Tiaan Heunis

Nanofibers Offer Alternative Ways to the Treatment of Skin Infections

Injury to the skin causes a breach in the protective layer surrounding the body. Many pathogens are resistant to antibiotics, rendering conventional treatment less effective. This led to the use of alternative antimicrobial compounds, such as silver ions, in skin treatment. In this review nanofibers, and the incorporation of natural antimicrobial compounds in these scaffolds, are discussed as an alternative way to control skin infections. Electrospinning as a technique to prepare nanofibers is discussed. The possibility of using these structures as drug delivery systems is investigated.

Evaluation of a Nisin-Eluting Nanofiber Scaffold To Treat Staphylococcus aureus-Induced Skin Infections in Mice

ABSTRACT Staphylococcus aureus is a virulent pathogen and a major causative agent of superficial and invasive skin and soft tissue infections (SSSTIs). Antibiotic resistance in S. aureus, among other bacterial pathogens, has rapidly increased, and this is placing an enormous burden on the health care sector and has serious implications for infected individuals, especially immunocompromised patients. Alternative treatments thus need to be explored to continue to successfully treat infections caused by S. aureus, including antibiotic-resistant strains of S. aureus. In this study, an antimicrobial nanofiber wound dressing was generated by electrospinning nisin (Nisaplin) into poly(ethylene oxide) and poly(d,l-lactide) (50:50) blend nanofibers. Active nisin diffused from the nanofiber wound dressings for at least 4 days in vitro, as shown by consecutive transfers onto plates seeded with strains of methicillin-resistant S. aureus (MRSA). The nisin-containing nanofiber wound dressings significantly reduced S. aureus Xen 36 bioluminescence in vivo and viable cell numbers in a murine excisional skin infection model. The bacterial burden of wounds treated with nisin-containing nanofiber wound dressings was 4.3 × 102 CFU/wound, whereas wounds treated with control nanofiber wound dressings had 2.2 × 107 CFU/wound on the last day of the trial (day 7). Furthermore, the wound dressings stimulated wound closure of excisional wounds, and no adverse effects were observed by histological analysis. Nisin-containing nanofiber wound dressings have the potential to treat S. aureus skin infections and to potentially accelerate wound healing of excisional wounds.

Release of bacteriocins from nanofibers prepared with combinations of poly(D,L-lactide) (PDLLA) and poly(ethylene oxide) (PEO)

Plantaricin 423, produced by Lactobacillus plantarum, and bacteriocin ST4SA produced by Enterococcus mundtii, were electrospun into nanofibers prepared from different combinations of poly(d,l-lactide) (PDLLA) and poly(ethylene oxide) (PEO) dissolved in N,N-dimethylformamide (DMF). Both peptides were released from the nanofibers with a high initial burst and retained 88% of their original antimicrobial activity at 37 °C. Nanofibers have the potential to serve as carrier matrix for bacteriocins and open a new field in developing controlled antimicrobial delivery systems for various applications.

Proteomic Profiling of the Acid Stress Response in Lactobacillus plantarum 423

Acid tolerance is considered an important characteristic of probiotic bacteria. Lactobacillus plantarum 423 tolerates acidic pH and is the ideal candidate in which to study molecular mechanisms that acid-tolerant lactic acid bacteria employ to survive such conditions. In this study we recorded changes in the protein profile of L. plantarum 423 when exposed to pH 2.5 by using a gel-free nanoLC-MS/MS proteomics approach. In total, 97 proteins were detected as more abundant, and 12 proteins were detected solely when strain 423 was exposed to pH 2.5. General stress response proteins, the utilization of a variety of carbohydrate sources in a glucose rich environment, altered pyruvate metabolism, increased lysine biosynthesis, and a significant oxidative stress response was observed in acid-stressed cells. The accumulation of basic compounds also seemed to play an integral role in the response to acid stress. We observed a marked decrease in proteins involved in cell wall and phospholipid biosynthesis, transcription, translation, and cell division. The most abundant protein detected was an uncharacterized protein, JDM1_2142. Functional analysis revealed that this protein plays a role in survival during acid stress. Our results contribute to the growing body of knowledge on the molecular mechanisms employed by lactobacilli, in particular L. plantarum, to ensure survival in acidic conditions.

Release of Enterococcus mundtii Bacteriocin ST4SA from Self-Setting Brushite Bone Cement

Maxillofacial and craniofacial surgery is on the increase, which exposes more patients at risk of acquiring microbial infections. The use of antibiotic-loaded calcium phosphate bone cements has been shown to reduce the incidence of infection. A marked increase in antibiotic-resistant pathogens, including multidrug-resistant pathogens, has been reported. This has led to the investigation of various compounds as alternatives to conventional treatments. In this paper, we report on the incorporation and release of a broad-spectrum class II antimicrobial peptide, bacteriocin ST4SA produced by Enterococcus mundtii, into a calcium orthophosphate-based bone cement. Our results suggest class II bacteriocins may be incorporated into self-setting bone cements to produce implants with antimicrobial activity over extended periods of time.