Sepsis (Streptococcus agalactiae - Group B Streptococcus)
Overview
Plain-Language Overview
Sepsis (Streptococcus agalactiae - Group B Streptococcus) is a serious infection that affects the whole body and occurs when bacteria enter the bloodstream. This condition primarily involves the immune system and can cause widespread inflammation, leading to damage in multiple organs. The bacteria responsible, Group B Streptococcus, commonly colonizes the genital and gastrointestinal tracts but can invade the bloodstream, especially in newborns and immunocompromised individuals. Symptoms often include fever, rapid heartbeat, and difficulty breathing. If untreated, it can progress to organ failure and become life-threatening. Early recognition and diagnosis are critical to managing the infection and preventing severe complications.
Clinical Definition
Sepsis (Streptococcus agalactiae - Group B Streptococcus) is a systemic inflammatory response syndrome caused by bloodstream infection with Streptococcus agalactiae, a gram-positive cocci that is a leading cause of neonatal and peripartum infections. The core pathology involves an overwhelming host immune response to bacterial invasion, resulting in widespread cytokine release, endothelial dysfunction, and microvascular thrombosis. This leads to tissue hypoperfusion, organ dysfunction, and potentially septic shock. Group B Streptococcus is a major pathogen in neonates, pregnant women, and immunocompromised adults, often acquired via vertical transmission or mucosal colonization. The clinical significance lies in its rapid progression and high morbidity and mortality if not promptly treated with appropriate antibiotics and supportive care.
Inciting Event
Vertical transmission of Group B Streptococcus from colonized mother to neonate during labor or delivery.
Colonization of mucosal surfaces such as the vagina or rectum in pregnant women.
Breakdown of skin or mucosal barriers allowing bacterial entry into the bloodstream.
Invasive medical procedures introducing bacteria into sterile sites.
Latency Period
Early-onset neonatal sepsis typically presents within 24 hours of birth due to intrapartum exposure.
Late-onset neonatal sepsis occurs between 7 and 90 days of life, often from nosocomial or community sources.
Maternal colonization may be asymptomatic for weeks before transmission occurs during delivery.
Diagnostic Delay
Nonspecific early symptoms such as poor feeding and lethargy in neonates delay recognition.
Overlap with other neonatal conditions like respiratory distress syndrome complicates diagnosis.
Lack of maternal screening or inadequate intrapartum antibiotic prophylaxis increases missed cases.
Blood cultures may take 24-48 hours, delaying definitive diagnosis.
Clinical Presentation
Signs & Symptoms
Fever or hypothermia with chills
Hypotension and signs of shock such as cold extremities
Tachypnea and respiratory distress
Confusion or decreased level of consciousness
Poor feeding and irritability in neonates
History of Present Illness
Rapid onset of fever or hypothermia in neonates often signals sepsis.
Respiratory distress including tachypnea and grunting is common early presentation.
Poor feeding, irritability, and lethargy develop as systemic infection progresses.
Signs of shock such as hypotension and mottled skin may appear in advanced stages.
Past Medical History
Maternal history of Group B Streptococcus colonization or previous infant with GBS disease increases risk.
Prematurity or low birth weight predisposes neonates to severe infection.
History of prolonged rupture of membranes or chorioamnionitis during labor.
Prior invasive procedures or hospitalization in neonates increase exposure risk.
Family History
There are no known hereditary syndromes directly associated with Group B Streptococcus sepsis.
Family history is generally not contributory to risk of infection.
Genetic predisposition to sepsis susceptibility is not well defined for this condition.
Physical Exam Findings
Fever and tachycardia indicating systemic inflammatory response
Hypotension suggesting septic shock in severe cases
Tachypnea with possible respiratory distress
Petechiae or purpura may be present in disseminated intravascular coagulation
Altered mental status ranging from confusion to coma in severe sepsis
Diagnostic Workup
Diagnostic Criteria
Diagnosis of sepsis due to Group B Streptococcus requires identification of clinical signs of infection such as fever, tachycardia, and hypotension combined with laboratory evidence of systemic inflammation. Confirmatory diagnosis is established by isolating Streptococcus agalactiae from blood cultures or other normally sterile sites. Additional supportive findings include elevated white blood cell count, increased C-reactive protein, and evidence of organ dysfunction such as elevated lactate or altered mental status. The presence of these criteria in a patient with suspected infection confirms the diagnosis of sepsis.
Pathophysiology
Key Mechanisms
Bacterial invasion of the bloodstream by Streptococcus agalactiae triggers a systemic inflammatory response.
Activation of the innate immune system leads to widespread release of proinflammatory cytokines such as TNF-alpha and IL-1.
Endothelial injury and increased vascular permeability cause hypotension and tissue hypoperfusion.
Disseminated intravascular coagulation (DIC) may develop due to systemic activation of coagulation pathways.
Impaired oxygen delivery to tissues results in organ dysfunction characteristic of sepsis.
| Involvement | Details |
|---|---|
| Organs | Lungs are commonly involved in sepsis, often leading to ARDS and respiratory failure. |
Kidneys are vulnerable to acute injury due to hypoperfusion and inflammatory damage in sepsis. | |
Heart may develop septic cardiomyopathy characterized by decreased contractility and hypotension. | |
Liver plays a role in clearing bacteria and toxins but can be impaired during sepsis leading to coagulopathy. | |
| Tissues | Vascular endothelium is critically involved in sepsis pathophysiology by mediating inflammation and vascular leakage. |
Lung tissue is often affected by sepsis-induced acute respiratory distress syndrome (ARDS). | |
| Cells | Neutrophils are the primary immune cells that phagocytose and kill Streptococcus agalactiae during sepsis. |
Macrophages produce proinflammatory cytokines that mediate systemic inflammatory response in sepsis. | |
Endothelial cells become activated and contribute to increased vascular permeability and coagulopathy. | |
| Chemical Mediators | Tumor necrosis factor-alpha (TNF-α) is a key proinflammatory cytokine driving systemic inflammation in sepsis. |
Interleukin-1 (IL-1) promotes fever and leukocyte activation during the septic response. | |
Prostaglandins mediate vasodilation and contribute to hypotension in septic shock. | |
Nitric oxide (NO) causes vasodilation and contributes to septic shock-associated hypotension. |
Treatments
Pharmacological Treatments
Penicillin G
- Mechanism:
Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to bacterial lysis.
