In -vitro Biofilm Formation of Vaginal Isolates of Streptococcus agalactiae; Effect of pH and Culture Media

Abstract Background: Streptococcus agalactiae (GBS), a major cause of neonatal morbidity and mortality, is transmitted from mother to neonate via placenta or during birth. Biofilm formation is an important factor in GBS pathogenesis. This study aimed to determine effects of pH, different culture media and nutritional composition on in vitro biofilm forming ability of GBS isolated from pregnant women. Methods: A total of 30 confirmed isolates of GBS from pregnant women were tested for biofilm formation in Todd Hewitt Broth (THB) at pH 4.5,6 and 7. Ten of these isolates were tested for biofilm formation in growth media THB, brain heart infusion broth, tryptic soy broth, Mueller Hinton broth and nutrient broth. Further they were tested for influence of glucose on biofilm formation using crystal violet and MTT assay. Results: Of 30 GBS isolates strong biofilm formation (SBF) was observed at pH 7 in 56.6 %(n=17) while 36.6%(n=11) isolates showed weak biofilm formation (WBF). At pH 4.5, 43.3% (n=13) were non biofilm formers. In THB without glucose, all 10 isolates were SBF while THB with 1% glucose, 3(30%) isolates were SBF, 5(50%) isolates were moderate biofilm producers and 2(20%) isolates were WBF. Ten isolates tested in 5 types of growth media did not show statistically significant difference in biofilm forming ability. Conclusion: All tested vaginal GBS isolates were able to produce biofilms, maximum biofilm formation of GBS was at pH 7.0. and pH 4.5 is not favorable, thus in normal vaginal pH (3.5 - 4.5), GBS finds it difficult to grow biofilms.

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.

Molecular characterisation and disease severity of leptospirosis in Sri Lanka

Leptospirosis is a re-emerging zoonotic disease all over the world, important in tropical and subtropical areas. A majority of leptospirosis infected patients present as subclinical or mild disease while 5-10% may develop severe infection requiring hospitalisation and critical care. It is possible that several factors, such as the infecting serovar, level of leptospiraemia, host genetic factors and host immune response, may be important in predisposition towards severe disease. Different Leptospira strains circulate in different geographical regions contributing to variable disease severity. Therefore, it is important to investigate the circulating strains at geographical locations during each outbreak for epidemiological studies and to support the clinical management of the patients. In this study immunochromatography, microscopic agglutination test and polymerase chain reaction were used to diagnose leptospirosis. Further restriction fragment length polymorphism and DNA sequencing methods were used to identify the circulating strains in two selected geographical regions of Sri Lanka. Leptospira interrogans, Leptospira borgpetersenii and Leptospira kirschneri strains were identified to be circulating in western and southern provinces. L. interrogans was the predominant species circulating in western and southern provinces in 2013 and its presence was mainly associated with renal failure.

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.