Neonatal infections

Neonatal infections US Medical PG Question 1: A neonate born at 33 weeks is transferred to the NICU after a complicated pregnancy and C-section. A week after being admitted, he developed a fever and became lethargic and minimally responsive to stimuli. A lumbar puncture is performed that reveals the following: Appearance Cloudy Protein 64 mg/dL Glucose 22 mg/dL Pressure 330 mm H20 Cells 295 cells/mm³ (> 90% PMN) A specimen is sent to microbiology and reveals gram-negative rods. Which of the following is the next appropriate step in management?

• A. MRI scan of the head
• B. Start the patient on IV ceftriaxone
• C. Provide supportive measures only
• D. Start the patient on IV cefotaxime (Correct Answer)
• E. Start the patient on oral rifampin

Neonatal infections Explanation: ***Start the patient on IV cefotaxime*** - The cerebrospinal fluid (CSF) analysis with **cloudy appearance, elevated protein, low glucose, high pressure, and predominant PMNs**, coupled with **gram-negative rods** on microscopy, is highly suggestive of **bacterial meningitis** in a neonate. - **Cefotaxime** is a third-generation cephalosporin commonly used for neonatal meningitis caused by gram-negative organisms due to its excellent CSF penetration and broad-spectrum activity, particularly against common neonatal pathogens like *E. coli* which can present as gram-negative rods. *MRI scan of the head* - An MRI would be considered **after initiating appropriate antibiotic treatment** to assess for complications like abscess formation or ventriculitis, not as the immediate next step in an acute, life-threatening infection. - Delaying antibiotic treatment for imaging in acute bacterial meningitis can lead to increased morbidity and mortality. *Start the patient on IV ceftriaxone* - While ceftriaxone is a third-generation cephalosporin, it is **generally avoided in neonates** due to the risk of **biliary sludging** and **kernicterus**. - Ceftriaxone competes with bilirubin for albumin binding sites, which is particularly risky in neonates who are already prone to hyperbilirubinemia. *Provide supportive measures only* - Given the strong evidence of **bacterial meningitis**, providing only supportive measures without specific antibiotic treatment would be inadequate and would lead to rapid deterioration and potentially fatal outcomes. - Bacterial meningitis requires prompt and aggressive antimicrobial therapy. *Start the patient on oral rifampin* - **Rifampin is never used as monotherapy for bacterial meningitis** due to rapid resistance development and its primary role is in specific infections like tuberculosis or as part of combination therapy for certain resistant bacteria. - Oral administration is also not ideal for acutely ill neonates with meningitis needing rapid, high-concentration antibiotics in the CSF.

Neonatal infections US Medical PG Question 2: A 2-day-old newborn male delivered at 38 weeks' gestation is evaluated for poor feeding and irritability. His temperature is 35°C (95°F), pulse is 168/min, respirations are 80/min, and blood pressure is 60/30 mm Hg. Blood culture on sheep agar grows motile, gram-positive bacteria surrounded by a narrow clear zone. Further testing confirms the presence of a pore-forming toxin. Which of the following is the most important factor in successful clearance of the causal pathogen?

• A. Secretion of interferon-α from infected cells
• B. Secretion of interleukin 10 by regulatory T cells
• C. Interferon-γ-induced macrophage activation (Correct Answer)
• D. Secretion of immunoglobulin G from plasma cells
• E. Formation of the membrane attack complex

