Surgical site infections can develop after any surgical procedure, increasing patient morbidity, costs, and mortality rates, with the necessity for wound management, antimicrobial treatment, revision surgery, and sometimes implant removal.1,2 Antimicrobial-resistant pathogens such as MRSP and AmpC-producing Escherichia coli are particularly challenging to treat.3 In small animal patients, MRSP is a leading cause of surgical site infections,2,4–8 and it can adhere to suture materials and form biofilms.9–12 Any surgical implant, such as suture material, can act as a substrate for bacterial adherence and biofilm formation, which facilitates evasion of the host immune system and systemic antimicrobial treatment, and can contribute to treatment failure and antimicrobial resistance.5,11
Suture materials coated with triclosan, a topical biocide, are available for use in human and veterinary patients. The effectiveness of triclosan-coated suture material has been investigated in vitro13,14 and in people,15–17 but data for veterinary patients are limited.18–21 Results of studies9,10 have shown reduced adherence of bacteria clinically relevant to human patients on triclosan-coated sutures in vitro, but to the authors’ knowledge, the efficacy of these materials against pathogens important in veterinary surgical site infections has not been shown. Etter et al18 found no significant difference in the rates of surgical site infection and postoperative inflammation when materials with and without antimicrobial coating were used in wound closure for tibial plateau leveling osteotomy in dogs, and Stine et al21 recommended the use of triclosan-coated suture materials as part of a protocol for reducing implant-associated surgical infections following this type of surgery, although efficacy of individual components of the recommended protocol was not investigated. Results of a study15 of human patients revealed a higher rate of incisional dehiscence following closure with triclosan-coated suture, compared with the rate of dehiscence when materials without triclosan coating were used; however, widespread adverse effects relating to the use of triclosan in human patients have not been reported. The current World Health Organization guidelines recommend that triclosan-coated suture materials should be considered as part of infection control and prevention measures in human patients.22
When considering the use of triclosan-coated materials for surgical closure in veterinary patients, it is important to know whether they are effective against the bacteria that are likely to be encountered for a clinically relevant period of time. The purposes of the study reported here were to determine the in vitro effects of triclosan-coated suture material on the growth of bacterial pathogens with clinical relevance to veterinary surgical site infections, assess the duration of any inhibition of such bacterial growth in the presence of triclosan-coated suture, and evaluate the adherence of bacteria to suture material with and without triclosan coating by examination with SEM.
Materials and Methods
Sample
The suture materials used in the study were 3–0 USP triclosan-coated polydioxanonea (monofilament), poliglecaprone-25b (monofilament), and polyglactin-910c (multifilament) and uncoated polydioxanone,d poliglecaprone-25,e and polyglactin-910.f The polyglactin-910 suture had a surface coating to improve the surface characteristics, and the term uncoated was used to describe the absence of triclosan coating only. The suture strands were cut to 1-cm lengths under sterile conditions and stored at room temperature in sterile containers until use.
Bacterial isolates
Clinical bacterial isolates were collected and identified as part of the routine diagnostic work at the Easter Bush Pathology Microbiology Laboratory of the Royal (Dick) School of Veterinary Studies, University of Edinburgh. Isolates were stored at −70°C in tryptone soy broth with 15% glycerol. The bacteria were grown on Columbia horse-blood agar and incubated at 37°C overnight. Isolates were subcultured prior to use for ZOI and sustained antimicrobial activity studies. Ten clinical isolates each of MSRP, MSSP, E coli, and ABL-ESBL–producing E coli obtained from clinical canine wound infections were used.
National Collection of Type Culturesg reference isolates of MRSA (NCTC12493) and MSSA (NCTC12973) and American Type Culture Collectionh reference isolates of ABL-ESBL–producing E coli (ATCC25922) and E coli (ATCC25922) were used as control strains. Strains of S aureus were used as controls because no standard isolate of S pseudintermedius was commercially available.
