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Biomedical subjects

Roland Leclercq

Publications and source records attributed to Roland Leclercq.

At least 19 recordsLinked to original sources
PubMed2007

Modes and modulations of antibiotic resistance gene expression.

Since antibiotic resistance usually affords a gain of function, there is an associated biological cost resulting in a loss of fitness of the bacterial host. Considering that antibiotic resistance is most often only transiently advantageous to bacteria, an efficient and elegant way for them to escape the lethal action of drugs is the alteration of resistance gene expression. It appears that expression of bacterial resistance to antibiotics is frequently regulated, which indicates that modulation of gene expression probably reflects a good compromise between energy saving and adjustment to a rapidly evolving environment. Modulation of gene expression can occur at the transcriptional or translational level following mutations or the movement of mobile genetic elements and may involve induction by the antibiotic. In the latter case, the antibiotic can have a triple activity: as an antibacterial agent, as an inducer of resistance to itself, and as an inducer of the dissemination of resistance determinants. We will review certain mechanisms, all reversible, that bacteria have elaborated to achieve antibiotic resistance by the fine-tuning of the expression of genetic information.

Bacteria↗
PubMed2006

Evaluation of MRSA Select, a new chromogenic medium for the detection of nasal carriage of methicillin-resistant Staphylococcus aureus.

MRSA Select is a new chromogenic medium for the detection from clinical specimens of methicillin-resistant Staphylococcus aureus (MRSA) growing as pink colonies. Screening samples (n=666) taken from patients were spread onto MRSA Select, oxacillin resistance screening agar base (ORSAB), mannitol salt agar and an in-house medium containing tobramycin-colistin-fungizone (TCF). Ninety-nine samples were positive for MRSA on at least one selective medium. Sensitivity and specificity were >94% for all media provided that incubation was extended to 48 h for ORSAB and that a coagulase test was performed for ORSAB and TCF. By contrast, on the single criterion of the colour of colonies for MRSA positivity, the specificity and sensitivity of MRSA Select were high (99.8% and 99%, respectively).

Amphotericin B↗
PubMed2006

Fluoroquinolone use and methicillin-resistant Staphylococcus aureus isolation rates in hospitalized patients: a quasi experimental study.

BACKGROUND: We investigated the possible association between fluoroquinolone use and the rate of methicillin-resistant Staphylococcus aureus (MRSA) recovery from consecutive hospitalized patients. METHODS: We conducted a nonrandomized, prospective, controlled interventional "fluoroquinolone-free" study at 4 large teaching hospitals in northwest France, catering to a total of 5,882,600 persons. During the intervention period (January through December 2001), fluoroquinolone use was prohibited at 1 of the 4 hospitals (Caen Hospital), unless no effective alternative was available. Three university hospitals were used as controls because they had similar preintervention rates of MRSA. RESULTS: During the intervention period (2001), the annual rate of fluoroquinolone use decreased from 54 to 5 defined daily doses per 1000 patients per day at Caen Hospital and remained stable in the control hospitals. At the end of the intervention, the rate of MRSA isolation was significantly lower at Caen Hospital than at the control hospitals (353 [32.3%] of 1093 S. aureus isolates were MRSA, compared with 2495 [36.8%] of 6787 isolates; odds ratio, 0.82; 95% confidence interval, 0.69-0.99; P=.036), as determined on the basis of a marginal model that took into account within-hospital clustering. In a before-after time series analysis, compared with forecasted rates, there was a significant downward trend in observed monthly rates of MRSA isolation at Caen Hospital at the end of the intervention. CONCLUSION: This quasi experimental study confirms the association between fluoroquinolone use and MRSA isolation among hospitalized patients.

Anti-Bacterial Agents↗
PubMed2006

Activity of a new oral streptogramin, XRP2868, against gram-positive cocci harboring various mechanisms of resistance to streptogramins.

