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  • 1. Adamsson, I
    et al.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institute.
    Nord, C E
    Microbial ecology and treatment of Helicobacter pylori infections: Review2000In: Journal of chemotherapy, ISSN 1120-009X, E-ISSN 1973-9478, Vol. 12, no 1, p. 5-16Article, review/survey (Refereed)
    Abstract [en]

    The aims of the present study were to investigate the ecological disturbances caused by four different anti-H. pylori regimens, to compare different methods for diagnosing H. pylori, and to study the genetic variability of H. pylori. The patients included in the study were all treated at the Center of Gastroenterology, Huddinge University Hospital, Karolinska Institute. All patients were H. pylori-positive before entering the study, confirmed by rapid urease test, histology, culture and urea breath test or PCR. Treatment regimens included in the study were omeprazole alone (OP), in combination with amoxicillin (OA), in combination with amoxicillin and metronidazole (OAM) and in combination with clarithromycin and metronidazole (OCM). Samples from the mouth (saliva and dental plaque), stomach (biopsies from the gastric mucosa in the corpus and in the antrum) and the intestine (feces) were collected before, during and after treatment. The oral microflora was challenged by the three treatment regimens including antimicrobial agents, with the emergence of resistant streptococci and staphylococci in the OCM group. Bacterial strains in the gastric mucosa increased in numbers during treatment in all treatment groups, probably due to the pH rise, which provides a better environment for the commensal microflora. This overgrowth was especially pronounced during treatment with omeprazole alone (OP), possibly due to the fact that a concomitant suppression exerted by the antimicrobial agents occurred in the other treatment groups. H. pylori was, on the other hand, suppressed during treatment in all treatment groups, possibly due to a direct effect of omeprazole and to the colonization resistance expressed by the normal microflora, An emergence of resistant commensal strains in the gastric mucosa was seen in the OCM and the OAM groups. The intestinal microflora was most altered in the OAM and the OCM groups, with persistent disturbances in the OCM group 4 weeks after treatment. The frequency of resistant Enterococcus spp, (OCM), Enterobacteriaceae spp, (OA and OAM) and Bacteroides spp, (OCM) was increased during and after treatment. Different detection methods for H. pylori were compared and PCR was shown to have higher sensitivity than other routine diagnostic tests. The patients in the present study seemed to be colonized with a single strain of H. pylori. Treatment failures in patients treated with OAM were caused by recrudescence. These four patients with relapsing H. pylori infection, were shown to be reinfected with the original H. pylori strain, indicating that H. pylori escapes treatment by a thus far unknown mechanism.

  • 2. Adamsson, I
    et al.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap.
    Seensalu, R
    Engstrand, L
    The use of AP-PCR and flaA-RFLP typing to investigate treatment failure in Helicobacter pylori infection2000In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 6, no 5, p. 265-267Article in journal (Refereed)
  • 3. Agvald-Öhman, C
    et al.
    Lund, B
    Edlund, Charlotta
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science.
    Multiresistant coagulase-negative staphylococci disseminate frequently between intubated patients in a multidisciplinary intensive care unit2004In: Critical Care, ISSN 1364-8535, E-ISSN 1466-609X, Vol. 8, no 1, p. R42-R47Article in journal (Refereed)
    Abstract [en]

    Introduction The intensive care unit is burdened with a high frequency of nosocomial infections often caused by multiresistant nosocomial pathogens. Coagulase-negative staphylococci (CoNS) are reported to be the third causative agent of nosocomial infections and the most frequent cause of nosocomial bloodstream infections. CoNS are a part of the normal microflora of skin but can also colonize the nasal mucosa, the lower airways and invasive devices. The main aim of the present study was to investigate colonization and the rate of cross-transmissions of CoNS between intubated patients in a multidisciplinary intensive care unit. Materials and methods Twenty consecutive patients, ventilated for at least 3 days, were included. Samples were collected from the upper and lower airways. All samples were cultured quantitatively and CoNS were identified by morphology and biochemical tests. A total of 199 CoNS isolates from 17 patients were genetically fingerprinted by pulsed-field gel electrophoresis in order to identify clones and to monitor dissemination within and between patients. Results An unexpected high number of transmission events were detected. Five genotypes were each isolated from two or more patients, and 14/20 patients were involved in at least one and up to eight probable transmission events. Conclusions A frequent transmission of CoNS was found between patients in the intensive care unit. Although transmission of bacteria does not necessarily lead to infection, it is nevertheless an indication that infection control measures can be improved.

  • 4. Agvald-Öhman, C
    et al.
    Wernerman, J
    Nord, C E
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap.
    Anaerobic bacteria commonly colonize the lower airways of intubated ICU patients2003In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 9, no 5, p. 397-405Article in journal (Refereed)
    Abstract [en]

    Objectives To investigate respiratory tract colonization by aerobic and anaerobic bacteria in mechanically ventilated patients. Methods Bacterial colonization of the stomach and the respiratory tract was qualitatively and quantitatively analyzed over time in 41 consecutive mechanically ventilated patients in a Swedish intensive care unit (ICU), with special emphasis on elucidation of the role of anaerobic bacteria in the lower respiratory tract. Samples were taken from the oropharynx, gastric juice, subglottic space and trachea within 24 h (median 14 h) of intubation, and then every third day until day 18 and every fifth day until day 33. Results The patients were often heavily colonized with microorganisms not considered to belong to a healthy normal oropharyngeal and gastric flora on admission to the ICU. A majority harbored enterococci, coagulase-negative staphylococci and Candida spp. in at least one site on day 1. Anaerobic bacteria, mainly peptostreptococci and Prevotella spp., were isolated from subglottic and/or tracheal secretions in 59% of the patients. Different routes of tracheal colonization for different groups of microorganisms were found. Primary or concomitant colonization of the oropharynx with staphylococci, enterococci, enterobacteria and Candida was often seen, while Pseudomonas spp., other non-fermenting Gram-negative rods and several anaerobic species often primarily colonized the trachea, indicating exogenous or direct gastrointestinal routes of colonization. Conclusions Mechanically ventilated patients were heavily colonized in their lower airways by potential pathogenic microorganisms, including a high load of anaerobic bacteria. Different routes of colonization were shown for different species.

