Group B streptococcus screening US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Group B streptococcus screening. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Group B streptococcus screening US Medical PG Question 1: An 18-month-old boy presents to the emergency department for malaise. The boy’s parents report worsening fatigue for 3 days with associated irritability and anorexia. The patient’s newborn screening revealed a point mutation in the beta-globin gene but the patient has otherwise been healthy since birth. On physical exam, his temperature is 102.4°F (39.1°C), blood pressure is 78/42 mmHg, pulse is 124/min, and respirations are 32/min. The child is tired-appearing and difficult to soothe. Laboratory testing is performed and reveals the following:
Serum:
Na+: 137 mEq/L
Cl-: 100 mEq/L
K+: 4.4 mEq/L
HCO3-: 24 mEq/L
Urea nitrogen: 16 mg/dL
Creatinine: 0.9 mg/dL
Glucose: 96 mg/dL
Leukocyte count: 19,300/mm^3 with normal differential
Hemoglobin: 7.8 g/dL
Hematocrit: 21%
Mean corpuscular volume: 82 um^3
Platelet count: 324,000/mm^3
Reticulocyte index: 3.6%
Which of the following is the most likely causative organism for this patient's presentation?
- A. Streptococcus pneumoniae (Correct Answer)
- B. Listeria monocytogenes
- C. Haemophilus influenzae
- D. Neisseria meningitidis
- E. Salmonella
Group B streptococcus screening Explanation: ***Streptococcus pneumoniae***
- Patients with **sickle cell disease** (indicated by the beta-globin gene mutation) are functionally **asplenic** and highly susceptible to encapsulated bacteria, with *S. pneumoniae* being the most common cause of **sepsis** in this population.
- The patient's presentation with **fever**, **hypotension**, **tachycardia**, and **leukocytosis** is consistent with **sepsis**, and the elevated reticulocyte index suggests a hemolytic process or bone marrow response, common in sickle cell crises exacerbated by infection.
*Listeria monocytogenes*
- This pathogen primarily affects **neonates**, **immunocompromised individuals**, and **elderly** patients, often presenting as meningitis or sepsis.
- While it can cause sepsis, it is a less common cause of severe infection in a non-neonatal toddler with sickle cell disease compared to *S. pneumoniae*.
*Haemophilus influenzae*
- Although *H. influenzae* is an encapsulated bacterium that can cause severe infections in functionally asplenic patients, routine childhood vaccinations have significantly reduced its incidence.
- While possible, it is less likely than *S. pneumoniae* in an 18-month-old, especially if vaccinated, and *S. pneumoniae* remains the leading cause of sepsis in sickle cell patients.
*Neisseria meningitidis*
- *N. meningitidis* is another encapsulated bacterium that can cause serious infections, including **meningitis** and **sepsis**, particularly in immunocompromised individuals like those with sickle cell disease.
- However, the incidence of **meningococcal disease** is generally lower than **pneumococcal disease** in this age group, and the absence of classic meningeal signs or petechial rash makes it a less probable primary suspect compared to *S. pneumoniae*.
*Salmonella*
- *Salmonella* species can cause **osteomyelitis** and **sepsis** in patients with sickle cell disease, often presenting with gastrointestinal symptoms.
- While a known pathogen in this population, the clinical picture of **rapidly progressive sepsis** without clear GI focus makes *S. pneumoniae* a more immediate and common concern.
Group B streptococcus screening US Medical PG Question 2: A 24-year-old woman presents to the ED with symptoms of pelvic inflammatory disease despite being previously treated with azithromycin for chlamydial infection. Based on your clinical understanding about the epidemiology of PID, you decide to obtain a gram stain which shows a gram-negative diplococci. What is the next step in order to confirm the identity of the organism described?
- A. Perform an RT-PCR
- B. Culture in TCBS agar
- C. Culture in Thayer-Martin media (Correct Answer)
- D. Obtain an acid fast stain
- E. Culture in Bordet-Gengou agar
Group B streptococcus screening Explanation: ***Culture in Thayer-Martin media***
- The presence of **gram-negative diplococci** in a patient with PID symptoms strongly suggests *Neisseria gonorrhoeae*.
