->Ala mutation resulted in a marked decrease in catalytic activity against imipenem, showing that Ser-237 contributes to the carbapenemase activity of the class A beta-lactamase Sme-1.

Alanine↗
PubMed1999

Culture-independent prediction of isoniazid resistance in Mycobacterium tuberculosis by katG gene analysis directly from sputum samples.

BACKGROUND: The molecular prediction of isoniazid (INH) resistance in Mycobacterium tuberculosis is hampered by the need for specialized equipment, expertise, high costs, a limited range of detectable mutations, or several of these factors. The rationale for the study was to find a practical alternative and to demonstrate generally valid problems. METHODS AND RESULTS: DNA extracted from decontaminated sputum pellets was used to amplify a 0.26 kb target sequence within the katG gene. Mutations of codon 315, frequently found in isoniazid-resistant isolates, could be discriminated in a simple agarose minigel format following an AciI digest of the nested polymerase chain reaction (PCR) product. Within a panel of 22 sputum samples, INH resistance could be predicted in 5 of 10 samples containing isoniazid-resistant M. tuberculosis. The protocol is robust, requires little expertise and no specialized equipment, and provides the test results within 2 days. CONCLUSION: The results show the feasibility to rapidly and easily detect mutations highly predictive of isoniazid resistance. Nevertheless, this, like any other molecular resistance prediction test, is affected by often neglected factors, including mutation prevalences, the phenomenon of heteroresistance, and a possible bias toward one's own method.

Antitubercular Agents↗
PubMed1999

Site-directed mutagenesis of residues 164, 170, 171, 179, 220, 237 and 242 in PER-1 beta-lactamase hydrolysing expanded-spectrum cephalosporins.

The class A beta-lactamase PER-1, which displays 26% identity with the TEM-type extended-spectrum beta-lactamases (ESBLs), is characterized by a substrate profile similar to that conferred by these latter enzymes. The role of residues Ala164, His170, Ala171, Asn179, Arg220, Thr237 and Lys242, found in PER-1, was assessed by site-directed mutagenesis. Replacement of Ala164 by Arg yielded an enzyme with no detectable beta-lactamase activity. Two other mutants, N179D and A164R+N179D, were also inactive. Conversely, a mutant with the A171E substitution displayed a substrate profile very similar to that of the wild-type enzyme. Moreover, the replacement of Ala171 by Glu in the A164R enzyme yielded a double mutant which was active, suggesting that Glu171 could compensate for the deleterious effect of Arg164 in the A164R+A171E enzyme. A specific increase in kcat for cefotaxime was observed with H170N, whereas R220L and T237A displayed a specific decrease in activity towards the same drug and a general increase in affinity towards cephalosporins. Finally, the K242E mutant displayed a kinetic behaviour very similar to that of PER-1. Based on three-dimensional models generated by homology modelling and molecular dynamics, these results suggest novel structure-activity relationships in PER-1, when compared with those previously described for the TEM-type ESBLs.

Amino Acids↗
PubMed1999

Type II topoisomerase mutations in ciprofloxacin-resistant strains of Pseudomonas aeruginosa.

We determined the sequences of the quinolone resistance-determining regions of gyrA, gyrB, and parC genes for 30 clinical strains of Pseudomonas aeruginosa resistant to ciprofloxacin that were previously complemented by wild-type gyrA and gyrB plasmid-borne alleles and studied for their coresistance to imipenem (E. Cambau, E. Perani, C. Dib, C. Petinon, J. Trias, and V. Jarlier, Antimicrob. Agents Chemother. 39:2248-2252, 1995). In the present study, we found mutations in type II topoisomerase genes for all strains. Twenty-eight strains had a missense mutation in gyrA (codon 83 or 87). Ten of them had an additional mutation in parC (codon 80 or 84), including a novel mutation of Ser-80 to Trp, but all were fully complemented by a plasmid-borne wild-type gyrA allele. The remaining two strains harbored the first gyrB mutation described in P. aeruginosa, leading to the substitution of phenylalanine for serine 464. The strains which had two mutations in type II topoisomerase genes (i.e., gyrA and parC) were significantly more resistant to fluoroquinolones than those with a single mutation in gyrA or gyrB (geometric mean MICs of ciprofloxacin, 39.4 versus 10.9 microg/ml, P < 0.01; geometric mean MICs of sparfloxacin, 64.0 versus 22.6, P < 0. 01). No mutant with a parC mutation alone was observed, which favors DNA gyrase being the primary target for fluoroquinolones. These results demonstrate that gyrA mutations are the major mechanism of resistance to fluoroquinolones for clinical strains of P. aeruginosa and that additional mutations in parC lead to a higher level of quinolone resistance.