Neonatal infections Explanation: ***Interferon-γ-induced macrophage activation*** - This clinical presentation of severe sepsis in a neonate, with a gram-positive, motile, pore-forming bacterium, is highly suggestive of **Listeria monocytogenes infection**. - **Listeria** is an intracellular bacterium that primarily targets macrophages and monocytes, and its clearance crucially depends on a strong **cell-mediated immune response**, specifically **IFN-γ-mediated macrophage activation** to kill the intracellular pathogens. *Secretion of interferon-α from infected cells* - **Interferon-α** is mainly involved in the antiviral response, inhibiting viral replication and activating natural killer (NK) cells. - While it has some role in innate immunity against bacteria, it is not the primary or most critical mechanism for clearing an intracellular bacterial infection like *Listeria*. *Secretion of interleukin 10 by regulatory T cells* - **Interleukin 10 (IL-10)** is an anti-inflammatory cytokine that downregulates the immune response, often associated with immune suppression and tolerance. - Secreting IL-10 would likely **hinder** the effective clearance of an active bacterial infection rather than promote it. *Secretion of immunoglobulin G from plasma cells* - **Immunoglobulin G (IgG)** provides humoral immunity against extracellular bacteria and toxins, mediating opsonization and neutralization. - While IgG may have some role in controlling the extracellular phase of *Listeria* infection, it is **ineffective** against the intracellular forms, which are the main challenge for clearance. *Formation of the membrane attack complex* - The **membrane attack complex (MAC)** is part of the complement system, which primarily targets and lyses extracellular bacteria. - *Listeria* is an intracellular pathogen, meaning the MAC would not be able to reach and effectively lyse the bacteria once inside host cells.

Neonatal infections US Medical PG Question 3: A 6-day-old newborn is brought to the emergency department by his mother due to a high fever that started last night. His mother says that he was born via an uneventful vaginal delivery at home at 38 weeks gestation and was doing fine up until yesterday when he became disinterested in breastfeeding and spit up several times. His temperature is 39.5°C (103.1°F), pulse is 155/min, respirations are 45/min, and O2 sats are 92% on room air. He is lethargic and minimally responsive to stimuli. While on his back, his head is quickly lifted towards his chest which causes his legs to flex. The mother had only a few prenatal care visits and none at the end of the pregnancy. What is the most likely source of this patients infection?

• A. Tick bite
• B. During birth (Correct Answer)
• C. Infection from surgery
• D. Contaminated food
• E. Mother’s roommate

Neonatal infections Explanation: ***During birth*** - The newborn's age (6 days old) and presentation with **fever**, **lethargy**, and **meningeal signs** (legs flexing upon lifting head, likely Brudzinski sign) are highly suggestive of **neonatal sepsis** or **meningitis**. - Given the history of a home birth with limited prenatal care, the most probable source of infection would be vertical transmission **during passage through the birth canal**, especially if the mother was colonized with pathogens like Group B Streptococcus (GBS), E. coli, or had an untreated sexually transmitted infection. *Tick bite* - While tick-borne illnesses can cause fever, they are generally less common in this age group and the symptoms presented are more indicative of a widespread bacterial infection rather than a localized vector-borne illness. - The neurological signs (meningeal irritation) are more consistent with meningitis, which is typically bacterial in newborns, rather than a common manifestation of a tick-borne disease in this age group. *Infection from surgery* - The patient had an **uneventful vaginal delivery at home**, meaning there was no surgical procedure involved, ruling out a surgical site infection. - Surgical infections are typically seen after procedures like C-sections or circumcisions and would present differently. *Contaminated food* - A 6-day-old newborn is typically fed breast milk or formula and has no exposure to **solid or contaminated food** that would cause such an infection. - Foodborne illnesses would usually present with prominent gastrointestinal symptoms like severe vomiting and diarrhea, which are not the primary features here. *Mother’s roommate* - While exposure to sick individuals can cause illness, the severe symptoms and rapid progression of the newborn's condition, along with the meningeal signs, point more towards a serious **vertical transmission during birth** rather than horizontal transmission from casual contact with a roommate. - Diseases transmitted this way would also typically affect the respiratory tract before causing severe systemic illness.

