| 1. |
- Baquero, María-Rosario, et al.
(author)
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Polymorphic mutation frequencies in Escherichia coli : emergence of weak mutators in clinical isolates
- 2004
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In: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 186:16, s. 5538-5542
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Journal article (peer-reviewed)abstract
- Polymorphisms in the rifampin resistance mutation frequency (f) were studied in 696 Escherichia coli strains from Spain, Sweden, and Denmark. Of the 696 strains, 23% were weakly hypermutable (4 x 10(-8) < or = f < 4 x 10(-7)), and 0.7% were strongly hypermutable (f > or = 4 x 10(-7)). Weak mutators were apparently more frequent in southern Europe and in blood isolates (38%) than in urinary tract isolates (25%) and feces of healthy volunteers (11%).
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| 2. |
- Frimodt-Møller, Niels, et al.
(author)
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Apramycin efficacy against carbapenem- and aminoglycoside-resistant Escherichia coli and Klebsiella pneumoniae in murine bloodstream infection models
- 2024
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In: International Journal of Antimicrobial Agents. - : Elsevier. - 0924-8579 .- 1872-7913. ; 64:1
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Journal article (peer-reviewed)abstract
- BackgroundThe aminoglycoside apramycin has been proposed as a drug candidate for the treatment of critical Gram-negative systemic infections. However, the potential of apramycin in the treatment of drug-resistant bloodstream infections (BSIs) has not yet been assessed.MethodsThe resistance gene annotations of 40 888 blood-culture isolates were analysed. In vitro profiling of apramycin comprised cell-free translation assays, broth microdilution, and frequency of resistance determination. The efficacy of apramycin was studied in a mouse peritonitis model for a total of nine Escherichia coli and Klebsiella pneumoniae isolates.ResultsGenotypic aminoglycoside resistance was identified in 87.8% of all 6973 carbapenem-resistant Enterobacterales blood-culture isolates, colistin resistance was shown in 46.4% and apramycin in 2.1%. Apramycin activity against methylated ribosomes was > 100-fold higher than that for other aminoglycosides. Frequencies of resistance were < 10-9 at 8 × minimum inhibitory concentration (MIC). Tentative epidemiological cut-offs (TECOFFs) were determined as 8 µg/mL for E. coli and 4 µg/mL for K. pneumoniae. A single dose of 5 to 13 mg/kg resulted in a 1-log colony-forming unit (CFU) reduction in the blood and peritoneum. Two doses of 80 mg/kg resulted in an exposure that resembles the AUC observed for a single 30 mg/kg dose in humans and led to complete eradication of carbapenem- and aminoglycoside-resistant bacteraemia.ConclusionEncouraging coverage and potent in vivo efficacy against a selection of highly drug-resistant Enterobacterales isolates in the mouse peritonitis model warrants the conduct of clinical studies to validate apramycin as a drug candidate for the prophylaxis and treatment of BSI.
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| 3. |
- Gustafsson, Ingegerd
(author)
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Biological and Pharmacological Factor that Influence the Selection of Antibiotic Resistance
- 2003
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Doctoral thesis (other academic/artistic)abstract
- Antibiotic treatment causes an ecological disturbance on the human microflora. Four commensal bacteria: E. coli, enterococci, a-streptococci and coagulase-negative staphylococci, from patients with extensive, high antibiotic usage were investigated with regard to resistance pattern and mutation frequency. Among 193 investigated strains it was found that high antibiotic usage selected for resistant bacteria and enriched for bacteria with a small but significantly increased mutation frequency.The relative biological fitness cost of resistance in Staphylococcus epidermidis was assessed in a human in vivo model where the indigenous flora was present. In vitro data of the bacterial growth rate correlated well to in vivo fitness assayed in the competition experiments on skin.An in vitro kinetic model was shown to be a useful tool to establish the pharmacokinetic and pharmacodynamic (PK/PD) indices for efficacy of antibiotics. It was confirmed that the time, when the concentration exceeds the minimal inhibitory concentration (MIC), correlates with efficacy for b-lactam antibiotics. To achieve maximal killing for penicillin-resistant pneumococci, with an MIC of 2 mg/L, the peak concentration was also of importance.Suboptimal dosing regimen facilitates selection of resistance. Penicillin-resistant pneumococci were easily selected in a mixed population with penicillin-sensitive, -intermediate and -resistant pneumococci in an in vitro kinetic model. The selection of the resistant strain was prevented when the benzylpenicillin concentration exceeded the MIC for approximately 50% of 24 h.