Antimicrobial activity assessment by ZOI determination
Colonies of each bacterial isolate were suspended in sterile PBS solution to obtain a density equivalent to a 0.5-McFarland standard solution as evaluated with a calibrated standard colorimeter.i Mueller-Hinton agar plates were divided into 4 sections, and the bacterial isolates were spread to achieve confluent growth. A 1-cm coated suture, a 1-cm length of uncoated suture, and an antimicrobial disc to which the bacteria had known susceptibility were applied to seperate quadrants of each agar plate, leaving 1 quadrant blank as a negative control. Inoculation of the agar, application of suture strands and antimicrobial diffusion disks, and plate incubation were performed within a 15-minute period in accordance with the European Committee on Antimicrobial Susceptibility Testing guidelines.23 The antimicrobial disks used for MSRP, MSSP, E coli, and ABL-ESBL–producing E coli as well as their respective control isolates were doxycycline (30 μg), amoxicillin–clavulanic acid (30 μg), amoxicillin–clavulanic acid (30 μg), and gentamicin (10 μg), respectively.j
For these experiments, 1 plate was used for each of the 10 clinical and control isolates of each bacteria and each suture type (polydioxanone, poliglecaprone-25, and polyglactin-910). The plates were incubated at 37°C for 16 to 20 hours. The ZOIs around each suture strand and antimicrobial disk were measured in millimeters with a ruler and recorded (Figure 1). Measurements between millimeter markings were recorded as 0.5 mm.
Photograph depicting a typical ZOI for MRSP around triclosan-coated polydioxanone suture material after culture at 37°C for 16 to 20 hours on a Mueller-Hinton agar plate.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Photograph depicting a typical ZOI for MRSP around triclosan-coated polydioxanone suture material after culture at 37°C for 16 to 20 hours on a Mueller-Hinton agar plate.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Photograph depicting a typical ZOI for MRSP around triclosan-coated polydioxanone suture material after culture at 37°C for 16 to 20 hours on a Mueller-Hinton agar plate.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Sustained antimicrobial activity assay
Following ZOI determinations, 1 isolate each of MSSP, MRSP, E coli, and ABL-ESBL–producing E coli that had inhibition identified when cultured with all of the triclosan-coated suture materials was arbitrarily selected for a sustained antimicrobial activity experiment, which was performed in duplicate (2 plates/isolate/suture material). Selected isolates were subcultured and prepared as previously described. The Mueller-Hinton agar plates were prepared and inoculated, suture strands and antimicrobial diffusion disks were placed, and plates were incubated as described for the ZOI experiments. An additional subculture was prepared on Columbia horse-blood agar and incubated overnight for use the following day.
The ZOIs around each suture strand and antimicrobial disk were measured and recorded as previously described. A Mueller-Hinton agar plate was prepared with the freshly subcultured bacterial isolate. The previously used piece of uncoated suture material was transferred to a quadrant of the fresh plate, followed by placement of the triclosan-coated suture in the second quadrant. A fresh antimicrobial disk to which the bacteria was determined to be susceptible was applied. This process was repeated daily until the predetermined end point was reached when a ZOI was no longer observed around the triclosan-coated suture or suture hydrolysis had occurred. Any size ZOI was considered to represent antimicrobial activity.
Evaluation of suture material structure and bacterial adherence by SEM
The same 4 isolates used to assess sustained antimicrobial activity of the various suture types were subcultured on Columbia horse-blood agar and incubated overnight at 37°C. Colonies of each bacterial isolate were added to 3 mL of sterile PBS solution to obtain a density equivalent to a 0.5-McFarland standard solution and then further diluted with the PBS solution to achieve concentrations of 1 × 105 CFUs/mL. Samples were prepared in duplicate.
Two 1-cm lengths of each triclosan-coated and uncoated suture material were prepared for SEM as previously described.12 The suture strands were exposed to the bacterial suspension for 2 minutes, rinsed 3 times with sterile PBS solution, and then transferred to a tube containing 5 mL of tryptone soy broth with 1% glucose and incubated for 24 hours at 37°C with gentle rotation. The suture strands were rinsed 3 times with sterile PBS solution to remove any nonadherent bacteria, placed in 3% glutaraldehyde fixative solution, and stored at 4°C for 24 hours.