- **Thayer-Martin media** is a selective **agar** specifically designed for the isolation and identification of *Neisseria* species, including *N. gonorrhoeae*, by inhibiting the growth of most commensal bacteria and fungi.
*Perform an RT-PCR*
- While **RT-PCR** can detect *Neisseria gonorrhoeae* nucleic acids, it is primarily used for **molecular diagnosis** and not directly for confirming the identity of a cultured organism visualized on gram stain.
- **RT-PCR** is generally used for direct detection from clinical samples and is particularly useful in situations where culture is difficult or unavailable.
*Culture in TCBS agar*
- **TCBS (Thiosulfate Citrate Bile Salts Sucrose) agar** is a selective medium primarily used for the isolation of *Vibrio* species, which are not typically associated with pelvic inflammatory disease or characterized as gram-negative diplococci.
- This medium is designed to differentiate between different *Vibrio* species based on sucrose fermentation.
*Obtain an acid fast stain*
- An **acid-fast stain** (e.g., Ziehl-Neelsen stain) is used to identify bacteria with a **waxy cell wall**, such as *Mycobacterium* species (e.g., *Mycobacterium tuberculosis*).
- *Neisseria gonorrhoeae* is not acid-fast, and this stain would not be appropriate for its identification.
*Culture in Bordet-Gengou agar*
- **Bordet-Gengou agar** is a specialized culture medium used for the isolation of *Bordetella pertussis*, the causative agent of whooping cough.
- This medium is not suitable for the isolation of *Neisseria gonorrhoeae*.
Group B streptococcus screening US Medical PG Question 3: A 21-year-old Cambodian patient with a history of rheumatic heart disease presents to his primary care physician for a routine check-up. He reports being compliant with monthly penicillin G injections since being diagnosed with rheumatic fever at age 15. He denies any major side effects from the treatment, except for the inconvenience of organizing transportation to a physician's office every month. On exam, the patient is found to have a loud first heart sound and a mid-diastolic rumble that is best heard at the apex. Which of the following is the next best step?
- A. Switch to intramuscular cefotaxime, which has fewer side effects
- B. Continue intramuscular penicillin therapy (Correct Answer)
- C. Stop penicillin therapy
- D. Stop penicillin therapy in 4 years
- E. Decrease frequency of injections to bimonthly
Group B streptococcus screening Explanation: ***Continue intramuscular penicillin therapy***
- This patient has a history of **rheumatic heart disease** and is showing signs of **mitral stenosis** (loud S1, mid-diastolic rumble at the apex), indicating previous rheumatic fever and the effectiveness of current prophylaxis.
- Continuing prophylaxis is crucial to prevent further episodes of **rheumatic fever** and progression of cardiac damage, especially in regions with endemic rheumatic fever.
*Switch to intramuscular cefotaxime, which has fewer side effects*
- **Cefotaxime** is a third-generation cephalosporin and is not typically used for rheumatic fever prophylaxis, nor is it proven to have significantly fewer side effects in this context.
- **Penicillin G** is the gold standard for preventing recurrent rheumatic fever due to its proven efficacy and low cost.
*Stop penicillin therapy*
- Stopping prophylaxis would put the patient at high risk for **recurrent rheumatic fever** and worsening of their established **rheumatic heart disease**, which can lead to severe cardiac complications.
- The patient's current heart sounds suggest ongoing valvular disease, making continued prevention of exacerbations critical.
*Stop penicillin therapy in 4 years*
- The duration of **rheumatic fever prophylaxis** is determined by the patient's age and the presence of **rheumatic heart disease**. For patients with documented rheumatic heart disease, prophylaxis often continues for much longer periods, often until age 40 or even lifelong.
- Stopping at "4 years" from age 21 (i.e., at age 25) is too early for a patient with established rheumatic heart disease.
*Decrease frequency of injections to bimonthly*
- Monthly intramuscular **penicillin G** is the standard and most effective regimen for secondary prophylaxis of rheumatic fever.
- Decreasing the frequency would reduce the drug's therapeutic levels and significantly increase the risk of breakthrough streptococcal infections and subsequent episodes of **rheumatic fever**.