  • 5.
    Edlund, Charlotta
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institute.
    Alvan, G
    Barkholt, L
    Vacheron, F
    Nord, C E
    Pharmacokinetics and comparative effects of telithromycin (HMR 3647) and clarithromycin on the oropharyngeal and intestinal microflora2000In: Journal of Antimicrobial Chemotherapy, ISSN 0305-7453, E-ISSN 1460-2091, Vol. 46, no 5, p. 741-749Article in journal (Refereed)
    Abstract [en]

    The pharmacokinetics in plasma and saliva of a new ketolide, telithromycin (HMR 3647), and the effect on the normal oropharyngeal and intestinal microflora were studied in healthy volunteers and compared with those of clarithromycin. Ten subjects received 800 mg telithromycin perorally once daily and 10 other subjects received 500 mg clarithromycin bid for 10 days. Blood, saliva and faecal specimens were collected at defined intervals before, during and after administration for pharmacokinetic and microbiological analyses. In subjects receiving telithromycin, the mean C(max), AUC and C(24) (24 h) in saliva exceeded the values obtained from plasma, while saliva and serum pharmacokinetic parameters were in the same range for the clarithromycin group. The quantitative ecological disturbances in the normal microflora during administration of telithromycin were moderate and comparable to those associated with clarithromycin administration. No overgrowth of yeasts or Clostridium difficile occurred. Emergence of resistant strains was seen in both treatment groups. Administration of both telithromycin and clarithromycin was associated with significant increases in MICs for intestinal Bacteroides isolates, which persisted 2 weeks after discontinuation of treatment. In addition, a significant emergence of highly clarithromycin-resistant a-haemolytic streptococci, intestinal enterococci and Enterobacteriaceae was detected at day 10 in the clarithromycin group. In conclusion, administration of telithromycin resulted in high drug levels in saliva, which indicates a good therapeutic profile for throat infections. Telithromycin seems to have a more favourable ecological profile compared with clarithromycin in terms of resistance development in the normal microflora.

  • 6.
    Edlund, Charlotta
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institute.
    Beyer, G.
    Free University of Berlin, Berlin, Germany.
    Hiemer-Bau, M.
    Free University of Berlin, Berlin, Germany.
    Ziege, S.
    Free University of Berlin, Berlin, Germany.
    Lode, H.
    Free University of Berlin, Berlin, Germany.
    Nord, C. E.
    Karolinska Institute.
    Comparative effects of moxifloxacin and clarithromycin on the normal intestinal microflora2000In: Scandinavian Journal of Infectious Diseases, ISSN 0036-5548, E-ISSN 1651-1980, Vol. 32, no 1, p. 81-85Article in journal (Refereed)
    Abstract [en]

    Twelve healthy male subjects age range 24-40 y participated in the investigation. The trial was divided into 2 35-d periods. The 2 treatment regimens were: (i) 1 x 400 mg moxifloxacin tablet in the morning and 1 placebo tablet in the evening for 7 d; and (ii) 1 x 500 mg clarithromycin tablet in the morning and 1 x 500 mg clarithromycin tablet in the evening for 7 d. Each subject received firstly 1 treatment regimen and secondly the other treatment regimen. The wash-out period was 6 weeks between the two treatment regimens. Moxifloxacin caused significant decreases of enterococci and enterobacteria during the administration period while the numbers of staphylococci, streptococci, Bacillus and Candida were not affected. No impact on peptostreptococci, lactobacilli, Veillonella, Bacteroides or fusobacteria was observed, while bifidobacteria and clostridia decreased during moxifloxacin administration. The microflora was normalized after 35 d. Clarithromycin caused significant reduction of Escherichia coli while the numbers of enterococci, Enterobacter, Citrobacter, Klebsiella and Pseudomonas increased markedly. No significant changes in the numbers of staphylococci, streptococci, Bacillus and Candida were noticed. In the anaerobic microflora bifidobacteria, lactobacilli and clostridia were suppressed, while no changes in peptostreptococci, Veillonella, Bacteroides and fusobacteria were found. The microflora was normalized in all volunteers after 35 d.

