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Survival of infectious agents and detection of their resistance and virulence factors
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. (Klinisk bakteriologi, Clinical Bacteriology)
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the first study, three different transport systems for bacteria were evaluated. The CLSI M40-A guideline was used to monitor the maintenance of both mono- and polymicrobial samples during a simulated transportation at room temperature that lasted 0-48 h. All systems were able to maintain the viability of all organisms for 24 h, but none of them could support all tested species after 48 h.  The most difficult species to recover was Neisseria gonorrhoeae, and in polymicrobial samples overgrowth was an observed problem. The aim of the second study was to study the presence of TSST-1 and three other important toxin genes in invasive isolates of Staphylococcus aureus collected during the years 2000-2012 at two tertiary hospitals. The genes encoding the staphylococcal toxins were detected by PCR, and whole-genome sequencing was used for analyzing the genetic relatedness between isolates. The results showed that the most common toxin was TSST-1, and isolates positive for this toxin exhibited a clear clonality independent of year and hospital. The typical patient was a male aged 55-74 years and with a bone or a joint infection. The third study was a clinical study of the effect of silver-based wound dressings on the bacterial flora in chronic leg ulcers. Phenotypic and genetic silver-resistance were investigated before and after topical silver treatment, by determining the silver nitrate MICs and by detecting sil genes with PCR. The silver-based dressings had a limited effect on primary wound pathogens, and the activity of silver nitrate on S. aureus was mainly bacteriostatic. A silver-resistant Enterobacter cloacae strain was identified after only three weeks of treatment, and cephalosporin-resistant members of the Enterobacteriaceae family were relatively prone to developed silver-resistance after silver exposure in vitro. The last study was undertaken in order to develop an easy-to-use method for simulating the laundering process of hospital textiles, and apply the method when evaluating the decontaminating efficacy of two different washing temperatures. The laundering process took place at professional laundries, and Enterococcus faecium was used as a bioindicator. The results showed that a lowering of the washing temperature from 70°C to 60°C did not affect the decontamination efficacy; the washing cycle alone reduced the number of bacteria with 3-5 log10 CFU, whereas the following tumble drying reduced the bacterial numbers with another 3-4 log10 CFU, yielding the same final result independent of the washing temperature. To ensure that sufficient textile hygiene is maintained, the whole laundering process needs to be monitored. The general conclusion is that all developmental work in the bacterial field requires time and a large strain collection.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 48 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1098
Keyword [en]
Transportation system; swab; polymicrobial samples; Neisseria gonorrhoeae; bacteremia; exotoxins; Staphylococcus aureus; TSST-1; silver; silver resistance; wound dressing; sil genes; laundry; tumble drying; bacterial decontamination
National Category
Clinical Laboratory Medicine
Identifiers
URN: urn:nbn:se:uu:diva-248786ISBN: 978-91-554-9232-8 (print)OAI: oai:DiVA.org:uu-248786DiVA: diva2:801448
Public defence
2015-05-28, Hörsalen, Klinisk Mikrobiologi, Dag Hammarskjöldsväg 17, Ing D1, Uppsala, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2015-05-05 Created: 2015-04-08 Last updated: 2015-07-07
List of papers
1. Evaluation of three swab transport systems for the maintenance of clinically important bacteria in simulated mono- and polymicrobial samples
Open this publication in new window or tab >>Evaluation of three swab transport systems for the maintenance of clinically important bacteria in simulated mono- and polymicrobial samples
2011 (English)In: Acta Pathologica, Microbiologica et Immunologica Scandinavica (APMIS), ISSN 0903-4641, E-ISSN 1600-0463, Vol. 119, no 3, 198-203 p.Article in journal (Refereed) Published
Abstract [en]

In this study, three swab transport systems were evaluated: M40 Transystem, Amies broth with a relatively new type of swab (both Copan Diagnostics, Corona, CA, USA), and SSI transportmedium (Statens Serum Institut, Copenhagen Denmark). The CLSI M40-A standard procedures and 11 culture collection strains were used. The transport systems were tested at room temperature for holding times of 0, 24, and 48 h, and both mono- and polymicrobial samples were included. After 24 h of simulated transportation, all systems were able to maintain the viability of all organisms tested. SSI transportmedium exhibited the lowest maintaining ability, whereas the two Copan systems were the most growth-promoting system. In polymicrobial samples, this latter feature was a problem. At 48 h, no transport system could maintain the viability of all strains, and the recovery rates differed depending on organism and device. The species most difficult to recover in all the three systems was Neisseria gonorrhoeae. When selecting a swab transport system, consideration must be given to the sample type, the conditions that prevail locally, and the performance in the clinical setting.