Following this fixation, the suture strands were washed 3 times with Sorensen phosphate buffer solution, incubated with 1% osmium tetroxide solution for 1 hour at 22°C, and washed again 3 times in Sorensen phosphate buffer solution. The strands were then immersed in a series of ethanol solutions (50%, 70%, 80%, and 90%) with 3 final immersions in 100% ethanol (15 min/immersion). Scanning electron microscopy was performed to evaluate bacterial adherence to each suture; the burden of adhered bacteria was assessed qualitatively.
The same process was repeated with negative controls (2 suture strands of each type prepared as described for SEM without exposure to bacterial suspensions). The structure of each suture type (2 strands/type) was also subjectively evaluated by SEM.
Statistical analysis
Statistical analysis was performed with commercially available statistical software.k,l The data residuals from the ZOI and sustained efficacy assays were calculated, and normal probability plots were created that confirmed normal data distributions. One-way ANOVA with Tukey post hoc tests was used to compare the ZOI measurement results and the mean durations of sustained efficacy to determine the influence of suture type and bacterial isolate on the degree of inhibition and duration of sustained efficacy. For all comparisons, values of P < 0.05 were considered significant.
Results
Antimicrobial activity assessment by ZOI determination
Microbial growth with no inhibition was observed for all uncoated sutures. Triclosan-coated sutures inhibited growth of clinical MRSP, MSSP, E coli, and ABL-ESBL–producing E coli isolates, although 2 isolates each of E coli and ABL-ESBL–producing E coli were not inhibited by triclosan-coated polyglactin-910 (Table 1). The mean ZOI sizes around the triclosan-coated suture material for clinical wound isolates appeared similar to those for the control isolates. The sizes of the ZOIs for clinical isolates were significantly (P < 0.05) smaller for the triclosan-coated polyglactin-910, compared with polydioxanone and poliglecaprone-25 sutures. Significantly (P < 0.05) larger ZOIs were observed around the triclosan-coated sutures for gram-positive (MSSP and MRSP) than for gram-negative (E coli and ABL-ESBL–producing E coli) isolates.
Measurements of ZOIs around 3 types of triclosan-coated suture (polydioxanone, poliglecaprone-25, and polyglactin-910) for commercially obtained standard bacterial isolates (1 each of MSSA, MRSA, Escherichia coli, and ABL-ESBL–producing E coli) and for clinical bacterial isolates (10 each of MSSP, MRSP, E coli, and ABL-ESBL–producing E coli) obtained from wound infections of dogs.
| ZOI measurement (mm) | |||
|---|---|---|---|
| Bacteria | TC-Polydioxanone | TC-Poliglecaprone-25 | TC-Polyglactin-910 |
| Standard MSSA isolate | 22.00 | 22.00 | 14.00 |
| Clinical MSSP isolates | 20.00 ± 0.81 | 22.10 ± 1.10 | 10.00 ± 2.16 |
| Standard MRSA isolate | 25.00 | 25.00 | 16.00 |
| Clinical MRSP isolates | 19.90 ± 1.60 | 22.20 ± 1.03 | 10.70 ± 2.83 |
| Standard E coli isolate | 6.00 | 8.00 | 2.00 |
| Clinical E coli isolates | 7.00 ± 1.63 | 8.50 ± 1.35 | 1.85 ± 1.20* |
| Standard ABL-ESBL–producing E coli isolate | 7.00 | 9.00 | 2.00 |
Isolates were cultured on Mueller-Hinton agar plates at 37°C for 16 to 20 hours. Values represent measurements for 1 standard isolate of each type and mean ± SD measurements of 1 replicate each for 10 clinical isolates of each bacteria.
No ZOI was observed for 2 isolates in each category.
TC = Triclosan-coated.