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| 4. |
- Jansåker, Filip, et al.
(author)
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Novel risk factors associated with common vaginal infections : a nationwide primary health care cohort study: Novel risk factors for vaginal infections
- 2022
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In: International Journal of Infectious Diseases. - : Elsevier BV. - 1201-9712. ; 116, s. 380-386
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Journal article (peer-reviewed)abstract
- Objective: This study aimed to estimate the association between potential risk factors and common vaginal infections using nationwide primary health care and other national registers. Methods: An open cohort study consisting of 2,357,711 women aged 15 years to 50 years (2001 to 2018) was conducted in Sweden. The outcomes were first event of vulvovaginal candidiasis (VVC) and bacterial vaginosis (BV) in relation to sociodemographic factors. Cox regression models were used. Sensitivity analyses including diabetes mellitus, contraceptive use, and cervical cancer were conducted. Results: The incidence rates per 1,000 person-years for VVC and BV were 3.3 (95% confidence interval [CI] 3.2-3.3) and 3.4 (95% CI 3.4-3.4), respectively. In the fully adjusted model, sociodemographic factors were significantly associated with both outcomes. Compared with Swedish-born women, women from Middle East/North Africa had the highest risk of VVC (hazard ratio [HR] 2.77, 95% CI, 2.72-2.83), followed by Africa (excluding North Africa) (HR 2.53, 95% CI, 2.45-2.61), and Latin America and the Caribbean (HR 2.18, 95% CI, 2.09-2.27). For BV, women from Latin America and the Caribbean had the highest risk (HR 1.83, 95% CI, 1.75-1.92). Conclusion: This study presents novel risk factors associated with medically attended vaginal infections. Women from non-Western countries seem to develop these conditions disproportionately.
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| 5. |
- Jansåker, Filip, et al.
(author)
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The association between common urogenital infections and cervical neoplasia – A nationwide cohort study of over four million women (2002–2018)
- 2022
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In: The Lancet Regional Health - Europe. - : Elsevier BV. - 2666-7762. ; 17
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Journal article (peer-reviewed)abstract
- Background: Cervical cancer is a major cause of mortality and morbidity in women worldwide. This study aimed to estimate the association between common urogenital infections and cervical neoplasia. Methods: A multi-register national cohort study of 4,120,557 women aged ≥15 years (2002–2018) was conducted. The outcomes were cervical cancer and carcinoma in situ (Swedish Cancer Register). The main predictors were urogenital infections—(urinary) cystitis, (bacterial) vaginosis, (candida) vulvovaginitis. Incidence rates per 10,000 person-years were calculated (using the European Standard Population). Cox regression was used to estimate hazard ratios (HR) while adjusting for possible confounders—other genital infections (e.g., cervicitis, salpingitis, urogenital herpes), parity, and sociodemographic factors. Findings: In 39·0 million person-years of follow-up, the incidence rate for cervical cancer was 1·2 (95% CI 1·1–1·2) per 10,000 person-years and the figure for cervical carcinoma in situ was more than tenfold higher. The fully adjusted HRs for cervical cancer were 1·31 (95% CI 1·15 and 1·48) and 1·22 (95% CI 1·16 and 1·29) for vaginosis and cystitis, respectively. Vaginosis showed a gradient association to carcinoma in situ. Vulvovaginitis was inversely associated with cervical cancer, but not significantly related with carcinoma in situ in the fully adjusted model. A temporal association with cervical cancer was observed for vaginosis and vulvovaginitis (inversely) but not for cystitis. Interpretation: In this large nationwide cohort of women, medically attended common urogenital infections were independently associated with cervical neoplasia, but cystitis was not temporally associated with cervical neoplasia. These findings could be used to increase focus on preventive measures, HPV-vaccination programmes, HPV-analyses- and cervical cancer screening, especially in women suffering from vaginosis. Future studies on the causal mechanism are warranted before generalized public health recommendations can be made. Funding: Region Skåne, Tore Nilsons Stiftelse, and Swedish Society of Medicine.
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| 6. |
- Jansåker, Filip, et al.