The antibacterial activity of XRP2868, a new oral streptogramin composed of a combination of RPR132552 (streptogramin A) and RPR202868 (streptogramin B), was evaluated against a collection of clinical gram-positive isolates with characterized phenotypes and genotypes of streptogramin resistance. The effects of genes for resistance to streptogramin A or B on the activity of XRP2868 and its components were also tested by cloning these genes individually or in various combinations in gram-positive recipient strains susceptible to quinupristin-dalfopristin. The species tested included Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus faecalis, Enterococcus faecium, Streptococcus pneumoniae, and other species of streptococci. XRP2868 was generally fourfold more potent than quinupristin-dalfopristin against S. aureus, E. faecium, and streptococci and had activity against E. faecalis (MICs = 0.25 to 1 microg/ml). XRP2868 appeared to be affected by the same mechanisms of resistance as those to quinupristin-dalfopristin. Nevertheless, the strong activity of factor A of the oral streptogramin enabled the combination to be very potent against streptogramin-susceptible staphylococci, streptococci, and E. faecium (MICs = 0.03 to 0.25 microg/ml) and to retain low MICs against the strains harboring a mechanism of resistance to factor A or factor B of the streptogramin. However, the combination of mechanisms of resistance to factors A and B caused an increase in the MICs of XRP2868, which reached 1 to 4 mug/ml. As with the other streptogramins, there was a reduction in the bactericidal effect of XRPR2868 when the staphylococcal strains acquired a constitutively expressed erm gene.

Administration, Oral↗
PubMed2006

Identification of pathogenic Leptospira strains in tissues of a premature foal by use of polymerase chain reaction analysis.

Studies were carried out to determine the cause of death in a prematurely born Thoroughbred foal that died 24 hours after birth. Necropsy revealed gross lesions suggestive of septicemia. A commercial Leptospira polymerase chain reaction (PCR) assay designed to specifically amplify the hemolysis-associated protein 1 (hap1) gene present only in pathogenic Leptospira strains detected the presence of Leptospira DNA in various tissues of the foal. Histologic examination of lung, liver, kidney, and myocardium revealed numerous spirochetes in Warthin-Starry-stained tissue sections. Results of PCR analysis and histologic examination suggested a leptospiral infection in the newborn foal. At the moment of death, the infection coexisted with a streptococcal-associated aspiration bronchopneumonia and postpartum septicemia. These findings indicate that the PCR assay based on the amplification of the hap1 gene represents a useful tool for specific detection of pathogenic leptospira in field samples taken from horses.

Animals↗
PubMed2005

Mutation of L4 ribosomal protein conferring unusual macrolide resistance in two independent clinical isolates of Staphylococcus aureus.

The aim of this study was to characterize the resistance mechanisms of two strains of Staphylococcus aureus UCN42 and UCN43 isolated from cystic fibrosis patients that displayed an unusual phenotype of resistance to macrolides. The strains were resistant to erythromycin and the 16-membered macrolide spiramycin but susceptible to clindamycin. None of the strains contained erm or msr(A) genes by PCR. Sequencing of genes encoding ribosomal targets of macrolides revealed mutations in conserved regions of the L4 ribosomal protein, a R168S mutation for S. aureus UCN43 and mutations at positions G69A and T70P for both strains. This observation extends previous reports of similar mutations in streptococci and mycoplasma to S. aureus.

Amino Acid Sequence↗
PubMed2005

Hypermutable and fluoroquinolone-resistant clinical isolates of Staphylococcus aureus.

Over 124 methicillin-susceptible Staphylococcus aureus 0/74 fluoroquinolone-susceptible versus 5/50 fluoroquinolone-resistant isolates were hypermutable. Hypermutable isolates combined mutations in gyrA, parC, and/or parE genes. One strain had a large deletion of the mutator mutS and mutL genes. No relevant mutation in mutS and mutL genes was found in the other isolates.

Anti-Infective Agents↗
PubMed2005

New lnu(C) gene conferring resistance to lincomycin by nucleotidylation in Streptococcus agalactiae UCN36.

Streptococcus agalactiae UCN36 was resistant to lincomycin (MIC = 16 microg/ml) but susceptible to clindamycin (MIC = 0.12 microg/ml) and erythromycin (MIC = 0.06 microg/ml). A 4-kb HindIII fragment was cloned from S. agalactiae UCN36 total DNA on plasmid pUC18 and introduced into Escherichia coli AG100A, where it conferred resistance to lincomycin. The sequence analysis of the fragment showed the presence of a 1,724-bp element delineated by imperfect inverted repeats (22 of 25 bp) and inserted in the operon for capsular synthesis of S. agalactiae UCN36. This element carried two open reading frames (ORF). The deduced amino acid sequence of the upstream ORF displayed similarity with transposases from anaerobes and IS1. The downstream ORF, lnu(C), encoded a 164-amino-acid protein with 26% to 27% identity with the LnuA(N2), LnuA, and LnuA' lincosamide nucleotidyltransferases reported for Bacteroides and Staphylococcus, respectively. Crude lysates of E. coli AG100A containing the cloned lnu(C) gene inactivated lincomycin and clindamycin in the presence of ATP and MgCl2. Mass spectrometry experiments demonstrated that the LnuC enzyme catalyzed adenylylation of lincomycin.

