01. Introduction
02. Gram-Positive Cocci
03. Gram-Positive Bacilli
04. Gram-Positive Branched Filaments
05. Gram-Negative Diplococci
06. Gram-Negative Bacilli
07. Gram-Negative Coccobacilli
08. Additional Bacteria
09. RNA Viruses
10. DNA Viruses
11. Fungi
12. Opportunistic Fungi
13. Protozoa (single-celled eukaryotes - small parasites)
14. Helminths (parasitic worms - large macroparasites)
15. Prions

2.04 Streptococcus agalactiae

Streptococcus agalactiae – Audio and Lecture Notes – Click to Expand

Streptococcus agalactiae is a catalase-negative, beta-haemolytic, gram-positive coccus. Strep Agalactiae is a Lancefield Group B Streptococcus (GBS).  It appears as gram-positive cocci in chains. 

Another beta haemolytic gram-positive coccus is Streptococcus pyogenes, we differentiate the two by the fact that Strep agalactiae is bacitracin resistant whilst Strep pyogenes is bacitracin sensitive.

Strep Agalactiae’s virulence factors include:

    • A polysaccharide capsule. 

Strep Agalactiae preferentially colonises the gastrointestinal (GI) tract and the genitourinary (GU) tract, particularly the vagina; with transmission to the baby either in utero or during the birthing process. 

Obstetric complications provide added opportunities for Strep Agalactiae transmission to the neonate e.g. premature birth, or prolonged membrane rupture.

Strep Agalactiae can cause:

    • sepsis, meningitis and pneumonia in neonates. 

And can cause:

    • UTI in pregnant women.

Blood culture and Cerebro-Spinal Fluid (CSF) analysis can aid in diagnosing Strep Agalactiae.

Treatment is with:

    • penicillins
    • Alternatively, cephalosporin and vancomycin may be used.

Screening of pregnant women in their 3rd trimester is recommended; as well as penicillin prophylaxis for those positive with Strep agalactiae. 

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