Group B streptococcus screening US Medical PG Question 4: You are treating a neonate with meningitis using ampicillin and a second antibiotic, X, that is known to cause ototoxicity. What is the mechanism of antibiotic X?
- A. It binds the 50S ribosomal subunit and inhibits formation of the initiation complex
- B. It binds the 30S ribosomal subunit and inhibits formation of the initiation complex (Correct Answer)
- C. It binds the 30S ribosomal subunit and reversibly inhibits translocation
- D. It binds the 50S ribosomal subunit and inhibits peptidyltransferase
- E. It binds the 50S ribosomal subunit and reversibly inhibits translocation
Group B streptococcus screening Explanation: ***It binds the 30s ribosomal subunit and inhibits formation of the initiation complex***
- The second antibiotic, X, is likely an **aminoglycoside**, such as **gentamicin** or **amikacin**, which are commonly used in combination with ampicillin for neonatal meningitis and are known to cause ototoxicity.
- Aminoglycosides exert their bactericidal effect by **irreversibly binding to the 30S ribosomal subunit**, thereby **inhibiting the formation of the initiation complex** and leading to misreading of mRNA.
*It binds the 50S ribosomal subunit and inhibits formation of the initiation complex*
- This mechanism is characteristic of **linezolid**, which targets the 50S ribosomal subunit to prevent the formation of the initiation complex.
- While linezolid can cause side effects, **ototoxicity** is less commonly associated with it compared to aminoglycosides, and it is not a primary drug for neonatal meningitis alongside ampicillin.
*It binds the 50S ribosomal subunit and inhibits peptidyltransferase*
- This is the mechanism of action for **chloramphenicol**, which inhibits **peptidyltransferase** activity on the 50S ribosomal subunit, preventing peptide bond formation.
- Although chloramphenicol can cause **ototoxicity** and **aplastic anemia**, its use in neonates is limited due to the risk of **Gray Baby Syndrome**.
*It binds the 30s ribosomal subunit and reversibly inhibits translocation*
- This describes the mechanism of action of **tetracyclines**, which reversibly bind to the 30S ribosomal subunit and prevent the attachment of aminoacyl-tRNA, thereby inhibiting protein synthesis.
- Tetracyclines are **contraindicated in neonates** due to their potential to cause **tooth discoloration** and **bone growth inhibition**, and ototoxicity is not their primary adverse effect.
*It binds the 50s ribosomal subunit and reversibly inhibits translocation*
- This mechanism of reversibly inhibiting translocation by binding to the 50S ribosomal subunit is characteristic of **macrolides** (e.g., erythromycin, azithromycin) and **clindamycin**.
- While some macrolides can cause **transient ototoxicity**, they are not typically the second antibiotic of choice for neonatal meningitis in combination with ampicillin, and clindamycin's side effect profile is different.
Group B streptococcus screening US Medical PG Question 5: A 27-year-old G1P0 female presents for her first prenatal visit. She is in a monogamous relationship with her husband, and has had two lifetime sexual partners. She has never had a blood transfusion and has never used injection drugs. Screening for which of the following infections is most appropriate to recommend this patient?
- A. Syphilis and HIV
- B. Syphilis, HIV, and HBV (Correct Answer)
- C. Syphilis, HIV, HBV, and chlamydia
- D. Syphilis, HIV, and chlamydia
- E. No routine screening is recommended for this patient
Group B streptococcus screening Explanation: ***Syphilis, HIV, and HBV***
- The **American College of Obstetricians and Gynecologists (ACOG)** and the **Centers for Disease Control and Prevention (CDC)** recommend universal screening for syphilis, HIV, and hepatitis B virus (HBV) in all pregnant women at the first prenatal visit.
- This **routine screening** is crucial due to the potential for vertical transmission and severe adverse outcomes for the neonate if untreated.
*Syphilis and HIV*
- While screening for syphilis and HIV is essential, it is **incomplete** as it omits HBV, which is also universally recommended for antenatal screening.
- This option does not align with the standard comprehensive screening guidelines for pregnancy.
