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{{Group B streptococcal infection}}
{{Group B streptococcal infection}}
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==Overview==
==Overview==
'''''Streptococcus agalactiae''''' also known as '''Group B Streptococcus''' is a [[gram-positive]] [[streptococcus]] characterized by the presence of group B [[Rebecca Lancefield|Lancefield]] antigen. These bacteria cause [[Group B streptococcal infection]]. Streptococcus agalactiae is a species of the normal flora of the gut and female urogenital tract. Early perinatal infection causes pneumonia or septicemia, which are associated with a high mortalityDuring delivery, a baby can acquire ''S. agalactiae'' and develop neonatal [[sepsis]], neonatal [[meningitis]], and/or neonatal [[pneumonia]]Neonates with meningitis do not present with the hallmark sign of adult meningitis, a stiff neck.  They display nonspecific symptoms such as fever, vomiting, poor feeding, and irritability.  The polysaccharide antiphagocytic capsule is this bacterium's main [[Virulence|virulence factor]].
Group B Streptococcus (GBS) disease is caused by the infection with the bacterium GBS which is a beta hemolytic [[gram-positive]] [[streptococcus]] characterized by the presence of group B [[Rebecca Lancefield|Lancefield]] antigen. GBS displays beta-hemolysis when cultured on a blood agar plate and produces zones of hemolysis that are only slightly larger than the colonies themselves. The species other name S. agalactiae, where "agalactiae" means "no milk", alludes to thisGBS hydrolyzes sodium hippurate and gives a positive response in the [[CAMP test]]. GBS is also sensitive to [[bile]] and will lyse in its presenceGBS is a species of the normal flora of the gut and female urogenital tract.  The polysaccharide antiphagocytic capsule is this bacterium's main [[Virulence|virulence factor]].


''S. agalactiae'' displays [[beta-hemolysis]] when cultured on a blood agar plate and produce zones of hemolysis that are only slightly larger than the colonies themselves.  Group B streptococci hydrolyze sodium hippurate and give a positive response in the CAMP test. ''S. agalactiae'' is also sensitive to [[bile]] and will lyse in its presence.
==Taxonomy==
'''''Cellular organisms; Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae; Streptococcus'''''


S. galactias
==Biology==
GBS is characterized by the following features:
* [[Gram-positive]]
* Cocci in pairs and short chains
* Group B [[Rebecca Lancefield|Lancefield]] antigen
* Non-motile
* [[Catalase]]-negative
* Non-[[spore]] forming
* Polysaccharide antiphagocytic capsule (main virulence factor)
* Surface proteins
* Beta hemolysis
 
==Identification==
The [[CAMP test]] is an important test for identification. GBS are screened through this test. It is characterized by the presence of [[Rebecca Lancefield|Lancefield]] antigen and by its ability to hydrolyze sodium hippurate.
 
GBS is also sensitive to [[bile]], and will lyse in its presence.
 
Shown below is an image depicting an example of a positive [[CAMP test]] proving that GBS is present. The arrowhead formation on the Blood agarose gel, BAP (5% sheep blood) indicates that this bacteria is GBS.
 
[[File:CAMP test GBS.JPG|400px]]
 
Shown below is an image depicting colonies of GBS under microscope.
 
[[File:Colonies of GBS seen under microscope.jpg]]
 
Shown below is an image depicting the growth of colonies of GBS on ChromID CPS chromogenic agar.
 
[[File:GBS on ChromID CPS chromogenic agar.jpg|300px]]
 
Shown below is an image depicting the growth of colonies of GBS on Columbia horse blood agar.
 
[[File:GBS on Columbia Horse blood agar.jpg|300px]]
 
 
==Gallery==
<gallery>
Image: Group A streptococcus28.jpeg| Right elbow of a patient with group B Streptococcus (GBS) bacteremia, with localized edema and erythema. <SMALL><SMALL>''[http://phil.cdc.gov/phil/home.asp From Public Health Image Library (PHIL).] ''<ref name=PHIL> {{Cite web | title = Public Health Image Library (PHIL) | url = http://phil.cdc.gov/phil/home.asp}}</ref></SMALL></SMALL>
Image: Group A streptococcus05.jpeg| Group-B streptococci (GBS) identified by CAMP test, which takes advantage of the capacity of GBS to produce this CAMP factor that most other hemolytic streptococci do not produce. <SMALL><SMALL>''[http://phil.cdc.gov/phil/home.asp From Public Health Image Library (PHIL).] ''<ref name=PHIL> {{Cite web | title = Public Health Image Library (PHIL) | url = http://phil.cdc.gov/phil/home.asp}}</ref></SMALL></SMALL>
 
