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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

Examples of the normalised phase angle profiles from the single suspension experiments: (a) Control, MHB-only; (b) RN4220 culture 1; (c) RN4220 culture 2. Dotted line indicates the normalized phase angle peak.
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biosensors-02-00171-f002: Examples of the normalised phase angle profiles from the single suspension experiments: (a) Control, MHB-only; (b) RN4220 culture 1; (c) RN4220 culture 2. Dotted line indicates the normalized phase angle peak.

Mentions: The normalised profiles showed some clear trends and differences between the control vial and the vial with bacterial suspension. The most significant difference in the normalised magnitude was that in the MHB-only vials the value of the reading between 0.1 and 1 Hz decreased to a value of 0.5 while the RN4220 culture vials decreased to values of 0.4 and 0.3. However the discernible differences were more pronounced in the normalised phase angle. In the control (MHB-only), a peak in the normalised phase angle occurred between 50 and 100 Hz at the start and decreased over time to between 0.79 and 2.00 Hz at 17 h (Figure 2(a)). The normalised phase angle peak of the control (MHB-only) descended below 10 Hz between 4 and 10 h across all five separate samples. In contrast, in the RN4220 cultures, the normalised phase peak after 10 h remained between 32 and 20 Hz and hence never descended below 10 Hz (Figure 2(b)). This was repeatable over 5 separate culture experiments. Therefore it appears that the two cultures do have separate signature traces in the phase angle over frequency and is the first indication that peaks in signature traces of phase angles in normalised impedance plots could distinguish between the absence and/or growth of bacteria. In three of the five RN4220 cultures, a secondary peak appeared at a frequency less than 10 Hz and reached a higher magnitude by 17 h than the primary peak (Figure 2(c)). However the primary peak was still visible and allows the RN4220 cultures to be distinguished from the MHB-only samples by comparison of the normalised phase angle plots.


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

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

Examples of the normalised phase angle profiles from the single suspension experiments: (a) Control, MHB-only; (b) RN4220 culture 1; (c) RN4220 culture 2. Dotted line indicates the normalized phase angle peak.
© Copyright Policy
Related In: Results  -  Collection

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

biosensors-02-00171-f002: Examples of the normalised phase angle profiles from the single suspension experiments: (a) Control, MHB-only; (b) RN4220 culture 1; (c) RN4220 culture 2. Dotted line indicates the normalized phase angle peak.
Mentions: The normalised profiles showed some clear trends and differences between the control vial and the vial with bacterial suspension. The most significant difference in the normalised magnitude was that in the MHB-only vials the value of the reading between 0.1 and 1 Hz decreased to a value of 0.5 while the RN4220 culture vials decreased to values of 0.4 and 0.3. However the discernible differences were more pronounced in the normalised phase angle. In the control (MHB-only), a peak in the normalised phase angle occurred between 50 and 100 Hz at the start and decreased over time to between 0.79 and 2.00 Hz at 17 h (Figure 2(a)). The normalised phase angle peak of the control (MHB-only) descended below 10 Hz between 4 and 10 h across all five separate samples. In contrast, in the RN4220 cultures, the normalised phase peak after 10 h remained between 32 and 20 Hz and hence never descended below 10 Hz (Figure 2(b)). This was repeatable over 5 separate culture experiments. Therefore it appears that the two cultures do have separate signature traces in the phase angle over frequency and is the first indication that peaks in signature traces of phase angles in normalised impedance plots could distinguish between the absence and/or growth of bacteria. In three of the five RN4220 cultures, a secondary peak appeared at a frequency less than 10 Hz and reached a higher magnitude by 17 h than the primary peak (Figure 2(c)). However the primary peak was still visible and allows the RN4220 cultures to be distinguished from the MHB-only samples by comparison of the normalised phase angle plots.

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