  • 7.
    Edlund, Charlotta
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institute.
    Nord, C E
    Effect on the human normal microflora of oral antibiotics for treatment of urinary tract infections2000In: Journal of Antimicrobial Chemotherapy, ISSN 0305-7453, E-ISSN 1460-2091, Vol. 46, p. 41-48Article in journal (Refereed)
    Abstract [en]

    Oral administration of antibiotics for treatment of urinary tract infections (UTIs) can cause ecological disturbances in the normal intestinal microflora. Poorly absorbed drugs can reach the colon in active form, suppress susceptible microorganisms and disturb the ecological balance. Suppression of the normal microflora may lead to reduced colonization resistance with subsequent overgrowth of pre-existing, naturally resistant microorganisms, such as yeasts and Clostridium difficile. New colonization by resistant potential pathogens may also occur and may spread within the body or to other patients and cause severe infections. It is therefore important to learn more about the ecological effects of antibacterial agents on the human microflora. The impact on intestinal microorganisms of oral antibiotics used for the treatment of UTIs is reviewed here. Ampicillin, amoxycillin and co-amoxiclav suppress both the aerobic and anaerobic intestinal microflora with overgrowth of ampicillin-resistant Enterobacteriaceae. Pivmecillinam also affects the intestinal microflora, suppressing Escherichia coli, but does not have a major effect on the anaerobic microflora. Several orally administered cephalosporins, such as cefixime, cefpodoxime, cefprozil and ceftibuten, reduce the number of Enterobacteriaceae and increase the number of enterococci. Colonization with C. difficile has also been observed. Fluoroquinolones eliminate or strongly suppress intestinal Enterobacteriaceae, but affect enterococci and anaerobic bacteria only slightly. When antimicrobial agents are prescribed for the treatment of UTIs, not only the antimicrobial spectrum of the agent but also the potential ecological disturbances, including the risk of emergence of resistant strains, should be considered.

  • 8.
    Edlund, Charlotta
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institute.
    Nord, C E
    The evaluation and prediction of the ecologic impact of antibiotics in human phase I and II trials2001In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 7, p. 37-41Article in journal (Refereed)
  • 9.
    Fang, Hong
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Univesity Hospital, Huddinge.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Karolinska Univesity Hospital, Huddinge.
    Hultenby, K
    Karolinska Univesity Hospital, Huddinge.
    Hedberg, M
    Karolinska Univesity Hospital, Huddinge.
    Effects of cefoxitin on the growth and morphology of Bacteroides thetaiotaomicron strains with different cefoxitin susceptibility2002In: Anaerobe, ISSN 1075-9964, E-ISSN 1095-8274, Vol. 8, no 2, p. 55-61Article in journal (Refereed)
    Abstract [en]

    To examine the effects of cefoxitin on bacterial growth and cell morphology, two pairs of Bacteroides thetaiotaomicron strains (238, 238 m and 1186, 1186 m) with different susceptibilities to this antibiotic were investigated in the present study. B. thetaiotaomicron 238m and 1186m were resistant laboratory mutants originating from the susceptible wild-type strains B. thetaiotaomicron 238 and 1186, respectively. It has been shown, in a previous study, that the mutant strains had alterations in their penicillin-binding proteins (PBPs) as compared to the parent strains. In the present study, strains 238 and 238m presented almost identical genomic fingerprints by PCR, so did strains 1186 and 1186m, which indicates that the parent and mutant strains have similar genomic background. In comparison with the parent strains, the growth rate of mutant strains was slower in cultures without antibiotic. The growth patterns challenged with cefoxitin were also different between the parent and the mutant strains. In case of the morphological responses to cefoxitin, the mutant strains were more resistant to the effect of cefoxitin than the parent strains. In conclusion, the growth patterns and the morphological changes induced by cefoxitin, of the investigated strains, were associated with the properties of PBPs. The resistant mutants with deficiency in PBPs grew slower than the susceptible parent strains, and cefoxitin caused filamentation at sub-MIC in B. thetaiotaomicron.

  • 10. Fang, Hong
    et al.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap.
    Nord, C E
    Hedberg, M
    Selection of cefoxitin-resistant Bacteroides thetaiotaomicron mutants and mechanisms involved in beta-lactam resistance2002In: Clinical Infectious Diseases, ISSN 1058-4838, E-ISSN 1537-6591, Vol. 35, p. S47-S53Article in journal (Refereed)
    Abstract [en]

    The beta-lactam antibiotics are the most widely used of all the groups of antimicrobials, but beta-lactam resistance is increasingly common among members of the Bacteroides fragilis group. Three major mechanisms are involved in beta-lactam resistance, and they act together in certain instances. In the present study, 2 resistant mutants (238m and 1186m) of Bacteroides thetaiotaomicron, obtained from clinical isolates (238 and 1186) by selection with increasing concentrations of cefoxitin, showed decreased susceptibilities to cefoxitin and other beta-lactam antibiotics. Alterations in both penicillin-binding proteins (PBPs) and outer-membrane proteins (OMPs) were observed in the mutants in comparison with their parent strains. The similar alteration in OMPs was also observed in clinical isolates. In conclusion, the beta-lactam-resistant mutants of B. thetaiotaomicron with deficiency in both PBPs and OMPs can be selected for by exposure to cefoxitin, and several mechanisms are involved in the beta-lactam resistance in the strains investigated.

