Microbiology-Bacterial Infections of Newborn Flashcards
What protections are provided to the fetus and newborn?
Physical barrier (fetal membranes), placenta (transmits maternal IgG and cytokines) and breast feeding (protects against GI infections w/IgA)
When would you recommend against breastfeeding?
If the mother has HIV
What are the unique susceptibilities of the fetus and newborn to infection?
Mother blood-borne infection w/no protective antibody (syphilis can cross placenta from maternal blood) and any damage to fetal membranes (due to reproductive tract infections like BV and STDs). Also, the immune system is not competent until 2 years old because they don’t make antibodies to polysaccharides, have decreased phagocytic capacity and have lower levels of circulating complement.
What type of immunity is suppressed in the mother when pregnant?
Cell-mediated
Why are the conjugate vaccines great for kids under 2 years old?
They don’t make antibodies to capsule, so by conjugating it with protein you can illicit an immune response to the protein that will protect from H. influenzae.
Majority of prenatal infections are transmitted how?
Blood borne (e.g. syphilis and listeria). Some are also ascending infections from the lower genital tract (BV or STIs)
What would histology look like in a the uterus of a woman who’s membranes ruptured > 12 hours before the child’s birth?
Chorioamnionitis risk is greatly increased when membranes rupture > 12 hours before birth. You would see infected chorionic and amniotic membranes.
What type of infections are commonly acquired during the delivery of a baby?
Natal or perinatal infections. GBS is the second most common cause of bacterial meningitis in children (strep pneumo is most common). Infections may also be nosocomial (s. aureus in the umbilicus).
What infections present anytime right before, at or 4 weeks after birth?
Congenital (right before or at birth) and postnatal (up to 4 weeks after birth) infections.
Most common transplacental transmissions in pre-natal infections.
T. pallidum (syphilis), listeria and M. Tb. Less common causes include viruses (rubella, CMV, enterovirus, EBV, HIV, Parvovirus B19 and lymphocoriomeningitis virus) and fungi (toxoplasmosis and plasmodium)
What are the most common pre-natal infections that result from ascending infection and ruptured membranes?
GBS, E. Coli K1, Listeria, Chlamydia, Mycoplasma and Ureaplasma. Note that this is overall the more common way babies get infected. Less common causes are viral (CMV and HSV)
Why is it so hard for neonates to clear E. coli K1 infection? What other bug is similar?
The capsule has sialic acid on it (like N. meningitidis).
What are the most common natal infections?
GBS, E. Coli K1, N. gonorrhoeae and C. trachomatis. Other common causes are viral (HSV, CMV, enteroviruses, Hep B/C, VSV and HIV).
A mother has a baby and the next day the child becomes lethargic, feverish and has no interest in breast feeding. Blood culture of the child is shown below. Gram stain shows a gram positive, catalase negative and bacitracin sensitive diplococci. What is the most likely diagnosis? Why wasn’t this child vaccinated for this infection?
GBS, note the beta hemolytic pattern. Despite having a polysaccharide capsule, there is no vaccine for GBS.
Common causes of post-natal infections that colonized during the pre-natal or post-natal periods?
GBS, E. coli K1, listeria, viruses (HSV, CMV, enteroviruses, VZV and HIV) and nosocomial infections (staph, RSV, gram negative rods and influenza).
A mother has a baby and the next day the child becomes lethargic, feverish and has no interest in breast feeding. CSF culture and lactose fermentation from the child is shown below. What is causing this child’s condition?
Note the gram negative rods that ferment lactose on McConkey’s agar (pink on agar). This is E. coli K1. This bacteria contains a sialic acid capsule (K1) which is anti-phagocytic and not recognized as foreign so it is not opsinized.
A mother has a baby and the next day the child becomes lethargic, feverish and has no interest in breast feeding. CSF culture and CAMP test are shown below. What is causing this child’s condition?
Listeria monocytogenes. Note the gram-positive rods that are catalase and CAMP test positive (lyses w/s. aureus). Note that these bacteria often come from refrigerated food because they can grow at low temperatures.
A woman presents with premature rupture of membranes and birth. The child is born with pus filled orbits and it is determined that the mother had and infection of N. gonorrhoeae. What would you expect to see on laboratory evaluation of the maternal infection?
Gram-negative diplococci that are oxidase positive and require chocolate agar and 5% CO2 to grow.
A 6 day old baby presents with unilateral conjunctivitis, otitis media and pneumonia. The mother had an STD on delivery. What causes this child’s infection?
Chlamydia trachomatis.
List the microbial traits of each organism below
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List the mode of transmission for each of the organisms below
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List the clinical presentation for each of the organisms below
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A 3 month old presents with minimal weight gain since birth. Her mother is a commercial sex worker. She says that she eats about half the normal intake of her friend’s kid that is the same age (12 oz a day). Physical exam reveals a small, wrinkled and fussy baby with hepatosplenomegaly, psoriatic rash and generalized edema. Hgb 8.6, platelet 72,000 and albumin 1.8g/dL. On x-ray is shown below. What is your diagnosis? How would you confirm this? How do you treat?
Note the diffuse fuzzy periostitis on x-ray, indicating saber shins from congenital syphilis. You would confirm this with RPR (rapid plasma reagin looking for non-specific antibodies), FTA-ABS (fluorescent treponomal absorption). Treat with IV penicillin.