- Side effects:
Allergic reactions
Anaphylaxis
Gastrointestinal upset
- Clinical role:
First-line
Ampicillin
- Mechanism:
Broad-spectrum beta-lactam antibiotic that inhibits bacterial cell wall synthesis.
- Side effects:
Rash
Diarrhea
Hypersensitivity reactions
- Clinical role:
First-line
Gentamicin
- Mechanism:
Binds to the 30S ribosomal subunit, causing misreading of mRNA and inhibiting bacterial protein synthesis.
- Side effects:
Nephrotoxicity
Ototoxicity
Neuromuscular blockade
- Clinical role:
Adjunctive
Vancomycin
- Mechanism:
Inhibits bacterial cell wall synthesis by binding to D-Ala-D-Ala terminus of cell wall precursors.
- Side effects:
Nephrotoxicity
Red man syndrome
Ototoxicity
- Clinical role:
Second-line
Non-pharmacological Treatments
Aggressive intravenous fluid resuscitation to maintain hemodynamic stability and organ perfusion.
Supportive care including oxygen therapy and mechanical ventilation if respiratory failure develops.
Continuous monitoring of vital signs and organ function in an intensive care setting.
Removal or drainage of any infectious foci or indwelling devices if present.
Prevention
Pharmacological Prevention
Intrapartum antibiotic prophylaxis with penicillin or ampicillin to colonized pregnant women
Empiric broad-spectrum antibiotics in suspected neonatal sepsis until culture results
Targeted antibiotic therapy based on susceptibility testing
Use of beta-lactam antibiotics as first-line treatment
Avoidance of unnecessary antibiotic use to prevent resistance
Non-pharmacological Prevention
Screening pregnant women at 35-37 weeks for Streptococcus agalactiae colonization
Proper hand hygiene and infection control in neonatal units
Early identification and management of maternal risk factors such as prolonged rupture of membranes
Timely delivery planning to reduce neonatal exposure
Supportive care measures including fluid resuscitation and oxygenation
Outcome & Complications
Complications
Septic shock with multiorgan failure
Disseminated intravascular coagulation causing bleeding and thrombosis
Acute respiratory distress syndrome (ARDS)
Meningitis especially in neonates
Endocarditis in rare cases
| Short-term Sequelae | Long-term Sequelae |
|---|---|
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Differential Diagnoses
Sepsis (Streptococcus agalactiae - Group B Streptococcus) versus Escherichia coli Sepsis
Sepsis (Streptococcus agalactiae - Group B Streptococcus) | Escherichia coli Sepsis |
|---|---|
Gram-positive cocci in chains bacteremia | Gram-negative rod bacteremia |
Neonatal colonization from maternal genital tract | Urinary tract infection or intra-abdominal source |
Primarily affects neonates and pregnant women | Common in neonates and elderly |
Sepsis (Streptococcus agalactiae - Group B Streptococcus) versus Listeria monocytogenes Sepsis
Sepsis (Streptococcus agalactiae - Group B Streptococcus) | Listeria monocytogenes Sepsis |
|---|---|
Gram-positive cocci in chains bacteremia | Gram-positive rod bacteremia |
Vertical transmission during birth | Consumption of unpasteurized dairy or deli meats |
Primarily neonates and pregnant women | Neonates, elderly, and immunocompromised adults |
Sepsis (Streptococcus agalactiae - Group B Streptococcus) versus Staphylococcus aureus Sepsis
Sepsis (Streptococcus agalactiae - Group B Streptococcus) | Staphylococcus aureus Sepsis |
|---|---|
Gram-positive cocci in chains | Gram-positive cocci in clusters |
Maternal genital tract colonization | Skin infections, intravenous drug use, or indwelling catheters |
Often presents with early-onset neonatal sepsis | Rapid onset with potential for abscess formation |
Sepsis (Streptococcus agalactiae - Group B Streptococcus) versus Neonatal Herpes Simplex Virus (HSV) Infection
Sepsis (Streptococcus agalactiae - Group B Streptococcus) | Neonatal Herpes Simplex Virus (HSV) Infection |
|---|---|
Bacterial culture positive for Gram-positive cocci | Viral DNA detected by PCR |
Maternal colonization with Group B Streptococcus | Maternal genital herpes infection |
Predominantly systemic bacterial infection without vesicles | Vesicular skin lesions and CNS involvement |
Sepsis (Streptococcus agalactiae - Group B Streptococcus) versus Neonatal Candida Sepsis
Sepsis (Streptococcus agalactiae - Group B Streptococcus) | Neonatal Candida Sepsis |
|---|---|
Gram-positive cocci in chains | Yeast cells detected in blood culture |
Maternal genital tract colonization | Prematurity, broad-spectrum antibiotics, or central lines |
Acute onset neonatal bacterial sepsis | Subacute onset with potential for disseminated candidiasis |