  • 11.
    Fang, Hong
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Zhang, G.
    Karolinska Institutet.
    Hedberg, M.
    Karolinska Institutet.
    Detection of imipenem-resistant and metronidazole-resistant Bacteroides fragilis group strains in fecal samples1999In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 5, no 12, p. 753-758Article in journal (Refereed)
    Abstract [en]

    Objective: To investigate the imipenem and metronidazole resistance profiles of Bacteroides fragilis group strains in fecal samples and to detect the resistance genes (ccrA and nim) coding for imipenem and metronidazole resistance in B. fragilis group strains. Methods: In total, 925 fecal samples, 729 from consecutive diarrhea patients and 196 from healthy controls, were collected at Huddinge University Hospital in 1997. A modified disk diffusion method was employed to screen for imipenem-resistant and metronidazole-resistant B. fragilis group strains. In strains considered resistant by the modified disk diffusion method, the minimum inhibitory concentrations (MICs) were further determined by the agar dilution method. PCR assays were used to detect the carbapenem-hydrolyzing metallo-P-lactamase gene (ccrA) and the 5-nitroimidazole resistance genes (nim) in pure cultures (purePCR), directly from fecal samples through direct broth enrichment (dirPCR) and by immunomagnetic separation (imsPCR). Results: Two imipenem-resistant B. fragilis strains, one of which was simultaneously resistant to metronidazole, and two B. fragilis group strains with MICs near the breakpoint for metronidazole resistance, were isolated from the fecal samples of diarrhea patients. The ccrA gene was identified in all the imipenem-resistant B. fragilis strains by purePCR, dirPCR and imsPCR. The nim genes were also detectable by these PCR assays. Conclusions: The incidences of imipenem-resistant and metronidazole-resistant B. fragilis group strains were low in the investigated diarrhea patients. Simultaneous resistance to imipenem and metronidazole is of great concern in clinical medicine, and the proposed PCR assays may be useful in epidemiologic studies of distribution of resistance genes in the fecal microflora.

  • 12.
    Fang, Hong
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Hedberg, M
    Karolinska Institutet.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Karolinska Instiutet.
    Nord, C E
    Karolinska Institutet.
    Identification of the metallo-beta-lactamase gene from clinical isolates of Bacteroides fragilis1999In: Anaerobe, ISSN 1075-9964, E-ISSN 1095-8274, Vol. 5, no 3-4, p. 431-434Article in journal (Refereed)
    Abstract [en]

    Bacteroides fragilis is one of the organisms known to produce carbapenem-hydrolysing metallo-beta-lactamase, which can confer resistance to a wide variety of beta-lactams. The purpose of this study was to identify carbapenem-hydrolysing metallo-beta-lactamase-producing B. fragilis strains by means of PCR assay, nucleotide sequencing and enzyme inhibition studies. Ten beta-lactam-resistant B. fragilis isolates were investigated. Four imipenem-resistant strains among the 10 isolates gave positive reactions in the PCR assay. The nucleotide sequences of the PCR products from two imipenem-resistant strains shared >98% similarity with the metallo-beta-lactamase gene from B. fragilis TAL 3636, which was used as a control. The amino acid sequence homology between the two imipenem-resistant strains and B. fragilis TAL 3636 was 99.2%. These strains produced high amounts of Zn2+-dependent beta-lactamases which were inactivated by EDTA.

  • 13.
    Jernberg, Cecilia
    et al.
    Karolinska Institutet.
    Löfmark, Sonja
    Karolinska Institutet.
    Edlund, Charlotta
    Karolinska Institutet / Medical Products Agency.
    Jansson, Janet K.
    Swedish University of Agricultural Sciences.
    Long-term ecological impacts of antibiotic administration on the human intestinal microbiota2007In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 1, no 1, p. 56-66Article in journal (Refereed)
    Abstract [en]

    Antibiotic administration is known to cause short-term disturbances in the microbiota of the human gastrointestinal tract, but the potential long-term consequences have not been well studied. The aims of this study were to analyse the long-term impact of a 7-day clindamycin treatment on the faecal microbiota and to simultaneously monitor the ecological stability of the microbiota in a control group as a baseline for reference. Faecal samples from four clindamycin-exposed and four control subjects were collected at nine different time points over 2 years. Using a polyphasic approach, we observed highly significant disturbances in the bacterial community that persisted throughout the sampling period. In particular, a sharp decline in the clonal diversity of Bacteroides isolates, as assessed by repetitive sequence-based PCR (rep-PCR) and long-term persistence of highly resistant clones were found as a direct response to the antibiotic exposure. The Bacteroides community never returned to its original composition during the study period as assessed using the molecular fingerprinting technique, terminal restriction fragment length polymorphism (T-RFLP). Furthermore, using real-time PCR we found a dramatic and persistent increase in levels of specific resistance genes in DNA extracted from the faeces after clindamycin administration. The temporal variations in the microbiota of the control group were minor compared to the large and persistent shift seen in the exposed group. These results demonstrate that long after the selection pressure from a short antibiotic exposure has been removed, there are still persistent long term impacts on the human intestinal microbiota that remain for up to 2 years post-treatment.

  • 14.
    Jernberg, Cecilia
    et al.
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science. Karolinska Institute.
    Sullivan, A
    Karolinska Institute.
    Edlund, Charlotta
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science. Karolinska Institute.
    Jansson, J K
    Swedish University of Agricultural Sciences.
    Monitoring of antibiotic-induced alterations in the human intestinal microflora and detection of probiotic strains by use of terminal restriction fragment length polymorphism2005In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 71, no 1, p. 501-506Article in journal (Refereed)
    Abstract [en]

    Terminal restriction fragment length polymorphism (T-RFLP) was investigated as a tool for monitoring the human intestinal microflora during antibiotic treatment and during ingestion of a probiotic product. Fecal samples from eight healthy volunteers were taken before, during, and after administration of clindamycin. During treatment, four subjects were given a probiotic, and four subjects were given a placebo. Changes in the microbial intestinal community composition and relative abundance of specific microbial populations in each subject were monitored by using viable counts and T-RFLP fingerprints. T-RFLP was also used to monitor specific bacterial populations that were either positively or negatively affected by clindamycin. Some dominant bacterial groups, such as Eubacterium spp., were easily monitored by T-RFLP, while they were hard to recover by cultivation. Furthermore, the two probiotic Lactobacillus strains were easily tracked by T-RFLP and were shown to be the dominant Lactobacillus community members in the intestinal microflora of subjects who received the probiotic.

