Access Microbiology - Volume 1, Issue 10, 2019

Wounds from various sources such as burns and ulcers which have been in a prolonged state of inflammation and rubor, both exudative and non-exudative, are decidedly prone to becoming infected by various opportunistic and commensal microorganisms, both bacterial and fungal due to the warm moist environment at the wound site (Que et al.,2019). The typical approach in treating these wounds is to reduce the level of infection and inflammation, thus encouraging an appropriate environment for successful re-epithelisation resulting in faster healing of the wound.

Bacterial cellulose (BC) is an ideal material to produce wound dressings due to the intrinsic properties such as; high chemical stability, high tensile strength and flexibility, large water holding capacity, permeable to gases and liquids, and excellent biocompatibility (Gupta et al., 2016; Gupta et al.,2017, Wahid et al., 2019).

In this study, BC produced by Komagataeibacter xylinus was used as a hydrogel matrix and loaded with a well-known antimicrobial agent- curcumin encapsulated in solubility enhancing carriers, hydroxypropyl- β-cyclodextrin (CUR:HPβCD) (Abbas et al., 2019, Gupta et al., 2019). BC was loaded with 2% (w/v) aqueous CUR:HPβCD inclusion complex under constant agitation at 170 rpm at 20°C (room temperature) for 24 hours.

Antimicrobial activity was tested against two representative organisms:

Candida albicans and Staphylococcus aureus by disc diffusion method. We have previously reported the antibacterial activity of CUR:HPβCD-loaded BC (Gupta et al., 2019). The current study is an extension of our ongoing research where we made an attempt of testing the anti-fungal activity of CUR:HPβCD-loaded BC and compared it with anti-bacterial activity. 8mm discs were aseptically cut and placed on TSA plates seeded with overnight cultures of one of the microorganisms under investigation and incubated at 37°C for 24 hours.

The results indicated that C. albicans and S. aureus were both susceptible to CUR:HPβCD inclusion complex with an average zone of inhibition of 12.25±2.2mm and 11±1.2mm respectively (n=4, ±=SD, p <0.05). The results against S. aureus are in accordance with our previously reported findings (Gupta et al., 2019). Current findings support the wound management applications of CUR:HPβCd-loaded BC hydrogels for chronic wounds.

References

Abbas, M., Hussain, T., Arshad, M., Ansari, A., Irshad, A., Nisar, J., Hussain, F., Masood, N., Nazir, A. and Iqbal, M. (2019). Wound healing potential of curcumin cross-linked chitosan/polyvinyl alcohol. International Journal of Biological Macromolecules, 140, pp.871-876.

Gupta, A., Keddie, D., Kannappan, V., Gibson, H., Khalil, I., Kowalczuk, M., Martin, C., Shuai, X. and Radecka, I. (2019). Production and characterisation of bacterial cellulose hydrogels loaded with curcumin encapsulated in cyclodextrins as wound dressings. European Polymer Journal, 118, pp.437-450.

Gupta, A., Low, W., Britland, S., Radecka, I. and Martin, C. (2017). Physicochemical characterisation of biosynthetic bacterial cellulose as a potential wound dressing material. British Journal of Pharmacy, 2(2), pp.S37-S38.

Gupta, A., Low, W., Radecka, I., Britland, S., Mohd Amin, M. and Martin, C. (2016). Characterisation and in vitro antimicrobial activity of biosynthetic silver-loaded bacterial cellulose hydrogels. Journal of Microencapsulation, 33(8), pp.725-734.

Que, A., Nguyen, N., Do, N., Nguyen, N., Tran, N. and Le, T. (2019). Infection of burn wound by Aspergillus fumigatus with gross appearance of fungal colonies. Medical Mycology Case Reports, 24, pp.30-32.

Wahid, F., Hu, X., Chu, L., Jia, S., Xie, Y. and Zhong, C. (2019). Development of bacterial cellulose/chitosan based semi-interpenetrating hydrogels with improved mechanical and antibacterial properties. International Journal of Biological Macromolecules, 122, pp.380-387.

Wounds from various sources such as burns and ulcers which have been in a prolonged state of inflammation and rubor, both exudative and non-exudative, are decidedly prone to becoming infected by various opportunistic and commensal microorganisms, both bacterial and fungal due to the warm moist environment at the wound site (Que et al.,2019). The typical approach in treating these wounds is to reduce the level of infection and inflammation, thus encouraging an appropriate environment for successful re-epithelisation resulting in faster healing of the wound.

Bacterial cellulose (BC) is an ideal material to produce wound dressings due to the intrinsic properties such as; high chemical stability, high tensile strength and flexibility, large water holding capacity, permeable to gases and liquids, and excellent biocompatibility (Gupta et al., 2016; Gupta et al.,2017, Wahid et al., 2019).

In this study, BC produced by Komagataeibacter xylinus was used as a hydrogel matrix and loaded with a well-known antimicrobial agent- curcumin encapsulated in solubility enhancing carriers, hydroxypropyl- β-cyclodextrin (CUR:HPβCD) (Abbas et al., 2019, Gupta et al., 2019). BC was loaded with 2% (w/v) aqueous CUR:HPβCD inclusion complex under constant agitation at 170 rpm at 20°C (room temperature) for 24 hours.

