A review of the scientific evidence for biofilms in wounds.

Both chronic and acute dermal wounds are susceptible to infection due to sterile loss of the innate barrier function of the skin and dermal appendages, facilitating the development of microbial communities, referred to as biofilms, within the wound environment. Microbial biofilms are implicated in both the infection of wounds and failure of those wounds to heal. The aim of this review is to provide a summary of published papers detailing biofilms in wounds, the effect they have on infection and wound healing, and detailing methods employed for their detection. The studies highlighted within this paper provide evidence that biofilms reside within the chronic wound and represent an important mechanism underlying the observed, delayed healing and infection. The reasons for this include both protease activity and immunological suppression. Furthermore, a lack of responsiveness to an array of antimicrobial agents has been due to the biofilms' ability to inherently resist antimicrobial agents. It is imperative that effective strategies are developed, tested prospectively, and employed in chronic wounds to support the healing process and to reduce infection rates. It is increasingly apparent that adoption of a biofilm-based management approach to wound care, utilizing the "antibiofilm tool box" of therapies, to kill and prevent reattachment of microorganisms in the biofilm is producing the most positive clinical outcomes and prevention of infection.

The visualisation and speed of kill of wound isolates on a silver alginate dressing.

In chronic wound management, alginate dressings are used to absorb exudate and reduce the microbial burden. Silver alginate offers the added benefit of an additional antimicrobial pressure on contaminating microorganisms. This present study compares the antimicrobial activity of a RESTORE silver alginate dressing with a silver-free control dressing using a combination of in vitro culture and imaging techniques. The wound pathogens examined included Candida albicans, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, ß-haemolytic Streptococcus, and strictly anaerobic bacteria. The antimicrobial efficacy of the dressings was assessed using log(10) reduction and 13-day corrected zone of inhibition (CZOI) time-course assays. Confocal laser scanning microscopy (CLSM) was used to visualise the relative proportions of live/dead microorganisms sequestered into the dressings over 24 hours and estimate the comparative speed of kill. The RESTORE silver alginate dressing showed significantly greater log(10) reductions and CZOIs for all microorganisms compared with the control, indicating the antimicrobial effect of ionic silver. Antimicrobial activity was evident against all test organisms for up to 5 days and, in some cases, up to 12 days following an on-going microbial challenge. Imaging bacteria sequestered in the silver-free dressing showed that each microbial species aggregated in the dressing and remained viable for more than 20 hours. Growth was not observed inside of the dressing, indicating a possible microbiostatic effect of the alginate fibres. In comparison, organisms in the RESTORE silver alginate dressing were seen to lose viability at a considerably greater rate. After 16 hours of contact with the RESTORE silver alginate dressing, >90% of cells of all bacteria and yeast were no longer viable. In conclusion, collectively, the data highlights the rapid speed of kill and antimicrobial suitability of this RESTORE silver alginate dressing on wound isolates and highlights its overwhelming ability to manage a microbial wound bioburden in the management of infected wounds.

An in vitro comparison of two silver-containing antimicrobial wound dressings .

 Preclinical studies have shown that release of silver by different wound dressings varies. The purpose of this in vitro study was to compare the antimicrobial activity of silver alginate (SA) and silver carboxymethylcellulose (SCM) dressings. An- timicrobial activity was tested using nine bacterial strains with log10 reduction and corrected zone of inhibition (CZOI) as- says. Antimicrobial effect was visualized using confocal microscopy (CLSM). Log10 reduction was comparable between both dressings for Staphylococcus aureus NCIMB 9518, Candida albicans ATCC 90028, Finegoldia magna NCTC 11804T, and Pseudomonas aeruginosa NCTC 10662. Log10 reduction was higher for SCM than SA dressing-exposed Escherichia coli (P = 0.035) and P. aeruginosa ATCC 15692 (P = 0.032), and lower for SCM than SA dressing-exposed Streptococcus pyogenes (P = 0.007), Peptoniphilus asaccharolyticus (P = 0.045), and S. aureus NCTC 8325 (P = 0.012). Both dressings were equivalent against four strains (5 to 8 days' activity) in the CZOI assay. SA dressing silver activity lasted >24 hours longer than SCM activity when exposed to C. albicans (9 days' activity), E. coli (7 days' activity), F. magna (5 days' activity), and P. asaccharolyticus (5 days' activity), whereas the SMC exhibited greater persistence against S. pyogenes (13 days' activity). CLSM showed complete kill of S. aureus after 20 hours for both dressings. The results of this study confirm the broad-spectrum, in vitro activity of some dressings containing ionic silver. The in vitro antimicrobial efficacy of both wound dressings was comparable, but clinical studies comparing the efficacy and effectiveness of silver-containing dressings to nonionic silver-containing dressings are needed.

Exploring the link between microorganisms and oral cancer: a systematic review of the literature.

The majority of cases of oral cancer have been related to tobacco use and heavy alcohol consumption. However, the incidence of oral cavity carcinoma appears to be increasing in many parts of the world in a manner that it is difficult to explain with traditional risk factors alone. Meanwhile, interest in the possible relationships between microorganisms and the different stages of cancer development has been rising and numerous mechanisms by which bacteria and yeast may initiate or promote carcinogenesis are currently under investigation. In particular, a persuasive body of evidence suggests a possible etiological role involving the metabolism and production of carcinogenic products, such as acetaldehyde. Other suggested mechanisms include the induction of chronic inflammation and direct interference with eukaryotic cell cycle and signaling pathways. This review aims to summarize the known associations between microbial infection and cancer and draw attention to how they may relate to oral carcinoma.