(author)
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The Risk of Pyelonephritis Following Uncomplicated Cystitis : A Nationwide Primary Healthcare Study
- 2022
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In: Antibiotics. - : MDPI AG. - 2079-6382. ; 11:12
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Journal article (peer-reviewed)abstract
- Background: The risk of pyelonephritis following uncomplicated lower urinary tract infection (cystitis) in women has not been studied in well-powered samples. This is likely due to the previous lack of nationwide primary healthcare data. We aimed to examine the risks of pyelonephritis following cystitis in women and explore if antibiotic treatment, cervical cancer, parity, and sociodemographic factors are related to these risks. Methods: This was a nationwide cohort study (2006–2018) of 752,289 women diagnosed with uncomplicated cystitis in primary healthcare settings. Of these, 404 696 did not redeem an antibiotic prescription within five days from cystitis. Logistic regression models were used to calculate odds ratios for pyelonephritis within 30 days and 90 days following the cystitis event. Results: Around one percent (7454) of all women with cystitis were diagnosed with pyelonephritis within 30 days, of which 78.2% had not redeemed an antibiotic for their cystitis. Antibiotic treatment was inversely associated with both outpatient registration and hospitalization due to pyelonephritis, with odds ratios of 0.85 (95% CI 0.80 to 0.91) and 0.65 (95% CI 0.55 to 0.77), respectively. Sociodemographic factors, parity, and cervical cancer were, with few exceptions (e.g., age and region of residency), not associated with pyelonephritis. Conclusions: Antibiotic treatment was inversely associated with pyelonephritis, but the absolute risk reduction was low. Non-antibiotic treatment for cystitis might be a safe option for most women. Future studies identifying the women at the highest risks will help clinicians in their decision making when treating cystitis, while keeping the ecological costs of antibiotics in mind.
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| 7. |
- Knudsen, Jenny Dahl, et al.
(author)
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Selection of Resistant Streptococcus pneumoniae during Penicillin Treatment In Vitro and in Three Animal Models.
- 2003
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In: Antimicrobial Agents and Chemotherapy. - 1098-6596. ; 47:8, s. 2499-2506
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Journal article (peer-reviewed)abstract
- Pharmacokinetic (PK) and pharmacodynamic (PD) properties for the selection of resistant pneumococci were studied by using three strains of the same serotype (6B) for mixed-culture infection in time-kill experiments in vitro and in three different animal models, the mouse peritonitis, the mouse thigh, and the rabbit tissue cage models. Treatment regimens with penicillin were designed to give a wide range of T>MICs, the amounts of time for which the drug concentrations in serum were above the MIC. The mixed culture of the three pneumococcal strains, 107 CFU of strain A (MIC of penicillin, 0.016 µg/ml; erythromycin resistant)/ml, 106 CFU of strain B (MIC of penicillin, 0.25 µg/ml)/ml, and 105 CFU of strain C (MIC of penicillin, 4 µg/ml)/ml, was used in the two mouse models, and a mixture of 105 CFU of strain A/ml, 104 CFU of strain B/ml, and 103 CFU of strain C/ml was used in the rabbit tissue cage model. During the different treatment regimens, the differences in numbers of CFU between treated and control animals were calculated to measure the efficacies of the regimens. Selective media with erythromycin or different penicillin concentrations were used to quantify the strains separately. The efficacies of penicillin in vitro were similar when individual strains or mixed cultures were studied. The eradication of the bacteria, independent of the susceptibility of the strain or strains or the presence of the strains in a mixture or on their own, followed the well-known PK and PD rules for treatment with ß-lactams: a maximum efficacy was seen when the T>MIC was >40 to 50% of the observation time and the ratio of the maximum concentration of the drug in serum to the MIC was >10. It was possible in all three models to select for the less-susceptible strains by using insufficient treatments. In the rabbit tissue cage model, a regrowth of pneumococci was observed; in the mouse thigh model, the ratio between the different strains changed in favor of the less-susceptible strains; and in the mouse peritonitis model, the susceptible strain disappeared and was overgrown by the less-susceptible strains. These findings with the experimental infection models confirm the importance of eradicating all the bacteria taking part in the infectious process in order to avoid selection of resistant clones.
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| 8. |
- Marcusson, Linda L, et al.
