Frederik Boetius Hertz

Infectious Diseases, Microbiology

MD
8.79

Publications

  • [Show abstract] [Hide abstract] ABSTRACT: Background Escherichia coli is the most common cause of urinary tract infection (UTI). The pathogenic isolates are becoming increasingly resistant to antibiotics; with a worldwide dissemination of resistant sequence types (ST). We characterized three different uropathogenic E. coli populations, from non-hospitalized patients to describe the genetic kinship between resistant and susceptible isolates. We studied the populations by use of multi-locus sequence typing (MLST) and abbreviated-multi locus variable number of tandem repeat analysis (a-MLVA). Urine samples submitted for testing, by general practitioners, were identified at Dept. of Clinical Microbiology at Hvidovre Hospital, Denmark, from Oct. 2011 to July 2012. We included 94 fully susceptible, 94 resistant (non-ESBL) and 98 Extended Spectrum Beta-lactamases- (ESBL)-producing E. coli isolates. Results The ESBL population was dominated vastly by ST131 (51 %), ST38 (9 %) and ST69 (6 %). In the resistant group ST69 (18 %), ST73 (11 %) and ST131 (15 %) were the largest clusters. In the susceptible population more STs and a-MLVA codes were identified compared to the other groups and ST73 and ST95 were found as the only clusters with 16 % and 6 %, respectively. Ninety-eight per cent of the ESBL-producing E. coli isolates were CTX-M-producers. Conclusion ST131 dominated the population of community-associated uropathogenic ESBL-producing E. coli, but was less frequent among non-ESBL-producing E. coli. The fully susceptible E. coli population was a much more diverse group than the resistant and ESBL-producing E. coli populations. Overall, these findings suggest that dominant ESBL-producing lineages are derived from UPEC lineages already established in the general UPEC population. Electronic supplementary material The online version of this article (doi:10.1186/s12866-016-0681-z) contains supplementary material, which is available to authorized users.
    No preview · Article · Apr 2016 · BMC Microbiology
  • [Show abstract] [Hide abstract] ABSTRACT: The purpose of the study was to evaluate how use of antibiotics precedes the presence of ESBL-producing E.coli in general practice. The authors performed a triple-case-control study where three case groups were individually compared to a single control group of uninfected individuals. Urine samples were prospectively collected and retrospective statistical analyses were done. This study included 98 cases with urinary tract infection (UTI) caused by ESBL-producing E. coli, 174 with antibiotic-resistant (non-ESBL) E. coli, 177 with susceptible E. coli and 200 with culture negative urine samples. Case groups had significantly higher use of antibiotics than the control group within 30 days before infection (p < 0.0001). The ESBL group had significantly more hospital admissions than the other case groups (p < 0.05). Hospital admission was an independent risk factor for community onset UTI by ESBL-producing E. coli. Exposure to antibiotics was a risk factor for UTI with E. coli, while prior antibiotic usage was not an indisputable predictor for infection with ESBL-producing E.coli in general practice.
    No preview · Article · Nov 2015
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    Hansen KG Hertz FB
    Preview · Article · Jan 2015
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    Frederik Boetius Hertz · Anders Løbner-Olesen · Niels Frimodt-Møller
    [Show abstract] [Hide abstract] ABSTRACT: The ability of different antibiotics to select for extended-spectrum β-lactamase (ESBL)-producing Escherichia coli remains a topic of discussion. In a mouse intestinal colonization model, we evaluated the selective abilities of nine common antimicrobials (cefotaxime, cefuroxime, dicloxacillin, clindamycin, penicillin, ampicillin, meropenem, ciprofloxacin, and amdinocillin) against a CTX-M-15-producing E. coli sequence type 131 (ST131) isolate with a fluoroquinolone resistance phenotype. Mice (8 per group) were orogastrically administered 0.25 ml saline with 108 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 fecal samples were studied, with intervals, until day 8. Bacteroides was used as an indicator organism for impact on the Gram-negative anaerobic population. For three antibiotics, prolonged colonization was investigated with additional fecal CFU counts determined on days 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-positive organisms. 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-positive organisms. The results showed 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 role in upholding colonization resistance. Other, so-far-unknown bacterial populations must be of importance for preventing colonization by incoming E. coli.
    Full-text · Article · Aug 2014 · Antimicrobial Agents and Chemotherapy
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    [Show abstract] [Hide abstract] 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.
    Full-text · Article · Mar 2012 · Scandinavian Journal of Infectious Diseases

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