Bacteriological pathogen spectrum of chronic leg ulcers: Results of a multicenter trial in dermatologic wound care centers differentiated by regions

How effective is simple mechanical wound debridement in reducing bacterial colonisation? Results of a prospective clinical study

BACKGROUND AND AIMS

Bacteria in wounds can lead to stagnation of wound healing as well as to local or even systemic wound infections up to potentially lethal sepsis. Consequently, the bacterial load should be reduced as part of wound treatment. Therefore, the efficacy of simple mechanical wound debridement should be investigated in terms of reducing bacterial colonisation.

PATIENTS AND METHODS

Patients with acute or chronic wounds were assessed for bacterial colonisation with a fluorescence camera before and after mechanical wound debridement with sterile cotton pads. If bacterial colonisation persisted, a second, targeted wound debridement was performed.

RESULTS

A total of 151 patients, 68 (45.0%) men and 83 (55.0%) women were included in this study. The male mean age was 71.0 years and the female 65.1 years. By establishing a new analysis method for the image files, we could document that the bacterial colonised areas were distributed 21.9% on the wound surfaces, 60.5% on the wound edges (up to 0.5 cm) and 17.6% on the wound surroundings (up to 1.5 cm). One mechanical debridement achieved a significant reduction of bacterial colonised areas by an average of 29.6% in the wounds, 18.9% in the wound edges and 11.8% in the wound surroundings and was increased by performing it a second time.

CONCLUSIONS

It has been shown that even a simple mechanical debridement with cotton pads can significantly reduce bacterial colonisation without relevant side effects. In particular, the wound edges were the areas that were often most contaminated with bacteria and should be included in the debridement with special attention. Since bacteria remain in wounds after mechanical debridement, it cannot replace antimicrobial therapy strategies, but offer a complementary strategy to improve wound care. Thus, it could be shown that simple mechanical debridement is effective in reducing bacterial load and should be integrated into a therapeutic approach to wounds whenever appropriate.

Quantitative Insights and Visualization of Antimicrobial Tolerance in Mixed-Species Biofilms

Biofilms are a major problem in hard-to-heal wounds. Moreover, they are composed of different species and are often tolerant to antimicrobial agents. At the same time, interspecific synergy and/or competition occurs when some bacterial species clash. For this reason, the tolerance of two dual-species wound biofilm models of Pseudomonas aeruginosa and Staphylococcus aureus or Enterococcus faecium against antimicrobials and antimicrobial dressings were analyzed quantitatively and by confocal laser scanning microscopy (CLSM). The results were compared to findings with planktonic bacteria. Octenidine-dihydrochloride/phenoxyethanol and polyhexamethylene biguanide (PHMB) irrigation solutions showed a significant, albeit delayed reduction in biofilm bacteria, while the PHMB dressing was not able to induce this effect. However, the cadexomer-iodine dressing caused a sustained reduction in and killed almost all bacteria down to 102 cfu/mL within 6 days compared to the control (1010 cfu/mL). By means of CLSM in untreated human biofilm models, it became evident that P. aeruginosa dominates over E. faecium and S. aureus. Additionally, P. aeruginosa appeared as a vast layer at the bottom of the samples, while S. aureus formed grape-like clusters. In the second model, the distribution was even clearer. Only a few E. faecium were visible, in contrast to the vast layer of P. aeruginosa. It seems that the different species avoid each other and seek their respective niches. These mixed-species biofilm models showed that efficacy and tolerance to antimicrobial substances are nearly species-independent. Their frequent application appears to be important. The bacterial wound biofilm remains a challenge in treatment and requires new, combined therapy options.

Human skin biofilm model: translational impact on swabbing and debridement

OBJECTIVE

Wound biofilms are one of the greatest challenges in the therapy of hard-to-heal (chronic) wounds, as potent antimicrobial substances fail to eradicate bacteria within short incubation periods. Preclinical investigations using novel model systems that closely mimic the human wound environment and wound biofilm are required to identify new and effective therapeutic options. This study aims to identify bacterial colonisation patterns that are relevant for diagnosis and therapy.

