Topical and systemic antibiotics in the prevention of wound infection

Robust antibacterial activity of functionalized carbon nanotube- levofloxacine conjugate based on in vitro and in vivo studies

A new nano-antibiotic was synthesized from the conjugation of multi-walled carbon nanotubes with levofloxacin (MWCNT-LVX) through covalent grafting of drug with surface-modified carbon nanotubes in order to achieve an effective, safe, fast-acting nano-drug with the minimal side effects. This study is the first report on the evaluation of in vitro cell viability and antibacterial activity of nano-antibiotic along in addition to the in vivo antibacterial activity in a burn wound model. The drug-loading and release profile at different pH levels was determined using an ultraviolet–visible spectrometer. MWCNT-LVX was synthesized by a simple, reproducible and cost-effective method for the first time and characterized using various techniques, such as scanning electron microscope, transmission electron microscopy, and Brunauer–Emmett–Teller analysis, and so forth. The noncytotoxic nano-antibiotic showed more satisfactory in vitro antibacterial activity against Staphylococcus aureus compared to Pseudomona aeruginosa. The novel synthetic nano-drug possessed high loading capacity and pH-sensitive release profile; resultantly, it exhibited very potent bactericidal activity in a mouse S. aureus wound infection model compared to LVX. Based on the results, the antibacterial properties of the drug enhanced after conjugating with surface-modified MWCNTs. The nano-antibiotic has great industrialization potential for the simple route of synthesis, no toxicity, proper drug loading and release, low effective dose, and strong activity against wound infections. In virtue of unique properties, MWCNTs can serve as a controlled release and delivery system for drugs. The easy penetration to biological membranes and barriers can also increase the drug delivery at lower doses compared to the main drug alone, which can lead to the reduction of its side effects. Hence, MWCNTs can be considered a promising nano-carrier of LVX in the treatment of skin infections.

Current In Vitro Biofilm-Infected Chronic Wound Models for Developing New Treatment Possibilities

Significance: The prevalence of chronic wounds is increasing worldwide. The most recent estimates suggest that up to 2% of the population in the industrialized countries is affected. Recent Advances: During the past few decades, bacterial biofilms have been elucidated as one of the primary reasons why chronic wounds fail to heal. Critical Issues: There is a lack of direct causation and evidence of the role that biofilms play in persistent wounds, which complicates research on new treatment options, since it is still unknown which factors dominate. For this reason, several different in vitro wound models that mimic the biofilm infections observed in chronic wounds and other chronic infections have been created. These different models are, among other purposes, used to test a variety of wound care products. However, chronic wounds are highly complex, and several different factors must be taken into consideration along with the infection, including physiochemical and human-supplemented factors. Furthermore, the limitations of using in vitro models, such as the lack of a responsive immune system should always be given due consideration. Future Directions: Present understandings of all the elements and interactions that take place within chronic wounds are incomplete. As our insight of in vivo chronic wounds continues to expand, so too must the in vitro models used to mimic these infections evolve and adapt to new knowledge.

Effects of prophylactic antibiotic-treatment on post-surgical recovery following intraperitoneal bio-logger implantation in rainbow trout

Bio-logging devices can provide unique insights on the life of freely moving animals. However, implanting these devices often requires invasive surgery that causes stress and physiological side-effects. While certain medications in connection to surgeries have therapeutic capacity, others may have aversive effects. Here, we hypothesized that the commonly prescribed prophylactic treatment with enrofloxacin would increase the physiological recovery rate and reduce the presence of systemic inflammation following the intraperitoneal implantation of a heart rate bio-logger in rainbow trout (Oncorhynchus mykiss). To assess post-surgical recovery, heart rate was recorded for 21 days in trout with or without enrofloxacin treatment. Contrary to our hypothesis, treated trout exhibited a prolonged recovery time and elevated resting heart rates during the first week of post-surgical recovery compared to untreated trout. In addition, an upregulated mRNA expression of TNFα in treated trout indicate a possible inflammatory response 21 days post-surgery. Interestingly, the experience level of the surgeon was observed to have a long-lasting impact on heart rate. In conclusion, our study showed no favorable effects of enrofloxacin treatment. Our findings highlight the importance of adequate post-surgical recovery times and surgical training with regards to improving the welfare of experimental animals and reliability of research outcomes.

Anti-bacterial materials based on hyaluronic acid: Selection of research methodology and analysis of their anti-bacterial properties

In the frame of the presented research, highly-porous structures made of hyaluronic acid modified with bioactive compounds were prepared. The method of microbiological testing of hygroscopic materials has been elaborated by verification of the JIS L 1902:2002 and ASTM E2149-13a test methods. The research has shown that the method developed in accordance with ASTM E2149-13a is suitable for testing the activity of hyaluronic acid samples against bacteria. E. coli and S. aureus. In the case of E. coli it is preferred to use as a medium the phosphoric buffer and for S. aureus NaCl solution from NB. By analysing the results of the antibacterial properties, it is important to note that the introduction of a small amount of zinc and zinc oxide in the matrix from the hyaluronic acid (in the amount of 3% by weight of the polymer) makes it possible to obtain a material with a strong activity against the bacterial strains. It enables to use this type of material as a treatment for hard-to-treat, infected wounds. On the other hand, using a relatively small dose of the cephalosporin antibiotic did not result in high levels of activity against the bacteria Gram "+" and Gram "-".

