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Efficacy of ultraviolet C light at sublethal dose in combination with antistaphylococcal antibiotics to disinfect catheter biofilms of methicillin-susceptible and methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis in vitro

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ABSTRACT

Background: Biofilm formation inside inserted medical devices leads to their failure and acts as a source of refractory infections. The ultraviolet C (UVC) light is a potential therapy that can be used against the biofilm of bacterial pathogens.

Objective: We evaluated the efficacy of sublethal dose of UVC light with anti-staphylococcal antibiotics against biofilms made from 30 isolates of methicillin-susceptible Staphylococcus aureus and methicillin-resistant S. aureus and S. epidermidis on vascular catheters.

Materials and methods: A novel biofilm device was used to assess the combined approach. The biofilms on the catheters were irradiated with the UVC light at 254 nm and irradiance of 6.4 mW followed by treatment with vancomycin or quinupristin/dalfopristin at twice their minimum bactericidal concentrations or with linezolid at 64 µg/mL for 24 hours. The catheters were cut into segments and sonicated, and the number of the sessile cells was determined colorimetrically using XTT viable cells assay. The effect of UVC radiation followed by treatment with an antistaphylococcal antibiotic on the viability of the bacteria in the biofilm was visualized using LIVE/DEAD BacLight bacterial viability stain and confocal laser scanning microscopy.

Results: Exposure of the bacterial biofilms to the UVC light or each of the antibiotics alone was ineffective in killing the bacteria. Treatment of the biofilms with the antibiotics following their exposure to UVC light significantly (P<0.001) reduced the number of viable cells within the biofilms but did not completely eradicate them.

Conclusion: To our knowledge, this combinatorial approach has not been investigated before. The combined approach can be used as a therapeutic modality for managing biofilm-associated infections by preventing the establishment of biofilms and/or disrupting the formed biofilms on the inserted medical devices with the goal of increasing their usefulness and preventing infectious complications. Further investigations are needed to assess the effectiveness of the combined approach in the clinical settings.

No MeSH data available.


Related in: MedlinePlus

CLSM images of S. epidermidis biofilms on plastic coverslips after incubation for 48 hours followed by one of the following treatments: (A) control (untreated), (B) UVC light alone followed by 24 hours of incubation, (C) VAN alone at twice of its MBC and incubation for 24 hours, and (D) UVC light followed by VAN at double of its MBC and incubation for 24 hours.Notes: The bacterial cells were stained with LIVE/DEAD BacLight bacterial viability stain to directly visualize the effects of the UVC light and the antibiotic. The green fluorescence reflects processing of the dye by metabolically active cells, while the red fluorescence is characteristic of dead cells. The green fluorescence was considerably prominent in all the samples with few dead cells when the biofilm was treated with either the UVC light or the antibiotic alone, and the dead cells increased when both were used in sequence. Magnification 1000×.Abbreviations: CLSM, confocal laser scanning microscopy; S. epidermidis, Staphylococcus epidermidis; UVC, ultraviolet C; VAN, vancomycin; MBC, minimum bactericidal concentration.
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f5-idr-9-181: CLSM images of S. epidermidis biofilms on plastic coverslips after incubation for 48 hours followed by one of the following treatments: (A) control (untreated), (B) UVC light alone followed by 24 hours of incubation, (C) VAN alone at twice of its MBC and incubation for 24 hours, and (D) UVC light followed by VAN at double of its MBC and incubation for 24 hours.Notes: The bacterial cells were stained with LIVE/DEAD BacLight bacterial viability stain to directly visualize the effects of the UVC light and the antibiotic. The green fluorescence reflects processing of the dye by metabolically active cells, while the red fluorescence is characteristic of dead cells. The green fluorescence was considerably prominent in all the samples with few dead cells when the biofilm was treated with either the UVC light or the antibiotic alone, and the dead cells increased when both were used in sequence. Magnification 1000×.Abbreviations: CLSM, confocal laser scanning microscopy; S. epidermidis, Staphylococcus epidermidis; UVC, ultraviolet C; VAN, vancomycin; MBC, minimum bactericidal concentration.

Mentions: The CLSM was used to visualize the effect of the UVC light exposure alone or followed by treatment with VAN at double of its MBC on the viability of S. epidermidis using LIVE/DEAD BacLight bacterial viability stain (Figure 5A–D). The images show inability of either the UVC light or the antibiotic alone to kill the bacteria in the biofilms, which is indicated by predominantly green fluorescence of viable cells with a small number of dead cells showing red fluorescence (Figure 5B and C). Adding VAN after the exposure of the biofilm to the UVC light resulted in an increase in the number of dead cells compared to the UVC light or the antibiotic alone (Figure 5D).


