Culture media profoundly affect Candida albicans and Candida tropicalis growth, adhesion and biofilm development

As there are sparse data on the impact of growth media on the phenomenon of biofilm development for Candida we evaluated the efficacy of three culture media on growth, adhesion and biofilm formation of two pathogenic yeasts, Candida albicans and Candida tropicalis. The planktonic phase yeast growth, either as monocultures or mixed cultures, in sabouraud dextrose broth (SDB), yeast nitrogen base (YNB), and RPMI 1640 was compared, and adhesion as well as biofilm formation were monitored using MTT and crystal violet (CV) assays and scanning electron microscopy. Planktonic cells of C. albicans, C. tropicalis and their 1:1 co-culture showed maximal growth in SDB. C. albicans/C. tropicalis adhesion was significantly facilitated in RPMI 1640 although the YNB elicited the maximum growth for C. tropicalis. Similarly, the biofilm growth was uniformly higher for both species in RPMI 1640, and C. tropicalis was the slower biofilm former in all three media. Scanning electron microscopy images tended to confirm the results of MTT and CV assay. Taken together, our data indicate that researchers should pay heed to the choice of laboratory culture media when comparing relative planktonic/biofilm growth of Candida. There is also a need for standardisation of biofilm development media so as to facilitate cross comparisons between laboratories.

Susceptibility to rubella among pregnant women and the serological evidence of congenital rubella in newborn babies at Colombo South Teaching Hospital.

OBJECTIVE: To determine the susceptibility to rubella infection in early pregnancy and the incidence of seropositivity of cord blood for rubella specific IgM among the newborn babies at Colombo South Teaching Hospital. METHODS: 1000 cord blood samples and 500 maternal blood samples from pregnant women before the 16th week of gestation were taken from the labour room and the antenatal clinic of the University Unit, Colombo South Teaching Hospital during the period of February 1999 to February 2001. These samples were tested for rubella specific IgM and IgG antibodies by ELISA. A detailed questionnaire was filled during the time of sampling. RESULTS: Of the 500 antenatal blood samples 82% were positive for rubella specific IgG. 373(75%) women gave a history of vaccination against rubella before their present pregnancy. Among the vaccinated 2(0.5%) were negative for IgG antibodies by ELISA. Out of 127 unvaccinated women 12(9%) gave a history of past infection with rubella and of this 3(25%) were seronegative for rubella specific IgG. 18% of pregnant women at 16 weeks of gestation were at risk of giving birth to a baby with congenital rubella syndrome. Among the tested 1000 cord blood samples three were seropositive (0.3%) for rubella specific IgM. CONCLUSIONS: A significant proportion of pregnant women were susceptible to rubella infection in the studied population. The present strategy of selective rubella vaccination should be reconsidered if we are to get closer to eliminating rubella syndrome in Sri Lanka.