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ABSTRACT: The prevalence of plasmid-mediated quinolone resistance (PMQR) determinants (qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA) was investigated in a collection of 47 extended-spectrum β-lactamase (ESBL) producing enterobacterial isolates with reduced susceptibility to fluoroquinolones, recovered at Nantes University hospital, in 2006. qnr, aac(6')-Ib-cr, and qepA genes were screened by PCR, and positive results were subsequently confirmed by sequencing. The epidemiological relationship between positive isolates was studied by pulsed-field gel electrophoresis (PFGE). qnr-positive isolates were analyzed for antimicrobial susceptibility and presence of mutations in the quinolone resistance-determining region (QRDR) of gyrA and parC genes. ESBL genes were characterized by PCR and sequencing. Conjugation experiments were performed to determine whether the qnr-carrying plasmids were self-transferable. Two Klebsiella pneumoniae isolates (4.3%), not clonally related, harboured a qnrS1 gene, whereas no qnrA- or qnrB-positive isolate was detected. The aac(6')-Ib-cr gene was detected in 11 Escherichia coli and one K. pneumoniae isolates. None of the 47 isolates carried the qepA gene. ESBLs associated with QnrS1 were CTX-M-14 and CTX-M-15. The CTX-M-15 producing isolate was highly resistant to fluoroquinolones and harboured three mutations in the QRDR and two PMQR determinants (qnrS1 and aac(6')-Ib-cr). The CTX-M-14-producing isolate exhibited reduced susceptibility or resistance to fluoroquinolones without resistance to nalidixic acid. This strain harboured only a qnr gene on a single 170 kb transferable plasmid, without any mutation in the QRDR. In conclusion, our study showed that aac(6')-Ib-cr gene had occurred in multiclonal ESBL-producing enterobacterial isolates collected at Nantes University hospital in 2006, with a higher prevalence than qnr genes.
Pathologie Biologie 06/2009; 59(3):151-6. · 1.53 Impact Factor
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Journal of Antimicrobial Chemotherapy 04/2009; 63(6):1290-2. · 5.07 Impact Factor
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ABSTRACT: This study assessed the incidence of gastrointestinal colonisation by resistant Enterobacteriaceae among hospitalised patients, and identified risk-factors for ceftazidime and ofloxacin resistance. A prospective cohort study was performed in five wards in a French teaching hospital during a 2-year period. Patients hospitalised for > 48 h were enrolled between 17 April 2000 and 30 April 2002. A rectal swab was taken at admission, then once-weekly and/or on the day of discharge. In total, 933 patients were investigated and 585 amoxycillin-resistant isolates were obtained. Resistance rates for ceftazidime and ofloxacin were 9.4% and 4.8%, respectively. Multivariate analysis indicated that previous hospitalisation (p < 0.004) and exposure to amoxycillin-clavulanate (p < 0.003) and ceftriaxone (p < 0.002) were associated significantly with ceftazidime resistance. Hospitalisation in the urology ward (p < 0.02) and previous exposure to fluoroquinolones (p < 0.01) were the two independent risk-factors associated with ofloxacin resistance. The results of the study confirmed that antibiotic use selected resistant Enterobacteriaceae from the gut flora. Resistance was observed mostly in patients with previous antibiotic exposure and previous hospitalisation in wards with a high antibiotic selection pressure.
Clinical Microbiology and Infection 10/2006; 12(10):974-9. · 4.54 Impact Factor
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ABSTRACT: The prospective cohort study presented here assessed the risk factors associated with Pseudomonas aeruginosa gastrointestinal colonization (PAGIC) in 933 patients hospitalized in five different wards in a French university hospital. A total of 195 patients were colonized. By logistic regression, hospitalization in an intensive care unit and length of hospital stay were independent risk factors. A significant association was observed between fluoroquinolone use and PAGIC caused by an ofloxacin-resistant strain (p < 0.0001), imipenem use and PAGIC caused by an imipenem-resistant strain (p < 0.0002) and ceftazidime use and PAGIC caused by a ceftazidime-resistant strain (p < 0.02). The ecological impact of antibiotic use is of great clinical relevance and clinicians should consider antimicrobial resistance in order to limit the development and dissemination of resistant microorganisms.
European Journal of Clinical Microbiology 09/2006; 25(9):600-3. · 2.86 Impact Factor
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ABSTRACT: The clinical significance of coagulase-negative staphylococci isolated from blood culture is typically assessed on the basis of a combination of clinical and microbiological criteria. However, these criteria are difficult to apply to haematology patients who are highly immunosuppressed and from whom blood cultures are obtained most frequently through a central venous catheter. This study analysed 112 episodes of Staphylococcus epidermidis bacteraemia that occurred in 79 bone marrow transplant recipients. In 73 (65%) episodes, only one blood culture set was positive for S. epidermidis, while 39 (35%) episodes grew S. epidermidis from multiple blood cultures. Nine patients had two or more episodes of bacteraemia with the same strain, as determined by pulsed-field gel electrophoresis (PFGE). The PFGE method also showed that 34 (31%) isolates belonged to seven clusters, indicating the persistence of certain clones in the environment. Of the 109 isolates analysed, 59 (54%) produced biofilm and 91 (83.5%) carried the ica operon. Isolates that produced biofilm were observed to colonise central venous catheters faster than non-biofilm-producing isolates (18 vs. 37 days; p 0.03). No clinical features were associated with carriage of the ica operon, but the ica operon was carried more frequently by the isolates that formed clusters.