  • 15.
    Lund, Bodil
    et al.
    Södertörn University, Avdelning Naturvetenskap. Huddinge University Hospital, Karolinska Institutet.
    Adamsson, I
    Huddinge University Hospital, Karolinska Institutet.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Huddinge University Hospital, Karolinska Institutet.
    Gastrointestinal transit survival of an Enterococcus faecium probiotic strain administered with or without vancomycin2002In: International Journal of Food Microbiology, ISSN 0168-1605, E-ISSN 1879-3460, Vol. 77, no 1-2, p. 109-115Article in journal (Refereed)
    Abstract [en]

    The primary aim of this study was to evaluate if an ingested probiotic, containing viable Enterococcus faecium could survive gastrointestinal transit and if so, correlate the amount of the recovered probiotic strain with the host's own enterococci. The second aim was to investigate if simultaneous vancomycin intake influenced the survival and persistence of the probiotic strain and the stability of endogenous enterococci strains. Twenty healthy volunteers were given the probiotic product once daily for 10 days. Half of the subjects were simultaneously given vancomycin. Isolates of E. faecium strains were genotypically or phenotypically analysed with pulsed-field gel electrophoresis (PFGE) and the PhenePlate(TM) system, respectively. In eight of the ten volunteers given only the probiotic, the ingested E. faecium could be detected on day 10, while in none on day 31. From subjects given both probiotic and vancomycin no ingested E. faecium could be detected on day 10 or day 31. The estimated amount of ingested E. faecium recovered from faeces on day 10 ranged from 1.2 x 10(3) to 4.2 x 10(6) colony forming units per gram faeces, which in several cases were a substantial part of the total amount of E. faecium. The E. faecium isolated before probiotic plus vancomycin administration showed no close relationship to the ones isolated 3 weeks after ceased intake in any subjects. In conclusion, the ingested E. faecium strain can survive gastrointestinal transit. After intake, the E. faecium probiotic strain might become a large part of the total E, faecium population. The occurrence of the probiotic strain in the human gut seems to be transient after intake stop. Re-colonization of E. faecium after simultaneous probiotic plus vancomycin intake occurs mainly with strains without close genetic relationship to the strains harboured before treatment or to the ingested E. faecium strain.

  • 16.
    Lund, Bodil
    et al.
    Södertörn University, Avdelning Naturvetenskap. Huddinge University Hospital, Karolinska Institutet.
    Agvald-Öhman, C
    Huddinge University Hospital, Karolinska Institutet.
    Hultberg, Anna
    Södertörn University, Avdelning Naturvetenskap. Huddinge University Hospital, Karolinska Institutet.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Huddinge University Hospital, Karolinska Institutet.
    Frequent transmission of enterococcal strains between mechanically ventilated patients treated at an intensive care unit2002In: Journal of Clinical Microbiology, ISSN 0095-1137, E-ISSN 1098-660X, Vol. 40, no 6, p. 2084-2088Article in journal (Refereed)
    Abstract [en]

    The objectives of this investigation were to study the respiratory tract colonization and transmission of enterococci between 20 patients treated with mechanical ventilation at an intensive care unit (ICU), to compare genotyping with phenotyping, and to determine the antibiotic susceptibilities of the isolated enterococci. Samples were collected from the oropharynx, stomach, subglottic space, and trachea within 24 It of intubation, every third day until day 18, and thereafter every fifth day until day 33. Enterococcal isolates (n = 170) were analyzed by pulsed-field gel electrophoresis and with the PhenePlate (PhP) system. The antimicrobial susceptibilities to five agents were determined. Seventeen of the 20 subjects were colonized with enterococci in the respiratory tract; 12 were colonized in the lower respiratory tract. Genotype analyses suggested that 13 patients were involved in a transmission event, including all patients intubated more than 12 days. In conclusion, colonization of resistant enterococci in the respiratory tract of intubated patients treated at an ICU was common. Transmission of enterococci between patients occurred frequently. Prolonged intubation period seems to be a risk factor for enterococcal cross-transmission.

  • 17.
    Lund, Bodil
    et al.
    Södertörn University, School of Life Sciences. Karolinska Univesity Hospital, Huddinge.
    Billström, H
    Karolinska Univesity Hospital, Huddinge.
    Edlund, Charlotta
    Södertörn University, School of Life Sciences. Karolinska Univesity Hospital, Huddinge.
    Increased conjugation frequencies in clinical Enterococcus faecium strains harbouring the enterococcal surface protein gene esp2006In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 12, no 6, p. 588-591Article in journal (Refereed)
    Abstract [en]

    This study compared the in-vitro ability of Enterococcus faecium isolates of different origin to acquire vanA by conjugation in relation to the occurrence of the esp gene. In total, 29 clinical isolates (15/29 esp+), 30 normal intestinal microflora isolates (2/30 esp+) and one probiotic strain (esp-) were studied with a filter-mating assay. Conjugation events were confirmed by PCR and pulsed-field gel electrophoresis. Among the infection-derived isolates, the esp+ isolates had higher conjugation frequencies compared with esp- isolates (p < 0.001), with a median value of 6.4 x 10(-6) transconjugants/donor. The probiotic strain was shown to acquire vanA vancomycin resistance in in-vitro filter mating experiments.