Keyword
Transportation, swab, fastidious bacteria, polymicrobial samples, Neisseria gonorrhoeae
National Category
Clinical Medicine
Identifiers
urn:nbn:se:uu:diva-149062 (URN)10.1111/j.1600-0463.2010.02710.x (DOI)000286838400005 ()21284737 (PubMedID)
Available from: 2011-03-15 Created: 2011-03-15 Last updated: 2017-12-11Bibliographically approved
2. Overrepresentation of the toxic shock syndrome toxin-1 gene among eldery men with bacteremic bone and joint infections caused by Staphylococcus aureus
Open this publication in new window or tab >>Overrepresentation of the toxic shock syndrome toxin-1 gene among eldery men with bacteremic bone and joint infections caused by Staphylococcus aureus
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Staphylococcus aureus is a leading causative agent of Gram-positive septicemia. In recent years, there have been indications that both the severity and the number of staphylococcal infections have increased. In order to study the presence of genes encoding exfoliative toxins (eta/etb), Panton-Valentine leucocidin (lucS-PV-lucF-PV), and toxic shock syndrome toxin-1 (tst) in invasive isolates over time and space, 528 blood isolates of S. aureus collected during the years 2000-2012 from two Swedish university hospitals were investigated.  Age, gender and diagnosis of patients were registered, and the antibiotic susceptibility was tested. Toxin genes were detected with PCR, and the genetic relatedness was assessed with pulsed-field gel electrophoresis and whole genome sequencing. Blood cultures positive for S. aureus increased with 57.6% during the study period. Ninety-six of the isolates (18.2%) carried 97 toxin genes (one isolate carried both eta and etb). All isolates except one (PVL-producing and methicillin-resistant) were fully susceptible to the tested antibiotics. Most frequent was tst (79.4%), followed by eta (12.4%), lucS-PV-lucF-PV (7.2%), and etb (1.0%). The typical tst-positive patient was a male aged 55-74 years with a bone or joint infection. Tst-positive isolates exhibited a clear clonality, and that was independent of year and hospital. Most common was ST30-t012. To summarize, bacteremia caused by S. aureus increased during the study period, but the frequency of four important staphylococcal toxins and the antibiotic susceptibility remained low. To screen for these toxins is only cost-effective in Swedish patients with a typical clinical presentation.

National Category
Infectious Medicine
Research subject
Microbiology
Identifiers
urn:nbn:se:uu:diva-248754 (URN)
Available from: 2015-04-08 Created: 2015-04-08 Last updated: 2015-07-07Bibliographically approved
3. Effects of Silver-based Wound Dressings on the Bacterial Flora in Chronic Leg Ulcers and Its Susceptibility In vitro to Silver
Open this publication in new window or tab >>Effects of Silver-based Wound Dressings on the Bacterial Flora in Chronic Leg Ulcers and Its Susceptibility In vitro to Silver
Show others...
2012 (English)In: Acta Dermato-Venereologica, ISSN 0001-5555, E-ISSN 1651-2057, Vol. 92, no 1, 34-39 p.Article in journal (Refereed) Published
Abstract [en]

Silver-based dressings have been used extensively in wound management in recent years, but data on their antimicrobial activity in the clinical setting are limited. In order to explore their effects on chronic leg ulcer flora, 14 ulcers were cultured after at least 3 weeks treatment with Aquacel Ag (R) or Acticoat (R). Phenotypic and genetic silver resistance were investigated in a total of 56 isolates. Silver-based dressings had a limited effect on primary wound pathogens, which were present in 79% of the cultures before, and 71% after, treatment. One silver-resistant Enterobacter cloacae strain was identified (silver nitrate minimal inhibitory concentration (MIC)>512 mg/l, positive for silE, silS and silP). Further studies in vitro showed that inducible silver-resistance was more frequent in Enterobacteriaceae with cephalosporin-resistance and that silver nitrate had mainly a bacteriostatic effect on Staphylococcus aureus. Monitoring of silver resistance should be considered in areas where silver is used extensively.

Keyword
silver, silver-resistance, wound dressing, ESBL, derepressed mutant
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-171444 (URN)10.2340/00015555-1170 (DOI)000300388400007 ()
Available from: 2012-03-19 Created: 2012-03-19 Last updated: 2017-12-07Bibliographically approved
4. Level of decontamination after washing textiles at 60°C or 70°C followed by tumble drying
Open this publication in new window or tab >>Level of decontamination after washing textiles at 60°C or 70°C followed by tumble drying
2014 (English)In: Infection Ecology & Epidemiology, ISSN 2000-8686, E-ISSN 2000-8686, Vol. 4, 24314Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Several major outbreaks in healthcare facilities have occurred with the emergence of multi-resistant bacteria. A possible route for dissemination is the hospital textiles and inadequate laundering of them. The aim of this study was to develop an easy-to-use method for simulating the laundering process of hospital textiles, and thereafter apply the method when evaluating the decontaminating efficacy of two different washing temperatures.

METHODS: The laundering process, including tumble drying, took place at two professional laundries. Enterococcus faecium was used as bioindicator.

RESULTS: The results showed that a lowering of the washing temperature from 70°C to 60°C did not affect the decontamination efficacy; the washing cycle alone reduced the number of bacteria with 3-5 log10 CFU, whereas the following tumble drying reduced the bacterial numbers with another 3-4 log10 CFU, yielding the same final result independent of washing temperature. Without tumble drying, there was an obvious risk of adding non-fermenting gram-negative bacteria to the fabric. These bacteria originated from the washing cycle.

CONCLUSION: A simple method to simulate hospital laundering was developed. To save energy, it is possible to use a washing temperature of 60°C, but the washing cycle should be followed by tumble drying, and the whole laundering process needs to be monitored to maintain sufficient textile hygiene.

National Category
Other Medical Sciences
Identifiers
urn:nbn:se:uu:diva-246138 (URN)10.3402/iee.v4.24314 (DOI)25413829 (PubMedID)
Available from: 2015-03-02 Created: 2015-03-02 Last updated: 2017-12-04Bibliographically approved

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