Antimicrobial Preservative Efficacy and Microbial Content Testing*
Philip A. Geis in Cosmetic Microbiology, 2020
The size of the inoculum can also have an effect on the apparent activity of the antimicrobial as reported by Van Doorne and Vringer (73) in 1994 after a study conducted with Candida albicans and Aspergillus niger and by Steels et al. in 2000 (74). When conducting a laboratory preservative efficacy test, it is necessary to have a large inoculum so that the microbiologist can measure the required reduction. It is difficult to measure a 3-log10 reduction if an inoculum is smaller than 100,000 (105) CFU/mL. However, these authors showed microbial growth in a cream formulation when the inoculum was relatively small, a growth not observed with greater inocula. They note that these results are not consistent with earlier work that employed prokaryotic challenge organisms.
Antimicrobial preservative efficacy and microbial content testing
Philip A. Geis in Cosmetic Microbiology, 2006
The size of the inoculum can also have an effect on the apparent activity of the antimicrobial as reported by Van Doorne and Vringer67 in 1994 after a study conducted with Candida albicans and Aspergillus niger and by Steels et al. in 2000.68 When conducting a laboratory preservative efficacy test, it is necessary to have a large inoculum so that the microbiologist can measure the required reduction. It is difficult to measure a 3-log10 reduction if an inoculum is smaller than 100,000 (105) CFU/ml. However, these authors showed microbial growth in a cream formulation when the inoculum was relatively small, a growth not observed with greater inocula. They note that these results are not consistent with earlier work that employed prokaryotic challenge organisms.
Manufacturing and Standardizing Allergen Extracts in Europe
Richard F. Lockey, Dennis K. Ledford in Allergens and Allergen Immunotherapy, 2014
Source materials are obtained by growing the fungi under controlled conditions. The harvested source materials should consist of mycelia and spores. Due to difficulties in maintaining a constant composition of fungal cultures, an extract should be derived from at least five independent cultures of the same species. Production of the source material should be conducted under aseptic conditions to reduce the risk of contamination by microorganisms or other fungi. The inoculum should be obtained from established fungal culture banks, namely, the American Type Culture Collection (ATCC) available through the offices of LGC Standards in Europe (see http://www.lgcstandards-atcc.org/) or Centraalbureau voor Schimmelcultures (CBS), Utrecht, the Netherlands (http://www.cbs.knaw.nl/). The cultivation medium should be synthetic or at least devoid of antigenic constituents, that is, proteins. Controls performed in fungal allergen extract production must include tests for suspected toxins.
The effect of gold and silver nanoparticles, chitosan and their combinations on bacterial biofilms of food-borne pathogens
Published in Biofouling, 2020
Ondrej Chlumsky, Sabina Purkrtova, Hana Michova (Turonova), Viviana Svarcova (Fuchsova), Petr Slepicka, Dominik Fajstavr, Pavel Ulbrich, Katerina Demnerova
For the determination of MICPC80, MICBF80, and MICBM80, 75 µl of inoculum were transferred into a pre-sterilized polystyrene 96-well flat-bottomed microtitre plate in three replicates and were then carefully mixed with 75 µl of a test substance at a particular concentration. For a positive control of bacterial growth, the inoculum was mixed with pure sterile medium. Furthermore, sterile medium was included in the plate as a marker of potential microbial contamination. The optical density of the well contents in the microtitre plates were measured spectrophotometrically at 620 nm before and after cultivation for 24 h of at 37 °C (25 °C for S. Infantis strains). The difference in A620 was considered as a measure of the ability of planktonic cells to grow in the presence of the test compounds and was used to determine the MICPC80. After the cultivation, the biofilm was quantified using the crystal violet assay or tested for metabolic activity.
Antibacterial activity and physicochemical properties of a sealer containing copaiba oil
Published in Biofouling, 2023
Lara Rodrigues Schneider, Andressa da Silva Barboza, Juliana Silva Ribeiro de Andrade, Daniela Coelho dos Santos, Carlos Enrique Cuevas-Suárez, Evandro Piva, Angela Diniz Campos, Rafael Guerra Lund
This test used strains of E. faecalis (ATCC 4083) and S. aureus (ATCC 19095). E. faecalis was cultured overnight at 37 °C in tryptic soy agar (TSA) plates in an anaerobic atmosphere and then inoculated in tryptic soy broth (TSB). S. aureus was cultured overnight at 37 °C in tryptic soy agar (TSA) plates in an aerobic atmosphere and then inoculated in tryptic soy broth (TSB). For both microorganisms, culture suspensions were prepared for inoculum standardization. The suspensions were diluted in 0.9% saline solution on a 0.5 MacFarland scale to obtain approximately 1.5 × 108 Colony Forming Units (CFU/mL) for bacteria and 2.0 × 106 CFU/mL for yeast and, the bacterial turbidity was adjusted to an optical density of 0.5 at 600 nm.
Methicillin Resistant Staphylococcus aureus and public fomites: a review
Published in Pathogens and Global Health, 2020
Ziad W Jaradat, Qutaiba O Ababneh, Sherin T Sha’aban, Ayesha A Alkofahi, Duaa Assaleh, Anan Al Shara
A critical factor that allows the transmission of MRSA from a person to the environment and then to other people, is the pathogen’s ability to survive on different types of surfaces under low humidity conditions, and its persistence on these surfaces for extended periods [39,183]. It is noteworthy that the antibiotic-resistance trait of MRSA does not affect the length of the survival period on fomites compared to, for example, Methicillin-sensitive S. aureus (MSSA). Rather, MRSA survival time on fomites is affected by inoculum concentration [184]. This is consistent with the phenomenon of cryptic growth; where cells in a nutrient-limited environment will live on the remains of surrounding dying cells, and thus, an increased inoculum concentration will provide more dying cells for longer periods of time to sustain the lives of the remaining bacteria [185]. However, others reported contradictory data on the differences in the survival ability/length of MRSA vs MSSA. For instance, Wagenvoort and Penders (1997) reported the survival of an MRSA linage for 175 days in hospital dust while an MSSA linage survived only for 4 weeks under the same conditions [186]. Zarpellon et al. (2015) reported the survival of MRSA and vancomycin-resistant S. aureus (VRSA) on vinyl floors and formica for 40–45 days while on latex for only 2 days while MSSA survived on latex for only one day (Table 5) [187].
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