Efficacy of ultraviolet C light at sublethal dose in combination with antistaphylococcal antibiotics to disinfect catheter biofilms of methicillin-susceptible and methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis in vitro
CLSM images of S. epidermidis biofilms on plastic coverslips after incubation for 48 hours followed by one of the following treatments: (A) control (untreated), (B) UVC light alone followed by 24 hours of incubation, (C) VAN alone at twice of its MBC and incubation for 24 hours, and (D) UVC light followed by VAN at double of its MBC and incubation for 24 hours.Notes: The bacterial cells were stained with LIVE/DEAD BacLight bacterial viability stain to directly visualize the effects of the UVC light and the antibiotic. The green fluorescence reflects processing of the dye by metabolically active cells, while the red fluorescence is characteristic of dead cells. The green fluorescence was considerably prominent in all the samples with few dead cells when the biofilm was treated with either the UVC light or the antibiotic alone, and the dead cells increased when both were used in sequence. Magnification 1000×.Abbreviations: CLSM, confocal laser scanning microscopy; S. epidermidis, Staphylococcus epidermidis; UVC, ultraviolet C; VAN, vancomycin; MBC, minimum bactericidal concentration.
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f5-idr-9-181: CLSM images of S. epidermidis biofilms on plastic coverslips after incubation for 48 hours followed by one of the following treatments: (A) control (untreated), (B) UVC light alone followed by 24 hours of incubation, (C) VAN alone at twice of its MBC and incubation for 24 hours, and (D) UVC light followed by VAN at double of its MBC and incubation for 24 hours.Notes: The bacterial cells were stained with LIVE/DEAD BacLight bacterial viability stain to directly visualize the effects of the UVC light and the antibiotic. The green fluorescence reflects processing of the dye by metabolically active cells, while the red fluorescence is characteristic of dead cells. The green fluorescence was considerably prominent in all the samples with few dead cells when the biofilm was treated with either the UVC light or the antibiotic alone, and the dead cells increased when both were used in sequence. Magnification 1000×.Abbreviations: CLSM, confocal laser scanning microscopy; S. epidermidis, Staphylococcus epidermidis; UVC, ultraviolet C; VAN, vancomycin; MBC, minimum bactericidal concentration.
Mentions: The CLSM was used to visualize the effect of the UVC light exposure alone or followed by treatment with VAN at double of its MBC on the viability of S. epidermidis using LIVE/DEAD BacLight bacterial viability stain (Figure 5A–D). The images show inability of either the UVC light or the antibiotic alone to kill the bacteria in the biofilms, which is indicated by predominantly green fluorescence of viable cells with a small number of dead cells showing red fluorescence (Figure 5B and C). Adding VAN after the exposure of the biofilm to the UVC light resulted in an increase in the number of dead cells compared to the UVC light or the antibiotic alone (Figure 5D).

View Article: PubMed Central - PubMed

ABSTRACT

Background: Biofilm formation inside inserted medical devices leads to their failure and acts as a source of refractory infections. The ultraviolet C (UVC) light is a potential therapy that can be used against the biofilm of bacterial pathogens.

Objective: We evaluated the efficacy of sublethal dose of UVC light with anti-staphylococcal antibiotics against biofilms made from 30 isolates of methicillin-susceptible Staphylococcus aureus and methicillin-resistant S. aureus and S. epidermidis on vascular catheters.

Materials and methods: A novel biofilm device was used to assess the combined approach. The biofilms on the catheters were irradiated with the UVC light at 254 nm and irradiance of 6.4 mW followed by treatment with vancomycin or quinupristin/dalfopristin at twice their minimum bactericidal concentrations or with linezolid at 64 µg/mL for 24 hours. The catheters were cut into segments and sonicated, and the number of the sessile cells was determined colorimetrically using XTT viable cells assay. The effect of UVC radiation followed by treatment with an antistaphylococcal antibiotic on the viability of the bacteria in the biofilm was visualized using LIVE/DEAD BacLight bacterial viability stain and confocal laser scanning microscopy.

Results: Exposure of the bacterial biofilms to the UVC light or each of the antibiotics alone was ineffective in killing the bacteria. Treatment of the biofilms with the antibiotics following their exposure to UVC light significantly (P<0.001) reduced the number of viable cells within the biofilms but did not completely eradicate them.

Conclusion: To our knowledge, this combinatorial approach has not been investigated before. The combined approach can be used as a therapeutic modality for managing biofilm-associated infections by preventing the establishment of biofilms and/or disrupting the formed biofilms on the inserted medical devices with the goal of increasing their usefulness and preventing infectious complications. Further investigations are needed to assess the effectiveness of the combined approach in the clinical settings.

No MeSH data available.


Related in: MedlinePlus