METHOD

In this study, a recently established human plasma biofilm model (hpBIOM) was incorporated into a wound within human dermal resectates after abdominoplasty. The interaction of the biofilm-forming bacteria meticillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa with the skin cells was investigated. Possible effects on wound healing processes in correlation with the persistence of the biofilm in the wound environment were analysed in patients with leg ulcers of different aetiologies and biofilm burden.

RESULTS

Using haematoxylin and eosin staining, species-dependent infiltration modes of the bacteria into the wound tissue were determined for the pathogens MRSA and Pseudomonas aeruginosa. The spreading behaviour correlated with clinical observations of the spatial distributions of the bacteria. In particular, the clinically prominent Pseudomonas aeruginosa-specific distension of the wound margin was identified as epidermolysis due to persistent infiltration.

CONCLUSION

The hpBIOM applied in this study represents a potential tool for preclinical analyses dealing with approval processes for new antimicrobial applications. In terms of clinical practice, a microbiological swabbing technique including the wound margin should be routinely applied to prevent wound exacerbation.

Relative Abundance and Detection of Pseudomonas aeruginosa from Chronic Wound Infections Globally

Pseudomonas aeruginosa is a difficult-to-treat pathogen that is frequently involved with chronic wound infections. Here, we conducted a literature search of world-wide studies published between 2005 and 2022 that described the microbiological profiles of chronic wound infections. For each continent, a hierarchy of pathogens was created to define the organisms that were most frequently isolated in each region. Except for South America, P. aeruginosa was the second most common organism in each major continent, with Staphylococcus aureus being the most abundant pathogen overall. When individual countries were evaluated, P. aeruginosa was the most frequently isolated organism in several Southeast Asia nations including India and Malaysia. P. aeruginosa was less commonly isolated from diabetic foot infections in North America, Europe, and Africa in comparison to other types of chronic wound infections. Additionally, the Levine wound swab technique may be a quick and painless way to isolate P. aeruginosa from wound infections, but the isolation of P. aeruginosa does not seem to be an informative predictor of the patient's clinical course. A multivariate risk assessment that accounts for the regional frequency of P. aeruginosa isolation may be an appropriate way to guide empiric management of chronic wound infections.

Inhibition of bacterial growth through LED (light-emitting diode) 465 and 630 nm: in vitro

Photobiomodulation has been used to inactivate bacterial growth, in different laser or LED protocols. Thus, the aim of this study was to verify the inhibition of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, in ATCC strains and bacteria collected from patients with skin burns, after irradiation with LED; 300 μl of saline solution with bacterial suspension was irradiated at a concentration of 0.5-0.63, by the McFarland scale, after five serial dilutions, with evaluation of pre- and post-irradiation pH and temperature control. The cultures were placed in a bacteriological incubator at 37 °C for 24 h for later counting of colony-forming units (CFU). Data were analyzed by Shapiro-Wilk tests and single-factor ANOVA, with Tukey post hoc (p < 0.05). Both wavelengths and energy densities tested showed inhibition of bacterial growth. The comparison of the irradiated groups (ATCC) with the control group showed the following: S. aureus and P. aeruginosa 465 nm (40 J/cm²) and 630 nm (50 J/cm²) and E. coli 465 nm (40 J/cm²) and 630 nm (30 J/cm²). Among the ATCC S. aureus groups, there was a difference for 630 nm (30 J/cm²) and 465 nm (30, 40, 50 J/cm²). The bacteria from the burned patients were S. aureus (30 and 50 J/cm²) and P. aeruginosa (50 J/cm²). We conclude that different bacterial strains were reduced into colony-forming units after LED irradiation.