*Syphilis, HIV, HBV, and chlamydia*
- Although syphilis, HIV, and HBV screening are appropriate, adding **chlamydia** to the universal prenatal screening for *all* pregnant women in the first trimester is not standard practice unless specific risk factors are present or local prevalence is high.
- Chlamydia screening is typically recommended for pregnant women who are **25 years or younger** or those with **risk factors** for sexually transmitted infections (STIs).
*Syphilis, HIV, and chlamydia*
- This option incorrectly includes chlamydia as a universal screen for all pregnant women while **omitting HBV**, which is universally recommended.
- Missing HBV screening leaves a critical gap in prenatal care, as it can be transmitted vertically and cause severe neonatal disease.
*No routine screening is recommended for this patient*
- This statement is incorrect as **universal screening** for syphilis, HIV, and HBV is recommended for all pregnant women, regardless of reported risk factors or monogamous relationships.
- Maternal infection can still occur, and screening helps prevent severe outcomes for both mother and child through timely detection and intervention.
Group B streptococcus screening US Medical PG Question 6: A 28-year-old man presents with painless anal ulcer. Dark-field microscopy shows spirochetes. He is allergic to penicillin with history of anaphylaxis. Which of the following is the most appropriate treatment?
- A. Erythromycin 500 mg four times daily for 14 days
- B. Penicillin desensitization followed by benzathine penicillin
- C. Doxycycline 100 mg orally twice daily for 14 days (Correct Answer)
- D. Azithromycin 2 g orally once
- E. Ceftriaxone 250 mg IM
Group B streptococcus screening Explanation: **Doxycycline 100 mg orally twice daily for 14 days**
- **Doxycycline** is the recommended alternative for treating **primary syphilis** in patients with a **penicillin allergy**, especially with a history of anaphylaxis.
- The 14-day duration for doxycycline is appropriate for treating early syphilis, including primary syphilis.
*Erythromycin 500 mg four times daily for 14 days*
- While erythromycin is an alternative, its efficacy for syphilis is **lower than doxycycline**, and it requires a longer duration of treatment.
- It is generally considered a less preferred option than doxycycline for penicillin-allergic patients due to adherence issues and potential for gastrointestinal side effects.
*Penicillin desensitization followed by benzathine penicillin*
- **Penicillin desensitization** is typically reserved for situations where penicillin is the **only truly effective treatment** and alternatives are not suitable, such as in neurosyphilis or syphilis in pregnancy.
- For primary syphilis in a non-pregnant patient with a clear anaphylactic allergy, an effective alternative like doxycycline is preferred over the risks associated with desensitization.
*Azithromycin 2 g orally once*
- **Azithromycin** resistance in *Treponema pallidum* is increasingly prevalent, making it an unreliable treatment for syphilis.
- A single dose is insufficient for effective treatment and carries a higher risk of treatment failure.
*Ceftriaxone 250 mg IM*
- **Ceftriaxone** is an alternative in some cases of syphilis, but the recommended dose for primary syphilis is typically higher and given for a longer duration (e.g., 1-2 g IM or IV daily for 10-14 days).
- A single 250 mg IM dose is insufficient for the treatment of syphilis and is more commonly used for gonorrhea.
Group B streptococcus screening US Medical PG Question 7: A 27-year-old woman, gravida 2, para 1, at 36 weeks' gestation comes to the physician for a prenatal visit. She feels well. Fetal movements are adequate. This is her 7th prenatal visit. She had an ultrasound scan performed 1 month ago that showed a live intrauterine pregnancy consistent with a 32-week gestation with no anomalies. She had a Pap smear performed 1 year ago, which was normal. Vital signs are within normal limits. Pelvic examination shows a uterus consistent in size with a 36-week gestation. Her blood group and type is A negative. Which of the following is the most appropriate next step in management?
- A. Transabdominal doppler ultrasonography
- B. Rh antibody testing
- C. Swab for GBS culture (Correct Answer)
- D. Serum PAPP-A and HCG levels
- E. Complete blood count
Group B streptococcus screening Explanation: ***Swab for GBS culture***
- All pregnant women should be screened for **Group B Streptococcus (GBS)** between **36 weeks 0 days and 37 weeks 6 days** of gestation.