Sustained antimicrobial activity (inhibition)
Triclosan-coated suture materials had sustained antimicrobial activity against all isolates for 3 to 29 days, whereas no inhibition of isolates was detected for uncoated sutures. The mean durations of sustained antimicrobial activity against each bacterial isolate for the 3 triclosan-coated suture types were summarized (Figure 2). Poliglecaprone-25 and polydioxanone each had significantly (P < 0.05) greater durations of sustained antimicrobial activity against all bacterial isolates (mean ± SD, 23.13 ± 5.25 days and 20.13 ± 9.06 days, respectively), compared with polyglactin-910 (5.13 ± 1.81 days). The duration of sustained antimicrobial activity for all coated suture materials against each of the 2 staphylococcal isolates (mean ± SD, 20.83 ± 10.82 days and 20.83 ± 11.11 days) was greater than that against each of the 2 E coli isolates (12.17 ± 6.82 days and 11.00 ± 7.67 days); however, this was not a significant difference.
Mean duration of sustained in vitro antimicrobial activity for 3 types of triclosan-coated suture (polydioxanone, poliglecaprone-25, and polyglactin-910) against clinical isolates of MSSP (black bars), MRSP (white bars), E coli (light gray bars), and ABL-ESBL–producing E coli (dark gray bars) obtained from wound infections of dogs. The error bars indicate the standard error of the mean. Mean values represent the results of duplicate experiments (2 plates/experiment) for 1 randomly selected isolate of each type for which inhibition by all triclosan-coated suture materials was observed in ZOI assays. After initial overnight culture of an isolate with the designated suture type on Mueller-Hinton agar plates with appropriate controls and ZOI assessment, the same piece of suture was transferred to a new plate with the same (freshly subcultured) isolate and incubated. The process was repeated daily until a ZOI was no longer present or suture hydrolysis was evident.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Mean duration of sustained in vitro antimicrobial activity for 3 types of triclosan-coated suture (polydioxanone, poliglecaprone-25, and polyglactin-910) against clinical isolates of MSSP (black bars), MRSP (white bars), E coli (light gray bars), and ABL-ESBL–producing E coli (dark gray bars) obtained from wound infections of dogs. The error bars indicate the standard error of the mean. Mean values represent the results of duplicate experiments (2 plates/experiment) for 1 randomly selected isolate of each type for which inhibition by all triclosan-coated suture materials was observed in ZOI assays. After initial overnight culture of an isolate with the designated suture type on Mueller-Hinton agar plates with appropriate controls and ZOI assessment, the same piece of suture was transferred to a new plate with the same (freshly subcultured) isolate and incubated. The process was repeated daily until a ZOI was no longer present or suture hydrolysis was evident.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Mean duration of sustained in vitro antimicrobial activity for 3 types of triclosan-coated suture (polydioxanone, poliglecaprone-25, and polyglactin-910) against clinical isolates of MSSP (black bars), MRSP (white bars), E coli (light gray bars), and ABL-ESBL–producing E coli (dark gray bars) obtained from wound infections of dogs. The error bars indicate the standard error of the mean. Mean values represent the results of duplicate experiments (2 plates/experiment) for 1 randomly selected isolate of each type for which inhibition by all triclosan-coated suture materials was observed in ZOI assays. After initial overnight culture of an isolate with the designated suture type on Mueller-Hinton agar plates with appropriate controls and ZOI assessment, the same piece of suture was transferred to a new plate with the same (freshly subcultured) isolate and incubated. The process was repeated daily until a ZOI was no longer present or suture hydrolysis was evident.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
SEM evaluation
Qualitative analysis by SEM revealed various degrees of bacterial adherence between the suture materials and bacterial pathogens. The most consistent finding across all isolates was a large bacterial burden adhered to uncoated polyglactin-910 (Figure 3). Fewer bacteria were observed on the triclosan-coated polyglactin-910 equivalent, although the amount seen was still much greater than on the uncoated and triclosan-coated monofilament materials.
Representative SEM images obtained during qualitative assessment of bacterial adherence to triclosan-coated or uncoated polydioxanone, poliglecaprone-25, and polyglactin-910 suture by the same 4 clinical isolates as in Figure 2. A—A large number of adherent E coli on a strand of uncoated polyglactin-910 (multifilament) suture. B—A single adherent E coli is seen on a strand of triclosan-coated polyglactin-910 suture. Bar = 20 μm (marks spaced 2 μm apart).
