Methicillin-Susceptible Staphylococcus aureus Biofilm Formation on Vascular Grafts: an In Vitro Study

Antibiotic Efficacy against Methicillin-Susceptible Staphylococcus aureus Biofilms on Synthetic and Biological Vascular Grafts

BACKGROUND

Biofilm formation is one of the greatest challenges encountered in vascular graft infections. Our aim is to compare the efficacy of 5 antibiotics against methicillin-susceptible Staphylococcus aureus (MSSA) biofilms on the surface of 4 vascular grafts.

METHODS

In vitro study of 2 clinical MSSA strains (MSSA2 and MSSA6) and 4 vascular grafts (Dacron, Dacron-silver-triclosan (DST), Omniflow-II, and bovine pericardium). After a 24-hr incubation period, the graft samples were divided into 6 groups: growth control (no treatment), ciprofloxacin 4.5 mg/L, cloxacillin 100 mg/L, dalbavancin 300 mg/L, daptomycin 140 mg/L, and linezolid 20 mg/L. Quantitative cultures were obtained and results expressed as log10 colony-forming units per milliliter (CFU/mL). Analysis of variance was performed to compare biofilm formation between the different groups.

RESULTS

The mean ± standard deviation MSSA2 count on the growth control Dacron graft was 10.05 ± 0.31 CFU/mL. Antibiotic treatment achieved a mean reduction of 45%; ciprofloxacin was the most effective antibiotic (64%). Baseline MSSA2 counts were very low on the DST (0.50 ± 1.03 CFU/mL) and Omniflow-II (0.33 ± 0.78 CFU/mL) grafts. On the bovine pericardium patch, the count was 9.87 ± 0.50 CFU/mL, but this was reduced by a mean of 45% after antibiotic treatment (61% for ciprofloxacin). The mean MSSA6 count on the growth control Dacron graft was 9.63 ± 0.53 CFU/mL. Antibiotics achieved a mean reduction of 48%, with ciprofloxacin performing best (67% reduction). The baseline MSSA6 count on the DST graft was 8.54 ± 0.73 CFU/mL. Antibiotics reduced biofilm formation by 72%; cloxacillin was the most effective treatment (86%). The MSSA6 count on the untreated Omniflow-II graft was 1.17 ± 1.52 CFU/mL. For the bovine pericardium patch, it was 8.98 ± 0.67 CFU/mL. The mean reduction after antibiotic treatment was 46%, with cloxacillin achieving the greatest reduction (68%).

CONCLUSIONS

In this in vitro study, ciprofloxacin and cloxacillin performed best at reducing biofilms formed by clinical MSSA strains on the surface of biological and synthetic vascular grafts.

Omniflow® II biosynthetic graft offers acceptable early and mid-term outcomes in redo surgery in patients with critical limb-threatening ischemia with no available autologous vein material

BACKGROUND

In this study, the early and mid-term outcomes of Omniflow® II (LeMaitre Vascular, Inc., Burlington, MA, USA) biosynthetic graft in redo surgery in patients with critical limb-threatening ischemia (CLTI) with no available autologous vein material were investigated with the aim to compare the outcomes obtained in "de novo" surgery versus redo surgery.

METHODS

From January 2018 until December 2022, data of CLTI patients from 18 centers in Italy with no autologous vein material underwent infrainguinal bypass with Omniflow® II biosynthetic graft were collected. Thirty-day outcome measures including intraoperative technical success, major morbidity, mortality, and graft patency were assessed and compared. At two-year follow-up, estimated outcomes of survival, primary patency, primary assisted patency, secondary patency, freedom from reintervention, and amputation-free survival were analyzed using Kaplan-Meier curves and compared between groups using the log-rank test.

