CASE 13 MED MICRO

Question 1

What is a congenital infection?

Answer 1

A congenital infection is an infection transmitted transplacentally from the mother to the fetus during pregnancy. It is acquired in utero and affects the developing fetus, leading to potentially severe outcomes.

Question 2

What is vertical transmission, and how does it occur?

Answer 2

Vertical transmission refers to the infection transmission from mother to baby during pregnancy (transplacental), childbirth (through contact with the infected genital tract), or breastfeeding, potentially leading to severe neonatal infections.

Question 3

Name some bacteria that commonly cause congenital infections.

Answer 3

Common bacteria that cause congenital infections include Listeria monocytogenes, Streptococcus agalactiae (Group B Streptococcus), Escherichia coli, Treponema pallidum (causing syphilis), and Mycobacterium tuberculosis.

Question 4

What is the difference between intrauterine and intrapartum infections?

Answer 4

Intrauterine infections occur within the uterus, while intrapartum infections happen during labor and delivery. Each type poses distinct risks to the fetus and requires specific preventive strategies.

Question 5

How does Listeria monocytogenes typically infect humans?

Answer 5

Listeria monocytogenes primarily infects humans through the ingestion of contaminated food, such as cheese, vegetables, and meats. It can survive in refrigerated and high-salt environments, making it a persistent threat.

Question 6

What are the primary disease manifestations of Listeria in neonates?

Answer 6

Neonatal Listeria infections can cause severe outcomes, including meningitis, sepsis, and pneumonia. Symptoms may include respiratory distress, fever, jaundice, and lethargy, often with high mortality if untreated.

Question 7

How is Listeria monocytogenes diagnosed in a laboratory setting?

Answer 7

Laboratory diagnosis includes isolating L. monocytogenes from sterile sources like blood or CSF, identifying its characteristic Gram-positive bacilli on microscopy, and culturing it, where colonies show beta hemolysis on blood agar.

Question 8

What is the recommended treatment for Listeria meningitis?

Answer 8

Listeria meningitis is treated with ampicillin, often combined with gentamicin for 21 days. Cephalosporins are ineffective against Listeria due to inherent resistance.

Question 9

Describe the transmission routes for Streptococcus agalactiae (GBS).

Answer 9

GBS can be transmitted from mother to infant in utero by an ascending infection or during delivery when the baby contacts urogenital fluid, with a 50% vertical transmission rate in untreated cases.

Question 10

What are the early-onset symptoms of GBS infection in neonates?

Answer 10

Early-onset GBS infection (within the first 7 days) can cause systemic signs at birth, such as sepsis, pneumonia, and meningitis, often acquired during birth.

Question 11

What factors increase the risk of early-onset GBS disease in neonates?

Answer 11

Risk factors include maternal GBS colonization, a history of delivering an infant with GBS disease, premature delivery, prolonged rupture of membranes, and maternal fever during labor.

Question 12

How is GBS diagnosed in a laboratory setting?

Answer 12

GBS diagnosis involves isolating the bacteria from sterile sites (e.g., blood or CSF), Gram staining to identify characteristic Gram-positive cocci, and confirming susceptibility to antibiotics like ampicillin or penicillin.

Question 13

What are common symptoms of Escherichia coli infections in neonates?

Answer 13

Neonatal E. coli infections often present as bacteremia, with or without meningitis. The presence of the K1 capsular antigen increases virulence, making E. coli resistant to immune responses and capable of causing severe infections.

Question 14

How is Escherichia coli diagnosed in a neonate?

Answer 14

Diagnosis includes isolating E. coli from blood, CSF, or urine. The bacteria show as Gram-negative bacilli on microscopy, and culture reveals lactose-fermenting colonies. Antibiotic susceptibility testing is crucial due to resistance patterns.

Question 15

What treatment is typically used for E. coli infections in neonates?

Answer 15

Treatment commonly involves third-generation cephalosporins like cefotaxime or ceftriaxone, with the duration depending on the infection site. Meningitis cases require a prolonged 21-day IV therapy.

Question 16

Is there a prevention strategy for Escherichia coli congenital infections?

