| 1. |
- Bonnedahl, Jonas, 1970-, et al.
(författare)
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Dissemination of Escherichia coli with CTX-M Type ESBL between Humans and Yellow-Legged Gulls in the South of France
- 2009
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Ingår i: PLOS ONE. - San Francisco, CA, United States : Public Library of Science (PLoS). - 1932-6203. ; 4:Article number: e5958
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Tidskriftsartikel (refereegranskat)abstract
- Extended Spectrum beta-Lactamase (ESBL) producing Enterobacteriaceae started to appear in the 1980s, and have since emerged as some of the most significant hospital-acquired infections with Escherichia coli and Klebsiella being main players. More than 100 different ESBL types have been described, the most widespread being the CTX-M beta-lactamase enzymes (bla(CTX-M) genes). This study focuses on the zoonotic dissemination of ESBL bacteria, mainly CTX-M type, in the southern coastal region of France. We found that the level of general antibiotic resistance in single randomly selected E. coli isolates from wild Yellow-legged Gulls in France was high. Nearly half the isolates (47,1%) carried resistance to one or more antibiotics (in a panel of six antibiotics), and resistance to tetracycline, ampicillin and streptomycin was most widespread. In an ESBL selective screen, 9,4% of the gulls carried ESBL producing bacteria and notably, 6% of the gulls carried bacteria harboring CTX-M-1 group of ESBL enzymes, a recently introduced and yet the most common clinical CTX-M group in France. Multi locus sequence type and phylogenetic group designations were established for the ESBL isolates, revealing that birds and humans share E. coli populations. Several ESBL producing E. coli isolated from birds were identical to or clustered with isolates with human origin. Hence, wild birds pick up E. coli of human origin, and with human resistance traits, and may accordingly also act as an environmental reservoir and melting pot of bacterial resistance with a potential to re-infect human populations.
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| 2. |
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| 3. |
- Sandegren, Linus, et al.
(författare)
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Nitrofurantoin resistance mechanism and fitness cost in Escherichia coli
- 2008
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 62:3, s. 495-503
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES The biological fitness cost of antibiotic resistance is a key parameter in determining the rate of appearance and spread of antibiotic-resistant bacteria. We identified mutations conferring nitrofurantoin resistance and examined their effect on the fitness of clinical Escherichia coli isolates. METHODS By plating bacterial cells on agar plates containing nitrofurantoin, spontaneous nitrofurantoin-resistant E. coli mutants were isolated. The fitness of susceptible and resistant strains was measured as growth rate in the presence and absence of nitrofurantoin in rich culture medium. Time-kill kinetics of the resistant mutants was compared with the susceptible strains. Resistance mutations were identified by DNA sequencing. RESULTS Spontaneous resistant mutants of initially susceptible clinical E. coli appeared with a rate of 10(-7)/cell/generation, and these mutants showed a reduction in the growth rate compared with the susceptible parent strain. Similarly, comparison of a set of susceptible and resistant clinical isolates of E. coli showed that the average growth rate of the resistant mutants was approximately 6% lower than the susceptible strains. Furthermore, the bacterial growth rate in the presence of nitrofurantoin at therapeutic levels was greatly reduced even for nitrofurantoin-resistant mutants. The resistance-conferring mutations were identified in the nsfA and nfsB genes that encode oxygen-insensitive nitroreductases. CONCLUSIONS Nitrofurantoin resistance confers a reduction in fitness in E. coli in the absence of antibiotic. In the presence of therapeutic levels of nitrofurantoin, even resistant mutants are so disturbed in growth that they are probably unable to become enriched and establish an infection.
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| 4. |
- Schon, Thomas, et al.