Anti-Bacterial Agents↗
PubMed2005

Combined antimicrobial resistance in Enterococcus faecium isolated from chickens.

Nineteen E. faecium strains isolated from chicken caecum samples, collected in slaughterhouses and highly resistant to vancomycin or gentamicin, were coresistant to erythromycin, and/or tetracyclines, and/or streptogramins, and/or avilamycin. Multiple antibiotic resistance was related to the presence in various combinations of aac(6')-aph(2"), erm(B), emtA, mef(A), tet(L), tet(M), and vanA genes.

Animals↗
PubMed2005

Role of mutS and mutL genes in hypermutability and recombination in Staphylococcus aureus.

The mutator phenotype has been linked in several bacterial genera to a defect in the methyl-mismatch repair system, in which the major components are MutS and MutL. This system is involved both in mismatch repair and in prevention of recombination between homeologous fragments in Escherichia coli and has been shown to play an important role in the adaptation of bacterial populations in changing and stressful environments. In this report we describe the molecular analysis of the mutS and mutL genes of Staphylococcus aureus. A genetic analysis of the mutSL region was performed in S. aureus RN4220. Reverse transcriptase PCR experiments confirmed the operon structure already reported in other gram-positive organisms. Insertional inactivation of mutS and mutL genes and complementation showed the role of both genes in hypermutability in this species. We also designed an in vitro model to study the role of MutS and MutL in homeologous recombination in S. aureus. For this purpose, we constructed a bank of S. aureus RN4220 and mutS and mutL mutants containing the integrative thermosensitive vector pBT1 in which fragments with various levels of identity (74% to 100%) to the S. aureus sodA gene were cloned. MutS and MutL proteins seemed to have a limited effect on the control of homeologous recombination. Sequence of mutS and mutL genes was analyzed in 11 hypermutable S. aureus clinical isolates. In four of five isolates with mutated or deleted mutS or mutL genes, a relationship between alterations and mutator phenotypes could be established by negative complementation of the mutS or mutL mutants.

Adenosine Triphosphatases↗
PubMed2005

Antibiotic susceptibility of bacteria isolated from pasteurized milk and characterization of macrolide-lincosamide-streptogramin resistance genes.

The presence of antibiotic-resistant bacteria in pasteurized milk was detected by plating 18 milk samples on selective media containing beta-lactams, macrolides, or a glycopeptide. Most samples contained gram-positive bacteria that grew on agar plates containing oxacillin, erythromycin, and/or spiramycin. The disk-diffusion method confirmed resistance to erythromycin and/or spiramycin in 86 and 65% of the coryneform bacteria and Micrococcaceae tested, respectively. PCR and sequence analysis revealed the presence of an ermC gene in 2 of the 25 Micrococcaceae strains investigated for their resistance to erythromycin and/or spiramycin. None of the 14 corynebacteria strains resistant to erythromycin and/or spiramycin harbored the erm(X) gene. No gene transfer could be demonstrated between the two erm(C) staphylococcal isolates and recipient strains of Enterococcus faecalis JH2-2 or Staphylococcus aureus 80CR5.

Animals↗
PubMed2005

Risk factors for Gram-negative bacterial infections in febrile neutropenia.

BACKGROUND AND OBJECTIVES: The objective of this study was to evaluate the risk of Gram-negative bacterial infections in febrile neutropenic patients and to develop a specific risk score. DESIGN AND METHODS: This prospective study included 513 consecutive febrile neutropenic, evaluable patients. Forty-five per cent of the patients were receiving prophylactic gut decontamination, and 6% were receiving prophylactic quinolones at the onset of febrile neutropenia. Data were collected from the onset of febrile neutropenia until 30 days later. Risk factors for Gram-negative bacterial infection were identified by comparing baseline characteristics of patients with and without Gram-negative bacterial infection. Independent risk factors in multivariate analysis were used to build a predictive score for Gram-negative bacterial infection. RESULTS: The prevalence of Gram-negative bacterial infection was 55/513 (10.7%). Gram-negative bacterial infections were due to E. coli in 30 patients, other enterobacteriae in 11, Pseudomonas spp. in 13, and Salmonella spp. in one. In multivariate analysis, the occurrence of Gram-negative bacterial infection was significantly associated with age > 45 years (p=0.009), recent administration of betalactams (p=0.04), chills (p=0.0001), urinary symptoms (p=0.01), and absence of gut decontamination with both colimycin and aminoglycosides (p=0.001). The relative risk for Gram-negative bacterial infection was 4.4, 12.6, 25.4 and 100 in the presence of 1, 2, 3 , or at least 4 parameters, respectively. The performances of our scoring system and the post-test probabilities according to different prevalence rates of Gram-negative bacterial infection (0.05, 0.10, 0.20) lead us to propose a Gram-negative risk score of >or=3 as indicating a high probability of Gram-negative bacterial infection. INTERPRETATION AND CONCLUSIONS: Our scoring system identifies patients with a high probability of Gram-negative bacterial infection as those with a score >or=3. If confirmed in a validation set, this score could be considered in the choice of the first-line antibiotics in febrile neutropenic patients.