(author)
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Interplay in the Selection of Fluoroquinolone Resistance and Bacterial Fitness
- 2009
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In: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 5:8, s. e1000541-
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Journal article (peer-reviewed)abstract
- Fluoroquinolones are antibacterial drugs that inhibit DNA Gyrase and Topoisomerase IV. These essential enzymes facilitate chromosome replication and RNA transcription by regulating chromosome supercoiling. High-level resistance to fluoroquinolones in E. coli requires the accumulation of multiple mutations, including those that alter target genes and genes regulating drug efflux. Previous studies have shown some drug-resistance mutations reduce bacterial fitness, leading to the selection of fitness-compensatory mutations. The impact of fluoroquinolone-resistance on bacterial fitness was analyzed in constructed isogenic strains carrying up to 5 resistance mutations. Some mutations significantly decreased bacterial fitness both in vitro and in vivo. We identified low-fitness triple-mutants where the acquisition of a fourth resistance mutation significantly increased fitness in vitro and in vivo while at the same time dramatically decreasing drug susceptibility. The largest effect occurred with the addition of a parC mutation (Topoisomerase IV) to a low-fitness strain carrying resistance mutations in gyrA (DNA Gyrase) and marR (drug efflux regulation). Increased fitness was accompanied by a significant change in the level of gyrA promoter activity as measured in an assay of DNA supercoiling. In selection and competition experiments made in the absence of drug, parC mutants that improved fitness and reduced susceptibility were selected. These data suggest that natural selection for improved growth in bacteria with low-level resistance to fluoroquinolones could in some cases select for further reductions in drug susceptibility. Thus, increased resistance to fluoroquinolones could be selected even in the absence of further exposure to the drug.
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| 9. |
- Nielsen, Karen Leth, et al.
(author)
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Escherichia coli causing recurrent urinary tract infections: Comparison to non-recurrent isolates and genomic adaptation in recurrent infections
- 2021
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In: Microorganisms. - : MDPI. - 2076-2607. ; 9:7
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Journal article (peer-reviewed)abstract
- Recurrent urinary tract infection (rUTI) remains a major problem for many women and therefore the pursuit for genomic and phenotypic traits which could define rUTI has been ongoing. The present study applied a genomic approach to investigate recurrent urinary tract infections by comparative analyses of recurrent and non-recurrent Escherichia coli isolates from general practice. From whole-genome sequencing data, phylogenetic clustering and genomic traits were studied on a collection of isolates which caused recurrent infection compared to non-recurrent isolates. In addition, genomic variation between the 1st and following infection was studied on a subset of the isolates. Evidence of limited adaptation between the recurrent infections based on single nucleotide polymorphism analyses with a range of 0–13 non-synonymous single nucleotide polymorphisms (SNPs) between the paired isolates. This included an overrepresentation of SNPs in metabolism genes. We identified several genes which were more common in rUTI isolates, including nine fimbrial genes, however, not significantly after false-discovery rate. Finally, the results show that recurrent isolates of the present dataset are not distinctive by variation in the core genome, and thus, did not cluster distinct from non-rUTI isolates in a SNP phylogeny.
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| 10. |
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| 11. |
- Sandberg, Anne, et al.
(author)
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Intra- and Extracellular Activities of Dicloxacillin and Linezolid against a Clinical Staphylococcus aureus Strain with a Small-Colony-Variant Phenotype in an In Vitro Model of THP-1 Macrophages and an In Vivo Mouse Peritonitis Model
- 2011
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In: Antimicrobial Agents and Chemotherapy. - 0066-4804 .- 1098-6596. ; 55:4, s. 1443-1452
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Journal article (peer-reviewed)abstract
- The small colony variant (SCV) phenotype of Staphylococcus aureus has been associated with difficult-to-treat infections, reduced antimicrobial susceptibility and intracellular persistence. This study represents a detailed intra- and extracellular investigation of a clinical wild type (WT) S. aureus strain and its counterpart SCV phenotype both in vitro and in vivo, using the THP-1 cell line model and mouse peritonitis model respectively. Both phenotypes infected the mouse peritoneum intra- and extracellularly. The SCV phenotype was less virulent, showed distinct bacterial clearance, reduced multiplication capacity and reduced internalization ability. Some of the SCV infected mice were, however, still culture positive up to 96 h post infection and the phenotype could spread to the mouse kidney and furthermore revert to the more virulent WT phenotype in both the mouse- peritoneum and kidney. The SCV phenotype is therefore, despite reduced virulence, an important player in the S. aureus pathogenesis. In the THP-1 cell line model, both dicloxacillin (DCX) and linezolid (LZD) reduced the intracellular inoculum of both phenotypes by approximately 1-1.5 log10 in vitro, while DCX was considerably more effective against extracellular bacteria. In the mouse peritonitis model, DCX and LZD were also able to control both the intra- and extracellular infection caused by either phenotype. Treatment with a single dose of DCX and LZD was, however, insufficient to clear the SCVs in the kidneys and the risk of recurrent infection remained. This stresses the importance of optimal dosing of the antibiotic when SCVs are present.