- A positive GBS culture requires **intrapartum antibiotic prophylaxis** to prevent early-onset neonatal GBS disease.
*Transabdominal doppler ultrasonography*
- **Doppler ultrasonography** is primarily used to assess **fetal well-being** in cases of **fetal growth restriction**, preeclampsia, or other high-risk conditions.
- This patient has a **normal-sized uterus** and **adequate fetal movements**, indicating no immediate need for fetal Doppler assessment.
*Rh antibody testing*
- **Rh antibody testing** (indirect Coombs test) is performed early in pregnancy for Rh-negative women and typically repeated at **28 weeks' gestation** before anti-D immune globulin administration.
- Repeating this test at 36 weeks is not the most appropriate *next* step as the routine schedule for Rh immune globulin would typically be managed prior to this point.
*Serum PAPP-A and HCG levels*
- **Serum PAPP-A and HCG levels** are components of **first-trimester screening** for chromosomal abnormalities, performed between 11 and 14 weeks of gestation.
- At 36 weeks' gestation, these markers are not relevant for current fetal assessment.
*Complete blood count*
- A **complete blood count (CBC)** is routinely performed in the first trimester and often repeated in the **late second or early third trimester** (around 28 weeks) to check for anemia.
- While a CBC might be done as part of general prenatal care, it is not the most urgent or specifically indicated test at 36 weeks in the absence of symptoms.
Group B streptococcus screening US Medical PG Question 8: A 27-year-old woman, gravida 2, para 1, at 37 weeks' gestation is admitted to the hospital in active labor. She has received routine prenatal care, but she has not been tested for group B streptococcal (GBS) colonization. Pregnancy and delivery of her first child were complicated by an infection with GBS that resulted in sepsis in the newborn. Current medications include folic acid and a multivitamin. Vital signs are within normal limits. The abdomen is nontender and contractions are felt every 4 minutes. There is clear amniotic fluid pooling in the vagina. The fetus is in a cephalic presentation. The fetal heart rate is 140/min. Which of the following is the most appropriate next step in management?
- A. Obtain vaginal-rectal swab for nucleic acid amplification testing
- B. Obtain vaginal-rectal swab for GBS culture
- C. Administer intrapartum intravenous penicillin (Correct Answer)
- D. Reassurance
- E. Obtain vaginal-rectal swab for GBS culture and nucleic acid amplification testing
Group B streptococcus screening Explanation: ***Administer intrapartum intravenous penicillin***
- This patient has a **previous infant with invasive GBS disease**, which is a strong indication for **intrapartum antibiotic prophylaxis (IAP)** regardless of current GBS colonization status.
- Penicillin is the **first-line agent** for GBS prophylaxis during labor to prevent vertical transmission to the newborn.
*Obtain vaginal-rectal swab for nucleic acid amplification testing*
- While **NAAT** can provide rapid results, the presence of a prior infant with invasive GBS disease is an **absolute indication** for IAP, making testing unnecessary.
- Waiting for NAAT results would **delay necessary antibiotic administration**, increasing the risk of GBS transmission.
*Obtain vaginal-rectal swab for GBS culture*
- A **GBS culture** typically takes 24-48 hours for results, which is too long given the patient is in active labor and requires immediate management.
- As with NAAT, a prior affected infant means that **IAP is indicated regardless of current culture results**.
*Reassurance*
- Reassurance alone is **insufficient** given the patient's history of a previous infant with GBS sepsis, which places her current fetus at high risk.
- **Active intervention** with antibiotics is crucial to prevent recurrence of GBS disease in the newborn.
*Obtain vaginal-rectal swab for GBS culture and nucleic acid amplification testing*
- Performing both tests is **unnecessary and delays treatment** in a patient with a clear indication for intrapartum antibiotics.
- The patient's history of a prior infant with GBS sepsis is classified as a **high-risk factor, necessitating immediate antibiotic prophylaxis** without waiting for test results.