Amino Acid Sequence↗
PubMed1999

Characterization of new mutations in pyrazinamide-resistant strains of Mycobacterium tuberculosis and identification of conserved regions important for the catalytic activity of the pyrazinamidase PncA.

A new set of mutations, including transposition of the insertion sequence IS6110, was identified in the pncA gene from 19 pyrazinamide-resistant Mycobacterium tuberculosis strains. Alignment of the PncA protein from M. tuberculosis with homologous proteins from different bacterial species revealed three highly conserved regions in PncA which may play an important role in the processing of pyrazinamide.

Amidohydrolases↗
PubMed1999

Emergence and spread in French hospitals of methicillin-resistant Staphylococcus aureus with increasing susceptibility to gentamicin and other antibiotics.

Oxacillin (methicillin) resistance in methicillin-resistant Staphylococcus aureus (MRSA) is associated with an increased incidence of resistance to other antibiotics, which has increased since it was first reported in 1969. In 1992 a new phenotype of MRSA arose in France; this was characterized by a heterogeneous expression of resistance to oxacillin and susceptibility to various antibiotics, including gentamicin but also tetracycline, minocycline, lincomycin, pristinamycin, co-trimoxazole, rifampin, and fusidic acid. In French hospitals a longitudinal nationwide surveillance of antibiotic resistance in S. aureus has allowed for the detection of changes in antibiotic susceptibility profiles. Seven French clinical laboratories (six from the mainland and one from the West Indies) reported the results of susceptibility testing of 57,347 S. aureus strains isolated in their institutes between 1992 and 1998. Over a 7-year period the incidence of isolation of gentamicin-susceptible MRSA (GS-MRSA) strains has steadily increased to represent, in 1998, 46.8 to 94.4% of the MRSA strains, irrespective of the overall incidence of MRSA. Two predominant types recognized by pulsed-field gel electrophoresis (PFGE) accounted for the majority of the GS-MRSA in different mainland hospitals, both differing from the predominant type observed in the French West Indies. Some GS-MRSA and gentamicin-resistant MRSA (GR-MRSA) strains had closely related PFGE profiles, and hybridization studies confirmed the lack in GS-MRSA of the aac6'-aph2" gene, which confers resistance to all aminoglycosides, with conservation of the ant4' gene, which confers resistance to kanamycin, tobramycin, and amikacin. Thus, it is likely that certain GS-MRSA strains could have emerged from GR-MRSA strains by excision or deletion of the aac6'-aph2" gene.

Cross Infection↗
PubMed1999

Evaluation of the new MB redox system for detection of growth of mycobacteria.

We evaluated a new mycobacterial culture system, MB Redox, for recovery rate and time to detection of mycobacteria from 742 consecutive respiratory specimens and compared the results to those found with Löwenstein-Jensen (LJ) medium. Twenty specimens (2.7%) were positive for M. tuberculosis: 17 on LJ medium and 19 in MB Redox, with 16 specimens positive in both media. In addition, 24 specimens (3.2%) were positive for nontuberculous mycobacteria (NTM), 20 on LJ medium, 18 in MB Redox, and 14 in both media. For M. tuberculosis, the mean times to detection were 28.9 days on LJ medium and 23.6 days in MB Redox, and for NTM, the mean times to detection were 40.6 days on LJ medium and 32.3 days in MB Redox.

Bronchoalveolar Lavage Fluid↗
PubMed1999

Outcome of multi-drug-resistant tuberculosis in France: a nationwide case-control study.

The factors related to the outcome of 51 cases of multi-drug-resistant tuberculosis (MDR-TB) reported in 1994 to the French National Reference Center were retrospectively analyzed. The patients (median age, 45 yr) were mainly male (75%), foreign-born (63%), and had pulmonary involvement (95%). Sixteen percent were human immunodeficiency virus (HIV)-coinfected. The number of drugs to which the Mycobacterium tuberculosis isolates were susceptible was four. Only 82% of the patients have been hospitalized at any time (median duration, 33 d). Five patients (9%) received no antituberculosis drugs, although three had drug susceptibility results, indicating that two or more active drugs were available; 46 (91%) received drugs, including 37 who received two or more active drugs. Among the nine cases who received only one active drug, three had drug susceptibility results, indicating that two or more active drugs were available. By December 1996, 10 patients were lost before treatment completion, 24 had treatment failure, and 17 had a favorable outcome. The median survival time was 31 mo. Factors related to a poorer outcome were HIV-coinfection (hazard ratio [HR] = 41), treatment with less than two active drugs (HR = 9.9), and MDR status knowledge at the time of diagnosis (HR = 3.3). The country of birth was not associated with a poorer outcome. The management and outcome of MDR-TB in France has to be improved. A solution would be to develop a specialized unit or team for the treatment of MDR-TB, as recommended by the World Health Organization (WHO).

