Volume: 55 Issue: 4
Year: 2024, Page: 675-679, Doi: https://doi.org/10.51966/jvas.2024.55.4.675-679
Received: Nov. 6, 2024 Accepted: Nov. 30, 2024 Published: Dec. 31, 2024
Streptococcus agalactiae belongs to Group B Streptococcus (GBS), an important Gram-positive pathogen
attributed to mastitis and elevated somatic cell counts (SCC) in dairy cows, which invariably exhibits complete
β-haemolysis on blood agar (BA) / Polymixin Nalidixic acid Blood Agar (PNBA) and fails to grow on MacConkey agar
(MCA). The present study conducted in the Advanced Agricultural Laboratories under the Almarai company, Riyadh,
KSA, reports the isolation, identification and characterization of β-haemolytic Strepotococcus agalactiae which exhibited
lactose fermenting colonies on MCA. Though the colony characteristics on BA/ PNBA were suggestive of Streptococcus,
the observation of pink colored colonies on MCA was deemed unusual and was subjected to further confirmatory
tests viz., Gram’s staining, Lancefield grouping, catalase, oxidase and CAMP tests. Further, real-time PCR and Oxford
nanopore sequencing of the 16S ribosomal RNA gene were performed for molecular characterization. The findings of
the study would add to the existing knowledge on cultural characteristics of Streptococcus agalactiae for its presumptive
identification.
Keywords: Streptococcus agalactiae, MacConkey agar, nanopore sequencing
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© 2024 Jobin et al. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in
any medium, provided the original author and source are credited.
Jobin, T., Harikrishna, P., Sreenath, B., Gian, L., Goncalo, L. and Siju, J. 2024. Isolation of S. agalactiae growing
in MacConkey Agar and its confirmation by biochemical tests, qPCR and Nanopore Sequencing.
J. Vet. Anim. Sci. 55 (4):675-679