Clinical Microbiology and Infection 06/2006; 12(5):446-52. · 4.54 Impact Factor
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ABSTRACT: A mutation was discovered in the Pribnow box of the ampC promoter in a clinical Escherichia coli strain. This -11 C-to-T transition created a perfect homology with the -10 consensus sequence. The new promoter was cloned upstream of the cat gene of pKK232-8 and induced a sixfold increase in promoter strength.
Antimicrobial Agents and Chemotherapy 11/2002; 46(10):3265-7. · 4.84 Impact Factor
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European Journal of Clinical Microbiology 07/2000; 19(6):489-91. · 2.86 Impact Factor
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ABSTRACT: Escherichia coli usually produces only very small amounts of a constitutive AmpC beta-lactamase, but clinical strains overproducing this enzyme have been isolated. Three different ampC promoters of E. coli clinical strains were cloned upstream of the chloramphenicol acetyltransferase (CAT) gene in the pKK232-8 reporter plasmid and their relative strengths were compared by two different methods. The strength of the promoters from AmpC hyperproducers was 70- to 120-fold higher than those from a low-level AmpC producer. One of the strong promoters, which differs from strain K12 at bases -88, -82, -42, -18, -1 and +58, was mutated to abolish the -42 mutation. This change resulted in a 43-fold decrease in CAT concentration. In another promoter, with eight different mutations at positions -88, -82, -32, -18, -1, +5, +24 and +58, the -32T-->A transversion, which created perfect homology with the -35 consensus sequence, was reverted; this led to a 13-fold decrease in CAT concentration. The -42 and -32 mutations play an important role in E. coli resistance to beta-lactams by increasing ampC transcription.
Journal of Antimicrobial Chemotherapy 07/2000; 45(6):783-8. · 5.07 Impact Factor
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ABSTRACT: This study analyzes the epidemiology of hospital and community-acquired infections caused by Escherichia coli. The antimicrobial resistance pattern was used to characterize the isolates, and a prospective observational study was performed to assess the relationship between antimicrobial use and bacterial resistance. The study was conducted during a 3-month period in a 1,200-bed tertiary care hospital in Nantes, France. An E. coli infection was diagnosed in 3.8% of the patients (507 of 13,384) admitted to the hospital between 1 January and 31 March 1996. Of the 507 isolates, 205 (40.4%) were resistant to at least one antimicrobial; 40% were resistant to amoxicillin, 30% to amoxicillin/clavulanate, 38% to ticarcillin, and 16% to trimethoprim-sulfamethoxazole, while resistance to other antimicrobials was low. Prior receipt of antimicrobial and/or immunosuppressive therapy was significantly associated with infection caused by a resistant organism.
Clinical Infectious Diseases 10/1999; 29(3):548-52. · 9.15 Impact Factor
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ABSTRACT: Escherichia coli strains showing an increased resistance to oxyiminocephalosporins without an extended spectrum beta-lactamase production have been screened for mutations in their ampC beta-lactamase gene promoter. Mutations were found by direct sequencing of seven promoters at positions -42, -32 (box -35), -18, -1, +5, +24 (attenuator), +31 (attenuator) and +58. By using rapid and simple methods, three of these mutations (-42, -32 and +24), which could enhance transcription, were searched in 37 resistant and 25 sensitive isolates. The -42 mutation was present in 33 of the 37 promoters from the resistant isolates. The -32 and +24 mutations were present only in three and two promoters, respectively, and they were combined in the most resistant strain of the study. The +24 mutation was detected in another strain associated with a 1-bp insertion between the -35 and -10 conserved sequences. None of these mutations was detected in the ampC beta-lactamase from the sensitive isolates.
FEMS Microbiology Letters 05/1999; 173(2):459-65. · 2.04 Impact Factor
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ABSTRACT: Rahnella aquatilis was isolated from the blood cultures of two patients who were in different units of the same hospital. Both isolates were susceptible to aminoglycosides, fluoroquinolones, cotrimoxazole, piperacillin, third generation cephalosporins and amoxicillin-clavulanate, but resistant to amoxicillin, ticarcillin, and first generation cephalosporins. The synergistic activity of amoxicillin and clavulanic acid suggested the presence of a beta-lactamase, confirmed by a positive nitrocefin test and by analytical isoelectric focusing. Pulsed-field gel electrophoresis and ribotyping with the pKK3535 probe showed that the isolates shared the same banding pattern. The results of an epidemiological study suggested that an in-house total parenteral nutrition solution might be the source of this unusual gram-negative rod.
European Journal of Clinical Microbiology 06/1998; 17(5):349-52. · 2.86 Impact Factor
