Identifying Streptococci Classification Systems
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Questions and Answers

What is the most common manifestation of GBS infections in otherwise healthy adults?

  • Pneumonia
  • Urinary tract infections
  • Peripartum fever (correct)
  • Soft tissue infections

    • Which condition is often associated with peripartum fever?

  • Osteomyelitis
  • Chronic respiratory disease
  • Heart disease
  • Chorioamnionitis (correct)

    • Which group is at greater risk for GBS infections that are not related to the peripartum period?

  • Pregnant women in their third trimester
  • Young adults in urban areas
  • Elderly individuals and those with chronic illnesses (correct)
  • Children under 5 years old

    • What percentage of cases report relapse or recurrence of invasive GBS infections weeks to months after the first episode?

    <p>4%</p> Signup and view all the answers

    What is a common infection associated with Group B Streptococcal disease in adults?

    <p>Septic arthritis</p> Signup and view all the answers

    How does GBS's sensitivity to penicillin compare to GAS?

    <p>Less sensitive than GAS</p> Signup and view all the answers

    Which complication can occur occasionally from bacteremia due to GBS infection?

    <p>Meningitis</p> Signup and view all the answers

    What type of infection is cellulitis considered in the context of GBS infections in adults?

    <p>Occasional manifestation</p> Signup and view all the answers

    What hemolytic pattern is produced by streptococci that form large colonies on blood agar?

    <p>Beta (β)</p> Signup and view all the answers

    Which Lancefield group is associated with β-hemolytic streptococci that are commonly linked to human infections?

    <p>All of the above</p> Signup and view all the answers

    What is a key characteristic of α-hemolytic streptococci when cultured on blood agar?

    <p>Partial hemolysis and a greenish appearance</p> Signup and view all the answers

    How are enterococci classified in the context of streptococci?

    <p>As group D streptococci within a distinct genus</p> Signup and view all the answers

    Which species of streptococci is known for causing pneumonia and meningitis?

    <p>Streptococcus pneumoniae</p> Signup and view all the answers

    What characterizes streptococci with γ hemolysis?

    <p>They do not produce any hemolysis.</p> Signup and view all the answers

    What is the role of biochemical testing in identifying certain streptococci?

    <p>Identifying α-hemolytic streptococci species</p> Signup and view all the answers

    What association do Lancefield groups have with β-hemolytic streptococci?

    <p>They are classified based on serologic reactions with antisera.</p> Signup and view all the answers

    What is the recommended timeframe for screening for anogenital colonization in pregnant women?

    <p>35–37 weeks</p> Signup and view all the answers

    What is the loading dose of penicillin G recommended for intrapartum chemoprophylaxis?

    <p>5 million units</p> Signup and view all the answers

    Which alternative is recommended for women with a history of penicillin allergy?

    <p>Cefazolin</p> Signup and view all the answers

    What is the primary reason Gemella morbillorum was reclassified from Streptococcus morbillorum?

    <p>Genetic-relatedness studies</p> Signup and view all the answers

    Under what condition should vancomycin be used for intrapartum chemoprophylaxis?

    <p>When susceptibility testing results are unavailable or indicate resistance</p> Signup and view all the answers

    What percentage of pregnant women and newborns may be exposed to antibiotics due to treatment of colonization or risk factors?

    <p>33%</p> Signup and view all the answers

    What type of infections are commonly associated with the viridans streptococci?

    <p>Suppurative infections and abscesses</p> Signup and view all the answers

    Which of the following factors is NOT a risk factor for viridans streptococcal bacteremia?

    <p>Hypertension</p> Signup and view all the answers

    What is one potential risk associated with the treatment of colonized pregnant women?

    <p>Increase in antibiotic-resistant organisms</p> Signup and view all the answers

    What is one of the main focuses of ongoing research regarding Group B Streptococcus (GBS)?

    <p>Developing a GBS vaccine</p> Signup and view all the answers

    When does transient viridans streptococcal bacteremia typically occur?

    <p>Induced by eating or oral hygiene activities</p> Signup and view all the answers

    Which group of streptococci includes species that may cause various types of abscesses?

    <p>S.milleri group</p> Signup and view all the answers

    What is necessary for pregnant women who develop premature labor but have unknown culture status?

    <p>Intrapartum chemoprophylaxis</p> Signup and view all the answers

    What type of infection is NOT typically associated with viridans streptococci?

    <p>Pneumonia</p> Signup and view all the answers

    How do the hemolytic patterns of the S.milleri group differ from other viridans streptococci?

    <p>They may be α-, β-, or nonhemolytic</p> Signup and view all the answers

    Which of the following statements about viridans streptococci is false?

