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David J McCanna, Lucy Liu, Junghee Seo, Lakshman N Subbaraman, Lyndon William Jones; Assessment of the growth of Stenotrophomonas maltophilia, Elizabethkingia meningoseptica and Delftia acidovorans in contact lens cases and on recovery media. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6051.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the growth characteristics of the emerging ocular pathogens Stenotrophomonas maltophilia (Sm), Elizabethkingia meningoseptica (Em) and Delftia acidovorans (Da) in order to determine their potential to form active biofilms in lens cases and to optimize their recovery to accurately determine the number of live bacteria.
Biofilms of Sm, Em and Da were formed in lens cases by incubating the bacteria in either phosphate buffered saline (PBS), 1% tryptic soy broth (TSB) in PBS or 10% TSB in PBS at 32°C and 37°C for two days for Sm and one day at 37°C for Em and Da. After incubation the lens cases were then rinsed in PBS and evaluated for metabolic activity using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Sm, Em, and Da were also evaluated for their growth characteristics on different growth media. Each organism was plated onto Columbia agar with 5% sheep's blood, chocolate agar, tryptic soy agar, brain heart infusion agar, Mueller-Hinton agar and MacConkey agar and the number of colony forming units (CFU) were recorded after two, three, and four days of incubation at 37°C for Em and Da and at 32°C and 37°C for Sm.
Sm was inhibited by the higher growth temperature of 37°C both in the lens case and on recovery media. Sm showed greater metabolic activity in contact lens cases (p<0.01) and more CFU were recovered on gowth media (p<0.01) when incubated at 32°C than when it was incubated at 37°C. Compared to the PBS control the presence of 10% organic load in the lens case caused an increase in the metabolic activity of Sm (p<0.05). The increase in metabolic activity due to the presence of TSB was greater for Sm than for Da and Em (p<0.05). The optimal incubation time and recovery media for all three microorganisms was determined to be three days of growth on Columbia agar with 5% sheep's blood.
Biofilms of Sm have different metabolic activities when grown at different growth temperatures. Also, it was demonstrated that appropriate growth media, growth temperature and incubation times must be selected in order to maximize the recovery of Sm, Em and Da. These optimal growth conditions should be conducted when assessing contact lens cases for Sm, Em and Da contamination.
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