Antimicrobial activity was tested against two representative organisms:

Candida albicans and Staphylococcus aureus by disc diffusion method. We have previously reported the antibacterial activity of CUR:HPβCD-loaded BC (Gupta et al., 2019). The current study is an extension of our ongoing research where we made an attempt of testing the anti-fungal activity of CUR:HPβCD-loaded BC and compared it with anti-bacterial activity. 8mm discs were aseptically cut and placed on TSA plates seeded with overnight cultures of one of the microorganisms under investigation and incubated at 37°C for 24 hours.

The results indicated that C. albicans and S. aureus were both susceptible to CUR:HPβCD inclusion complex with an average zone of inhibition of 12.25±2.2mm and 11±1.2mm respectively (n=4, ±=SD, p <0.05). The results against S. aureus are in accordance with our previously reported findings (Gupta et al., 2019). Current findings support the wound management applications of CUR:HPβCd-loaded BC hydrogels for chronic wounds.

References

Abbas, M., Hussain, T., Arshad, M., Ansari, A., Irshad, A., Nisar, J., Hussain, F., Masood, N., Nazir, A. and Iqbal, M. (2019). Wound healing potential of curcumin cross-linked chitosan/polyvinyl alcohol. International Journal of Biological Macromolecules, 140, pp.871-876.

Gupta, A., Keddie, D., Kannappan, V., Gibson, H., Khalil, I., Kowalczuk, M., Martin, C., Shuai, X. and Radecka, I. (2019). Production and characterisation of bacterial cellulose hydrogels loaded with curcumin encapsulated in cyclodextrins as wound dressings. European Polymer Journal, 118, pp.437-450.

Gupta, A., Low, W., Britland, S., Radecka, I. and Martin, C. (2017). Physicochemical characterisation of biosynthetic bacterial cellulose as a potential wound dressing material. British Journal of Pharmacy, 2(2), pp.S37-S38.

Gupta, A., Low, W., Radecka, I., Britland, S., Mohd Amin, M. and Martin, C. (2016). Characterisation and in vitro antimicrobial activity of biosynthetic silver-loaded bacterial cellulose hydrogels. Journal of Microencapsulation, 33(8), pp.725-734.

Que, A., Nguyen, N., Do, N., Nguyen, N., Tran, N. and Le, T. (2019). Infection of burn wound by Aspergillus fumigatus with gross appearance of fungal colonies. Medical Mycology Case Reports, 24, pp.30-32.

Wahid, F., Hu, X., Chu, L., Jia, S., Xie, Y. and Zhong, C. (2019). Development of bacterial cellulose/chitosan based semi-interpenetrating hydrogels with improved mechanical and antibacterial properties. International Journal of Biological Macromolecules, 122, pp.380-387.

Honey is a natural product with many beneficial properties including antimicrobial action. Production of hydrogen peroxide (H2O2) in diluted honey is central to this action. Here, we describe an optimized method for measuring levels of H2O2 in honey. This method is based on established methods, with the level of dilution, the time between dilution and reading the assay, and aeration of the samples during the assay identified as critical points for ensuring reliability and reproducibility. The method is cost-effective and easy to perform using common laboratory equipment. Using this method, we quantified the hydrogen peroxide content of five different, unprocessed polyfloral honeys collected in NC, USA. Our results show that H2O2 production by these honeys varies greatly, with some samples producing negligible levels of H2O2. We assessed the effect of colour on the assay by measuring the recovery of spiked H2O2 from light and dark honey and from serially diluted dark corn syrup, and found the amount of H2O2 that could be detected was lower in dark corn syrup and darker honey samples.

Purpose. To investigate the effect of daily toothbrushing with 0.2 % chlorhexidine digluconate (CHX) on the colonization of dental plaque by pathogens associated with pneumonia amongst non-ventilated adults with a neuro-disability.

Methodology. Forty-nine patients living in long-term care were recruited. Daily toothbrushing with 0.2 % CHX gel was conducted for 48 weeks. Plaque accumulation was assessed and microbiological sampling was undertaken every 6 weeks.

Results. At any one time point at least 65 % (n=32) of subjects were found to harbour respiratory pathogens. Although there were significant changes in the proportion of individuals colonized over time with Gram-negative bacilli and Pseudomonas aeruginosa, the changes were not sustained. By week 48 there was no significant difference from the levels that had been recorded at baseline.

Conclusions. Bacteria known to be causal in pneumonia are present and colonize the dental plaque of non-ventilated adults with a neuro-disability. Daily toothbrushing with 0.2 % CHX gel did not produce a sustained reduction in intra-oral respiratory pathogen counts after 48 weeks.