    <p>They are predominantly β-hemolytic.</p> Signup and view all the answers

    What type of infections are commonly produced by viridans streptococci?

    <p>Suppurative infections, particularly abscesses</p> Signup and view all the answers

    What is the recommended presumptive treatment for neutropenic patients with bacteremia suspected to be caused by viridans streptococci?

    <p>Vancomycin</p> Signup and view all the answers

    What must nutritionally variant streptococci require for growth in laboratory culture?

    <p>Supplemental thiol compounds or active forms of vitamin B6</p> Signup and view all the answers

    Which species is categorized under the genus Abiotrophia?

    <p>Abiotrophia defectiva</p> Signup and view all the answers

    How does the treatment outcome of endocarditis due to nutritionally variant streptococci compare to that of usual viridans streptococci?

    <p>Treatment failure and relapse are more common with nutritionally variant streptococci</p> Signup and view all the answers

    What two genera have nutritionally variant streptococci been reclassified into?

    <p>Abiotrophia and Granulicatella</p> Signup and view all the answers

    What is the recommended addition to the penicillin regimen for treating endocarditis caused by nutritionally variant streptococci?

    <p>Gentamicin</p> Signup and view all the answers

    Which of the following infections is NOT commonly associated with viridans streptococci?

    <p>Diabetic foot infections</p> Signup and view all the answers

    Study Notes

    Classification of Streptococci

    • Streptococci are classified by hemolytic pattern, Lancefield group, species name, and trivial name.
    • β-hemolytic streptococci show complete hemolysis in blood agar cultures, producing large colonies (≥0.5 mm).
    • Lancefield system groups β-hemolytic streptococci into groups A, B, C, and G, each linked to specific human infections.
    • α-hemolytic streptococci display partial hemolysis, resulting in a green appearance on blood agar and include Streptococcus pneumoniae and viridans streptococci.
    • Nonhemolytic streptococci, referred to as γ hemolysis, include group D streptococci and enterococci.

    Screening and Treatment for Group B Streptococcus (GBS)

    • The CDC recommends screening for GBS colonization at 35-37 weeks of pregnancy via lower vaginal and anorectal cultures.
    • Intravenous chemoprophylaxis is advised for culture-positive women or those with a history of GBS infection or bacteriuria.
    • Penicillin G is the preferred chemoprophylaxis, with cefazolin as an alternative for women with penicillin allergies.
    • Clindamycin is used for those with immediate hypersensitivity if susceptibility to the colonizing isolate is confirmed.
    • A GBS vaccine is under development, targeting childbearing-age women to enhance maternal antibody levels in newborns.

    Infections Caused by GBS in Adults

    • GBS infections in healthy adults are primarily linked to pregnancy, with peripartum fever being common.
    • Other infections include endometritis, chorioamnionitis, bacteremia, cellulitis, urinary tract infections, pneumonia, and septic arthritis.
    • Relapses or recurrences of invasive infections occur in approximately 4% of cases.

    Treatment of GBS Infections

    • GBS is less sensitive to penicillin compared to Group A Streptococcus (GAS), requiring higher dosages for treatment.

    Viridans Streptococci

    • Viridans streptococci induce transient bacteremia, often following dental procedures or minor trauma, and are notable for their role in endocarditis.
    • These organisms are often isolated in mixed flora from sites of sinusitis, brain abscesses, and liver abscesses.
    • Neutropenic patients are at higher risk for viridans streptococcal bacteremia, particularly after intensive chemotherapy.

    S. Milleri Group Infections

    • The S. milleri group includes S. intermedius, S. anginosus, and S. constellatus, causing various suppurative infections, especially abscesses.
    • These species may present with various hemolytic patterns and are associated with oral and respiratory tract infections.

    Treatment Considerations for Viridans Streptococci

    • Neutropenic patients with bacteremia likely require early treatment with vancomycin due to potential penicillin resistance.
    • Viridans streptococci isolated in other cases reliably respond to penicillin, requiring susceptibility testing for serious infections.

    Nutritionally Variant Streptococci (NVS)

    • NVS, including Abiotrophia and Granulicatella species, require special growth factors for laboratory culture and are grouped with viridans streptococci.
    • Endocarditis caused by NVS has a higher rate of treatment failure, often necessitating the addition of gentamicin to the treatment regimen with penicillin.

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    Chapter 148: Streptococcal Infections PDF

    Description

    This quiz explores the classification methods used by clinicians and clinical microbiologists to identify streptococci. It focuses on hemolytic patterns, Lancefield groups, and the characteristics of β-hemolytic streptococci. Test your knowledge on these essential microbiological techniques.

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