RESULTS

In the study period 119 CLTI patients had an infrainguinal bypass with Omniflow® II biosynthetic graft. Seventy-seven patients (64.7%) underwent bypass as "de novo" treatment (group de novo), whilst in the remaining 42 patients (35.3%) the procedure was performed as redo surgery due to occlusion and/or infection of a previous bypass graft (group redo). Two groups were homogeneous in terms of demographic, clinical, and morphological data. In group redo explantation of an infected prosthetic graft was needed in 4 cases (9.5%). Intraoperative technical success was achieved in all cases in both groups. At 30 days, the overall patency rate did not differ between the two groups (69/77, 89.6%, group de novo vs. 35/42, 83.3%, group redo; P=0.24), whilst in group redo limb loss was higher with a statistically significant different 30-day major amputation rate between the two groups (11.9% group redo vs. 1.3% group de novo; P<0.001). Overall median duration of follow-up was eight months (IQR 6-13). At two-year follow-up there were no differences between the two groups in terms of survival (67.7% group de novo vs. 55.8% group redo, P=0.53), primary patency (34.4% group de novo vs. 26.8% group redo, P=0.25), primary assisted patency (43.6% group de novo vs. 28.8% group redo, P=0.12), freedom from reintervention (64.1% group de novo vs. 68.8% group redo, P=0.98), and amputation-free survival (67.8% group de novo vs. 60% group redo, P=0.12). Secondary patency was significantly higher in group de novo (53.7% vs. 32.3%, P=0.05). During the follow-up, the overall rates of graft infection and aneurysmal degeneration were 3.4%, and 0.8%, respectively.

CONCLUSIONS

Nevertheless, poorer early outcomes in terms of limb salvage, Omniflow® II biosynthetic graft offers acceptable ywo-year outcomes in redo surgery in CLTI patients with no available autologous vein material. Further studies with larger population sizes are needed to validate these outcomes.

Assessing silver nanoparticle and antimicrobial combinations for antibacterial activity and biofilm prevention on surgical sutures

AIMS

To evaluate the effect of silver nanoparticles alone and in combination with Triclosan, and trans-cinnamaldehyde against Staphylococcus aureus and Escherichia coli biofilms on sutures to improve patients' outcomes.

METHODS AND RESULTS

Silver nanoparticles were prepared by chemical method and characterized by UV-visible spectrophotometer and dynamic light scattering. The minimum inhibitory concentration was assessed by the Microdilution assay. The antibiofilm activity was determined using crystal violet assay. A checkerboard assay using the fractional inhibitory concentration index and time-kill curve was used to investigate the synergistic effect of silver nanoparticle combinations. The hemolytic activity was determined using an erythrocyte hemolytic assay. Our results revealed that silver nanoparticles, Triclosan, and trans-cinnamaldehyde (TCA) inhibited S.aureus and E.coli biofilms. Silver nanoparticles with TCA showed a synergistic effect (FICI values 0.35 and 0.45 against S. aureus and E. coli biofilms, respectively), and silver nanoparticles with Triclosan showed complete inhibition of S. aureus biofilm. The hemolytic activity was <2.50% for the combinations.

The Safety and Efficacy of Phage Therapy for Infections in Cardiac and Peripheral Vascular Surgery: A Systematic Review

New approaches to managing infections in cardiac and peripheral vascular surgery are required to reduce costs to patients and healthcare providers. Bacteriophage (phage) therapy is a promising antimicrobial approach that has been recommended for consideration in antibiotic refractory cases. We systematically reviewed the clinical evidence for phage therapy in vascular surgery to support the unlicensed use of phage therapy and inform future research. Three electronic databases were searched for articles that reported primary data about human phage therapy for infections in cardiac or peripheral vascular surgery. Fourteen reports were eligible for inclusion, representing 40 patients, among which an estimated 70.3% of patients (n = 26/37) achieved clinical resolution. A further 10.8% (n = 4/37) of patients showed improvement and 18.9% (n = 7/37) showed no improvement. Six of the twelve reports that commented on the safety of phage therapy did not report adverse effects. No adverse effects documented in the remaining six reports were directly linked to phages but reflected the presence of manufacturing contaminants or release of bacterial debris following bacterial lysis. The reports identified by this review suggest that appropriately purified phages represent a safe and efficacious treatment option for infections in cardiac and peripheral vascular surgery.