Traumatic lacerations: what are the risks for infection and has the 'golden period' of laceration care disappeared?

OBJECTIVE

To determine risk factors associated with infection and traumatic lacerations and to see if a relationship exists between infection and time to wound closure after injury.

METHODS

Consecutive patients presenting with traumatic lacerations at three diverse emergency departments were prospectively enrolled and 27 variables were collected at the time of treatment. Patients were followed for 30 days to determine the development of a wound infection and desire for scar revision.

RESULTS

2663 patients completed follow-up and 69 (2.6%, 95% CI 2.0% to 3.3%) developed infection. Infected wounds were more likely to receive a worse cosmetic rating and more likely to be considered for scar revision (RR 2.6, 95% CI 1.7 to 3.9). People with diabetes (RR 2.70, 95% CI 1.1 to 6.5), lower extremity lacerations (RR 4.1, 95% CI 2.5 to 6.8), contaminated lacerations (RR 2.0, 95% CI 1.2 to 3.4) and lacerations greater than 5 cm (RR 2.9, 95% CI 1.6 to 5.2) were more likely to develop an infection. There were no differences in the infection rates for lacerations closed before 3% (95% CI 2.3% to 3.8%) or after 1.2% (95% CI 0.03% to 6.4%) 12 h.

CONCLUSIONS

Diabetes, wound contamination, length greater than 5 cm and location on the lower extremity are important risk factors for wound infection. Time from injury to wound closure is not as important as previously thought. Improvements in irrigation and decontamination over the past 30 years may have led to this change in outcome.

Bacterial counts in experimental, contaminated crush wounds irrigated with various concentrations of cefazolin and penicillin

The objective of this study was to determine if three different concentrations of cefazolin and penicillin irrigation solutions reduce quantitative bacterial counts in experimental crush wounds contaminated with multiple species of bacteria. The design used was a randomized, blinded, experimental animal study. An animal bite wound model was created by innoculating crushed incisions with three species of bacteria. Four paravertebral incisions extending to deep fascia were created in each of twelve anesthetized albino guinea pigs. Wound edges were clamped with a hemostat for five seconds to create crushed, devitalized tissue within each wound. Wounds were inoculated with 0.4 mL of a standard solution of Staphylococcus aureus, Bacterioides fragilis, and Pasturella multocida and covered. Four hours after inoculation, each wound was scrubbed for 30 seconds with 20% poloxamer 188 and then irrigated with 100 mL of one of four solutions: normal saline solution (control); cefazolin (CZ) 2 mg/mL, plus penicillin G (PCN) 200 units/mL (low dose); CZ 10 mg/mL, plus PCN 2,000 units/mL (intermediate dose); and CZ 50 mg/mL, plus PCN 20, 000 units/mL (high dose). Investigators were blinded to the solutions used. Wounds were covered with a vapor-permeable dressing. Six days after treatment, each wound was examined for signs of infection and then excised for quantitative bacteriologic analysis. Colony counts were reported as counts per gram of tissue. Wounds in the four irrigation solution groups were compared using ANOVA. A log difference of 3 was considered significant. The average log total bacteria/gram tissue for the four groups were: control, 4.35 (95% CI; 1.01); low dose, 4.09 (95% CI; 1.42); intermediate dose, 4.47 (95% CI; 1.27); and high dose, 3.45 (95% CI; 1.33). No wounds in the high-dose group had any clinical signs of infection, whereas 50% of wounds in the intermediate dose group, 42% in the low dose group, and 33% in the control group had either erythema, induration, or purulence. There were no statistically significant differences in the bacterial counts/gram tissue or clinical infection rates in any of the groups. A formal trend analysis failed to find a significant linear trend for decreasing bacterial counts for either antibiotic. In this experimental bite wound model containing contaminated, crushed tissue, irrigation with various solutions of cefazolin plus penicillin G did not reduce quantitative bacterial counts more than 3.1 log total bacteria/gram tissue.

Use of cefazolin microspheres to treat localized methicillin-resistant Staphylococcus aureus infections in rats

BACKGROUND

In a previous study, the topical administration of biodegradable, controlled-release poly-(dl-lactide-co-glycolide) cefazolin microspheres could effectively prevent surgical wound infections with a sensitive strain of Staphylococcus aureus in an experimental animal model. The objective of the current study was to evaluate and compare the efficacy of topical antibiotic therapy with cefazolin microspheres to systemic cefazolin therapy for the treatment of experimental rat surgical wounds contaminated with a methicillin-resistant strain of S. aureus (MRSA).

METHODS

A local infection model in rats was used. MRSA was used to infect pockets surgically produced in the paraspinous muscles. Groups of rats received either topical cefazolin microspheres, topical cefazolin powder, parenteral cefazolin, or no treatment. Feces were cultured to evaluate the effect of antibiotic therapy on gut flora.

