Therapeutics and delivery vehicles for local treatment of osteomyelitis

Osteomyelitis, or the infection of the bone, presents a major complication in orthopedics and may lead to prolonged hospital visits, implant failure, and in more extreme cases, amputation of affected limbs. Typical treatment for this disease involves surgical debridement followed by long-term, systemic antibiotic administration, which contributes to the development of antibiotic-resistant bacteria and has limited ability to eradicate challenging biofilm-forming pathogens including Staphylococcus aureus—the most common cause of osteomyelitis. Local delivery of high doses of antibiotics via traditional bone cement can reduce systemic side effects of an antibiotic. Nonetheless, growing concerns over burst release (then subtherapeutic dose) of antibiotics, along with microbial colonization of the nondegradable cement biomaterial, further exacerbate antibiotic resistance and highlight the need to engineer alternative antimicrobial therapeutics and local delivery vehicles with increased efficacy against, in particular, biofilm-forming, antibiotic-resistant bacteria. Furthermore, limited guidance exists regarding both standardized formulation protocols and validated assays to predict efficacy of a therapeutic against multiple strains of bacteria. Ideally, antimicrobial strategies would be highly specific while exhibiting a broad spectrum of bactericidal activity. With a focus on S. aureus infection, this review addresses the efficacy of novel therapeutics and local delivery vehicles, as alternatives to the traditional antibiotic regimens. The aim of this review is to discuss these components with regards to long bone osteomyelitis and to encourage positive directions for future research efforts.     

慢性伤口细菌生物膜感染的研究进展

细菌生物膜感染已被证实与慢性伤口的迁延不愈密切相关,此类伤口若治疗控制不佳,伤口极易恶化甚至引发全身感染导致患者死亡。因此,如何有效预防及治疗慢性伤口细菌生物膜感染已成为全球伤口管理专家关注的热点问题。本文就慢性伤口细菌生物膜感染的定义、流行病学、常见致病菌及其产生生物膜的能力、形成机制、影响因素、识别诊断、治疗策略等方面进行综述,旨在为临床更好的认识、管理慢性伤口细菌生物膜感染,以期提高此类伤口的治疗效果。     

Impact of environmental biofilms: Industrial components and its remediation

The growth of technology and requirements globally for various commodities has brought about new challenges. Biofilms are aggregations of microbial cells, which contaminate and spoil industrial components and environments. These microbial cells with extracellular polymeric substances colonize living and nonliving surfaces and pose a serious problem for all industries, affecting their processes, leading to a reduction of product quality and economic loss. Industries, such as medical, food, water, dairy, wine, marine, power plants are exposed to biofilm formation. Pipe blockages, waterlogging and reduction of the heat-transfer efficiency, hamper the operating system of plants. Many industries do not set up remedial measures to control biofilm formation as they are not aware of this threat. Various conventional methods to control these biofilms are adopted by industries in their regular workflow, but these are temporary solutions. This calls for further research into remediation of the biofilm and its control for industrial components. This review article addresses the problems of biofilms and proposes solutions for various industrial components. Nanotechnology promises several options, and bring about a new aspect into the industrial economy, by solving the problems of environmental biofilms.     

The efficacy of immediate versus delayed antibiotic administration on bacterial growth and biofilm production of selected strains of uropathogenic Escherichia coli and Pseudomonas aeruginosa

Purpose

The treatment of urinary tract infections (UTI) with antibiotics is commonly used, but recurrence and antibiotic resistance have been growing and concerning clinicians. We studied whether the rapid onset of a protective biofilm may be responsible for the lack of effectiveness of antibiotics against selected bacteria.

Materials and Methods

Two established uropathogenic Escherichia coli strains, UTI89 and CFT073, and two Pseudomonas aeruginosa strains, PA01 and Boston-41501, were studied to establish a reliable biofilm formation process. Bacterial growth (BG) was determined by optical density at 600 nm (OD 600) using a spectrophotometer, while biofilm formation (BF) using crystal violet staining was measured at OD 550. Next, these bacterial strains were treated with clinically relevant antibiotics, ciprofloxacin HCl (200 ng/mL and 2 μg/mL), nitrofurantoin (20 μg/mL and 40 μg/mL) and ampicillin (50 μg/mL) at time points of 0 (T0) or after 6 hours of culture (T6). All measurements, including controls (bacteria -1% DMSO), were done in triplicates and repeated three times for consistency.

Results

The tested antibiotics effectively inhibited both BG and BF when administered at T0 for UPEC strains, but not when the antibiotic administration started 6 hours later. For Pseudomonas strains, only Ciprofloxacin was able to significantly inhibit bacterial growth at T0 but only at the higher concentration of 2 μg/mL for T6.

Conclusion

When established UPEC and Pseudomonas bacteria were allowed to culture for 6 hours before initialization of treatment, the therapeutic effect of selected antibiotics was greatly suppressed when compared to immediate treatment, probably as a result of the protective nature of the biofilm.     

