Assessing the effect of mercury pollution on cultured benthic foraminifera community using morphological and eDNA metabarcoding approaches.

Mercury (Hg) is a highly toxic element for living organisms and is known to bioaccumulate and biomagnify. Here, we analyze the response of benthic foraminifera communities cultured in mesocosm and exposed to different concentrations of Hg. Standard morphological analyses and environmental DNA metabarcoding show evidence that Hg pollution has detrimental effects on benthic foraminifera. The molecular analysis provides a more complete view of foraminiferal communities including the soft-walled single-chambered monothalamiids and small-sized hard-shelled rotaliids and textulariids than the morphological one. Among these taxa that are typically overlooked in morphological studies we found potential bioindicators of Hg pollution. The mesocosm approach proves to be an effective method to study benthic foraminiferal responses to various types and concentrations of pollutants over time. This study further supports foraminiferal metabarcoding as a complementary and/or alternative method to standard biomonitoring program based on the morphological identification of species communities.

[Comparative study of three culture media for detecting group B Streptococcus colonization in pregnant women]. / Estudio comparativo de tres medios de cultivo para detectar la colonización por estreptococo del grupo B en la mujer embarazada.

OBJECTIVE: To compare the efficacy of three culture media to detect vaginal and rectal colonization by group B streptococci (GBS) in pregnant women. METHODS: We processed 1334 samples from 861 pregnant women: in 388 patients only vaginal swab was cultured (Group A) and in 473 vaginal and rectal swabs were cultured (Group B). Samples were inoculated on blood agar with colistin-nalidixic acid (BA-CNA), on plates with Granada medium, and on Todd-Hewitt broth (THB) with amikacin followed by subculture in BA-CNA. RESULTS: GBS was isolated in 181 samples (13.6%): 114 vaginal swabs (13.2%) and 67 rectal swabs (14.2%). Among the positive samples, GBS was isolated on BA-CNA in 60.5% of vaginal swabs and in 59.7% of rectal swabs, on Granada medium in 80.7% of vaginal swabs and in 91% of rectal swabs, and on THB in 97.4% of vaginal swabs and in 97% of rectal swabs.We detected 130 GBS carriers, 54 (13.9%) in Group A and 76 (16.1%) in Group B. The percent of carriers detected in groups A and B, respectively, was 59.3% and 75% with BA-CNA, 77.8% and 93.4% with Granada medium, and 96.3% and 97.4% with THB. CONCLUSIONS: THB was the most reliable medium for the detection of GBS. Use of Granada medium allows fast detection of about 87% of carriers. The combination of THB and an initial plate of Granada medium or BA-CNA allows detection of more than 99% of GBS carriers.