Pseudomonas is the bacterial genus of Gram-negative bacteria with the highest number of recognized species. It is divided phylogenetically into three lineages and at least 11 groups of species. The Pseudomonas putida group of species is one of the most versatile and best studied. It comprises 15 species with validly published names. As a part of the Genomic Encyclopedia of Bacteria and Archaea (GEBA) project, we present the genome sequences of the type strains of five species included in this group: Pseudomonas monteilii (DSM 14164T), Pseudomonas mosselii (DSM 17497T), Pseudomonas plecoglossicida (DSM 15088T), Pseudomonas taiwanensis (DSM 21245T) and Pseudomonas vranovensis (DSM 16006T). These strains represent species of environmental and also of clinical interest due to their pathogenic properties against humans and animals. Some strains of these species promote plant growth or act as plant pathogens. Their genome sizes are among the largest in the group, ranging from 5.3 to 6.3 Mbp. In addition, the genome sequences of the type strains in the Pseudomonas taxonomy were analysed via genome-wide taxonomic comparisons of ANIb, gANI and GGDC values among 130 Pseudomonas strains classified within the group. The results demonstrate that at least 36 genomic species can be delineated within the P. putida phylogenetic group of species.

Azole drugs such as econazole, are active on Mycobacterium tuberculosis and Mycobacterium smegmatis ; however, the identification of their target(s) is still pending. It has been reported that mutations in the non-essential system mmpL5-mmpS5 conferred resistance to econazole in M. tuberculosis . We herein report that an azole-resistant mutant screen in M. smegmatis rendered mutations in rshA, encoding a non-essential anti-sigma H protein.

Introduction. Bartonella species are increasingly recognized as agents of culture-negative endocarditis. However, to date, almost all human cases have been associated with two members of the genus, Bartonella henselae and Bartonella quintana. B. henselae infections are zoonotic, with domestic cats serving as reservoir hosts for the pathogen. Bartonella clarridgeiae also exploits cats as reservoir hosts, but its zoonotic potential is far less established.

Case presentation. A 34-year-old male presented with palpitations after a history of aortic incompetence. During surgery for an aortic valve replacement, two vegetations were found on the aortic valve. PCR analysis of the vegetation demonstrated the presence of Bartonella species and so the patient was treated post-operatively with ceftriaxone and doxycycline, making a good recovery. Further PCR-based analysis of the patient’s aortic vegetation confirmed the presence of B. clarridgeiae .

Conclusion. This report expands the number of Bartonella species associated with endocarditis and provides clear evidence that B. clarridgeiae should be considered a zoonotic pathogen.

Septic arthritis of native joints is a potentially life-threatening disease. The most frequently isolated pathogens are Gram-positive cocci. Bacteroides fragilis is a rare pathogen in joint infections and is usually associated with immunocompromised and debilitated patients. Most cases of B. fragilis joint infection are related to skin or local perineal infections or are secondary to B. fragilis bacteraemia from another source, for example from the gastrointestinal tract. We present a clinical case of B. fragilis septic arthritis involving a native hip joint in a previously healthy paraplegic patient.

Introduction. Invasive infections due to Cellulosimicrobium spp. (a Gram-positive coryneform) are extremely rare. Only a few cases of bloodstream infections and endocarditis have been described, as bacteraemia due to coryneforms is usually discarded as blood culture contamination.

Case presentation. A 66-year-old female, with a history of aortic valve replacement, presented with fever, left leg purpura and acute kidney injury. Multiple repeated blood cultures were positive for Cellulosimicrobium cellulans , and targeted therapy was started. At first, endocarditis was excluded by echocardiograms, and the acute nephritis was interpreted as an atypical presentation of Henoch–Shönlein purpura. High-dose prednisone was started, and after 10 weeks the patient presented again with fever, mental confusion and acute left arm ischaemia. A subsequent echocardiogram and radiolabelled leukocyte scintigraphic evaluation revealed aortic prosthetic valve endocarditis with periprosthetic abscess and arterial brachial thrombosis. The patient deceased, and the autoptic examination confirmed an aortic valve periprosthetic abscess and revealed multiple arterial thromboses and septic embolisms in the kidneys, brain, spleen and myocardium.

Conclusion. Isolation of coryneform bacteria on blood culture should not always be discarded as blood culture contamination. In the case of endocarditis due to Cellulosimicrobium spp., the removal of any prosthetic material, along with prolonged in vitro active antimicrobial therapy, should be pursued in order to reduce persistence or relapses of infection.

Non-tuberculous mycobacteria (NTM) are ubiquitous environmental organisms found in soil and water. Infections caused by NTM are increasing with conditions ranging from harmless colonization to invasive infections, the latter being more common in immunocompromised hosts. In this report, we present a case of bacteraemia caused by Mycobacterium chelonae , a rapidly growing NTM belonging to Class IV in the Runyon classification, in a 71-year-old male with ocular myasthenia gravis undergoing treatment with oral prednisolone. Gram staining of these organisms from blood culture can be easily overlooked or confused with diptheroids. Detection of Gram-positive bacilli should prompt Ziehl–Neelsen staining to distinguish diphtheroids from rapidly growing mycobacteria in immunosuppressed patients. In addition, speciation and antimicrobial susceptibility testing are of paramount importance in such cases as there is considerable variation in the resistance patterns between different species of NTM. Line probe assay provides a rapid and reliable method for identification of NTM to the species level, which can guide treatment with appropriate antibiotics. This case report highlights the importance of early detection of such cases so as to optimize management and improve patient outcomes.