Characterization of Candida parapsilosis infection of an in vitro reconstituted human oral epithelium.

Oral candidosis is a common problem in immunocompromised patients, and whilst Candida albicans is regarded as the principal cause of infection, other non-Candida albicans Candida (NCAC) species are increasingly being recognized as human pathogens. Relatively little is known about the virulence factors associated with NCAC species, and the aim of this study was to use a reconstituted human oral epithelium (RHOE) to examine epithelial infection withCandida parapsilosis. Strains originating from the oral and vaginal mucosa and from the urinary tract were all shown to colonize RHOE in a strain-dependent manner. Strain differences were found in the colonizing morphology and in the extent of invasion of the RHOE. Low invasion of RHOE was detected for strains after 12 h, whereas extensive tissue damage was evident after 24 h when assessed using histological examination and lactate dehydrogenase activity determination. Tissue damage was reduced in the presence of pepstatin A, although C. parapsilosis invasion of the tissue was not inhibited. Real-time polymerase chain reaction of secreted aspartyl proteinase (SAP) genes (SAPP1-3) showed that expression was strain dependent, with an increased expression generally occurring for Candida infecting RHOE compared with planktonic equivalents. In summary, C. parapsilosis was not highly invasive of RHOE but did induce significant tissue damage, which could relate to specific SAPgene expression.

Prevotella histicola sp. nov., isolated from the human oral cavity.

Three strains of anaerobic, variably pigmenting, Gram-negative bacilli isolated from human oral mucosal tissue were subjected to a comprehensive range of phenotypic and genotypic tests and were found to comprise a homogeneous group. 16S rRNA gene sequence analysis and DNA-DNA hybridization revealed that the strains constituted a novel group within the genus Prevotella, being most closely related to Prevotella melaninogenica and Prevotella veroralis. A novel species, Prevotella histicola sp. nov., is proposed to accommodate these strains. Prevotella histicola is saccharolytic and produces acetic acid and succinic acid as major end products of fermentation and trace to minor amounts of isovaleric acid and lactic acid. The G+C content of the DNA of the type strain is 43 mol%. The type strain of Prevotella histicola is T05-04T (=DSM 19854T=CCUG 55407T).

A molecular analysis of the bacteria present within oral squamous cell carcinoma.

In order to characterize the bacterial microbiota present within oral cancerous lesions, tumorous and non-tumorous mucosal tissue specimens (approx. 1 cm(3)) were harvested from ten oral squamous cell carcinoma (OSCC) patients at the time of surgery. Any microbial contamination on the surface of the specimens was eliminated by immersion in Betadine and washing with PBS. Bacteria were visualized within sections of the OSCC by performing fluorescent in situ hybridization with the universal oligonucleotide probe, EUB338. DNA was extracted from each aseptically macerated tissue specimen using a commercial kit. This was then used as template for PCR with three sets of primers, targeting the 16S rRNA genes of Spirochaetes, Bacteroidetes and the domain Bacteria. PCR products were differentiated by TA cloning and bacterial species were identified by partial sequencing of the 16S rRNA gene fragments. A total of 70 distinct taxa was detected: 52 different phylotypes isolated from the tumorous tissues, and 37 taxa from within the non-tumorous specimens. Differences between the composition of the microbiotas within the tumorous and non-tumorous mucosae were apparent, possibly indicating selective growth of bacteria within carcinoma tissue. Most taxa isolated from within the tumour tissue represented saccharolytic and aciduric species. Whether the presence of these bacteria within the mucosa has any bearing on the carcinogenic process is a concept worthy of further investigation.

Viable bacteria present within oral squamous cell carcinoma tissue.

Despite increasing interest in the possible relationships between bacteria and the different stages of cancer development, the association of bacteria with cancer of the oral cavity has yet to be adequately examined. With that in mind, the primary objective of this study was to identify any bacterial species within oral squamous cell carcinoma tissue using a standard microbiological culture approach. At the time of surgery, a 1-cm3 portion of tissue was harvested from deep within the tumor mass using a fresh blade for each cut. Whenever possible, "superficial" portions from the mucosa overlying the tumor and nontumorous control specimens from at least 5 cm away from the primary tumor site were also obtained. Surface contamination was eliminated by immersion in Betadine and washing with phosphate-buffered saline. Each specimen was aseptically macerated and cultured on nonselective media under both aerobic and anaerobic conditions. Isolates were identified by 16S rRNA gene sequencing. Twenty deep-tissue specimens, 19 with corresponding superficial tissues and 12 with control tissues, were successfully processed. A diversity of bacterial taxa were isolated and identified, including several putatively novel species. Most isolates were found to be saccharolytic and acid-tolerant species. Notably, some species were isolated only from either the tumorous or nontumorous tissue type, indicating a degree of restriction. Successful surface decontamination of the specimens indicates that the bacteria detected were from within the tissue. A diversity of bacterial groups have been isolated from within oral squamous cell carcinoma tissue. The significance of these bacteria within the tumor warrants further study.