Neonatal infections US Medical PG Question 4: A 5-day-old male newborn is brought to the emergency department 1 hour after having a seizure. It lasted approximately 1 minute, and involved blinking and lip-smacking movements as well as left-sided jerking of the hand and foot. His mother says she measured a temperature of 38.2°C (100.7°F) at that time. He has had increasing difficulty feeding since yesterday. He was born at 39 weeks' gestation and weighed 3189 g (7 lb, 1 oz); he currently weighs 2980 g (6 lb, 9 oz). The mother's prenatal course was significant for gonorrhea infection diagnosed early in pregnancy and treated with ceftriaxone and azithromycin combination therapy. The boy appears irritable and lethargic. His temperature is 36.0°C (96.8°F). Examination shows clusters of vesicular lesions with an erythematous base on the patient's face and trunk. There is profuse lacrimation. Laboratory studies show: Leukocyte count 16,200/mm3 Segmented neutrophils 25% Bands 5% Lymphocytes 65% Monocytes 3% Eosinophils 2% Serum Glucose 80 mg/dL A lumbar puncture is performed. Cerebrospinal fluid analysis shows a leukocyte count of 117/μL, a protein concentration of 52 mg/dL, and a glucose concentration of 58 mg/dL. Results of blood cultures are pending. Which of the following is the most appropriate pharmacotherapy?

• A. IV acyclovir (Correct Answer)
• B. IV ceftriaxone
• C. Pyrimethamine
• D. IV ganciclovir
• E. IV vancomycin

Neonatal infections Explanation: ***IV acyclovir*** - The combination of **seizures**, **vesicular lesions** on the face and trunk, **profuse lacrimation**, and **lymphocytic pleocytosis** in the CSF in a newborn is highly suggestive of **Neonatal Herpes Simplex Virus (HSV) infection**. - **Acyclovir** is the antiviral drug of choice for treating HSV infections, especially severe systemic or CNS forms in neonates, to reduce morbidity and mortality. *IV ceftriaxone* - **Ceftriaxone** is a broad-spectrum antibiotic primarily used to treat bacterial infections like neonatal sepsis or meningitis, but it has no activity against viruses. - The patient's clinical presentation, including vesicular lesions and specific CSF findings, points away from a primary bacterial infection. *Pyrimethamine* - **Pyrimethamine** is an antiparasitic drug used in combination with sulfadiazine for treating **toxoplasmosis**. - The patient's symptoms are not consistent with congenital toxoplasmosis, which typically involves chorioretinitis, hydrocephalus, and intracranial calcifications. *IV ganciclovir* - **Ganciclovir** is an antiviral primarily used for treating **cytomegalovirus (CMV) infections**, particularly in immunocompromised patients. - While CMV can cause CNS disease in neonates, the characteristic **vesicular lesions** and **profuse lacrimation** are far more indicative of HSV. *IV vancomycin* - **Vancomycin** is an antibiotic used to treat severe bacterial infections, especially those caused by **methicillin-resistant Staphylococcus aureus (MRSA)** or other gram-positive bacteria. - It is not effective against viral infections, and the clinical picture does not suggest a bacterial etiology requiring vancomycin.

Neonatal infections US Medical PG Question 5: The occupational health department at a hospital implements new safety precautions to prevent laboratory-acquired infections. One of the new precautions includes disinfecting the microbiology laboratory benches with 70% ethanol before and after use. This measure is most likely to be effective in preventing the transmission of which of the following viruses?

• A. Hepatitis A virus
• B. Herpes simplex virus (Correct Answer)
• C. Poliovirus
• D. Parvovirus
• E. Polyomavirus

Neonatal infections Explanation: ***Herpes simplex virus*** - Herpes simplex virus is an **enveloped virus**, meaning it has a lipid outer layer that is easily disrupted by disinfectants like **70% ethanol**. - The disruption of its envelope renders the virus inactive and unable to infect host cells, making this a highly effective prevention strategy. *Hepatitis A virus* - Hepatitis A virus is a **non-enveloped virus**, making it relatively **resistant to many common disinfectants**, including alcohol-based ones. - Its robust protein capsid protects its genetic material, requiring stronger disinfection methods than 70% ethanol for inactivation. *Poliovirus* - Poliovirus is another **non-enveloped virus** that exhibits significant **resistance to alcohol-based disinfectants** due to its stable protein capsid. - Effective inactivation typically requires disinfectants with greater germicidal activity, such as chlorine-based solutions. *Parvovirus* - Parvovirus is one of the **most resistant non-enveloped viruses** to disinfection, including inactivation by 70% ethanol. - Its small size and extremely stable capsid make it challenging to eliminate from surfaces, often necessitating harsh chemical treatments. *Polyomavirus* - Polyomaviruses are **non-enveloped DNA viruses** that are generally more **resistant to alcohol-based disinfectants** than enveloped viruses. - Their lack of a lipid envelope provides protection against agents like ethanol that target lipid bilayers.