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Representative SEM images obtained during qualitative assessment of bacterial adherence to triclosan-coated or uncoated polydioxanone, poliglecaprone-25, and polyglactin-910 suture by the same 4 clinical isolates as in Figure 2. A—A large number of adherent E coli on a strand of uncoated polyglactin-910 (multifilament) suture. B—A single adherent E coli is seen on a strand of triclosan-coated polyglactin-910 suture. Bar = 20 μm (marks spaced 2 μm apart).
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Representative SEM images obtained during qualitative assessment of bacterial adherence to triclosan-coated or uncoated polydioxanone, poliglecaprone-25, and polyglactin-910 suture by the same 4 clinical isolates as in Figure 2. A—A large number of adherent E coli on a strand of uncoated polyglactin-910 (multifilament) suture. B—A single adherent E coli is seen on a strand of triclosan-coated polyglactin-910 suture. Bar = 20 μm (marks spaced 2 μm apart).
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
For all bacterial isolates, only occasional adherent bacteria were observed on triclosan-coated and uncoated poliglecaprone-25 suture. Following exposure of uncoated polydioxanone to E coli, multiple colonies of adherent bacteria were observed, whereas the triclosan-coated equivalent only had occasional adherent bacteria (Figure 4). This finding was not observed for the other 3 bacterial isolates, for which only occasional bacteria were observed on the surface of triclosan-coated and uncoated polydioxanone suture. As expected, no bacteria were present on the surface of the suture strands that had not been exposed to bacterial suspension.
Representative SEM image of uncoated polydioxanone suture showing adherence of E coli and a long rod prior to division. See Figure 3 for remainder of key.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Representative SEM image of uncoated polydioxanone suture showing adherence of E coli and a long rod prior to division. See Figure 3 for remainder of key.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Representative SEM image of uncoated polydioxanone suture showing adherence of E coli and a long rod prior to division. See Figure 3 for remainder of key.
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Subjective evaluation of suture materials by SEM revealed that triclosan-coated and uncoated poliglecaprone-25 were the smoothest materials (Figure 5). Longitudinal ridges were identified on the surface of all triclosan-coated and uncoated polydioxanone suture samples. Polyglactin-910 sutures of both types had many small gaps between the multifilament strands.
Representative SEM images of monofilament sutures obtained during subjective assessment of surface characteristics. A—Uncoated polydioxanone suture. Notice the longitudinal ridges on the surface of the material. B—Uncoated poliglecaprone-25 suture. Notice the smooth surface. Bar = 100 μm (marks spaced 10 μm apart).
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Representative SEM images of monofilament sutures obtained during subjective assessment of surface characteristics. A—Uncoated polydioxanone suture. Notice the longitudinal ridges on the surface of the material. B—Uncoated poliglecaprone-25 suture. Notice the smooth surface. Bar = 100 μm (marks spaced 10 μm apart).
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Representative SEM images of monofilament sutures obtained during subjective assessment of surface characteristics. A—Uncoated polydioxanone suture. Notice the longitudinal ridges on the surface of the material. B—Uncoated poliglecaprone-25 suture. Notice the smooth surface. Bar = 100 μm (marks spaced 10 μm apart).