Image: Group A streptococcus04.jpeg| Quantitative difference in hemolytic reactivity seen on BAP with group-D Streptococci (left wedge), group-B Streptococci (middle wedge), and group-A Streptococci (right wedge) bacteria.  <SMALL><SMALL>''[http://phil.cdc.gov/phil/home.asp From Public Health Image Library (PHIL).] ''<ref name=PHIL> {{Cite web | title = Public Health Image Library (PHIL) | url = http://phil.cdc.gov/phil/home.asp}}</ref></SMALL></SMALL>
Image: Group A streptococcus01.jpeg| Clindamycin-resistant Group-B Streptococcus (GBS), also known as S. agalactiae.  <SMALL><SMALL>''[http://phil.cdc.gov/phil/home.asp From Public Health Image Library (PHIL).] ''<ref name=PHIL> {{Cite web | title = Public Health Image Library (PHIL) | url = http://phil.cdc.gov/phil/home.asp}}</ref></SMALL></SMALL>
 
</gallery>
 
==Treatment==
 
==Antimicrobial therapy==
 
:*'''Streptococcus agalactiae treatment''' (GBS-group B Streptococcus)
::* 1. '''Early onset group B streptococcal infections'''<ref>{{cite web|title=group B Streptococcus infections|url=http://redbook.solutions.aap.org/book.aspx?bookid=1484}}</ref>
:::* 1.1 '''Bacteremia or sepsis or pneumonia'''
::::* 1.1.1 '''Empiric therapy'''
:::::* Preferred regimen: [[Ampicillin]] 150 mg/kg IV q12h for 10 days {{and}} [[Gentamicin]] 4 mg/kg IV q12h for 10 days-for infants born at ≥ 35 weeks gestation; [[Gentamicin]] 3 mg/kg IV q24h for 10 days-for infants born at < 35 weeks gestation
::::* 1.1.2 '''Definitive therapy'''
:::::* Preferred regimen: [[Penicillin G]] 50,000-100,000 units/kg per day IV divided q12h for 10 days
:::* 1.2 '''Meningitis'''
::::* 1.2.1 '''Empiric therapy'''
:::::* Preferred regimen: [[Ampicillin]] 100-150 mg/kg IV q8h for 14-21 days {{and}} [[Gentamicin]] 4 mg/kg IV q24h for 14-21 days-for infants born at ≥ 35 weeks gestation; [[Gentamicin]] 3 mg/kg IV q24h for 14-21 days-for infants born at < 35 weeks gestation
::::* 1.2.2 '''Definitive therapy'''
:::::* Preferred regimen: [[Penicillin G]] 250,000-450,000 units/kg per day IV divided q8h for 14-21 days
::::::* Note: Cellulitis is the most frequent clinical manifestation of GBS-associated skin and soft tissue infections.
::* 2. '''Late onset group b streptococcus infections in neonates and young infants (age > 1 week and body weight ≥ 1 kg with normal renal function)'''<ref>{{cite web|title=group B Streptococcus infections|url=http://redbook.solutions.aap.org/book.aspx?bookid=1484}}</ref>
:::* 2.1 Bacteremia without a focus
::::* 2.1.1 '''Empiric therapy'''
:::::* Preferred regimen: [[Ampicillin]] IV for 10 days, [[Nafcillin]] IV for 10 days, ({{or}} [[Vancomycin]] IV for 10 days) {{and}} [[Gentamicin]] IV for 10 days ({{or}} [[Cefotaxime]] IV for 10 days)
::::* 2.1.2 '''Definitive therapy'''
:::::* Preferred regimen: [[Penicillin-G]] 75,000-150,000 units/kg per day IV divided q8h for 10 days
:::* 2.2 '''Meningitis'''
::::* 2.2.1 '''Empiric therapy'''
:::::* Preferred regimen: [[Ampicillin]] IV for 14-21 days with or without [[Vancomycin]] IV for 14-21 day {{and}} [[Gentamicin]] IV for 14-21 days {{or}} [[Cefotaxime]] IV for 14-21 day
::::* 2.2.2 '''Definitive therapy'''
:::::* Preferred regimen: [[Penicillin-G]] 450,000-500,000 units/kg per day IV divided q6h for 14-21 days
:::* 2.3 '''Cellulitis or adenitis'''
::::* 2.3.1 '''Empiric therapy'''
:::::* Preferred regimen: [[Nafcillin]] IV for 10-14 days ({{or}} [[Vancomycin IV for 10-14 days) {{and}} [[Gentamicin]] IV for 10-14 days ({{or}} [[Cefotaxime]] IV for 10-14 days)
::::* 2.3.2 '''Definitive therapy'''
:::::* Preferred regimen: [[Penicillin-G]] 75,000-150,000 units/kg per day IV divided q8h for 10-14 days
:::* 2.4 '''Septic arthritis'''
::::* 2.4.1 '''Empiric therapy'''
:::::* Preferred regimen: [[Nafcillin]] IV for 14-21 days {{or}} [[Vancomycin]] IV for 14-21 days {{and}} [[Cefotaxime]] IV for 14-21 days
::::* 2.4.2 '''Definitive therapy'''
:::::* Preferred regimen: [[Penicillin-G]] 75,000-150,000 units/kg per day IV divided q8h for 14-21 days
:::* 2.5 Osteomyelitis
::::* 2.5.1 '''Empiric therapy'''
:::::* Preferred regimen: [[Nafcillin]] IV for 21-28 days {{or}} [[Vancomycin]] IV for 21-28 days {{and}} [[Cefotaxime]] IV for 21-28 days
::::* 2.5.2 '''Definitive therapy'''
:::::* Preferred regimen: [[Penicillin-G]] 75,000-150,000 units/kg per day IV divided q8h for 21-28 days
:::* 2.6 Urinary tract infection
::::* 2.6.1 '''Empiric therapy'''
:::::* Preferred regimen: [[Ampicillin]] IV for 10 days, [[Nafcillin]] IV for 10 days, ({{or}} [[Vancomycin]] IV for 10 days) {{and}} [[Gentamicin]] IV for 10 days ({{or}} [[Cefotaxime]] IV for 10 days)
::::* 2.6.2 '''Definitive therapy'''
:::::* Preferred regimen: [[Penicillin-G]] 75,000-150,000 units/kg per day IV divided q8h for 10 days
 