(författare)
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Evaluation of wild-type MIC distributions as a tool for determination of clinical breakpoints for Mycobacterium tuberculosis
- 2009
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 64:4, s. 786-793
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The aim of this study was to establish wild-type MIC distributions of first-line drugs for Mycobacterium tuberculosis, as well as to explore the usefulness of such distributions when setting clinical breakpoints. Methods: We determined the MICs of rifampicin, isonlazid and ethambutol for M. tuberculosis using a Middlebrook 7H10 dilution method for 90 consecutive clinical isolates, 8 resistant strains and 16 isolates from the WHO proficiency test panel. M. tuberculosis H37Rv was used for quality control and susceptibility results using 7H10 were compared with the results obtained with BACTEC460. Results: The agreement with BACTEC460 was very high for isonlazid (99.1%) and rifampicin (99.1%) but lower for ethambutol (94.7%). Intra- and inter-assay variation was below one MIC dilution. The MIC distributions for isoniazid and rifampicin provided a clear separation between susceptible and resistant strains. Regarding ethambutol, the current breakpoint for 7H10 (5 mg/L) is close to the wild-type and all strains (n=6) showing a disagreement between BACTEC460 and 7H10 were distributed very close to the breakpoint (MIC 4-8 mg/L). This problematic relation was confirmed by investigating isolates from the WHO panel with an agreement <95% (64%-88% among 26 laboratories, n=4) for which the MICs were 4-8 mg/L . Conclusions: Utilizing the wild-type MIC distribution was found to be as useful in M. tuberculosis as in other bacteria when setting clinical breakpoints. We suggest that the present clinical breakpoints should be re-evaluated, taking into account wild-type MIC distributions and available pharmacokinetic data.
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| 5. |
- Sjölund, M., et al.
(författare)
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Antimicrobial susceptibility in Escherichia coli of human and avian origin : a comparison of wild-type distributions
- 2009
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Ingår i: Clinical Microbiology and Infection. - : Elsevier BV. - 1198-743X .- 1469-0691. ; 15:5, s. 461-465
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, the antimicrobial susceptibilities of 97 Escherichia coli isolates from birds, and 100 clinical isolates from blood cultures, were determined by disk diffusion. The wild-type distributions were defined by the normalized resistance interpretation method. It is shown that the avian and clinical inhibition zone diameter distributions of wild-type E. coli are indistinguishable.
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| 6. |
- Sjölund, Maria, et al.
(författare)
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Dissemination of multidrug-resistant bacteria into the Arctic
- 2008
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Ingår i: Emerging Infectious Diseases. - Atlanta, GA, United States : Centers for Disease Control and Prevention (CDC). - 1080-6040 .- 1080-6059. ; 14:1, s. 70-72
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Tidskriftsartikel (refereegranskat)abstract
- We show that Escherichia coli isolates originating from Arctic birds carry antimicrobial drug resistance determinants. This finding implies that dissemination of drug-resistant bacteria is worldwide. Resistance genes can be found even in a region where no selection pressure for resistance development exists.
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| 7. |
- Sjölund, Maria, et al.
(författare)
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Staphylococci in primary skin and soft tissue infections in a Swedish county
- 2008
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 40:11-12, s. 894-8
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Tidskriftsartikel (refereegranskat)abstract
- Patients with skin and soft tissue infections (SSTI) are frequently encountered in primary health care. The majority are uncomplicated and treated empirically by surgical incision and drainage and/or antibiotics. This strategy may risk delaying the detection of methicillin-resistant Staphylococcus aureus (MRSA), which, although still rare in Sweden, is increasingly being found in patients with SSTI. To avoid 'late detection' of MRSA, primary health care physicians in Kronoberg county, Sweden, were asked to perform a culture as soon as the patient's first visit. Samples from 175 patients with primary SSTI confirmed that S. aureus is the dominant pathogen. Two cases of MRSA were detected. Furthermore, isolates of S. aureus producing the Panton-Valentine leukocidin (PVL) toxin were more common among isolates from SSTI than among S. aureus from secondary infections. Finally, we confirmed the importance of the coagulase-negative staphylococcal species S. lugdunensis as a pathogen as it was isolated as the only pathogen in 10% of the skin and soft tissue samples.
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| 8. |
- Sundqvist, Martin, et al.
