Identifying Streptococci Classification Systems

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?

4% Signup and view all the answers

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

Septic arthritis Signup and view all the answers

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

Less sensitive than GAS Signup and view all the answers

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

Meningitis Signup and view all the answers

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

Occasional manifestation Signup and view all the answers

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

Beta (β) Signup and view all the answers

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

All of the above Signup and view all the answers

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

Partial hemolysis and a greenish appearance Signup and view all the answers

How are enterococci classified in the context of streptococci?

As group D streptococci within a distinct genus Signup and view all the answers

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

Streptococcus pneumoniae Signup and view all the answers

What characterizes streptococci with γ hemolysis?

They do not produce any hemolysis. Signup and view all the answers

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

Identifying α-hemolytic streptococci species Signup and view all the answers

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

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

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

35–37 weeks Signup and view all the answers

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

5 million units Signup and view all the answers

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

Cefazolin Signup and view all the answers

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

Genetic-relatedness studies Signup and view all the answers

Under what condition should vancomycin be used for intrapartum chemoprophylaxis?

When susceptibility testing results are unavailable or indicate resistance 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?

33% Signup and view all the answers

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

Suppurative infections and abscesses Signup and view all the answers

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

Hypertension Signup and view all the answers

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

Increase in antibiotic-resistant organisms Signup and view all the answers

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

Developing a GBS vaccine Signup and view all the answers

When does transient viridans streptococcal bacteremia typically occur?

Induced by eating or oral hygiene activities Signup and view all the answers

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

S.milleri group Signup and view all the answers

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

Intrapartum chemoprophylaxis Signup and view all the answers

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

Pneumonia Signup and view all the answers

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

They may be α-, β-, or nonhemolytic Signup and view all the answers

Which of the following statements about viridans streptococci is false?

They are predominantly β-hemolytic. Signup and view all the answers

What type of infections are commonly produced by viridans streptococci?

Suppurative infections, particularly abscesses Signup and view all the answers

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

Vancomycin Signup and view all the answers

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

Supplemental thiol compounds or active forms of vitamin B6 Signup and view all the answers

Which species is categorized under the genus Abiotrophia?

Abiotrophia defectiva 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?

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

What two genera have nutritionally variant streptococci been reclassified into?

Abiotrophia and Granulicatella Signup and view all the answers

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

Gentamicin Signup and view all the answers

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

Diabetic foot infections 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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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.