:* '''Neonatal prophylaxis'''<ref name="pmid24446442">{{cite journal| author=Mukhopadhyay S, Dukhovny D, Mao W, Eichenwald EC, Puopolo KM| title=2010 perinatal GBS prevention guideline and resource utilization. | journal=Pediatrics | year= 2014 | volume= 133 | issue= 2 | pages= 196-203 | pmid=24446442 | doi=10.1542/peds.2013-1866 | pmc=PMC3904275 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=24446442  }} </ref>
::* Group B streptococcus infection (maternal dose for neonatal prophylaxis)
:::* Preferred regimen: [[Penicillin-G]], [[Ampicillin]] 2 g IV initial dose, {{then}} 1 g q4h until delivery, [[Cefazolin]] ≥ 4h prior to delivery.


==References==
==References==
 
{{Reflist|2}}
*Brooks, Geo F., Janet Butel, and Stephen Morse.  <u>Jawetz, Melnick, and Adelberg's Medical Microbiology, 22nd edition</u>. 2001.
*Gillespie, Stephen and Kathleen Bamford. <u>Medical Microbiology at a Glance</u>. 2000.


[[Category:Streptococcaceae]]
[[Category:Streptococcaceae]]
[[Category:Obstetrics]]
[[Category:Obstetrics]]
[[Category:Mature chapter]]
[[Category:Pediatrics]]
[[Category:Neonatology]]
[[Category:Infectious Disease Project]]




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Latest revision as of 17:51, 18 September 2017

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rim Halaby, M.D. [2]

Overview

Group B Streptococcus (GBS) disease is caused by the infection with the bacterium GBS which is a beta hemolytic gram-positive streptococcus characterized by the presence of group B Lancefield antigen. GBS displays beta-hemolysis when cultured on a blood agar plate and produces zones of hemolysis that are only slightly larger than the colonies themselves. The species other name S. agalactiae, where "agalactiae" means "no milk", alludes to this. GBS hydrolyzes sodium hippurate and gives a positive response in the CAMP test. GBS is also sensitive to bile and will lyse in its presence. GBS is a species of the normal flora of the gut and female urogenital tract. The polysaccharide antiphagocytic capsule is this bacterium's main virulence factor.

Taxonomy

Cellular organisms; Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae; Streptococcus

Biology

GBS is characterized by the following features:

  • Gram-positive
  • Cocci in pairs and short chains
  • Group B Lancefield antigen
  • Non-motile
  • Catalase-negative
  • Non-spore forming
  • Polysaccharide antiphagocytic capsule (main virulence factor)
  • Surface proteins
  • Beta hemolysis

Identification

The CAMP test is an important test for identification. GBS are screened through this test. It is characterized by the presence of Lancefield antigen and by its ability to hydrolyze sodium hippurate.