Neonatal infections US Medical PG Question 6: You are a resident in the surgical ICU. One of the patients you are covering is a 35-year-old pregnant G1P0 in her first trimester admitted for complicated appendicitis and awaiting appendectomy. Your attending surgeon would like you to start the patient on moxifloxacin IV preoperatively. You remember from your obstetrics clerkship, however, that moxifloxacin is Pregnancy Category C, and animal studies have shown that immature animals exposed to fluoroquinolones like moxifloxacin may experience cartilage damage. You know that there are potentially safer antibiotics, such as piperacillin/tazobactam, which is in Pregnancy Category B. What should you do?

• A. Administer moxifloxacin since it is only Pregnancy Category C and, although studies may have revealed adverse effects in animals, there is no definite evidence that it causes risk in humans.
• B. Administer piperacillin/tazobactam instead of moxifloxacin without discussing with the attending since your obligation is to "first, do no harm" and both are acceptable antibiotics for complicated appendicitis.
• C. Discuss the adverse effects of each antibiotic with the patient, and then let the patient decide which antibiotic she would prefer.
• D. Wait to administer any antibiotics until you discuss your safety concerns with your attending. (Correct Answer)
• E. Administer moxifloxacin since the attending is the executive decision maker and had to know the patient was pregnant when deciding on an antibiotic.

Neonatal infections Explanation: **Wait to administer any antibiotics until you discuss your safety concerns with your attending.** - As a resident, you have a **professional and ethical obligation** to voice concerns about patient safety, especially regarding medication choices in vulnerable populations like pregnant women. - Discussing your concerns with the attending physician allows for a **re-evaluation of the treatment plan** based on current evidence and patient-specific factors, ensuring the safest care. *Administer moxifloxacin since it is only Pregnancy Category C and, although studies may have revealed adverse effects in animals, there is no definite evidence that it causes risk in humans.* - While Category C means risk cannot be ruled out and benefits *may* outweigh risks, the presence of **known adverse effects in animal studies** and the availability of a safer alternative warrant reconsideration. - Administering a drug with known potential harm without discussing alternatives or concerns goes against the principle of **prudence and patient safety**. *Administer piperacillin/tazobactam instead of moxifloxacin without discussing with the attending since your obligation is to "first, do no harm" and both are acceptable antibiotics for complicated appendicitis.* - While "first, do no harm" is paramount, **unilaterally changing a treatment plan** ordered by an attending physician is inappropriate and breaches professional hierarchy and communication protocols. - The correct approach is to **communicate concerns** to the attending, allowing for a collaborative decision, rather than making independent substitutions. *Discuss the adverse effects of each antibiotic with the patient, and then let the patient decide which antibiotic she would prefer.* - While patient autonomy and informed consent are crucial, decisions about specific antibiotic choices, especially for a complicated condition like appendicitis, require **medical expertise**. - As a resident, it is your role to present information but not to delegate such complex medical decisions to a patient, particularly when you yourself have **unresolved concerns** with the attending's order. *Administer moxifloxacin since the attending is the executive decision maker and had to know the patient was pregnant when deciding on an antibiotic.* - While the attending is the senior decision-maker, it is possible for **oversights or errors to occur**, even with experienced physicians. - Assuming the attending "had to know" and therefore dismissing your own clinical judgment and knowledge of potential harm is **irresponsible** and compromises patient safety.