  • 18.
    Lund, Bodil
    et al.
    Södertörn University, Avdelning Naturvetenskap. Huddinge University Hospital, Karolinska Institutet.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Huddinge University Hospital, Karolinska Institutet.
    Bloodstream isolates of Enterococcus faecium enriched with the enterococcal surface protein gene, esp, show increased adhesion to eukaryotic cells2003In: Journal of Clinical Microbiology, ISSN 0095-1137, E-ISSN 1098-660X, Vol. 41, no 11, p. 5183-5185Article in journal (Refereed)
    Abstract [en]

    Infection-derived Enterococcus faecium strains enriched with esp had increased ability to adhere to Caco-2 cells (P < 0.05) and were less genetically diverse than esp-negative isolates. esp-negative E. faecium fecal isolates from healthy individuals adhered significantly better than esp-negative infection isolates (P < 0.05), indicating additional factors of importance to adhesion.

  • 19.
    Lund, Bodil
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet, Huddinge University Hospital.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet, Huddinge University Hospital.
    Probiotic Enterococcus faecium strain is a possible recipient of the vanA gene cluster2001In: Clinical Infectious Diseases, ISSN 1058-4838, E-ISSN 1537-6591, Vol. 32, no 9, p. 1384-1385Article in journal (Refereed)
    Abstract [en]

    The characteristics of Enterococcus faecium have led to concern regarding the safety of probiotics that contain this bacterium. The results of an in vitro filter mating assay indicate that a probiotic E. faecium strain might be a potential recipient of vancomycin resistance genes.

  • 20.
    Lund, Bodil
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet, Huddinge University Hospital.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet, Huddinge University Hospital.
    Barkholt, L
    Karolinska Institutet, Huddinge University Hospital.
    Nord, C E
    Karolinska Institutet, Huddinge University Hospital.
    Tvede, M
    Rigshospitalet, Copenhagen, Denmark.
    Poulsen, R L
    Statens Seruminstitut, Copenhagen, Denmark.
    Impact on human intestinal microflora of an Enterococcus faecium probiotic and vancomycin2000In: Scandinavian Journal of Infectious Diseases, ISSN 0036-5548, E-ISSN 1651-1980, Vol. 32, no 6, p. 627-632Article in journal (Refereed)
    Abstract [en]

    The aims of this study were to evaluate the impact of a fermented milk product containing viable Enterococcus faecium on human intestinal microflora and to evaluate any risk of development of vancomycin-resistant enterococci (VRE). Twenty Danish and 20 Swedish healthy volunteers were given 150 mi of the fermented mill;. product once daily, equivalent to a daily dose of 4.5 x 10(9) to 7.5 x 10(9) CFU E. faecium, for 10 d. Half of the volunteers also received 125 mg vancomycin orally q.i.d. for 10 d. Faecal samples were collected on day 0 before intake, on day 10 directly after end of intake and on day 31, 3 weeks after the end of the experiment. There,Fas a significant increase in the total number of enterococci on day 10 (p < 0.01) in the group receiving only the E. faecium supplement, but 3 weeks later the level was as before intake. In the vancomycin group, the total number of enterococci was reduced on day 10 (p < 0.01) but had increased on day 31 (p < 0.01) in relation to day 0. In none of the Swedish and 4 of the Danish volunteers, VRE were sporadically detected, but without relation to intake of the probiotic or vancomycin. In healthy young Danish individuals the VRE carrier rate tended to be higher than previously found.

  • 21.
    Lund, Bodil
    et al.
    Södertörn University, Avdelning Naturvetenskap.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap.
    Rynnel-Dagoo, B
    Lundgren, Y
    Sterner, J
    Nord, C E
    Ecological effects on the oro- and nasopharyngeal microflora in children after treatment of acute otitis media with cefuroxime axetil or amoxycillin-clavulanate as suspensions2001In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 7, no 5, p. 230-237Article in journal (Refereed)
    Abstract [en]

    Objective To evaluate if the extent of normal microflora disturbances differed between treatment with amoxycillin-clavulanate administered in an active form and cefuroxime axetil administered as an inactive prodrug. Methods Twenty-eight children, 0.5-5 years old, diagnosed with acute otitis media (AOM), were treated with either amoxycillin-clavulanate (13.3 mg/kg 3 times daily) or cefuroxime axetil (15 mg/kg twice daily) for 7 days. Saliva samples and nasopharyngeal swabs were collected before, directly after and 2 weeks after treatment. The saliva samples were quantitatively and qualitatively analyzed and the nasopharyngeal swabs were qualitatively analyzed. All isolated strains were tested for beta -lactamase production. Results Both treatment regimens gave rise to similar alterations of the normal oropharyngeal microflora. In both groups, the amount of Streptococcus salivarius was significantly reduced (P < 0.05). The most common causative pathogens of acute otitis were S. pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. On the day of enrollment, approximately half of the patients, in both groups, were infected with more than one pathogen. The rate of infection or colonization with more than one potential pathogen was low on day 7 but recurred 2 weeks after treatment to similar levels as on day 0. The total number of patients with reinfection, recolonization or recurrence of pathogens on day 21 was 11/12 in the amoxycillin-clavulanate group and 4/7 in the cefuroxime axetil group. The most common <beta>-lactamase producer was M. catarrhalis. Conclusion The local high concentration of antibiotics in the oropharynx immediately after intake of antibiotic suspensions seem to have little or no impact on the extent of disturbance of the microflora in this region. Children of this age group seem prone to either reinfection, recolonization or persistence of pathogens within 2 weeks after treatment. Furthermore, co-infection with more than one pathogen seems common in children with AOM and infection with beta -lactamase producing microorganisms occurs frequently.

