Streptococcus anginosus group ( Streptococcus millieri group )

Publication: 18/11/2014  
Next review: 04/11/2023  
Clinical Guideline
ID: 4022 
Approved By: Trust Clinical Guidelines Group 
Copyright© Leeds Teaching Hospitals NHS Trust 2020  


This Clinical Guideline is intended for use by healthcare professionals within Leeds unless otherwise stated.
For healthcare professionals in other trusts, please ensure that you consult relevant local and national guidance.

Department of Microbiology Bacteraemia Guideline

Streptococcus anginosus group (Streptococcus millieri group)

Quick reference guide to the management of bacteraemia with
Streptococcus anginosus group

This document provides guidelines for doctors on the management of patients with confirmed bacteraemias (blood cultures). This document is supplementary to, and should be used in conjunction with, the antimicrobial guidelines.

Streptococcus anginosus group (Streoptococcus millinery group)

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The aim of this guideline is to:

  • Provide education to junior microbiology registrars
  • Support communication of Gram stain results from microbiologists to ward doctors
  • Support ward doctors in treating and investigating bacteraemic patients

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The blood culture process: Timings of culture, identification, susceptibility tests and clinical liaison.
How to use this guideline: This guideline should be used to help in the management of patients with a confirmed bacteraemia. The guideline should be used to support interaction with specialist advice e.g. Microbiology.

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About Streptococcus anginosus group

  • The “anginosus group” which is also known as the “Streptococcus millieri group” belongs among the Viridans streptococci and corresponds to three species-S. intremidius, S. constellatus, S .anginosus.
  • These organisms are part of the oropharyngeal flora and they are also found in the gastrointestinal tract and in the vagina.
  • Can cause invasive pyogenic infections, which usually differentiates them from other viridans streptococci3.

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Clinical differential diagnosis

The differential diagnosis of bacteraemia with S. anginosus group includes:

  • Abdominal infections (liver abscesses, peritonitis, appendicitis, cholangitis)
  • Pelvic infections
  • Thoracic infections (Lung abscesses, empyema)
  • Brain Abscesses
  • Skin and Soft tissue infections (cellulitis, subcutaneous abscesses)
  • Dental infections
  • Sinusitis
  • Endocarditis
  • Other infections ( osteomyelitis, septic arthritis, wound infections)

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Antimicrobial susceptibilities

  • Members of S. anginosus group are largely susceptible to beta-lactam agents. Resistance to penicillin is rare4,5
  • Vancomycin is an appropriate alternative agent if the patient has allergy to penicillin
  • Resistance to Clindamycin and Erythromycin has been described and appears to be emerging among S. anginosus group5
  • Resistance to quinolones tends to develop easily and therefore are not appropriate first line agents6
  • Most strains of anginosus group are resistant to aminoglycosides, however synergy with b-lactam agent usually can be demonstrated7

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Antimicrobial treatment

  • Antibiotic therapy should always be reviewed with speciation of the bacteria, and with results of sensitivity tests

History of the following are important to determine appropriate antimicrobial therapy

  • Source of infection
  • Allergy status

The table below outlines some of the common infections associated with each of the clinical syndromes.

Clinical diagnosis

Antimicrobial therapy

Intra-abdominal infections

See guideline

Pelvic infections

Discuss with microbiology

Lung abscesses

See guideline

Infected Parapneumonic Effusions and Empyema

See guideline

Brain abscesses

See guideline


See guideline


See guideline

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Supplementary Investigations

Consider further investigations as appropriate to source of infection, please see relevant guidelines.

Further Action:

Surgical drainage of an abscess is usually indicated as an adjunctive therapy.


Record: 4022
Clinical condition:
Target patient group:
Target professional group(s): Secondary Care Doctors
Adapted from:

Evidence base

  1. BNF Link
  2. EMC Link
  3. Claridge JE et al. Streptococcus intermidius, Streptococcus constellatus and Streptococcus anginosus are of different clinical importance and are not equally associated with abscess. Clin Infect Dis.2001;32:1511-1515
  4. Tracy M et al. Antibiotics susceptibilities of genetically characterizes Streptococcus millieri group strains. Antimicrob Agents Chemother.2001;45:1511-1514
  5. Trends in Antimicrobial Resistance in England and Wales 2004-2005. HPA
  6. Yamamoto N et al. In vitro activity of sitafloxacin compared with several fluoroquinolones against Streptococcus anginosus and Streptococcus constellatus. Int J Antimicrob Agents.2006;27(2):171
  7. Stelzmueller I et al. Relevance of group Milleri streptococci in thoracic surgery: a clinical update. Am Surg.2007;73(5):492

Approved By

Trust Clinical Guidelines Group

Document history

LHP version 1.0

Related information

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