Learning Outcomes:
- List the three genera of clinically significant bacteria found in the family Streptococcaceae.
- State the basis for classification used for most streptococci of clinical significance.
- State in which group the following belong:
- Streptococcus pyogenes
- Streptococcus agalactiae
- Enterococcus faecalis
- List three characteristics that may indicate a streptococcus belongs to the Streptococcus anginosus group
- List and know how to perform identification tests for Streptococci and Enterococci.
Streptococcus pyogenes or Group A Streptococcus
- Describe typical cellular and colonial morphology
- State optimum temperature, atmosphere and suitable medium for isolation
- Name the two hemolysins responsible for hemolysis.
- Describe the use of bacitracin susceptibility, SXT susceptibility and the PYR test in presumptive identification.
- State the basis for definitive identification of pyogenes.
- Name the two methods commonly used for identification of streptococcal group antigen and outline the principle and procedure for each.
- Outline the advantages and disadvantages of direct detection of group A antigen from throat swabs.
- State the susceptibility results for penicillin, erythromycin and tetracycline.
- List the four categories of clinical disease caused by pyogenes.
- Explain why rapid detection and reporting of group A Streptococcus from blood cultures is important.
- Name the two post-streptococcal diseases with a brief description of each.
Streptococcus agalactiae or Group B Streptococcus
- Describe typical cellular and colonial morphology.
- Explain why it may be necessary to detect group B Streptococci in vaginal specimens and briefly describe the principles used for slow and rapid detection.
- State typical reactions for CAMP test, hippurate hydrolysis, esculin hydrolysis, bacitracin and SXT susceptibility.
- State how definitive identification is established.
- State what body fluids may be used for direct detection of group B antigen.
- Describe group B infections in the neonate and explain the etiology
Group D Streptococci and Enterococci
- Describe typical cellular and colonial morphology.
- Explain why group D antigen is sometimes not detected by streptococcal grouping procedures.
- State the result of group D and enterococci for bile esculin and state how to differentiate enterococci from Group D using PYR and 6.5% sodium chloride.
- State how species identification of group D streptococcus and enterococci are accomplished and explain when this is required.
- Compare the relative susceptibility of enterococci and Group D streptococcus to penicillin and ampicillin.
- Name the two antibiotic groups commonly used together for treatment of systemic enterococcal infections.
- Describe the significance of Vancomycin Resistant Enterococci (VRE) and outline the method of detection.
- State where group D are found as normal flora and list common infections.
- Describe the clinical significance of Streptococcus gallolyticus (formerly known as Streptococcus bovis) in blood cultures.
Group C Streptococci
- Describe the colonial morphology and the usual method used for identification.
- Describe the clinical significance.
Group F Streptococci
- Describe the colonial morphology and state the relationship to the Streptococcus anginosus
- Describe the clinical significance.
Group G Streptococci
- Describe the clinical significance.
Streptococcus pneumoniae
- Describe typical cellular and colonial morphology and explain why bacteria may look like rods.
- Describe the effect of increased carbon dioxide on growth.
- State optimum temperature for growth and name a suitable medium for isolation.
- Describe how colonies change with age and how colonies are affected by anaerobic incubation and growth on chocolate agar.
- Explain why subcultures of blood cultures containing pneumoniae should be done as soon as growth is noted.
- State how to differentiate pneumoniae from viridans streptococci using bile solubility and optochin susceptibility.
- Describe the usual susceptibility to penicillin and explain why susceptibility testing may be necessary.
- List typical infections caused by pneumoniae.
- Describe typical findings in a spinal fluid from a patient with pneumococcal meningitis.
Viridans Streptococci
- Outline the criteria used to place an organism in the viridans Streptococci group.
- Describe typical cellular and colonial morphology.
- Describe the clinical significance.
Streptococcus iniae
- Describe characteristics indicative of this organism.
- Describe the clinical significance and usual source of bacteria.
Nutritionally Variant Streptococci- Granulicatella and Abiotrophia
- List other names used for this group and their clinical significance.
- Describe methods of growing these bacteria.
Aerococcus, Leuconostoc and Pediococcus
- List clinical significance
Hemolysis Production for Streptococci
- Explain why blood agar should be free of fermentable carbohydrate and list possible sources of carbohydrate in the media.
- State the preferred type of blood and usual concentration.
- Explain why reduced oxygen concentration is preferred during incubation and state the optimum method of obtaining this.
Lancefield grouping
- Explain how to perform the test
- State how this test is used for classification of streptococci and enterococci.
Bacitracin Susceptibility
- Describe the principle and procedure of the test and how to interpret the results
- List suitable quality control organisms.
- Explain why pure cultures should be used and why only beta hemolytic organisms should be tested.
CAMP Test
- Describe the principle and procedure of the test and how to interpret the results.
- State the type of blood agar required and how to select an appropriate strain of aureus.
- List suitable quality control organisms.
PYR Test
- Describe the principle and procedure of the test and how to interpret the results
- List suitable quality control organisms.
Rapid Hippurate Hydrolysis
- Describe the principle and procedure of the test and how to interpret the results.
- List suitable quality control organisms.
- Explain why the test medium should be free of peptone and why a pure culture should be used.
Bile Esculin Test
- Describe the principle and procedure of the test and how to interpret the results.
- List suitable control organisms.
- Explain why a pure culture is required for the test.
Bile Solubility Test
- Describe the principle and procedure of the test and how to interpret the results.
- Name suitable reagents.
- List suitable quality control organisms.
- Explain why a fresh culture should be used.
Optochin Susceptibility Test
- Describe the principle and procedure of the test and how to report the results
- List suitable quality control organisms.
- Describe the effect of incubation in increased carbon dioxide.
Course Revisions: Erin Jansen, MLT
Original Author: Helen Smith, MLT
Version Date: September 2021
PEP hours: 10
CPS credits: 0
*Note: PEP hours and/or CPS credits will only be awarded upon successful completion of Final Exam.
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