  • 22.
    Löfmark, Sonja
    et al.
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science. Karolinska Institutet.
    Fang, Hong
    Karolinska Institutet.
    Hedberg, Maria
    Karolinska Institutet.
    Edlund, Charlotta
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science. Karolinska Institutet.
    Inducible metronidazole resistance and nim genes in clinical Bacteroides fragilis group isolates2005In: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 49, no 3, p. 1253-1256Article in journal (Refereed)
    Abstract [en]

    Nitroimidazole resistance (nim) genes were detected in 2% of 1,502 clinical Bacteroides fragilis group strains isolated from 19 European countries, and a novel nim gene was identified. High metronidazole resistance could be induced in nim-positive strains, which emphasizes the importance of acknowledging metronidazole resistance in the clinical setting.

  • 23.
    Löfmark, Sonja
    et al.
    Karolinska Institute.
    Jernberg, Cecilia
    Södertörn University, School of Life Sciences. Karolinska Institute.
    Jansson, Janet K.
    Swedish University of Agricultural Sciences.
    Edlund, Charlotta
    Karolinska Institute / Medical Products Agency.
    Clindamycin-induced enrichment and long-term persistence of resistant Bacteroides spp. and resistance genes2006In: Journal of Antimicrobial Chemotherapy, ISSN 0305-7453, E-ISSN 1460-2091, Vol. 58, no 6, p. 1160-1167Article in journal (Refereed)
    Abstract [en]

    Objectives: The aim was to study the long-term consequences of 1 week clindamycin administration regarding selection and persistence of resistance, resistance determinants and diversity of the Bacteroides spp. in the intestinal microflora. Methods: A total of 1306 Bacteroides isolates were collected from constitutively cultured faecal samples during a 2 year period from eight healthy volunteers. The strains were identified by biochemical and genotyping methods. MIC values were determined by the agar dilution method and presence of resistance genes was screened by real-time PCR. Results: Ecological changes in the intestinal microflora persisting up to 24 months were recorded after a 7 day clindamycin administration to four healthy volunteers. Compared to a control group, not exposed to clindamycin, an enrichment and stabilization of resistant Bacteroides strains and resistance determinants were discovered up to 2 years after clindamycin exposure. Conclusions: The results indicate that even a short-term antibiotic administration can cause long-term alterations in the commensal microbiota of individual subjects, detectable 2 years after dosing. The recorded selection and persistence of resistant strains and resistance genes, illustrates the importance of increasing our knowledge of the role of the abundant intestinal microbial community as a reservoir for spread of resistance.

  • 24. Oh, H
    et al.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap.
    Mechanism of quinolone resistance in anaerobic bacteria2003In: Clinical Microbiology and Infection, ISSN 1198-743X, E-ISSN 1469-0691, Vol. 9, no 6, p. 512-517Article in journal (Refereed)
    Abstract [en]

    Several recently developed quinolones have excellent activity against a broad range of aerobic and anaerobic bacteria and are thus potential drugs for the treatment of serious anaerobic and mixed infections. Resistance to quinolones is increasing worldwide, but is still relatively infrequent among anaerobes. Two main mechanisms, alteration of target enzymes (gyrase and topoisomerase IV) caused by chromosomal mutations in encoding genes, or reduced intracellular accumulation due to increased efflux of the drug, are associated with quinolone resistance. These mechanisms have also been found in anaerobic species. High-level resistance to the newer broad-spectrum quinolones often requires stepwise mutations in target genes. The increasing emergence of resistance among anaerobes may be a consequence of previous widespread use of quinolones, which may have enriched first-step mutants in the intestinal tract. Quinolone resistance in the Bacteroides fragilis group strains is strongly correlated with amino acid substitutions at positions 82 and 86 in GyrA (equivalent to positions 83 and 87 of Escherichia coli ). Several studies have indicated that B. fragilis group strains possess efflux pump systems that actively expel quinolones, leading to resistance. DNA gyrase seems also to be the primary target for quinolones in Clostridium difficile , since amino acid substitutions in GyrA and GyrB have been detected in resistant strains. To what extent other mechanisms, such as mutational events in other target genes or alterations in outer-membrane proteins, contribute to resistance among anaerobes needs to be further investigated.

  • 25. Oh, H
    et al.
    El Amin, N
    Davies, T
    Appelbaum, P C
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap.
    gyrA Mutations associated with quinolone resistance in Bacteroides fragilis group strains2001In: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 45, no 7, p. 1977-1981Article in journal (Refereed)
    Abstract [en]

    Mutations in the gyrA gene contribute considerably to quinolone resistance in Escherichia coli. Mechanisms for quinolone resistance in anaerobic bacteria are less well studied. The Bacteroides fragilis group are the anaerobic organisms most frequently isolated from patients with bacteremia and intraabdominal infections. Forty-four clinafloxacin-resistant and-susceptible fecal and clinical isolates of the B. fragilis group (eight Bacteroides fragilis, three Bacteroides ovatus, five Bacteroides thetaiotaomicron, six Bacteroides uniformis, and 22 Bacteroides vulgatus) and six ATCC strains of the B. fragilis group were analyzed as follows: (i) determination of susceptibility to ciprofloxacin, levofloxacin, moxifloxacin, and clinafloxacin by the agar dilution method and (ii) sequencing of the gyrA quinolone resistance-determining region (QRDR) located between amino acid residues equivalent to Ala-67 through Gln-106 in E. coli. Amino acid substitutions were found at hotspots at positions 82 (n = 15) and 86 (n = 8). Strains with Ser82Leu substitutions (n = 13) were highly resistant to all quinolones tested. Mutations in other positions of gyrA were also frequently found in quinolone-resistant and -susceptible isolates. Eight clinical strains that lacked mutations in their QRDR were susceptible to at least two of the quinolones tested. Although newer quinolones have good antimicrobial activity against the B. fragilis group, quinolone resistance in B. fragilis strains can be readily selected in vivo. Mutational events in the QRDR of gyrA seem to contribute to quinolone resistance in Bacteroides species.