(författare)
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Effect of excluding duplicate isolates of Escherichia coli and Staphylococcus aureus in a 14 year consecutive database
- 2007
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 59:5, s. 913-918
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: It is recommended that duplicate isolates are excluded when reporting resistance rates. The rationale for this is that failing to do so will yield falsely high resistance rates. We analysed a 14 year consecutive database of Escherichia coli (n=62,380) and Staphylococcus aureus (n=28,178) using various cut-off algorithms to determine the importance of excluding duplicates and principal differences between the bacteria. METHODS: Susceptibility testing was performed according to the Swedish Reference Group for Antibiotics guidelines. Duplicates were excluded on the basis of species, individual and time (exclusion cut-offs of 7, 14, 30, 45, 90, 180, 270 and 365 days) from the first isolate. RESULTS: Although 30% of the isolates were excluded using a 365 day exclusion algorithm, the effects on resistance rates of excluding duplicates were small. Irrespective of cut-off, resistance in S. aureus decreased when duplicates were excluded. Using 7-30 days cut-offs, resistance in E. coli decreased or was not affected, whereas higher resistance rates were obtained when exclusion was based on a 365 day cut-off. Fluoroquinolone resistance was a clear exception to this rule. CONCLUSIONS: Although the effect of exclusion of duplicates was minor, we suggest that exclusion cut-offs should match the study timeline. The data presented on E. coli, from urinary tract infections, and S. aureus, from skin and soft tissue infections, suggest that E. coli infection, >90 days after the first culture, is mainly caused by new less-resistant strains. Patients with S. aureus continue to be colonized with the same strain.
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| 9. |
- Sundqvist, Martin, et al.
(författare)
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'Pre-emptive culturing' will improve the chance of 'getting it right' when empirical therapy of urinary tract infections fails
- 2009
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 64:2, s. 227-228
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Tidskriftsartikel (refereegranskat)abstract
- Antibiotic resistance is increasing and beginning to affect the outcome of empirical antimicrobial therapy of urinary tract infections. Associated resistance, i.e. the fact that a bacterium resistant to one antibiotic is often much more likely to be resistant to other antibiotics, drastically decreases our chances of getting a second empirical attempt right. To increase the use of narrow-spectrum antibiotics, which are considered to be less selective for resistance, we need to develop new strategies from the laboratory to support our clinical colleagues. We suggest that 'pre-emptive culturing' of urine (i.e. a culture obtained before empirical treatment is instituted) will prevent clinicians from making a second improper empirical choice or having to resort to expensive broad-spectrum antimicrobials, which may drive resistance further. This strategy will be especially important in settings with high levels of resistance.
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| 10. |
- Wimmerstedt, A, et al.
(författare)
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Associated antimicrobial resistance in Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes
- 2008
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Ingår i: Clinical Microbiology and Infection. - : Elsevier BV. - 1198-743X .- 1469-0691. ; 14:4, s. 315-321
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Tidskriftsartikel (refereegranskat)abstract
- Associated resistance to four to six related and unrelated antimicrobial agents was investigated in consecutive non-duplicate isolates of Escherichia coli (n = 39 425), Pseudomonas aeruginosa (n = 1070), Staphylococcus aureus (n = 7489), Streptococcus pneumoniae (n = 1604) and Streptococcus pyogenes (n = 2531). In all species, high proportions (76.5-88.9%) of isolates were susceptible to all the drugs investigated. Irrespective of species, isolates resistant to one drug were more likely to be resistant to any of the other drugs than were susceptible isolates. Thus, trimethoprim resistance in E. coli was 38.4% among ampicillin-resistant vs. 3.9% among ampicillin-susceptible isolates, and erythromycin resistance in Strep. pneumoniae was 41% among doxycycline-resistant vs. 1% among doxycycline-susceptible isolates. In all five species investigated, there was also significant associated resistance among unrelated drugs, highlighting the fact that resistance development occurs primarily among bacteria already resistant to one or more antimicrobial agents. For the clinician, pronounced resistance associations mean that when empirical therapy fails because of resistance, there is a reduced chance of choosing an alternative successful empirical agent. For the epidemiologist, who uses routine clinical susceptibility data to describe resistance development, resistance associations mean that if the dataset contains results for isolates selected on the basis of their susceptibility to another drug, structurally related or not, a bias of false resistance is introduced.
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