GBS is also sensitive to bile, and will lyse in its presence.

Shown below is an image depicting an example of a positive CAMP test proving that GBS is present. The arrowhead formation on the Blood agarose gel, BAP (5% sheep blood) indicates that this bacteria is GBS.

Shown below is an image depicting colonies of GBS under microscope.

Shown below is an image depicting the growth of colonies of GBS on ChromID CPS chromogenic agar.

Shown below is an image depicting the growth of colonies of GBS on Columbia horse blood agar.


Gallery

Treatment

Antimicrobial therapy

  • Streptococcus agalactiae treatment (GBS-group B Streptococcus)
  • 1. Early onset group B streptococcal infections[2]
  • 1.1 Bacteremia or sepsis or pneumonia
  • 1.1.1 Empiric therapy
  • Preferred regimen: Ampicillin 150 mg/kg IV q12h for 10 days AND Gentamicin 4 mg/kg IV q12h for 10 days-for infants born at ≥ 35 weeks gestation; Gentamicin 3 mg/kg IV q24h for 10 days-for infants born at < 35 weeks gestation
  • 1.1.2 Definitive therapy
  • Preferred regimen: Penicillin G 50,000-100,000 units/kg per day IV divided q12h for 10 days
  • 1.2 Meningitis
  • 1.2.1 Empiric therapy
  • Preferred regimen: Ampicillin 100-150 mg/kg IV q8h for 14-21 days AND Gentamicin 4 mg/kg IV q24h for 14-21 days-for infants born at ≥ 35 weeks gestation; Gentamicin 3 mg/kg IV q24h for 14-21 days-for infants born at < 35 weeks gestation
  • 1.2.2 Definitive therapy
  • Preferred regimen: Penicillin G 250,000-450,000 units/kg per day IV divided q8h for 14-21 days
  • Note: Cellulitis is the most frequent clinical manifestation of GBS-associated skin and soft tissue infections.
  • 2. Late onset group b streptococcus infections in neonates and young infants (age > 1 week and body weight ≥ 1 kg with normal renal function)[3]
  • 2.1 Bacteremia without a focus
  • 2.1.1 Empiric therapy
  • 2.1.2 Definitive therapy
  • Preferred regimen: Penicillin-G 75,000-150,000 units/kg per day IV divided q8h for 10 days
  • 2.2 Meningitis
  • 2.2.1 Empiric therapy
  • 2.2.2 Definitive therapy
  • Preferred regimen: Penicillin-G 450,000-500,000 units/kg per day IV divided q6h for 14-21 days
  • 2.3 Cellulitis or adenitis
  • 2.3.1 Empiric therapy
  • Preferred regimen: Nafcillin IV for 10-14 days (OR [[Vancomycin IV for 10-14 days) AND Gentamicin IV for 10-14 days (OR Cefotaxime IV for 10-14 days)
  • 2.3.2 Definitive therapy
  • Preferred regimen: Penicillin-G 75,000-150,000 units/kg per day IV divided q8h for 10-14 days
  • 2.4 Septic arthritis
  • 2.4.1 Empiric therapy
  • 2.4.2 Definitive therapy
  • Preferred regimen: Penicillin-G 75,000-150,000 units/kg per day IV divided q8h for 14-21 days
  • 2.5 Osteomyelitis
  • 2.5.1 Empiric therapy
  • 2.5.2 Definitive therapy
  • Preferred regimen: Penicillin-G 75,000-150,000 units/kg per day IV divided q8h for 21-28 days
  • 2.6 Urinary tract infection
  • 2.6.1 Empiric therapy
  • 2.6.2 Definitive therapy
  • Preferred regimen: Penicillin-G 75,000-150,000 units/kg per day IV divided q8h for 10 days
  • Neonatal prophylaxis[4]
  • Group B streptococcus infection (maternal dose for neonatal prophylaxis)

References

  1. 1.0 1.1 1.2 1.3 "Public Health Image Library (PHIL)".
  2. "group B Streptococcus infections".
  3. "group B Streptococcus infections".
  4. Mukhopadhyay S, Dukhovny D, Mao W, Eichenwald EC, Puopolo KM (2014). "2010 perinatal GBS prevention guideline and resource utilization". Pediatrics. 133 (2): 196–203. doi:10.1542/peds.2013-1866. PMC 3904275. PMID 24446442.


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