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Developing a real time sensing system to monitor bacteria in wound dressings.

Farrow MJ, Hunter IS, Connolly P - Biosensors (Basel) (2012)

Bottom Line: It is based on impedance sensors that could be placed at the wound-dressing interface and potentially monitor bacterial growth in real time.Impedance was measured using disposable silver-silver chloride electrodes.The main findings were that the impedance profiles obtained by silver-silver chloride sensors in bacterial suspensions could detect the presence of high cell densities.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of Strathclyde, Wolfson Centre, Glasgow, G4 0NW, UK. malcolm.farrow@strath.ac.uk.

ABSTRACT
Infection control is a key aspect of wound management strategies. Infection results in chemical imbalances and inflammation in the wound and may lead to prolonged healing times and degradation of the wound surface. Frequent changing of wound dressings may result in damage to healing tissues and an increased risk of infection. This paper presents the first results from a monitoring system that is being developed to detect presence and growth of bacteria in real time. It is based on impedance sensors that could be placed at the wound-dressing interface and potentially monitor bacterial growth in real time. As wounds can produce large volumes of exudate, the initial system reported here was developed to test for the presence of bacteria in suspension. Impedance was measured using disposable silver-silver chloride electrodes. The bacteria Staphylococcus aureus were chosen for the study as a species commonly isolated from wounds. The growth of bacteria was confirmed by plate counting methods and the impedance data were analysed for discernible differences in the impedance profiles to distinguish the absence and/or presence of bacteria. The main findings were that the impedance profiles obtained by silver-silver chloride sensors in bacterial suspensions could detect the presence of high cell densities. However, the presence of the silver-silver chloride electrodes tended to inhibit the growth of bacteria. These results indicate that there is potential to create a real time infection monitor for wounds based upon impedance sensing.

No MeSH data available.


Related in: MedlinePlus

(a) The final cell numbers of RN4220, SA081 and SA082 with Ag-AgCl sensors after 24 h with and without the application of impedance measurements. Four replicate cultures are shown for each of the three strains of Staphylococcus aureus. () Start value; () Final cell density without impedance measurements; () Control growth with no sensors; () Final cell density with impedance measurements. (b) Typical magnitudes of the normalised phase angle peak over time from the influence of impedance measurement experiments. The peak occurs at approximately 8 h and increases over time unless the bacteria reach cell densities in excess of 1×107 CFU∙mL−1 where upon it starts to decrease.
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biosensors-02-00171-f008: (a) The final cell numbers of RN4220, SA081 and SA082 with Ag-AgCl sensors after 24 h with and without the application of impedance measurements. Four replicate cultures are shown for each of the three strains of Staphylococcus aureus. () Start value; () Final cell density without impedance measurements; () Control growth with no sensors; () Final cell density with impedance measurements. (b) Typical magnitudes of the normalised phase angle peak over time from the influence of impedance measurement experiments. The peak occurs at approximately 8 h and increases over time unless the bacteria reach cell densities in excess of 1×107 CFU∙mL−1 where upon it starts to decrease.

Mentions: The final experiment investigated the influence of applying voltage to the electrodes, with impedance measurements and Ag-AgCl sensors, on the bacterial growth of the three Staphylococcus aureus strains. The controls of all three strains, which contained no sensors, always reached approximately 1 × 109 CFU∙mL−1 within 24 h. The strain RN4220 reached control levels without impedance measurements. However the 4 separate vials with impedance measurements had final cell densities between 2 × 103 and 6 × 103 CFU∙mL−1 (Figure 8(a)). In the vials without impedance measurements, the strain SA081 reached 1 × 108 CFU∙mL−1 in three vials and only 1 × 106 CFU∙mL−1 in the fourth. With impedance measurements the SA081 strain reached cell densities between 1 × 103 and 1 × 106 CFU∙mL−1. The strain SA082 without impedance measurements reached control densities in two vials and only 1 × 104 CFU∙mL−1 in the other two. Similarly, the strain SA082 had two vials reaching 1 × 108 CFU∙mL−1 and two vials reaching 3 × 104 CFU∙mL−1 with impedance measurements. These results suggest that performing impedance measurements every hour may have an influence on the bacterial growth. These final cell densities clearly show that the presence of the Ag-AgCl electrodes inhibits normal growth rates and that the application of electrical voltage during the impedance measurements increases this reduction.


