Enterococcus faecalis

The bacteria strains used were Staphylococcus aureus (ATCC 29213), S. aureus (MRSA) (NCTC 12493), Enterococcus faecalis (ATCC 29212), Enterococcus faecalis (ATCC 49532), Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), E. coli (NCTC 11954), and Klebsiella pneumoniae (ATCC700603).

The bacterial and fungal strains were obtained from the American Type Culture Collection (ATCC) and from the microbiology laboratory of the University of Québec in Trois-Rivières (UQTR). The microorganisms used were Escherichia coli (ATCC 35218), Salmonella enterica (ATCC 10708), Pseudomonas aeruginosa (ATCC 15442), Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Aspergillus niger (ATCC 10535), Candida albicans (from UQTR microbiology laboratory), Saccharomyces cerevisiae (from UQTR microbiology laboratory). The bacterial strains were grown on sterilized Mueller Hinton agar and incubated at 37 °C for 24 h, while the fungal strains were grown on Sabouraud dextrose agar and incubated at 37 °C for 72 h before use.

The microorganisms used in this study were obtained from the American Type Culture Collection (ATCC). They included five strains Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Saccharomyces cerevisiae ATCC 2601, Staphylococcus aureus. CIP were obtained from the CIP 106760, and the yeast strain Candida albicans ATCC 10231.

Escherichia coli O157:H7 ATCC 35150, Enterococcus faecalis ATCC 29212, Listeria monocytogenes ATCC 7644, Klebsiella pneumoniae ATCC 13833, Pseudomonas aeruginosa ATCC 9027, Staphylococcus aureus ATCC 43387, Salmonella enteritidis ATCC 13076 and Candida albicans ATCC 14053 were the reference human pathogens used in this study (American Type Culture Collection, USA). All strains were maintained in Tryptic Soy Agar (TSA, Oxoid, Milan, Italy) at 37 °C, while C. albicans ATCC 14053 was grown in Sabouraud Dextrose Agar (SDA, Oxoid). All stock cultures were kept at −80 °C in nutrient broth with glycerol 15%.

The growth inhibition effect of the chitosan–metal composites was tested against a range of microorganisms that acted as model organisms for gut microflora of livestock gastrointestinal tract. E. coli (ATCC 8739) and Staphylococcus aureus (ATCC 25923) were grown in tryptic soy media (Sigma-Aldrich). Enterococcus faecalis (ATCC 29212) was grown in brain heart infusion (BHI) media (BD Biosciences). Lactobacillus fermentum (ATCC 9338) was grown in MRS medium (BD Biosciences). All incubations were done at 37°C.

The effects of EOs were evaluated on 13 bacterial strains and 5 yeasts: Staphylococcus aureus (209 PCIP 53156), S. aureus (ATCC 29213), Micrococcus luteus (ATCC381), Bacillus cereus (ATCC 14579), Escherichia coli (ATCC 8739), E. coli (ATCC 35214), Pseudomonas aeruginosa (DSM 50090), P. aeruginosa (ATCC 27853), Klebsiella pneumoniae (CIP 104727), K. pneumoniae (clinical isolates), Enterococcus faecalis (ATCC 29212), Listeria monocytogenes (ATCC 19115), Salmonella enteritidis (DMB 560), Candida albicans (CCMM L4), C. krusei (CCMM L10), C. glabrata (CCMM L7), C. parapsilosis (CCMM L18) and Aspergilus niger (CCMM M100). The bacterial and yeast strains were provided by the Center of Biotechnology, Borj Cedria, Tunisia.