Rapid Diagnosis of Pseudomonas aeruginosa in Wounds with Point-Of-Care Fluorescence Imaing

Pseudomonas aeruginosa (PA) is a common bacterial pathogen in chronic wounds known for its propensity to form biofilms and evade conventional treatment methods. Early detection of PA in wounds is critical to the mitigation of more severe wound outcomes. Point-of-care bacterial fluorescence imaging illuminates wounds with safe, violet light, triggering the production of cyan fluorescence from PA. A prospective single blind clinical study was conducted to determine the positive predictive value (PPV) of cyan fluorescence for the detection of PA in wounds. Bacterial fluorescence using the MolecuLight i:X imaging device revealed cyan fluorescence signal in 28 chronic wounds, including venous leg ulcers, surgical wounds, diabetic foot ulcers and other wound types. To correlate the cyan signal to the presence of PA, wound regions positive for cyan fluorescence were sampled via curettage. A semi-quantitative culture analysis of curettage samples confirmed the presence of PA in 26/28 wounds, resulting in a PPV of 92.9%. The bacterial load of PA from cyan-positive regions ranged from light to heavy. Less than 20% of wounds that were positive for PA exhibited the classic symptoms of PA infection. These findings suggest that cyan detected on fluorescence images can be used to reliably predict bacteria, specifically PA at the point-of-care.

Prospective clinical study on the efficacy of bacterial removal with mechanical debridement in and around chronic leg ulcers assessed with fluorescence imaging

Bacterial colonisation in wounds delays healing, mandating regular bacterial removal through cleaning and debridement. Real-time monitoring of the efficacy of mechanical debridement has recently become possible through fluorescence imaging. Red fluorescence, endogenously produced during bacterial metabolism, indicates regions contaminated with live bacteria (>104 CFU/g). In this prospective study, conventional and fluorescence photos were taken of 25 venous leg ulcers before and after mechanical debridement, without use of antiseptics. Images were digitally segmented into wound bed and the periwound regions (up to 1.5 cm outside bed) and pixel intensity of red fluorescence evaluated to compute bacterial area. Pre-debridement, bacterial fluorescence comprised 10.4% of wound beds and larger percentages of the periwound area (~25%). Average bacterial reduction observed in the wound bed after a single mechanical debridement was 99.4% (p<0.001), yet periwound bacterial reduction was only 64.3%. On average, across bed and periwound, a single mechanical debridement left behind 29% of bacterial fluorescence positive tissue regions. Our results show the substantial effect that safe, inexpensive, mechanical debridement can have on bacterial load of venous ulcers without antiseptic use. Fluorescence imaging can localise bacterial colonised areas and showed persistent periwound bacteria post-debridement. Fluorescence-targeted debridement can be used quickly and easily in daily practice.

Bacterial Isolates and Their Antibiotics Susceptibility Pattern Among Patients Admitted With Chronic Lower Limb Ulcers at Kilimanjaro Christian Medical Centre Northern Zone Referral Hospital, Tanzania

Objective. To identify the bacterial isolates and their antibiotics susceptibility pattern among patients with lower limb ulcers admitted at a tertiary hospital in northern Tanzania. Methodology. A cross-sectional study was conducted between April and July 2018 at the Kilimanjaro Christian Medical Centre. Questionnaire was used to obtain the demographics and clinical information of participants. Wound samples were collected and culture method used to identify the bacteria and their susceptibility patterns. Results. Out of 65 participants, 55 (84.6%) had positive aerobic bacterial growth. Twelve (18 %) participants had more than one bacterium. Fifty-nine (88.1%) were gram-negative bacteria. Proteus vulgaris (13, 19.9%), Pseudomonas spp (10, 14.8%), and Staphylococcus aureus (8, 11.7%) were the common isolates. Out of 59 gram-negative bacterial, 47 (78%) were sensitive to amikacin. Staph were sensitive to oxacillin (75%; n = 8) and vancomycin (50%; n = 8). Gram-negative were common isolates and were resistant to amoxicillin/clavulanic acid but sensitive to amikacin. Conclusion. The observed resistance to antibiotics calls for continuous monitoring of the resistance pattern to guide the empirical management of patients with leg ulcer.

[Modern wound treatment-from best practice to innovation]

According to the Research Group for Primary Medical Care (PMV), approximately 890,000 people in Germany were suffering from a chronic wound in 2012. This corresponds to a prevalence of 1.1%. Ulcus cruris, diabetic ulcers and decubital ulcers are among the most frequent causes of chronic wounds (57-80%). The guarantee for successful wound care is based on a good understanding of the physiology of the wound healing process. A disorder of the phase-like course can lead to complications, delays or suspension of wound healing. There are many reasons for pathological wound healing including infections, oxygen deficiency and non-phase-adapted wound care. In addition to established wound products, innovative products such as dermal matrixes, cold plasma therapy and platelet-rich plasma represent promising therapeutic alternatives for non-healing chronic wounds.