Answer 16

Unlike GBS, there is no specific preventive strategy for E. coli. General hygiene practices and monitoring at-risk neonates are essential to reduce infection risk.

Question 17

How is congenital syphilis transmitted?

Answer 17

Congenital syphilis is primarily transmitted transplacentally from mother to fetus but can also occur during delivery if the neonate comes into contact with infectious lesions.

Question 18

What are the early symptoms of congenital syphilis in neonates?

Answer 18

Symptoms, often appearing within 4-8 weeks, include rash, hepatosplenomegaly, jaundice, snuffles, and sometimes central nervous system involvement, leading to complications like pneumonia and anemia.

Question 19

How is congenital syphilis diagnosed?

Answer 19

Diagnosis relies on serology to detect specific antibodies, as direct microscopy and culture are challenging due to the small size of Treponema pallidum. Specialized techniques like dark-field microscopy are sometimes used.

Question 20

What follow-up care is recommended for neonates with congenital syphilis?

Answer 20

Neonates should undergo regular RPR testing every 2-3 months until nonreactive. Non-reactivity should ideally be achieved by 6 months, and further testing or treatment may be needed if RPR remains reactive.

Question 21

How is congenital tuberculosis (TB) transmitted?

Answer 21

Congenital TB can be transmitted in utero via haematogenous spread or at birth through the ingestion or aspiration of contaminated amniotic fluid or direct contact with TB-infected genital lesions.

Question 22

What are key clinical features of congenital TB?

Answer 22

Clinical signs, appearing within weeks after birth, include failure to thrive, hepatosplenomegaly, lymphadenopathy, and lung or liver lesions. Severe cases may lead to meningitis, sepsis, and disseminated infections.

Question 23

How is congenital TB diagnosed?

Answer 23

Diagnosis involves collecting samples like gastric washings, CSF, and mycobacterial blood cultures, which are then examined with acid-fast staining and molecular tests like PCR or GeneXpert.

Question 24

What treatment is recommended for congenital TB?

Answer 24

Treatment follows South African TB guidelines, typically involving a combination of rifampicin, isoniazid, pyrazinamide, and possibly ethionamide or ethambutol, guided by TB drug susceptibility results.

Question 24

What is Toxoplasma gondii, and how is it transmitted?

Answer 24

Toxoplasma gondii is a protozoan parasite that commonly infects humans. In congenital cases, it is transmitted transplacentally, usually after maternal infection via ingestion of tissue cysts in undercooked meat or contact with contaminated materials.

Question 25

How is congenital toxoplasmosis diagnosed?

Answer 25

Diagnosis involves maternal serology (IgM/IgG testing), PCR of amniotic fluid, fetal ultrasound for anatomical abnormalities, and neonatal testing for IgG and IgM, with a follow-up of IgG levels over time.

Question 25

What are the preventive measures for congenital toxoplasmosis?

Answer 25

Pregnant women should avoid contact with cat litter, consume well-cooked meat, wash fruits and vegetables, and undergo screening if exposed, to reduce the risk of maternal infection and fetal transmission.

Question 26

Describe the classic triad of congenital toxoplasmosis.

Answer 26

The triad includes intracranial calcifications, hydrocephalus, and chorioretinitis, each of which can result in long-term neurological and visual impairments.

Question 27

What are the common long-term sequelae of congenital toxoplasmosis?

Answer 27

Long-term effects include cognitive delays, learning disabilities, blindness, and developmental issues due to the parasite’s impact on the nervous system.

Question 28

What prenatal treatment options exist for congenital toxoplasmosis?

Answer 28

Prenatal treatment options include spiramycin or a combination of pyrimethamine and sulfadiazine, especially if fetal infection is suspected through maternal testing and imaging.

Question 29

Describe the timing and risk of fetal infection with Toxoplasma gondii.

Answer 29

Fetal infection risk increases with gestational age, from 10-25% in the first trimester to 60-65% in the third, though earlier infections are associated with more severe outcomes.

Question 30

How is congenital toxoplasmosis treated postnatally?

Answer 30

Postnatal treatment typically involves pyrimethamine and sulfadiazine for 1-2 years to prevent long-term complications and manage any active infections.