Neonatal infections US Medical PG Question 7: Five weeks after delivery, a 1350-g (3-lb 0-oz) male newborn has respiratory distress. He was born at 26 weeks' gestation. He required intubation and mechanical ventilation for a month following delivery and has been on noninvasive pressure ventilation for 5 days. His temperature is 36.8°C (98.2°F), pulse is 148/min, respirations are 63/min, and blood pressure is 60/32 mm Hg. Pulse oximetry on 40% oxygen shows an oxygen saturation of 91%. Examination shows moderate intercostal and subcostal retractions. Scattered crackles are heard in the thorax. An x-ray of the chest shows diffuse granular densities and basal atelectasis. Which of the following is the most likely diagnosis?

• A. Bronchopulmonary dysplasia (Correct Answer)
• B. Tracheomalacia
• C. Bronchiolitis obliterans
• D. Interstitial emphysema
• E. Pneumonia

Neonatal infections Explanation: ***Bronchopulmonary dysplasia*** - The presentation of a premature infant (26 weeks' gestation) with persistent respiratory distress requiring prolonged mechanical ventilation and oxygen, along with characteristic chest X-ray findings (diffuse granular densities and basal atelectasis), is highly indicative of **bronchopulmonary dysplasia (BPD)**. - BPD is a chronic lung disease of prematurity defined by the need for supplemental oxygen and/or positive pressure ventilation for at least 28 days after birth, with severity classified at 36 weeks postmenstrual age (or discharge if earlier). - The pathophysiology involves ventilator-induced injury, oxygen toxicity, and inflammation in the developing lung, leading to impaired alveolarization and abnormal vascular development. *Tracheomalacia* - While **tracheomalacia** can cause respiratory symptoms, it typically presents with expiratory stridor, a characteristic "barking" cough, or wheezing that may improve with neck extension or prone positioning. - It is a structural abnormality of the trachea involving weakness of the tracheal wall, and would not typically manifest with diffuse granular densities or basal atelectasis on chest X-ray in this context. *Bronchiolitis obliterans* - **Bronchiolitis obliterans** is irreversible obstruction of the small airways, often occurring after severe viral infections (especially adenovirus or RSV), lung transplantation, or toxic inhalational injury. - While it can occur in neonates post-ventilation, it is less common in this specific context and would typically present with more severe obstructive findings, hyperinflation, and air trapping on imaging rather than chronic diffuse granular densities and atelectasis. *Interstitial emphysema* - **Pulmonary interstitial emphysema** usually occurs acutely in the first days to weeks of mechanical ventilation, characterized by air dissecting into the lung interstitium and perivascular spaces. - While it can be a complication that contributes to the development of BPD, the persistent nature of respiratory distress five weeks post-delivery, along with diffuse granular densities and chronic radiographic changes, points toward the established chronic lung disease of BPD rather than acute interstitial emphysema. *Pneumonia* - Neonatal **pneumonia** would typically present with acute onset or worsening of respiratory distress, temperature instability, and signs of systemic infection. - While a chest X-ray might show infiltrates or consolidations, the chronic progressive course over 5 weeks, history of extreme prematurity, and prolonged ventilation make BPD a more fitting diagnosis than acute pneumonia in this clinical scenario.

Neonatal infections US Medical PG Question 8: Three days after delivery, a 1100-g (2-lb 7-oz) newborn has a tonic seizure that lasts for 25 seconds. She has become increasingly lethargic over the past 18 hours. She was born at 31 weeks' gestation. Antenatal period was complicated by chorioamnionitis. Apgar scores were 3 and 6 at 1 and 5 minutes, respectively. She appears ill. Her pulse is 123/min, respirations are 50/min and irregular, and blood pressure is 60/30 mm Hg. Examination shows a tense anterior fontanelle. The pupils are equal and react sluggishly to light. Examination shows slow, conjugate back and forth movements of the eyes. Muscle tone is decreased in all extremities. The lungs are clear to auscultation. Which of the following is the most likely diagnosis?