Developing a real time sensing system to monitor bacteria in wound dressings.

Farrow MJ, Hunter IS, Connolly P - Biosensors (Basel) (2012)

(a) The final cell numbers of RN4220, SA081 and SA082 with Ag-AgCl sensors after 24 h with and without the application of impedance measurements. Four replicate cultures are shown for each of the three strains of Staphylococcus aureus. () Start value; () Final cell density without impedance measurements; () Control growth with no sensors; () Final cell density with impedance measurements. (b) Typical magnitudes of the normalised phase angle peak over time from the influence of impedance measurement experiments. The peak occurs at approximately 8 h and increases over time unless the bacteria reach cell densities in excess of 1×107 CFU∙mL−1 where upon it starts to decrease.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263571&req=5

biosensors-02-00171-f008: (a) The final cell numbers of RN4220, SA081 and SA082 with Ag-AgCl sensors after 24 h with and without the application of impedance measurements. Four replicate cultures are shown for each of the three strains of Staphylococcus aureus. () Start value; () Final cell density without impedance measurements; () Control growth with no sensors; () Final cell density with impedance measurements. (b) Typical magnitudes of the normalised phase angle peak over time from the influence of impedance measurement experiments. The peak occurs at approximately 8 h and increases over time unless the bacteria reach cell densities in excess of 1×107 CFU∙mL−1 where upon it starts to decrease.
Mentions: The final experiment investigated the influence of applying voltage to the electrodes, with impedance measurements and Ag-AgCl sensors, on the bacterial growth of the three Staphylococcus aureus strains. The controls of all three strains, which contained no sensors, always reached approximately 1 × 109 CFU∙mL−1 within 24 h. The strain RN4220 reached control levels without impedance measurements. However the 4 separate vials with impedance measurements had final cell densities between 2 × 103 and 6 × 103 CFU∙mL−1 (Figure 8(a)). In the vials without impedance measurements, the strain SA081 reached 1 × 108 CFU∙mL−1 in three vials and only 1 × 106 CFU∙mL−1 in the fourth. With impedance measurements the SA081 strain reached cell densities between 1 × 103 and 1 × 106 CFU∙mL−1. The strain SA082 without impedance measurements reached control densities in two vials and only 1 × 104 CFU∙mL−1 in the other two. Similarly, the strain SA082 had two vials reaching 1 × 108 CFU∙mL−1 and two vials reaching 3 × 104 CFU∙mL−1 with impedance measurements. These results suggest that performing impedance measurements every hour may have an influence on the bacterial growth. These final cell densities clearly show that the presence of the Ag-AgCl electrodes inhibits normal growth rates and that the application of electrical voltage during the impedance measurements increases this reduction.

Bottom Line: It is based on impedance sensors that could be placed at the wound-dressing interface and potentially monitor bacterial growth in real time.Impedance was measured using disposable silver-silver chloride electrodes.The main findings were that the impedance profiles obtained by silver-silver chloride sensors in bacterial suspensions could detect the presence of high cell densities.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of Strathclyde, Wolfson Centre, Glasgow, G4 0NW, UK. malcolm.farrow@strath.ac.uk.

ABSTRACT
Infection control is a key aspect of wound management strategies. Infection results in chemical imbalances and inflammation in the wound and may lead to prolonged healing times and degradation of the wound surface. Frequent changing of wound dressings may result in damage to healing tissues and an increased risk of infection. This paper presents the first results from a monitoring system that is being developed to detect presence and growth of bacteria in real time. It is based on impedance sensors that could be placed at the wound-dressing interface and potentially monitor bacterial growth in real time. As wounds can produce large volumes of exudate, the initial system reported here was developed to test for the presence of bacteria in suspension. Impedance was measured using disposable silver-silver chloride electrodes. The bacteria Staphylococcus aureus were chosen for the study as a species commonly isolated from wounds. The growth of bacteria was confirmed by plate counting methods and the impedance data were analysed for discernible differences in the impedance profiles to distinguish the absence and/or presence of bacteria. The main findings were that the impedance profiles obtained by silver-silver chloride sensors in bacterial suspensions could detect the presence of high cell densities. However, the presence of the silver-silver chloride electrodes tended to inhibit the growth of bacteria. These results indicate that there is potential to create a real time infection monitor for wounds based upon impedance sensing.

No MeSH data available.


Related in: MedlinePlus