Adolescent↗
PubMed2004

A new phenotype of resistance to lincosamide and streptogramin A-type antibiotics in Streptococcus agalactiae in New Zealand.

OBJECTIVES: To characterize a new type of resistance to clindamycin in Streptococcus agalactiae. METHODS: Nineteen erythromycin-susceptible, clindamycin-resistant S. agalactiae isolates from New Zealand were studied. MICs of macrolide, lincosamide and streptogramin antibiotics were determined. Clindamycin and streptogramin resistance genes were searched for by PCR. Isolates were compared by serotyping and by DNA macrorestriction patterns determined by PFGE. Conjugative transfer of resistance traits to recipient strains of S. agalactiae and Enterococcus faecium was assayed. RESULTS: The 19 S. agalactiae isolates were intermediate or resistant to clindamycin (MIC range: 0.5-2 mg/L) and lincomycin (MIC range: 1-8 mg/L) and had high MICs of dalfopristin (4-32 mg/L), a streptogramin A-type antibiotic, compared with controls. By contrast, the strains were susceptible to macrolides and quinupristin, a streptogramin B-type antibiotic. This new phenotype was called LSA (lincosamide-streptogramin A). Clindamycin resistance could not be transferred to recipient strains. Thirteen isolates belonged to serotype III and to a single PFGE genotype A, and five isolates belonged to serotype I and to genotype B. One isolate was non-typeable and belonged to a distinct genotype C. CONCLUSIONS: We have characterized a new LSA phenotype in S. agalactiae. Analysis of restriction patterns of S. agalactiae chromosomal DNA showed that the resistance was spread in a minimum of three bacterial clones. The genetic and biochemical basis for the resistance remains unknown.

Adult↗
PubMed2004

Phenotypic and molecular characterization of macrolide and streptogramin resistance in Streptococcus mitis from neutropenic patients.

OBJECTIVES: To determine the prevalence of macrolide and streptogramin resistance in Streptococcus mitis isolates from neutropenic patients and to identify mechanisms of macrolide and streptogramin resistance in resistant isolates. METHODS: MICs of erythromycin, spiramycin, lincomycin and pristinamycin were determined for S. mitis isolates. Macrolide-resistance genes were characterized by PCR and ribosomal mutations by sequencing. RESULTS: A total of 169 S. mitis isolates were recovered from 66 patients at the Tunisian Bone Marrow Transplant Centre. Of these, 120 (70%) were non-susceptible to erythromycin and one was resistant to pristinamycin; 48.5% of isolates had an MLSB phenotype with cross-resistance between erythromycin, spiramycin and lincomycin, 4% had a dissociated MLSB phenotype with resistance to erythromycin and spiramycin but apparent susceptibility to lincomycin and 47.5% displayed the M phenotype. Resistance determinants were characterized in 33 isolates. Ten of 14 isolates with the cross MLSB resistance contained an ermB-like gene and four a combination of ermB- and mefA-like genes. Four of the five isolates with a dissociated MLSB phenotype contained ermB-like and one a combination of ermB- and mefA-like genes. All the 14 isolates with an M phenotype contained mefA-like genes. The pristinamycin-resistant strain had G105 and A108 substitutions in the conserved C terminus of the L22 ribosomal protein. CONCLUSIONS: The prevalence of macrolide resistance is high in S. mitis from neutropenic patients and is due to the spread of ermB- or mefA-like genes alone or combined. Resistance to streptogramins is rare and in this case associated with ribosomal mutation.

