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In vitro susceptibility of CTX-M-producing Escherichia coli to non-beta-lactam agents
Linköping University, Department of Clinical and Experimental Medicine, Clinical Microbiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Clinical Microbiology.
Linköping University, Department of Clinical and Experimental Medicine, Clinical Microbiology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Clinical Microbiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Clinical Microbiology.
Linköping University, Department of Clinical and Experimental Medicine, Infectious Diseases. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Infectious Diseases in Östergötland.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Background: The objective of this study was to investigate the in vitro activity of different antibiotics against CTX-M-producing Escherichia coli, to determine the occurrence of multiresistance and plasmid mediated quinolone resistance among these isolates.

Methods: A total of 198 isolates of E. coli with ESBL phenotype and mainly CTX-M genotype, were studied. The MICs for amikacin, chloramphenicol, ciprofloxacin, colistin, fosfomycin, gentamicin, nalidixic acid, nitrofurantoin, tigecycline, tobramycin, trimethoprim and trimethoprim-sulphamethoxazole were determined with the Etest. Susceptibility was defined according to the breakpoints of the European Committee on Antimicrobial Susceptibility Testing (EUCAST). MIC(50) and MIC(90) values were calculated.

Results: ≥95% of isolates were susceptible to amikacin, nitrofurantoin, colistin, tigecyclin, and fosfomycin. CTX-M group 9 was more susceptible than CTX-M group 1 to ciprofloxacin, gentamicin, and tobramycin. 68% of the isolates were multiresistant, and the most common multi-resistance pattern was ESBL-phenotype with decreased susceptibility to trimethoprim, trimethoprim-sulphamethoxazol, ciprofloxacin, gentamicin and  tobramycin. Only one isolate carried a qnrS1-gene, nine isolates carried aac(6’)-Ib-cr.

Conclusions: The high frequency of multi-resistance found in this study is alarming and it is urgent to find strategies to limit the emergence and spread of these multi-resistant strains.

Keyword [en]
Etest, MIC, ESBL
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-76133OAI: oai:DiVA.org:liu-76133DiVA: diva2:512598
Available from: 2012-03-28 Created: 2012-03-28 Last updated: 2012-03-28Bibliographically approved
In thesis
1. Extended-spectrum beta-lactamase producing Enterobacteriaceae: aspects on detection, epidemiology and multi-drug resistance
Open this publication in new window or tab >>Extended-spectrum beta-lactamase producing Enterobacteriaceae: aspects on detection, epidemiology and multi-drug resistance
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Beta-lactam antibiotics are the largest and most commonly used group of antimicrobial agents in Sweden as well as world-wide. They show very good tolerability and many of the drugs can be administrated orally. Bacteria expressing extended-spectrum beta-lactamases (ESBLs), enzymes hydrolysing penicillins and cephalosporins, may not respond to therapy using some of these antibiotics. The isolates are also often co-resistant to other antimicrobial agents, thus further limiting treatment options. Often parenterally administrated carbapenems is one of few safe treatment options left.

In this thesis we have investigated the occurrence of ESBL producing Enterobacteriaceae in clinical isolates from Östergötland, Sweden, from 2002 until end of 2007 and the occurrence of multiresistance among ESBL producing E. coli. During these investigations we developed a simple method well suited for high-throughput analysis, for detection and sub typing of common ESBL genes.

During the six year period, the prevalence of ESBL producing Enterobacteriaceae in Östergötland was very low, <1%, but increasing. The number of patients with ESBL producing E. coli increased significantly from 5 to 47 per year; K. pneumoniae remained between one and four per year. The genes found were dominated by CTX-M group 1 (67%), followed by group 9 (27%). There has been no reason to suspect an outbreak of nosocomial origin. The total consumption of antimicrobial agents was 10.7-12.1 DID per year in primary care; 1.14-1.30 DID per year in hospital care.

Of eight oral agents tested, only three showed a generally high susceptibility; mecillinam (91%), nitrofurantoin (96%) and fosfomycin (99%). The corresponding figures for the fifteen tested parenterally administrated drugs were; amikacin (96%), tigecycline (99%), colistin (99%) and ≥99% susceptibility for the carbapenems.

Sixty eight percent of the isolates were multiresistant. The most common multiresistance pattern was ESBL phenotype with decreased susceptibility to trimethoprim, trimethoprimsulfamethoxazole, ciprofloxacin, gentamicin and tobramycin. A significant difference in susceptibility between CTX-M groups, in favor of group 9 over group 1, was seen for many of the antibiotics tested; amoxicillin-clavulanic acid, aztreonam, cafepime, ceftibuten, ceftazidime, ciprofloxacin, gentamicin, piperacillin-tazobactam, temocillin, and tobramycin.

In conclusion this thesis shows that the prevalence of ESBL producing Enterobacteriaceae in Östergötland was very low but increasing, and the total consumption of antimicrobial agents was stable. A majority of the isolates were multiresistant and a significant difference in susceptibility between CTX-M groups, in favor of group 9 over group 1, was seen for many of the antimicrobial agents tested.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 53 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1300
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-76134 (URN)978-91-7519-938-2 (ISBN)
Public defence
2012-04-26, Berzeliussalen, ingång 65, plan 09, Campus US, Linköpings universitet, Linköping, 13:00 (Swedish)
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Available from: 2012-03-28 Created: 2012-03-28 Last updated: 2012-03-28Bibliographically approved

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Östholm Balkhed, ÅseTärnberg, MariaMonstein, Hans-JurgHällgren, AnitaHanberger, HåkanNilsson, Lennart E

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Östholm Balkhed, ÅseTärnberg, MariaMonstein, Hans-JurgHällgren, AnitaHanberger, HåkanNilsson, Lennart E
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Clinical MicrobiologyFaculty of Health SciencesDepartment of Clinical MicrobiologyInfectious DiseasesDepartment of Infectious Diseases in Östergötland
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