Candida krusei

Reference strains of Candida spp. were obtained from the American Type Culture Collection (ATCC, Rockville, MD, USA): Candida albicans ATCC 90028, Candida albicans ATCC 60193, Candida tropicalis ATCC 13803, Candida krusei ATCC 6258, Candida parapsilosis ATCC 22019 and Candida glabrata ATCC 90030. Nystatin, ketoconazole, DMSO (Dimethyl Sulfoxide), Tween 80% and Ergosterol were obtained from Sigma-Aldrich^® Chemical Co. (St. Louis, MO, USA). Sorbitol (anhydrous D-sorbitol) was purchased from INLAB^® (São Paulo, Brazil).

The antimicrobial activity of the studied extract of lyophilized Aloe arborescens gel was tested by applying the agar well diffusion method. The reference strains cultured in thioglycolate broth were inoculated on a blood agar plate. Then, 100 µL of the studied extract (1 g dry weight of freeze-dried aloe pulp per 1 mL of 96% ethanol) was added to wells (5 mm × 5 mm) prepared on the agar plate’s surface; moreover, positive and negative controls were performed using 5.25% sodium hypochlorite and 0.9% sodium chloride, respectively. The plates were incubated for 24 h at 37 °C. The diameter of the clear zone (growth inhibition zone) around the wells with the extracts measured the antimicrobial activity.
The following microorganisms were used for the study: Gram-positive bacteria: Clostridium difficile ATCC 9689, Clostridiumbutyricum ATTC 860, Listeriamonocytogenes ATCC 7644, Bacillussubtilis ATCC 238557, Enterococcusfaecalis ATTC 29212, Staphylococcusaureus ATCC 25923, Staphylococcuspyogenes ATCC 19615; Gram-negative bacteria: Escherichia coli ATCC 25922, Klebsiella pneumonia ATCC 31488, Proteus mirabilis ATCC 12453, Salmonella typhimurium ATCC 14028, Pseudomonas aeruginosa ATCC 27853, Enterobacter aerogenes ATCC 13048; yeast: Candida krusei ATCC 14243, Candida albicans ATTC 10231.

Six microorganisms known for their pathogenic ability to cause skin diseases in humans were selected for the study. These American Type Culture Collection (ATCC) strains were purchased from Thermofisher Scientific, Johannesburg, South Africa. Two bacterial strains: Gram-negative Shigella flexneri (ATCC 12022) and Gram-positive Bacillus cereus (ATCC 10876), as well as four fungi: Trichophyton rubrium (ATCC 28188), Trichophyton tonsurans (ATCC 28942), Candida glabrata (ATCC 15126) and Candida krusei (ATCC 14243) were used for the in vitro antibacterial and antifungal evaluation. Sabouraud dextrose (SD) agar was used to culture Candida krusei and Candida glabrata while Yeast Malt (YM) agar (Becton Dickinson, Franklin Lakes, NJ, USA) was used to culture Trichophyton tonsurans and Trichophyton rubrium. Sabouraud dextrose (SD) broth and Yeast Malt (YM) broth were used to prepare overnight cultures for the respective fungal strains. Mueller Hinton (MH) agar and broth (Merck, Modderfontein, South Africa) were used to culture the bacteria and re-suspend the bacteria cultures overnight.

Reference strains of microorganisms that came from American Type Culture Collection (ATCC) (Manassas, VA, USA) were used for this study. The representative Gram-positive bacteria were as follows: Staphylococcus aureus ATCC 25923, Staphylococcus aureus ATCC 29213, Staphylococcus aureus ATCC 43300, Staphylococcus epidermidis ATCC 12228, Enterococcus faecalis ATCC 29212, Micrococcus luteus ATCC 10240, Bacillus subtilis ATCC 6633 and Bacillus cereus ATCC 10876. While, those of Gram-negative bacteria were as follows: Bordetella bronchiseptica ATCC 4617, Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 13883, Proteus mirabilis ATCC 12453, Salmonella Typhimurium ATCC 14028 and Pseudomonas aeruginosa ATCC 9027. Moreover, the following fungi belonging to yeasts were used: Candida albicans ATCC 10231, Candida albicans ATCC 2091, Candida parapsilosis ATCC 22019, Candida glabrata ATCC 90030 and Candida krusei ATCC 14243.

Luria-Bertani (LB) medium, Luria-Bertani agar (LBA), potato dextrose broth (PDB), and potato dextrose agar (PDA) were obtained from Solarbio Life Science. Cyclobutane pyrimidine dimer (CPD) antibody was purchased from Kamiya Biomedical Company (USA). Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 700603, methicillin-resistant Staphylococcus aureus (MRSA; 2104270609, clinical isolate), Pseudomonas aeruginosa ATCC 27853, Candida krusei ATCC 6258, Candida albicans ATCC 90028, and Candida glabrata ATCC MYA-2950 were obtained from the First Affiliated Hospital of the Xi’an Jiaotong University.

Both Candida spp. and bacterial strains were purchased from the American Type Culture Collection Centre (ATCC) and kindly provided by King Khalid University Hospital, Riyadh, Saudi Arabia. Several Candida strains were chosen for this study, which included Candida parapsilosis (ATCC-22019), Candida krusei (ATCC-6258), Candida albicans (ATCC-102310), Candida glabrata (ATCC-2950), and Candida auris (B21057582). The Candida strains were maintained on Sabouraud dextrose broth (SDB). The bacterial strains chosen were Staphylococcus epidermidis (ATCC 12228), Methicillin-resistant Staphylococcus aureus-MRSA (ATCC 43300), Bacillus subtilis (ATCC 6633), and Staphylococcus aureus (ATCC-25923). All the bacterial isolates were maintained on nutrient broth (NB).