Arthrospira Platensis - Potential in Dermatology and Beyond

The search for natural products with benefits for health in general and of potential for treating human disease has gained wider interest world-wide. Here, we analyse current data on the microalga Arthrospira platensis (AP), that has been used in nutrition since ancient times in Fare East and African communities, for medical purposes with a focus on dermatology. Extracts of AP have been investigated in vitro and in vivo. The alga is rich in proteins, lipopolysaccharides and gamma-linolenic acid. AP extracts, phycocyanin compounds and polysaccharide calcium spirulan (Ca-SP) have been evaluated in various models. It could be demonstrated, that AP has significant antioxidant activity, prevents viruses from entry into target cells and inhibits the colonisation of wounds by multi-resistant bacteria. Furthermore, anti-cancer activity was documented in models of oral cancer, melanoma, and UV-induced non-melanoma skin cancer.

Autolytic debridement and management of bacterial load with an occlusive hydroactive deressing impregnated with polyhexamethylene biguanide

Background:

Debridement and control of bacterial load are key-points of wound care. The aim of this study is to evaluate the effectiveness of autolytic debridement and management of bacterial load (bioburden) of an occlusive hydro-active dressing impregnated with polyhexamethylene biguanide (PHMB).

Methods:

We used an occlusive dressing of hydro-active for leg ulcers’ treatment (TenderWet-plus® – Hartmann). Inclusion criteria were: presence of a fibrinous ulcer with multiple etiopathogenesis, in absence of clinical infection, no hypersecretion and diameter within 5 cm. Swab for bacterial bioburden control were made at start of the study, after 3 and 7 days. We made also a measurement of the amount of granulation tissue and of pain with VAS scale; bacterial bioburden control inside the dressing was made too.

Results:

28 leg ulcers were treated (12 venous, 5 diabetic, 8 thraumatic, 3 mixed) in 25 patients. The ulcer has been completely covered with fibrin in almost all cases and the bacterial load was represented mainly by Staphylococcus aureus (80% of the cases) with a load within 10.000UFC/plate in 81,5% of the cases. Control at 3 and 7 days have shown the appearance of granulaton tissue up to 67,8% of the wound surface. Bacterial bioburden (load) remained constant in 50% of the cases, decreased in 15%, increased in 35% of the cases.

Conclusion:

TenderWet-plus® has proven to be effective and quick in autolytic debridement and at the same time be able to handle the bacterial load in most cases. It can then be used for home treatment. (www.actabiomedica.it)

Biofilm is a Major Virulence Determinant in Bacterial Colonization of Chronic Skin Ulcers Independently from the Multidrug Resistant Phenotype

Bacterial biofilm is a major factor in delayed wound healing and high levels of biofilm production have been repeatedly described in multidrug resistant organisms (MDROs). Nevertheless, a quantitative correlation between biofilm production and the profile of antimicrobial drug resistance in delayed wound healing remains to be determined. Microbial identification, antibiotic susceptibility and biofilm production were assessed in 135 clinical isolates from 87 patients. Gram-negative bacteria were the most represented microorganisms (60.8%) with MDROs accounting for 31.8% of the total isolates. Assessment of biofilm production revealed that 80% of the strains were able to form biofilm. A comparable level of biofilm production was found with both MDRO and not-MDRO with no significant differences between groups. All the methicillin-resistant Staphylococcus aureus (MRSA) and 80% of Pseudomonas aeruginosa MDR strains were found as moderate/high biofilm producers. Conversely, less than 17% of Klebsiella pneumoniae extended-spectrum beta-lactamase (ESBL), Escherichia coli-ESBL and Acinetobacter baumannii were moderate/high biofilm producers. Notably, those strains classified as non-biofilm producers, were always associated with biofilm producer bacteria in polymicrobial colonization. This study shows that biofilm producers were present in all chronic skin ulcers, suggesting that biofilm represents a key virulence determinant in promoting bacterial persistence and chronicity of ulcerative lesions independently from the MDRO phenotype.