Group B streptococcus screening US Medical PG Question 9: A 44-year-old with a past medical history significant for human immunodeficiency virus infection presents to the emergency department after he was found to be experiencing worsening confusion. The patient was noted to be disoriented by residents and staff at the homeless shelter where he resides. On presentation he reports headache and muscle aches but is unable to provide more information. His temperature is 102.2°F (39°C), blood pressure is 112/71 mmHg, pulse is 115/min, and respirations are 24/min. Knee extension with hips flexed produces significant resistance and pain. A lumbar puncture is performed with the following results:
Opening pressure: Normal
Fluid color: Clear
Cell count: Increased lymphocytes
Protein: Slightly elevated
Which of the following is the most likely cause of this patient's symptoms?
- A. Herpes simplex virus
- B. Group B streptococcus
- C. Cryptococcus (Correct Answer)
- D. Tuberculosis
- E. Neisseria meningitidis
Group B streptococcus screening Explanation: ***Cryptococcus***
- **Cryptococcus neoformans** is the **most common cause of meningitis** in HIV-positive patients, particularly those with CD4 counts <100 cells/μL.
- The CSF findings are **classic for cryptococcal meningitis**: clear fluid, **lymphocytic pleocytosis**, normal or mildly elevated opening pressure, and **slightly elevated protein** with normal or mildly decreased glucose.
- The patient's **subacute presentation** with confusion, fever, and meningeal signs in the context of **HIV infection** strongly suggests cryptococcal meningitis as the most likely diagnosis.
- Diagnosis is confirmed with **CSF cryptococcal antigen**, India ink stain, or fungal culture.
*Herpes simplex virus*
- While HSV can cause meningitis or encephalitis, it is **not the most common cause** of meningitis in HIV-positive patients.
- **HSV encephalitis** typically presents with more prominent temporal lobe involvement, including personality changes, seizures, and focal neurological deficits.
- HSV meningitis is more common in **immunocompetent individuals** and would be less likely than cryptococcal infection in an HIV patient.
*Group B streptococcus*
- This causes **bacterial meningitis** with a **neutrophilic predominance** in CSF, not lymphocytic.
- CSF would show **markedly elevated protein**, **decreased glucose**, and cloudy appearance.
- More common in neonates and elderly patients, not typically associated with HIV.
*Neisseria meningitidis*
- This is a cause of **acute bacterial meningitis** with rapid onset and often a **petechial rash**.
- CSF would show **neutrophilic predominance**, **high protein**, **low glucose**, and turbid appearance.
- The lymphocytic pleocytosis rules out typical bacterial meningitis.
*Tuberculosis*
- **Tuberculous (TB) meningitis** is an important consideration in HIV-positive patients and can present with lymphocytic pleocytosis.
- However, TB meningitis typically shows **markedly elevated protein** (often >100 mg/dL, not "slightly elevated"), **low glucose** (<45 mg/dL), and may have a "spider-web clot" on standing CSF.
- The **more subacute to chronic course** (weeks) and absence of very high protein make TB less likely than cryptococcal meningitis in this acute presentation.
Group B streptococcus screening US Medical PG Question 10: The following set of instruments are used for which procedure?
- A. Biopsy
- B. Dilatation and curettage
- C. Pap smear (Correct Answer)
- D. Hysteroscopy
Group B streptococcus screening Explanation: ***Pap smear***
- The image displays a complete set of instruments used for a **Pap smear**, including **glass slides** for sample collection, a **cervical brush**, a **spatula** (cytobrush and Ayre spatula), and a **speculum** to visualize the cervix.
- These tools are specifically designed for collecting cervical cells to screen for **cervical cancer** and **precancerous changes**.
*Biopsy*
- A biopsy typically involves specialized instruments like **punch biopsy tools**, **forceps**, or needles to extract tissue samples, which are not depicted here.
- While glass slides might be used for processing biopsy samples, the primary collection tools are absent.
*Dilatation and curettage*
- This procedure requires instruments such as **dilators** to open the cervix and **curetters** to scrape the uterine lining, which are not shown in the image.
- The instruments shown are for surface cell collection, not for uterine cavity procedures.
*Hysteroscopy*
- Hysteroscopy uses a **hysteroscope**—a thin, lighted tube with a camera—to visualize the inside of the uterus.
- The instruments in the image are for external examination and cervical cell collection, not for direct visualization of the uterine cavity.
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