AIDS-Related Opportunistic Infections↗
PubMed1999

A national survey of human Mycobacterium bovis infection in France. Network of Microbiology Laboratories in France.

OBJECTIVE: To evaluate the role of Mycobacterium bovis in the epidemiology of human tuberculosis in France. DESIGN: A national survey in France in 1995 using a questionnaire mailed to all French microbiological laboratories performing mycobacteria cultures. RESULTS: M. bovis was isolated in 38 out of 7075 cases of bacteriologically confirmed tuberculosis (0.5%) notified to the National Reference Centre (CNR) in 1995, resulting in an incidence of 0.07 per 100,000 population. Incidence rates increased with age, and were the highest among patients of 75 years or more (range 0.02-0.33/100,000). Two cases of tuberculosis due to M. bovis were reported in foreign-born children who had come to France for treatment of their disease. No cases were reported among French-born children. The site of tuberculosis was pulmonary in 17 cases, extra-pulmonary in 14, both pulmonary and extra-pulmonary in one, and unknown in six. Extra-pulmonary sites were more frequent in older patients, and pulmonary sites more frequent in younger patients. Two patients were coinfected with the human immunodeficiency virus. Occupational exposure was identified in 13 cases and ingestion of non pasteurised milk in three. In addition, 11 patients had a possible risk of exposure related to their country of birth, family contact or occupation. CONCLUSION: In France, the 0.5% proportion of human tuberculosis due to M. bovis is similar to that of other developed countries. The higher incidence of the disease among older people is likely to reflect the efficacy of the control measures for tuberculosis in cattle.

Adolescent↗
PubMed1998

Role of residues 104, 164, 166, 238 and 240 in the substrate profile of PER-1 beta-lactamase hydrolysing third-generation cephalosporins.

The class A beta-lactamase PER-1, which displays 26% identity with the TEM-type extended-spectrum beta-lactamases (ESBLs), catalyses the hydrolysis of oxyimino-beta-lactams such as cefotaxime (CTX), ceftazidime (CAZ) and aztreonam (AZT). Molecular modelling was used to identify in PER-1 the amino acid residues corresponding to those found at positions 104, 164, 238 and 240 in the TEM-type ESBLs, which are critical for hydrolysis of oxyimino-beta-lactams. The function of these residues in PER-1 was assessed by site-directed mutagenesis. In this enzyme, residue 104 could be either a glutamine, an asparagine or a threonine. The Gln-->Gly mutation did not significantly affect the catalytic efficiency, while Asn-->Gly and Thr-->Glu resulted in a marked decrease in catalytic activity, probably due to the alteration of a hydrogen bond network connecting the putative Asn-104 residue to Asn-132 and Glu-166. Replacement of Ala-164 by Arg in PER-1 resulted in a mutant with no detectable activity, thus suggesting that Ala-164 is important for catalysis and stability of PER-1. Conversely, Ser-238-->Gly and Gly-240-->Glu had little effect on kcat and Km values. Finally, the replacement of the catalytic residue Glu-166 by an alanine resulted in a complete loss of activity for CTX and a marked decrease of kcat for CAZ and AZT. These results suggest that Glu-166 is an important residue in PER-1. However, residues other than Glu-166 could contribute in maintaining residual activity towards oxyimino-beta-lactams in the Ala-166 mutant.

Amino Acid Sequence↗
PubMed1998

Mycobacterium avium complex common-source or cross-infection in AIDS patients attending the same day-care facility.

To delineate the epidemiology of Mycobacterium avium complex (MAC) infection in acquired immunodeficiency syndrome patients, we studied 32 case patients with disseminated MAC infection who attended the same daycare facility during a period of 13 months. Pulsed-field gel electrophoresis analysis showed very low similarity between MAC strains, suggesting that, despite close contacts between the patients, nosocomial cross-transmission or exposure to a common source of MAC did not occur.

AIDS-Related Opportunistic Infections↗
PubMed1998

Molecular basis of clarithromycin activity against Mycobacterium avium and Mycobacterium smegmatis.