Blue Laser Inhibits Bacterial Growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa

OBJECTIVE

The purpose of this study was to analyze the influence of blue laser on bacterial growth of the main species that usually colonize cutaneous ulcers, as well as its effect over time following irradiation.

BACKGROUND DATA

The use of blue laser has been described as an adjuvant therapeutic method to inhibit bacterial growth, but there is no consensus about the best parameters to be used.

METHODS

Strains of Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 25922 were suspended in saline solution at a concentration of 1.5×10(3) colony forming units (CFU)/mL. Next, 300 μL of this suspension was transferred to a microtitulation plate and exposed to a single blue laser irradiation (450 nm) at fluences of 0 (control), 3, 6, 12, 18, and 24 J/cm(2). Each suspension was spread over the surface of a Petri plate before being incubated at 37°C, and counts of CFU were determined after 24 and 48 h.

RESULTS

Blue laser inhibited the growth of S. aureus and P. aeruginosa at fluences >6 J/cm(2). On the other hand, E. coli was inhibited at all fluences tested, except at 24 J/cm(2).

CONCLUSIONS

Blue laser light was capable of inhibiting bacterial growth at low fluences over time, thus presenting no time-dependent effect.

Aetiology, comorbidities and cofactors of chronic leg ulcers: retrospective evaluation of 1 000 patients from 10 specialised dermatological wound care centers in Germany

Numerous comorbidities and cofactors have been known to influence wound healing processes. In this multicentre study, clinical data of 1 000 patients with chronic leg ulcers from ten specialised dermatological wound care centers were analysed. The patient cohort comprised 567 females and 433 males with an average age of 69·9 years. The wounds persisted on average for 40·8 months and had a mean size of 43·7 cm(2) . Venous leg ulcers represented the most common entity accounting for 51·3% of all chronic wounds, followed by mixed-type ulcers in 12·9% and arterial ulcerations in 11·0% of the patients. Vasculitis was diagnosed in 4·5%, trauma in 3·2%, pyoderma gangrenosum in 2·8%, lymphoedema in 1·7%, neoplasia in 1·0% and delayed post-surgical wound healing in 0·6% of the included patients. In total, 70·5% of patients suffered from arterial hypertension, 45·2% were obese, 27·2% had non-insulin dependent diabetes, and 24·4% dyslipidaemia. Altogether 18·4% suffered from metabolic syndrome. Cofactors and comorbidities of patients with chronic leg ulcers have previously been studied but not in detail. Here, we were able to demonstrate the existence of several potentially relevant cofactors, comorbidities of their associations and geographical distributions, which should be routinely examined in patients with chronic leg ulcers and - if possible - treated.

Virulence and resistance features of Pseudomonas aeruginosa strains isolated from chronic leg ulcers

Background

The purpose of this study was to evaluate the virulence profiles of Pseudomonas aeruginosa clinical strains recently isolated from patients hospitalized for chronic leg ulcers in the Dermatology Department of Central Military Emergency University Hospital “Carol Davila”, Bucharest, Romania.

Methods

The phenotypic screening evaluated eight soluble virulence factors (haemolysins, lecithinase, lipase, caseinase, gelatinase, amylase, DNase, aesculin hydrolysis), as well as adherence ability (Cravioto adapted method) and invasion capacity on HeLa cells (gentamicin protection assay). Seven virulence genes encoding for protease IV, 3 exoenzymes (exoS, exoT, exoU), two phospholipases plcH- haemolytic phospholipase C and plcN- non-haemolytic phospholipase C) and alginate were investigated by PCR.

Results

The pore forming toxins and enzymes were expressed in variable proportions, the majority of the tested strains producing beta haemolysin (92.3 %), lipase (76.9 %) and lecithinase (61.5 %). The most frequent virulence genes detected in the analyzed strains were the ExoT (100 %) and AlgD (92.3 %) genes, genes codifying for phospholipases (84.6 % each of them) and for protease IV (61.5 %).