Staphylococcus aureus Adhesion and Biofilm Formation on Vascular Polyester Grafts are Inhibited In Vitro by Triclosan

OBJECTIVE

This study evaluated Staphylococcus aureus adhesion and biofilm formation on vascular grafts, which has seldom been investigated.

METHODS

Adhesion and biofilm formation capabilities of three methicillin susceptible S. aureus strains (one biofilm forming reference strain and two clinical isolates) on five different vascular biomaterials were evaluated in vitro, including polyester (P), P + gelatin (PG), P + collagen (PC), PC + silver (PCS), and PCS + triclosan (PCST). Staphylococcus aureus adhesion on grafts was evaluated after one hour of culture and biofilm formation after 24 hours of culture by four different methods: spectrophotometry after crystal violet staining; sonicate fluid culture; metabolic assay; and scanning electron microscopy (SEM). Optical density was compared using Mann-Whitney pairwise test, and bacterial counts using Wilcoxon pairwise test.

RESULTS

PCST grafts were most efficient in preventing S. aureus adhesion and biofilm formation, regardless of the method used. Bacterial counts and metabolic activity were significantly lower on PCST grafts after 24 hours (5.65 vs. 9.24 [PCS], 8.99 [PC], 8.82 [PG], and 10.44 log10 CFU/mL [P]; p < .015), and only PCST grafts were bactericidal. Biofilm formation was significantly diminished on PCST grafts compared with all other grafts (p < .001). Bacterial viability and metabolic activity after 24 hours were more impaired on PG compared with PC graft, and were surprisingly higher on PCS compared with PC grafts. Biofilm biomass formed after exposure to P, PG, PC, and PCS grafts was also reduced after 24 hours of incubation with PCST grafts (p < .001). After 24 hours, few bacteria were visible by SEM on PCST grafts, whereas bacterial biofilm colonies were clearly identified on other graft surfaces.

CONCLUSION

Triclosan impregnated PCST grafts appeared to interfere with S. aureus adhesion from early stages of biofilm formation in vitro. Silver impregnation was not efficient in preventing biofilm formation, and collagen coating promoted S. aureus biofilm formation more than gelatin coating.

Combination of Bacteriophages and Antibiotics for Prevention of Vascular Graft Infections-An In Vitro Study

(1) Background: Implant-associated bacterial infections are usually hard to treat conservatively due to the resistance and tolerance of the pathogens to conventional antimicrobial therapy. Bacterial colonization of vascular grafts may lead to life-threatening conditions such as sepsis. The objective of this study is to evaluate whether conventional antibiotics and bacteriophages can reliably prevent the bacterial colonization of vascular grafts. (2) Methods: Gram-positive and Gram-negative bacterial infections were simulated on samples of woven PET gelatin-impregnated grafts using Staphylococcus aureus and Escherichia coli strains, respectively. The ability to prevent colonization was evaluated for a mixture of broad-spectrum antibiotics, for strictly lytic species-specific bacteriophage strains, and for a combination of both. All the antimicrobial agents were conventionally tested in order to prove the sensitivity of the used bacterial strains. Furthermore, the substances were used in a liquid form or in combination with a fibrin glue. (3) Results: Despite their strictly lytic nature, the application of bacteriophages alone was not enough to protect the graft samples from both bacteria. The singular application of antibiotics, both with and without fibrin glue, showed a protective effect against S. aureus (0 CFU/cm²), but was not sufficient against E. coli without fibrin glue (M = 7.18 × 10⁴ CFU/cm²). In contrast, the application of a combination of antibiotics and phages showed complete eradication of both bacteria after a single inoculation. The fibrin glue hydrogel provided an increased protection against repetitive exposure to S. aureus (p = 0.05). (4) Conclusions: The application of antibacterial combinations of antibiotics and bacteriophages is an effective approach to the prevention of bacteria-induced vascular graft infections in clinical settings.