• Frederik Boetius Hertz, Anders Løbner-Olesen, Niels Frimodt-Møller
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    ABSTRACT: The ability of different antibiotics to select for ESBL-producing E.coli is still discussed. In a mouse intestinal colonisation model we evaluated the selective abilities of nine common antimicrobials (cefotaxime, cefuroxime, dicloxacillin, clindamycin, penicillin, ampicillin, meropenem, ciprofloxacin and mecillinam) on a CTX-M-15-producing E.coli ST131 isolate with a flouroquinolone resistant phenotype. Mice (8 per group) were orogastrically administered 0.25mL saline with 10(8)CFU/mL E.coli ST131. On that same day antibiotic treatment was initiated and given subcutaneously once a day for three consecutive days. CFU of E.coli ST131, Bacteroides and Gram-positive aerobic bacteria in faecal samples were studied, with intervals, until day 8. Bacteroides were used as an indicator organism for impact on the Gram-negative anaerobic population. For three antibiotics, prolonged colonization was investigated with additional faecal CFU's studied on day 10 and 14 (cefotaxime, dicloxacillin and clindamycin). Three antibiotics (cefotaxime, dicloxacillin and clindamycin) promoted overgrowth of E.coli ST131 (P<0.05). Of these, only clindamycin suppressed Bacteroides while the remaining two antibiotics had no negative impact on Bacteroides or Gram-positives. Only clindamycin treatment resulted in prolonged colonization. The remaining six antibiotics, including ciprofloxacin, did not promote overgrowth of E.coli ST131, (P>0.95), nor did they suppress Bacteroides or Gram-positives. The results show that antimicrobials both with and without an impact on Gram-negative anaerobes can select for ESBL-producing E.coli, indicating that not only Gram-negative anaerobes have a responsibility upholding colonization resistance. Other, so far unknown bacterial populations must be of importance for preventing colonization of an incoming E.coli.
    Antimicrobial Agents and Chemotherapy 08/2014; · 4.45 Impact Factor
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    ABSTRACT: Most Gram-negative community-acquired and nosocomial infections are caused by Escherichia coli and Klebsiella pneumoniae, among which increasing resistance due to extended-spectrum β-lactamase (ESBL) is a major problem. We present data from the first Danish nationwide prevalence study on ESBL-producing E. coli, K. pneumoniae, and Proteus mirabilis in blood and urine cultures from hospitals and the community. During September and October 2007, 13 of 15 Danish departments of clinical microbiology collected data and strains. Confirmatory ESBL test-positive isolates were sent to a central laboratory for species and ESBL-phenotype confirmation, extended susceptibility testing, phylogenetic grouping of E. coli strains, and ESBL gene characterization. During the study, blood samples from 18,259 patients and urine samples from 47,504 patients were subjected to culture. Among 14,674 cultured isolates, 352 were confirmed to be ESBL-producers. Thus, the crude ESBL prevalence was 2.4% (range 1.5% of E. coli in community urine to 6.6% of K. pneumoniae in hospital urine). An average of 7.2 ESBL-producers per 100,000 consumed bed-days was calculated. Of the 352 reported ESBL-producers, 205 E. coli, 73 K. pneumoniae, and 1 P. mirabilis, were available for testing. CTX-M enzymes dominated, both in hospitals and in the community, occurring in 92% of E. coli and 88% of K. pneumoniae, and with CTX-M-15 constituting 60% and 77%, respectively. Compared to 2003 data the ESBL prevalence in Denmark has increased significantly. In the ESBL-producers, reduced susceptibility towards both gentamicin and ciprofloxacin was seen among 43% E. coli and 55% K. pneumoniae, leaving clinicians in these cases with only a carbapenem for the treatment of serious infections. Part of this study was presented at the 20(th) European Congress of Clinical Microbiology and Infectious Diseases, abstract P-1617.
    Scandinavian Journal of Infectious Diseases 03/2012; 44(3):174-81. · 1.64 Impact Factor

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