Amino Acid Sequence↗
PubMed2004

Comparison of daptomycin MIC results by DIN, NCCLS, SFM, and SRGA methods for 297 Gram-positive organisms.

Daptomycin is a novel lipopeptide antibiotic with potent in vitro antibacterial activity against Gram-positive pathogens. For daptomycin minimal inhibitory concentration (MIC) testing, National Committee for Clinical Laboratory Standards (NCCLS) recommends the use of broth containing physiological levels of calcium (50 microg/ml). The daptomycin susceptibility of 297 organisms was determined by NCCLS (Mueller-Hinton (MH) broth), Deutsches Institut für Normung (DIN; isotonic broth), Société Française de Microbiologie (SFM; three batches MH agar), and Swedish Reference Group for Antibiotics (SRGA; PDM agar). All media were supplemented to 50 microg/ml Ca(2+). There was good correlation between DIN and SFM methods (for staphylococci) with NCCLS results. Enterococci MICs using SFM methods were one to three dilutions lower and pneumococci results were one dilution higher than NCCLS. SRGA results were higher than NCCLS by one to four dilutions. Use of isotonic agar is an accepted alternative to isosensitest agar for the DIN method.

Anti-Bacterial Agents↗
PubMed2004

Alcoholic povidone-iodine to prevent central venous catheter colonization: A randomized unit-crossover study.

OBJECTIVE: To compare effectiveness in preventing central venous catheter colonization and infection of two protocols of cutaneous antisepsis using povidone-iodine solution in combination with ethanol or water. DESIGN: Randomized trial. SETTING: Medical intensive care department in a university hospital. PATIENTS: Consecutive patients requiring central venous catheter in two similar 11-bed units from January 1, 2001, to January 1, 2002. INTERVENTIONS: Alcoholic povidone-iodine solution protocol was randomly assigned to one of two units when the study began. Every 3 months the alcoholic protocol was switched from one unit to the other. Depending on the unit and the time the patient was admitted, catheters were inserted and cared for with 10% aqueous povidone-iodine solution or 5% povidone-iodine solution 70% ethanol-based combination. MEASUREMENTS AND MAIN RESULTS: Rates of catheter colonization, catheter-related bacteremia, and catheter-related infection were compared in the two protocols; 223 catheters were included in an intent-to-treat analysis. The incidence of catheter colonization was significantly lower in the alcoholic povidone-iodine solution protocol than in the aqueous povidone-iodine solution protocol (relative risk, 0.38; 95% confidence interval, 0.22-0.65, p <.001), and so was the incidence of catheter-related infection (relative risk, 0.34; 95% confidence interval, 0.13-0.91, p <.04). Catheter-related bacteremia were similar in both protocols. After adjusting for other risk factors, time to central venous catheter colonization was significantly longer in the alcoholic solution (adjusted hazards ratio, 0.3; 95% confidence interval, 0.2-0.6, p <.001). Based on a subgroup of 114 patients (57 in each protocol), analysis of 57 pairs of central venous catheters matched for age, duration, and site of insertion found similar results regarding the superiority of alcoholic povidone-iodine solution in preventing central venous catheter colonization and infection. CONCLUSIONS: The use of alcoholic povidone-iodine for skin disinfection reduced the incidence of catheter colonization and related infection compared with aqueous 10% povidone-iodine disinfection in an adult intensive care unit.

Anti-Infective Agents, Local↗
PubMed2004

Denaturing high-performance liquid chromatography detection of ribosomal mutations conferring macrolide resistance in gram-positive cocci.

Mutations in genes coding for L4 (rplD) or L22 (rplV) ribosomal proteins or in 23S rRNA (rrl gene) are reported as a cause of macrolide resistance in streptococci and staphylococci. This study was aimed at evaluating a denaturing high-performance liquid chromatography (DHPLC) technique as a rapid mutation screening method. Portions of these genes were amplified by PCR from total DNA of 48 strains of Streptococcus pneumoniae (n = 22), Staphylococcus aureus (n = 16), Streptococcus pyogenes (n = 6), Streptococcus oralis (n = 2), and group G streptococcus (n = 2). Thirty-seven of these strains were resistant to macrolides and harbored one or several mutations in one or two of the target genes, and 11 were susceptible. PCR products were analyzed by DHPLC. All mutations were detected, except a point mutation in a pneumococcal rplD gene. The method detected one mutated rrl copy out of six in S. aureus. This automated method is promising for screening of mutations involved in macrolide resistance in gram-positive cocci.

Chromatography, High Pressure Liquid↗