Citation: American Journal of Veterinary Research 81, 1; 10.2460/ajvr.81.1.84
Discussion
Triclosan-coated suture materials had sustained inhibition of growth of S pseudintermedius and E coli isolates, including the corresponding multidrug-resistant isolates (MRSP and ABL-ESBL–producing E coli), in vitro in the present study. Almost all of the triclosan-coated suture materials had a detectable ZOI for all standard (control; n = 4) and clinical (40) bacterial isolates tested by culture. The sizes of these zones and duration of sustained efficacy varied with the type of suture material and bacteria, with the triclosan-coated sutures creating larger ZOIs for S pseudintermedius than E coli isolates and sustaining antimicrobial activity in vitro against the staphylococcal isolates for greater durations, compared with those for E coli isolates. These results were similar to findings for monofilament suture in previous studies,14,19 in which ZOIs and durations of sustained efficacy against S aureus were greater than those against E coli. Overall, these findings might support that inhibition of E coli (including ABL-ESBL–producing strains) requires a higher concentration of triclosan than does inhibition of S pseudintermedius (including MRSP). The in vitro efficacy of triclosan-coated suture materials and reduced or inhibited colonization of these suture materials by MRSA and other pathogens of clinical importance in human medicine have been found in several studies,13,14,19 and our in vitro findings for clinically relevant canine wound isolates, including those with multidrug-resistant properties, were similar. The differences in mean sizes of the ZOIs may have reflected variable antimicrobial activity among the suture materials against the tested isolates. However, this must be interpreted with caution, as ZOI measurements cannot be related to the break points when assessing in vitro bacterial susceptibility by a disk diffusion method and therefore cannot be used to infer susceptibility or resistance of the bacteria to a substance.
Of the 3 triclosan-coated sutures used in the present study, polyglactin-910 had the smallest ZOIs for all of the bacterial isolates, and durations of inhibition were shorter for this suture type than for the 2 monofilament sutures. On visual assessment by SEM, uncoated polyglactin-910 suture was found to have the greatest burden of adherent bacteria (E coli). The adhered bacterial burden was considerably less for triclosan-coated polyglactin-910, although it was still appreciably greater than that for the uncoated monofilament suture materials. Rothenburger et al13 described similar results for the adherence of MSSA and MRSA and drug-sensitive and drug-resistant Staphylococcus epidermidis isolates to triclosan-coated and uncoated polyglactin-910. Those investigators also found a concentration-dependent effect of the triclosan coating of polyglactin-910.13 The larger ZOIs and greater duration of sustained antimicrobial activity for the monofilament versus multifilament triclosan-coated suture and the qualitative differences in bacterial adherence assessed by SEM in our study potentially could have been attributable to a lower concentration of triclosan coating on polyglactin-910, compared with that on poliglecaprone-25 and polydioxanone suture materials commercially available in the European Union, where our study was conducted. Most previous research regarding these materials has been conducted in the United States. The current maximum triclosan concentration permitted for the manufacturing process of triclosan-coated polyglactin-910 is 275 μg/m in the European Union and 472 μg/m in the United States. These maximum concentrations are considerably lower than that used for triclosan-coated polydioxanone and poliglecaprone-25 sutures, which is 2,360 μg/m worldwide.24–26
To the authors’ knowledge, ZOI and sustained efficacy assays have not previously been performed in parallel for these 3 suture materials in a single study, and sustained antimicrobial activity of triclosan-coated polyglactin-910 has not been previously investigated. The braided structure of polyglactin-910 may increase the surface area available for bacterial colonization and adherence and may also affect the ability of triclosan to diffuse into the surrounding substrate or patient tissues. Triclosan diffusion from suture materials was not evaluated in the present study. Further studies would be required to assess the efficacy of these suture materials in veterinary patients and to evaluate the elution qualities of triclosan from suture materials. Although results of the study suggested that the in vitro antibacterial effects of triclosan used for coating suture materials may have a concentration-dependent effect, this finding was confounded by the structures of braided and monofilament suture materials because these are not directly comparable. The multifilament structure of polyglactin-910 provides greater surface area for potential bacterial adherence, compared with monofilament sutures; therefore, further studies are required to determine the effect of suture structure on bacterial adherence to triclosan-coated materials.