Conclusions

This study reveals that correlating virulence profiles and infection clinical outcome is very useful for setting up efficient preventive and therapeutic procedures for hospitalized patients with chronic leg ulcers and positive P. aeruginosa cultures.

Red and infrared laser therapy inhibits in vitro growth of major bacterial species that commonly colonize skin ulcers

Low-level laser therapy (LLLT) is used in chronic wounds due to its healing effects. However, bacterial species may colonize these wounds and the optimal parameters for effective bacterial inhibition are not clear. The aim of this study was to analyze the effect of LLLT on bacterial growth in vitro. Bacterial strains including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were suspended in saline solution at a concentration of 10(3) cells/ml and exposed to laser irradiation at wavelengths of 660, 830, and 904 nm at fluences of 0 (control), 3, 6, 12, 18, and 24 J/cm(2). An aliquot of the irradiated suspension was spread on the surface of petri plates and incubated at 37 °C for quantification of colony-forming unit after 24, 48, and 72 h. Laser irradiation inhibited the growth of S. aureus at all wavelengths and fluences higher than 12 J/cm(2), showing a strong correlation between increase in fluence and bacterial inhibition. However, for P. aeruginosa, LLLT inhibited growth at all wavelengths only at a fluence of 24 J/cm(2). E. coli had similar growth inhibition at a wavelength of 830 nm at fluences of 3, 6, 12, and 24 J/cm(2). At wavelengths of 660 and 904 nm, growth inhibition was only observed at fluences of 12 and 18 J/cm(2), respectively. LLLT inhibited bacterial growth at all wavelengths, for a maximum of 72 h after irradiation, indicating a correlation between bacterial species, fluence, and wavelength.

Bacteriological Investigation of Chronic Wounds in a Specialized Wound Healing Department: A Retrospective Analysis of 107 Cases

To investigate the information of chronic wounds, especially in the aspect of microbiological profile and to explore the relationship between the wound culture result and chronic wounds infection, we retrospectively reviewed the medical records of 107 patients with chronic wounds from January 2011 to December 2013. The sociodemographic data, wound-related information, therapeutic type, and wound infection status were extracted. Microbial specimens were obtained and processed using standard hospital procedure for wound culture. The predominant pathogen isolated was Staphylococcus aureus (n = 11, 26.2%), followed by Escherichia coli (n = 6, 14.3%), Enterobacter cloacae (n = 3, 7.1%), and Pseudomonas aeruginosa (n = 3, 7.1%). Sixty percent of the infectious chronic wounds had positive culture, and 96.2% of the noninfectious wounds had negative culture. In conclusion, the microbial characteristics were mostly in the site of lower extremity, gram-negative bacteria, and monopathogen, respectively. Furthermore, the relationship between the wound culture result and chronic wound infection was not exactly coincident. It may be useful for guiding the empiric therapy of chronic wounds.

Recent developments in topical wound therapy: impact of antimicrobiological changes and rebalancing the wound milieu

Wound therapy improves every year by developing new wound treatment options or by advancing already existing wound materials, for example, adding self-releasing analgesic drugs or growth factors to wound dressings, or by binding and inactivating excessive proteases. Also new dressing materials based on silk fibers and enhanced methods to reduce bacterial burden, for example, cold argon plasma, might help to fasten wound healing.

[Microbial stress of skin and wounds in clinical aspects and practice. Between search and destroy and monitor and relax]

The antibiotic treatment of microbial pathogens of the skin and wounds could so far not fulfil the expectations of an effective and permanent elimination of pathogens so that local treatment with antiseptic agents as a flanking measure to wound cleansing and debridement has become increasingly more established. Because an antiseptic treatment does not actually represent a treatment of infections, the current antimicrobial treatment strategy for infections in skin and wound areas consists of combined antibiotic and flanking antiseptic administration following debridement. However, the combined therapy is not always successful. There is an urgent need for new forms of therapy particularly to combat multiresistant pathogens in biofilms in infections of chronic and other complicated wounds.