  • 26. Oh, H
    et al.
    Hedberg, M
    Wade, D
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap.
    Activities of synthetic hybrid peptides against anaerobic bacteria: Aspects of methodology and stability2000In: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 44, no 1, p. 68-72Article in journal (Refereed)
    Abstract [en]

    The increasing problem of antibiotic resistance among pathogenic bacteria requires development of new antimicrobial agents. One line of investigation is the synthesis of antimicrobial hybrid peptides, The aim of the present investigation was to determine the in vitro activities of 16 cecropin-melittin hybrid peptides (CAMEL analogues) against 60 anaerobic bacterial strains, to compare their activities with those of seven clinically used antimicrobial agents, and to compare different methods for anaerobic susceptibility testing of these peptides. The stability of one of the peptides, temporin B, with different stereoisomeric configurations was investigated in a fecal milieu. The CAMEL analogues showed antimicrobial activity against the anaerobic bacteria, with MICs ranging from 0.125 to 32 mu g/ml. The overall activities (the MICs at which 90% of isolates are inhibited) of the CAR IEL analogues against anaerobic bacteria were mainly inferior to those of imipenem, clindamycin, and piperacillin but were equal to or superior to those of metronidazole, cefoxitin, ciprofloxacin, and chloramphenicol. The agarose dilution method was found to be an accurate method for the testing of large numbers of bacterial strains. The D isomer of temporin B was inactivated more slowly in feces than the L isomer. This study shows that the CAMEL analogues are potential agents for the treatment of anaerobic infections.

  • 27. Oh, H
    et al.
    Nord, C E
    Barkholt, L
    Hedberg, M
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap.
    Ecological disturbances in intestinal microflora caused by clinafloxacin, an extended-spectrum quinolone2000In: Infection. Zeitschrift für Klinik und Therapie der Infektionen, ISSN 0300-8126, E-ISSN 1439-0973, Vol. 28, no 5, p. 272-277Article in journal (Refereed)
    Abstract [en]

    Background: The quinolones developed over the past few years have enhanced in vitro activity and a broader spectrum of antimicrobial activity compared to ma ny other antimicrobial agents including the older quinolones. The present study focuses on the effect of clinafloxacin, a member of the new broad-spectrum quinolone class of antibiotics, on the normal intestinal microflora. Subjects and Methods: A total of it healthy volunteers received clinafloxacin orally, zoo mg twice daily for 7 days. Fecal specimens were collected at defined intervals before, during and after the administration in order to study the effect of clinafloxacin on the intestinal microflora and to correlate this effect with fecal clinafloxacin concentrations. Intestinal microorganisms isolated before, during and 2 weeks after clinafloxacin administration were tested for their suseptibility to clinafloxacin. Results: Oral administration of clinafloxacin resulted in high drug levels in feces (mean value 176.2 mg/kg on day 7) and pronounced ecological disturbances. The aerobic microflora was eradicated in 11 of the 12 subjects and the anaerobic microflora was strongly suppressed during administration. There was a significant emergence of clinafloxacin-resistant Bacteroides spp, strains (MIC greater than or equal to 4 mg/ml) during administration. The elevated MIC values still remained 2 weeks after discontinuation of the antibiotic (p < 0.001). Conclusion: The emergence of clinafloxacin-resistant Bacteroides spp. demonstrates the necessity of restricting prescription for particular indications in order to preserve the efficacy of the highly active broad-spectrum quinolones.

  • 28.
    Oh, Herin
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Hedberg, M
    Karolinska Institutet.
    Edlund, Charlotta
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Efflux-mediated fluoroquinolone resistance in the Bacteroides fragilis group2002In: Anaerobe, ISSN 1075-9964, E-ISSN 1095-8274, Vol. 8, no 5, p. 277-282Article in journal (Refereed)
    Abstract [en]

    In order to investigate the role of efflux pumps in fluoroquinolone resistance, 35 Bacteroides fragilis group isolates with various resistance patterns against ciprofloxacin, levofloxacin, moxifloxacin and clinafloxacin were studied. The gyrA genotypes were known in all isolates studied. The accumulation of ciprofloxacin with and without carbonyl cyanide m-chlorophenylhydrazone (CCCP) was investigated using a silicon oil based fluorometric assay. Seventeen of 25 multiquinolone-resistant strains had significantly increased ciprofloxacin accumulation in the presence of CCCP compared to the corresponding susceptible type strains. Ten of the resistant isolates with increased efflux had no target mutations at positions 82 or 86 of their GyrA subunits. Strains with highly enhanced efflux were consequently shown to have a significant decrease of quinolone MIC values in the presence of efflux pump inhibitor. The results of the present study propose that high levels of resistance to older as well as newer fluoroquinolones, could be explained by increased activity of efflux pumps in B. fragilis group strains.

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