Effect of iron on bovine enamel and on the composition of the dental biofilm formed "in situ"

OBJECTIVES: This study investigated in situ the effect of iron (Fe) on the reduction of demineralization of bovine enamel, as well as on the composition of dental biofilm. DESIGN AND METHODS: Twelve volunteers were included in this blind crossover study, which was conducted in two stages of 14 days each. For each stage, the volunteers received palatal appliances containing four blocks of bovine enamel (4 mm x4 mm x 2.5 mm). Six volunteers dripped a solution of 15 mmol L(-1) ferrous sulphate onto the fragments and the remaining six dripped deionized water (eight times per day). After five minutes, a fresh 20% (w/v) sucrose solution was dripped onto all enamel blocks. During the experimental period the volunteers brushed their teeth with non-fluoridated dentifrice. After each stage, the percentage of surface microhardness change (%SMHC) and area of mineral loss (DeltaZ) were determined on enamel and the dental biofilm formed on the blocks was collected and analysed for F, P, Ca, Fe and alkali-soluble carbohydrates. The concentrations of F, Ca and Fe in enamel were also analysed after acid biopsies. RESULTS: There was a statistically significant increase in the P and Fe concentrations in the biofilms treated with ferrous sulphate (p<0.05), which was not observed for F, Ca and alkali-soluble carbohydrates. The group treated with ferrous sulphate had significantly lower %SMHC and DeltaZ when compared to control (p<0.05). CONCLUSIONS: These results showed that ferrous sulphate reduced the demineralization of enamel blocks and altered the ionic composition of the dental biofilm formed in situ.     

Synergy between Tannerella forsythia and Fusobacterium nucleatum in biofilm formation

During dental plaque formation, the interaction of different organisms is important in the development of complex communities. Fusobacterium nucleatum is considered a 'bridge-organism' that facilitates colonization of other bacteria by coaggregation-mediated mechanisms and possibly by making the environment conducive for oxygen intolerant anaerobes. These studies were carried out to determine whether coaggregation between F. nucleatum and Tannerella forsythia is important in the formation of mixed species biofilms. Further, the role of BspA protein, a surface adhesin of T. forsythia, in coaggregation and biofilm formation was investigated. The results showed the development of synergistic mixed biofilms of F. nucleatum and T. forsythia when these bacteria were cocultured. The BspA protein was not involved in biofilm formation. Though BspA plays a role in coaggregation with F. nucleatum, presumably other adhesins are also involved. The synergistic biofilm formation between the two species was dependent on cell-cell contact and soluble components of the bacteria were not required. This study demonstrates that there is a positive synergy between F. nucleatum and T. forsythia in the development of mixed biofilms and that the cell-cell interaction is essential for this phenomenon.     

Biofilm on the apical region of roots in primary teeth with vital and necrotic pulps with or without radiographically evident apical pathosis

Aim  To evaluate, by scanning electron microscopy (SEM), the presence of biofilms on the external surfaces of the apical third of roots of human primary teeth with vital or necrotic pulps with and without radiographically evident periradicular pathosis.
Methodology  Eighteen teeth were selected: group I – normal pulp ( n  = 5), group II – pulp necrosis without radiographic evidence of periapical pathosis ( n  = 7) and group III – pulp necrosis with well-defined radiographic periapical pathosis ( n  = 6). After extraction, the teeth were washed with saline and immersed in 0.03 g mL⁻¹ trypsin solution for 20 min. The teeth were then washed in sodium cacodilate buffer and stored in receptacles containing modified Karnovsky solution. The teeth were sectioned, dehydrated in an ethanol series, critical-point dried with CO₂, sputter coated with gold and the external root surface in the apical third examined by SEM.
Results  In the teeth of groups I and II, the apical root surfaces were covered by collagen fibres, with no evidence of bacteria (100%). In the teeth of group III, the root apices had no collagen fibres but revealed resorptive areas containing microorganisms (cocci, bacilli, filaments and spirochetes) in all cases (100%).
Conclusion  Microorganisms organized as biofilms on the external root surface (extraradicular infection) were detected in primary teeth with pulp necrosis and radiographically visible periapical pathosis.     

Effect of chlorhexidine/thymol and fluoride varnishes on dental biofilm formation in vitro

This study evaluated the effect of chlorhexidine/thymol (CHX/T) and fluoride (F) varnishes on biofilm formation in vitro. Hydroxyapatite discs coated with varnish were first immersed in saline for 0, 3, 7 or 14 d, then immersed in pasteurized saliva. The discs were incubated for 20 h with a bacterial suspension containing Actinomyces naeslundii, Fusobacterium nucleatum, Streptococcus oralis, and Veillonella dispar. Uncoated discs were used as controls. Growth of bacteria on the discs was evaluated by culture and by scanning electron microscopy (SEM). Bacterial vitality was examined by fluorescence staining. In the CHX/T-treated group, bacterial accumulation was delayed, and the total number of bacteria was significantly lower than in the controls. In the F-treated group, the total number of bacteria did not differ from the control, although the number of S. oralis was lower. Bacterial vitality in the CHX/T and F groups did not differ from that in the controls. The total number of bacteria on the CHX/T-treated discs immersed in saline was significantly higher than that on the non-immersed discs. Biofilm development was inhibited by the CHX/T varnish but not by the F varnish. The effect of the CHX/T varnish decreased following the immersion of discs in saline.