Streptococcus agalactiae (Group B Strep)

13,753views

00:00 / 00:00

Videos

Notes

Streptococcus agalactiae (Group B Strep)

Bacteriology

Introduction to bacteria

Bacterial structure and functions

Gram positive bacteria

Staphylococcus epidermidis

Staphylococcus aureus

Staphylococcus saprophyticus

Streptococcus viridans

Streptococcus pneumoniae

Streptococcus pyogenes (Group A Strep)

Streptococcus agalactiae (Group B Strep)

Enterococcus

Clostridium perfringens

Clostridium botulinum (Botulism)

Clostridium difficile (Pseudomembranous colitis)

Clostridium tetani (Tetanus)

Bacillus cereus (Food poisoning)

Listeria monocytogenes

Corynebacterium diphtheriae (Diphtheria)

Bacillus anthracis (Anthrax)

Nocardia

Actinomyces israelii

Gram negative bacteria

Escherichia coli

Salmonella (non-typhoidal)

Salmonella typhi (typhoid fever)

Pseudomonas aeruginosa

Enterobacter

Klebsiella pneumoniae

Shigella

Proteus mirabilis

Yersinia enterocolitica

Legionella pneumophila (Legionnaires disease and Pontiac fever)

Serratia marcescens

Bacteroides fragilis

Yersinia pestis (Plague)

Vibrio cholerae (Cholera)

Helicobacter pylori

Campylobacter jejuni

Neisseria meningitidis

Neisseria gonorrhoeae

Moraxella catarrhalis

Francisella tularensis (Tularemia)

Bordetella pertussis (Pertussis/Whooping cough)

Brucella

Haemophilus influenzae

Haemophilus ducreyi (Chancroid)

Pasteurella multocida

Mycobacteria

Mycobacterium tuberculosis (Tuberculosis)

Mycobacterium leprae

Mycobacterium avium complex (NORD)

Other bacteria

Mycoplasma pneumoniae

Chlamydia pneumoniae

Chlamydia trachomatis

Borrelia burgdorferi (Lyme disease)

Borrelia species (Relapsing fever)

Leptospira

Treponema pallidum (Syphilis)

Rickettsia rickettsii (Rocky Mountain spotted fever) and other Rickettsia species

Coxiella burnetii (Q fever)

Ehrlichia and Anaplasma

Gardnerella vaginalis (Bacterial vaginosis)

Assessments

Streptococcus agalactiae (Group B Strep)

Flashcards

0 / 13 complete

High Yield Notes

6 pages

Flashcards

Streptococcus agalactiae (Group B Strep)

of complete

External References

First Aid

2022

2021

2020

2019

2018

2017

2016

Hippurate test for Streptococcus agalactiae p. , 135

Meningitis

Streptococcus agalactiae p. , 135

Neonates

Streptococcus agalactiae in p. 135

Pneumonia p. 707

Streptococcus agalactiae p. , 135

Pregnancy p. 657

Streptococcus agalactiae in p. 135

Sepsis

Streptococcus agalactiae as cause p. 135

Streptococcus agalactiae (Group B strep) p. 135

β -hemolytic nature of p. 133

encapsulated bacteria p. 125

Gram-positive testing p. 132

immunodeficient patients p. 116

meningitis p. 177

in neonates p. 181

pneumonia p. 176

prophylaxis for p. 195

splenic dysfunction p. 96

External Links

Transcript

Content Reviewers

Contributors

Evode Iradufasha, MD

Tanner Marshall, MS

With Streptococcus agalactiae sometimes called Strep agalactiae, strepto means a chain, coccus means round shape, and agalactiae literally means “no milk”.

So, Strep agalactiae refers to the round bacteria that grow in chains and that was previously known to infect cattle, resulting in reduced milk production.

Later on, Strep agalactiae was found to also be a human potential pathogen responsible for a number of infections that most commonly affect pregnant women and newborns.

Strep agalactiae are also called Group B Strep – GBS - in Lancefield classification developed by an American microbiologist Rebecca Lancefield.

Ok now, a little bit of microbe anatomy and physiology.

Strep agalactiae has a thick peptidoglycan cell wall, which takes in purple dye when Gram stained - so this is a gram-positive bacteria.

It’s non-motile and doesn’t form spores, and also, it’s a facultative anaerobe, meaning that it can survive in both aerobic and anaerobic environments.

Now, a particular trait of Streptococcus species is that they are catalase negative, meaning they do not produce an enzyme called catalase.

This is unlike other common gram positive cocci, like Staphylococcus, which are catalase positive.

When cultivated on a medium called blood agar, Strep agalactiae colonies cause beta hemolysis, also called complete hemolysis.

That’s because Strep agalactiae makes a toxin called beta-hemolysin, that causes complete lysis of the hemoglobin in the red blood cells, making them blood agar change color from red to transparent yellow around the colonies.

However, other Streptococcus species, like Strep pyogenes, are also beta hemolytic.

So to identify Strep agalactiae specifically, the bacitracin test, the hippurate test, or the CAMP test can be done.

With the bacitracin test, a disk of bacitracin is added to the blood agar.

Strep agalactiae is bacitracin resistant, so the colonies remain intact, whereas Strep pyogenes is bacitracin sensitive, so the colonies die off.

With the CAMP test, Strep agalactiae is grown with Staphylococcus aureus on the same blood agar.

Both these bacteria are beta-hemolytic, but Strep agalactiae makes a substance called CAMP factor, which enhances the action of staphylococcal beta-hemolysin.

Summary

Streptococcus agalactiae, also known as group B streptococcus, is a gram-positive, beta-hemolytic, catalase-negative, and bacitracin-resistant bacterium, which can cause several infections in humans. Most frequently, Streptococcus agalactiae causes neonatal infections like pneumonia, sepsis, meningitis, and septic arthritis. It can also cause chorioamnionitis or cystitis in pregnant females. Treatment involves antibiotics like penicillin G or ampicillin, or Cefazolin and Vancomycin. To prevent Streptococcus agalactiae infections in neonates, intrapartum antibiotic prophylaxis can be administered to vaginally colonized pregnant females.

Elsevier

Copyright © 2023 Elsevier, except certain content provided by third parties

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.

RELX