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| 12. |
- Trobos, Margarita, 1980, et al.
(author)
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Natural transfer of sulphonamide and ampicillin resistance between Escherichia coli residing in the human intestine.
- 2009
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In: The Journal of antimicrobial chemotherapy. - : Oxford University Press (OUP). - 1460-2091 .- 0305-7453. ; 63:1, s. 80-6
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Journal article (peer-reviewed)abstract
- The aim of this study was to investigate whether the sulphonamide resistance gene sul2 could be transferred between Escherichia coli in the human gut.Nine volunteers ingested a 10(9) cfu suspension of sulphonamide-susceptible, rifampicin-resistant E. coli recipients of human origin. Three hours later, they ingested a 10(7) cfu suspension of a sulphonamide-resistant (MIC>1024 mg/L) E. coli donor of pig origin. Stool samples were collected 24 h prior to ingestion, daily for 7 days and at days 14 and 35. Samples were plated on selective plates and monitored for the acquisition of sulphonamide-resistance by the recipient from the indigenous or administrated donor E. coli. Possible transconjugants were typed by PFGE and tested for the presence of plasmids containing the sul2 gene, which was also sequenced.Concentrations of the human and animal E. coli reached a maximum of 7.5x10(6) cfu/g faeces and colonized for more than 7 days, and 2x10(8) cfu/g for more than 14 days, respectively. On day 2, a transconjugant was detected in one volunteer. This volunteer was colonized with sulphonamide-resistant E. coli at day 0. The transconjugant was sul2-positive, had an MIC>1024 mg/L for sulfamethoxazole and the same PFGE profile as the recipient. The resident E. coli transferred a plasmid (>63 kb), containing the sul2 gene, to the recipient. The sul2 sequence of the transconjugant was identical to that of the volunteer's own E. coli from day 0, but differed from the animal strain. Co-transfer of ampicillin resistance was also demonstrated.Transfer of sul2 was observed between E. coli bacteria in the human intestine. The transconjugant's sul2 gene came from the volunteer's own flora. The origin of the E. coli donor is unknown.
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| 13. |
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| 14. |
- Zorzet, Anna, et al.
(author)
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Compensatory mutations in agrC partly restore fitness in vitro to peptide deformylase inhibitor-resistant Staphylococcus aureus
- 2012
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In: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 67:8, s. 1835-1842
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Journal article (peer-reviewed)abstract
- OBJECTIVESTo determine how the fitness cost of deformylase inhibitor resistance conferred by fmt mutations can be genetically compensated.METHODSResistant mutants were isolated and characterized with regard to their growth rates in vitro and in neutropenic mice, MIC and DNA sequence. Faster-growing compensated mutants were isolated by serial passage in culture medium, and for a subset of the resistant and compensated mutants whole-genome sequencing was performed.RESULTSStaphylococcus aureus mutants resistant to the peptide deformylase inhibitor actinonin had mutations in the fmt gene that conferred high-level actinonin resistance and reduced bacterial growth rate. Compensated mutants that remained fully resistant to actinonin and showed increased growth rates appeared within 30-60 generations of growth. Whole-genome sequencing and localized DNA sequencing of mutated candidate genes showed that alterations in the gene agrC were present in the majority of compensated strains. Resistant and compensated mutants grew at similar rates as the wild-type in a mouse thigh infection model.CONCLUSIONSResistance to deformylase inhibitors due to fmt mutations reduces bacterial growth rates, but these costs can be reduced by mutations in the agrC gene. Mutants defective in fmt (with or without compensatory agrC mutations) grew well in an animal model, implying that they can also cause infection in a host.
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