RESULTS

The rate of clinical wound infection following topical application of cefazolin microspheres (13%) was significantly lower than the 53% infection rate observed in rats who had received a 2-week course of systemic cefazolin therapy (P = 0.046). Moreover, single-dose topical antibiotic therapy with cefazolin microspheres completely eradicated MRSA from the wounds of 7 of 15 (47%) animals. There was no statistically significant difference, however, in the rate of clinical wound infection between rats whose wounds were treated topically with free cefazolin powder and those treated with systemic cefazolin (P = 0.12). Importantly, selection of antibiotic-resistant bacteria was associated with systemic but not local cefazolin therapy.

CONCLUSION

The results of this study suggest that topical antibiotic therapy with controlled-release cefazolin microspheres may be effective for the prevention of wound infection with both methicillin-sensitive and methicillin-resistant strains of S. aureus in selected surgical procedures that are at high risk of developing postoperative wound infection.

Delayed local treatment of rabbit tibial fractures with biodegradable cefazolin microspheres

The prevention of infection is a primary objective in the treatment of open fractures. The objective of this study was to compare the efficacy of biodegradable, poly (DL-lactide-co-glycolide) cefazolin microspheres and free cefazolin powder in Staphylococcus aureus contaminated rabbit tibial fractures when treatment was delayed for 2 hours. Fractures were produced in the tibia of rabbits, inoculated with Staphylococcus aureus, and 2 hours later treated by either direct local application of cefazolin microspheres or an equivalent dose of free cefazolin powder. Control animals did not receive antibiotic therapy. The fractures then were stabilized with a bone plate, and the animals were observed for 8 weeks. Local antibiotic therapy with biodegradable cefazolin microspheres prevented the establishment of infection in all animals, and cultures of the tibiae were sterile in all cases. In contrast, clinical evidence of infection developed in 50% of the rabbits that had been treated with free cefazolin powder and 71% of the control animals. Staphylococcus aureus was recovered from the tibiae of 75% and 100% of these animals, respectively. The results of this study suggest that local antibiotic therapy with biodegradable, controlled release cefazolin microspheres may be useful for the management of open fractures in humans, even when treatment is delayed for several hours after bacterial contamination.

Evaluation of biodegradable cefazolin sodium microspheres for the prevention of infection in rabbits with experimental open tibial fractures stabilized with internal fixation

Immediate internal fixation of severe open tibial fractures usually is contraindicated due to the high risk of infection. The objective of this study was to evaluate the efficacy of local antibiotic therapy with biodegradable poly-(DL-lactide-co-glycolide) cefazolin-loaded microspheres for the prevention of infection in experimental open fractures stabilized with internal fixation. Rabbits with experimental tibial fractures that were contaminated with Staphylococcus aureus were treated with local application of cefazolin microspheres, an equivalent local dose of free Ancef powder, or systemic Ancef therapy. The bones then were fixed with a four-hole plate, and the animals were observed for 8 weeks. Clinically, deep infection was present in 86% of control animals that received no antibiotics and in 60% of animals that received a 7 day course of systemic Ancef therapy. In contrast, no infections were noted among any of the surviving rabbits that received local therapy with either cefazolin microspheres or free Ancef powder. Significantly higher levels of serum cefazolin were measured at 1 h for animals treated with free Ancef powder (18.7 +/- 6.1 micrograms/ml) than for those treated with cefazolin microspheres (0.57 +/- 0.27 micrograms/ml). Follow-up studies are in progress to evaluate further the potential clinical benefits of local antibiotic therapy for the management of contaminated open fractures in humans.

The effect of scrubbing and irrigation with normal saline, povidone iodine, and cefazolin on wound bacterial counts in a guinea pig model

This study examines the effects of povidone iodine, normal saline, and cefazolin alone and after scrubbing on bacterial counts in contaminated animal lacerations. Twelve albino guinea pigs each received four lacerations inoculated with a standard inoculum of Staphylococcus aureus. Twelve hours after inoculation, each wound was biopsied to ensure contamination and then either treated or left as an untreated control. One wound on each animal was an untreated control. The remaining three lacerations on six pigs were irrigated with cefazolin (CZ) solution, normal saline, or 1% (wt/vol) povidone iodine solution (PI). Three lacerations on another six pigs were treated with 20% poloxamer 188 scrub (scrub) alone, scrub followed by PI irrigation (SCR/PI), or scrub followed by CZ irrigation (SCR/CZ). Quantitative bacteriology was performed on tissue biopsies 2 hours (time 1), 7 hours (time 2), and 12 hours (time 3) after irrigation. Posttreatment counts for PI, CZ, and normal saline irrigation were not different from control or one another (P > .05). Bacterial counts for SCR/PI were significantly lower than control (P < .05) for all posttreatment biopsies (1.8 to 2.9 mean log(10) decrease). SCR/CZ was significantly lower than control (P < .05) at times 2 and 3 only (1.7 to 2.0 mean log(10) decrease). In this guinea pig model, cleansing 12-hour-old lacerations contaminated with S aureus using SCR/PI or SCR/CZ significantly reduced bacterial counts over 12 hours.