For almost all of the samples evaluated by SEM in our study, only occasional bacteria were observed on the surface of uncoated and triclosan-coated monofilament sutures. Owing to the small numbers of adherent bacteria, no appreciable difference in bacterial adherence was observed among most monofilament sutures, regardless of the presence of triclosan, on subjective evaluation. The exception to this was polydioxanone suture exposed to E coli, for which multiple microcolonies of adherent bacteria were observed, whereas the triclosan-coated equivalent only had occasional adherent bacteria present. Following adherence of E coli to uncoated polydioxanone, the organisms appeared to have replicated, forming colonies. The small numbers of drug-sensitive E coli adhered to the surface of triclosan-coated polydioxanone suggested that bacterial replication of the adherent organisms did not occur in the presence of the triclosan coating. However, it was unknown whether these observations were dependent on the bacterial strains tested. Both uncoated and triclosan-coated polydioxanone had shallow longitudinal ridges evident on the suture surface when evaluated by SEM; these ridges were consistently observed on every sample of polydioxanone evaluated, including the control samples that had not been exposed to bacterial suspensions. It is possible that the surface characteristics of suture materials may have a similar, or greater, effect on bacterial adherence than the concentration of triclosan coating. The findings of the present study provided compelling in vitro evidence to support the use of triclosan-coated materials in contaminated surgical sites or in patients for which the development of surgical site infection would lead to severe morbidity. Although in vivo prospective investigation is required to confirm that similar effects are present in the clinical situation, in consideration of the morbidity related to surgical site infections and patient welfare implications and other evidence suggesting that triclosan-coated suture materials are safe to use,15,16,27 their use may be recommended. Our results further suggested that triclosan-coated polyglactin-910 may be preferable to its uncoated counterpart to reduce the risk of surgical site infection, but that its antimicrobial effect may be short-lived (considering that a ZOI was present in vitro for only 3 to 6 days). The triclosan coating of this suture may provide antimicrobial activity against common isolates found in dogs during early healing of surgical incisions; however, it is unknown whether the triclosan-coated materials deliver a clinically meaningful advantage over uncoated sutures, and further research is needed to evaluate the effect of triclosan-coated suture materials on the rate of surgical site infection in vivo.
The present study had several limitations. The in vitro findings may not reflect the in vivo effects of triclosan coating in the presence of surgical site infection caused by the isolates used in our experiments or by other organisms. The isolates used in the study were obtained from clinical wound infections in dogs, but the bacterial burden of clean and contaminated surgical sites is unknown, and the quantity of inoculum and other experimental variables may not have adequately represented the clinical situation. The bacterial burden required to cause a surgical site infection is likely to vary on a case-by-case basis and to be influenced by many patient, biological, and mechanical factors.
Acknowledgments
Funded by Ethicon. The funding company had no role in the study design, data collection, analysis and interpretation of data, writing of the report, or decision to submit the article for publication.
The authors declare that there were no conflicts of interest.
Presented in abstract form at the 28th Annual Scientific Meeting of the European College of Veterinary Surgeons, Hungary, July 2019.
The authors thank Jennifer Harris, Easter Bush Pathology Microbiology Laboratory, University of Edinburgh, for technical assistance.
ABBREVIATIONS
| ABL-ESBL | AmpC β-lactamase and extended-spectrum β-lactamase |
| MRSP | Methicillin-resistant Staphylococcus pseudintermedius |
| MSSP | Methicillin-susceptible Staphylococcus pseudintermedius |
| SEM | Scanning electron microscopy |
| ZOI | Zone of inhibition |
Footnotes
PDS Plus Antibacterial, Ethicon Inc, Livingston, Scotland.
Monocryl Plus Antibacterial, Ethicon Inc, Livingston, Scotland.
Coated Vicryl Plus Antibacterial, Ethicon Inc, Livingston, Scotland.
PDS, Ethicon Inc, Livingston, Scotland.
Monocryl, Ethicon Inc, Livingston, Scotland.
Coated Vicryl, Ethicon Inc, Livingston, Scotland.
National Collection of Type Cultures, Public Health England, Salisbury, England.
American Type Culture Collection, Manassas, Va.
DensiCHEK, bioMerieux, Basingstoke, England.
Thermo Fisher Scientific products, Leistershire, England.
Minitab, version 18, Minitab Inc, Coventry, England.
Microsoft Office 365 Excel 2016, Microsoft Corp, Redmond, Wash.
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