Clarithromycin, the 6-O-methyl derivative of erythromycin, is approved for treatment of Mycobacterium avium infections and for prophylaxis in patients at risk. Since clarithromycin is more active against mycobacteria than the parent compound, erythromycin, we evaluated the interaction of erythromycin and clarithromycin with cells and ribosomes isolated from M. avium and Mycobacterium smegmatis. The MIC of clarithromycin was 32 and 64 times lower than that of erythromycin for M. smegmatis and M. avium, respectively. The cellular uptake rate for clarithromycin was two- to five-fold faster than for erythromycin, and cell-associated clarithromycin reached a plateau two-fold higher than that of erythromycin after 3 h. Energy was not required for uptake. Fractionation of cell-associated clarithromycin yielded 12% in the walls, 21% bound to ribosomes, with the remainder being lost during work-up. In addition, three- to six-fold more clarithromycin was associated with the isolated cell integument compared with erythromycin. The Kd for clarithromycin binding to ribosomes was 2.9- and 3.5-fold tighter for M. smegmatis and M. avium, respectively, than for erythromycin, due mainly to a slower off-rate. The log partition coefficients of the non-ionized form (log Pu) for clarithromycin and erythromycin were 3.24 and 2.92, respectively. Thus clarithromycin is more hydrophobic than erythromycin. This would favour more rapid diffusion within and across hydrophobic regions of the cell integument, since once a solute saturates a membrane the net flux across the membrane must equal the net flux within the membrane as dictated by diffusion. We conclude that the lower MIC of clarithromycin for M. avium and M. smegmatis is due to a combination of increased cellular uptake, the major factor, possibly through a peripheral hydrophobic layer, and increased binding affinity to ribosomes.

Anti-Bacterial Agents↗
PubMed1998

Correlation between quinolone susceptibility patterns and sequences in the A and B subunits of DNA gyrase in mycobacteria.

The in vitro activities of seven quinolones and the sequences of the quinolone resistance-determining regions (QRDR) in the A and B subunits of DNA gyrase were determined for 14 mycobacterial species. On the basis of quinolone activity, quinolones were arranged from that with the greatest to that with the least activity as follows: sparfloxacin, levofloxacin, ciprofloxacin, ofloxacin, pefloxacin, flumequine, and nalidixic acid. Based on MICs, the species could be organized into three groups: resistant (Mycobacterium avium, M. intracellulare, M. marinum, M. chelonae, M. abscessus [ofloxacin MICs, >/=8 microg/ml]), moderately susceptible (M. tuberculosis, M. bovis BCG, M. kansasii, M. leprae, M. fortuitum third biovariant, M. smegmatis [ofloxacin MICs, 0.5 to 1 microg/ml]), and susceptible (M. fortuitum, M. peregrinum, M. aurum [ofloxacin MICs, </=0.25 microg/ml]). Peptide sequences of the QRDR of GyrB were identical in all the species, including the amino acids at the three positions known to be involved in acquired resistance to quinolone, i.e., 426 (Asp), 447 (Arg), and 464 (Asn) (numbering system used for Escherichia coli). The last two residues could be involved in the overall low level of susceptibility of mycobacteria to quinolones since they differ from those found in the very susceptible E. coli (Lys-447 and Ser-464) but are identical to those found in the less susceptible Staphylococcus aureus and Streptococcus pneumoniae. Peptide sequences of the QRDR of GyrA were identical in all the species, except for the amino acid at position 83, which was an alanine in the two less susceptible groups and a serine in the most susceptible one, as in E. coli, suggesting that this amino acid is involved in the observed differences of quinolone susceptibility within the Mycobacterium genus.

Amino Acid Sequence↗
PubMed1998

Characterization of gentamicin-susceptible strains of methicillin-resistant Staphylococcus aureus involved in nosocomial spread.

We report an outbreak of epidemic Staphylococcus aureus strains characterized by an unusual heterogeneous resistance to methicillin and resistance to tobramycin but susceptibility to gentamicin (gentamicin-susceptible methicillin-resistant S. aureus [GS-MRSA]), contrasting with gentamicin-resistant homogeneous MRSA (GR-MRSA) that have been endemic in our hospital since the 1970s. A total of 97 GS-MRSA strains, which were shown by DNA hybridization to carry the mecA and ant(4')-Ia genes, were studied. The 40 GS-MRSA strains isolated at the beginning of the outbreak (January 1992 to June 1993) were typed by using resistance patterns, phage typing, serotyping, and pulsed-field gel electrophoresis and were compared with GR-MRSA and methicillin-susceptible S. aureus (MSSA) strains isolated during the same period. Two dominant clones, A::1 and B::3, and one minor clone, C::5, were identified among the 40 GS-MRSA strains, according to pulsotypes (A to C) and their resistance patterns (1, 3, and 5), which were distinguishable from those of GR-MRSA and MSSA strains. A selection of 57 GS-MRSA strains, isolated from 1994 to 1996, were clustered in the same three clones. However, their distribution had changed in comparison with that in the 1992 to 1993 period: clone A::1 remained dominant (47 versus 42.5%), whereas clone B::3 progressively declined (5 versus 35%) and clone C::5, the most susceptible to antibiotics, spread (44 versus 2.5%). Epidemiological investigations revealed that some clones had been introduced via patients transferred from other hospitals and that cross-infection occurred within and between wards. Major changes in the use of antibiotics, especially aminoglycosides, cyclines, and macrolides, likely played a role in the emergence and spread of GS-MRSA strains.

Anti-Bacterial Agents↗