• A. Intraventricular hemorrhage (Correct Answer)
• B. Spinal muscular atrophy
• C. Galactosemia
• D. Congenital hydrocephalus
• E. Phenylketonuria

Neonatal infections Explanation: ***Intraventricular hemorrhage*** - The combination of **prematurity** (31 weeks' gestation, 1100g), **tonic seizures**, increasing **lethargy**, tense **anterior fontanelle**, **sluggishly reactive pupils**, and **slow conjugate back-and-forth eye movements** (suggesting brainstem involvement from increased intracranial pressure) are classical signs of intraventricular hemorrhage (IVH) in a neonate. - **IVH** is common in premature infants due to the fragility of germinal matrix vessels and can manifest acutely with neurological deterioration and increased intracranial pressure, typically within the first 72 hours of life. - While maternal **chorioamnionitis** and low Apgar scores raise concern for neonatal sepsis/meningitis, the specific **ocular movement pattern** and acute neurological signs on day 3 are more characteristic of IVH in this extremely premature infant. *Spinal muscular atrophy* - This is a **neuromuscular genetic disorder** characterized by progressive muscle weakness and hypotonia due to anterior horn cell degeneration. - It would typically present with **decreased muscle tone but without acute neurological signs** like seizures, tense fontanelle, or sluggish pupillary responses. - Does not cause acute-onset seizures or rapidly progressing lethargy in the neonatal period. *Galactosemia* - This is a **metabolic disorder** that presents with symptoms such as **vomiting, jaundice, hepatomegaly**, and **sepsis-like symptoms** upon introduction of lactose-containing feeds (breast milk or regular formula), typically after several days of feeding. - While it can cause lethargy and seizures, the acute neurological findings including **tense fontanelle** and **abnormal eye movements** in the immediate postnatal period of a premature infant more strongly suggest an anatomical/structural etiology like IVH. *Congenital hydrocephalus* - While **hydrocephalus** can cause a **tense fontanelle** and seizures, the **acute onset** of symptoms (day 3 of life with rapid deterioration over 18 hours following a specific tonic seizure) in an extremely premature infant strongly suggests an **acute hemorrhagic event** rather than congenital hydrocephalus. - Congenital hydrocephalus typically presents with **progressively enlarging head circumference** over time, rather than such acute neurological deterioration in the first 72 hours of life. - IVH can lead to secondary post-hemorrhagic hydrocephalus, but the acute presentation favors primary IVH. *Phenylketonuria* - This is a **metabolic disorder** caused by phenylalanine hydroxylase deficiency that, if untreated, leads to **intellectual disability** and seizures. - Symptoms typically manifest **several months after birth** (usually 3-6 months) as phenylalanine accumulates, and are not associated with acute neonatal neurological distress like tense fontanelle, abnormal eye movements, or acute lethargy in the first few days of life. - Would not explain the acute deterioration on day 3 of life in this clinical context.

Neonatal infections US Medical PG Question 9: A 7-year-old boy is brought to the emergency department because of a 3-day history of generalized fatigue, myalgia, and fever. He has sickle cell disease. His current medications include hydroxyurea and folic acid. He appears ill. His temperature is 39.2°C (102.6°F), pulse is 103/min, and respirations are 28/min. Examination shows pale conjunctivae. The lungs are clear to auscultation. The abdomen is soft and nontender. Neurologic examination shows no focal findings, His hemoglobin concentration is 10.3 g/dL and leukocyte count is 14,100/mm3. Intravenous fluid is administered and blood cultures are obtained. Which of the following is the most appropriate next step in treatment?

• A. Clindamycin
• B. Prednisone
• C. Vancomycin
• D. Ceftriaxone (Correct Answer)
• E. Levofloxacin

Neonatal infections Explanation: ***Ceftriaxone*** - This patient presents with **fever** and **sickle cell disease**, placing him at high risk for bacterial infections, especially from **encapsulated organisms** like *Streptococcus pneumoniae* and *Haemophilus influenzae*. **Ceftriaxone** is a broad-spectrum third-generation cephalosporin that provides excellent coverage against these common pathogens. - Due to the high risk of **sepsis** and rapid progression of infection in sickle cell patients, empiric, prompt administration of **intravenous antibiotics** is crucial, even before culture results are available. *Clindamycin* - **Clindamycin** is primarily effective against **anaerobic bacteria** and some gram-positive organisms, including methicillin-sensitive *Staphylococcus aureus* (MSSA). - It does not provide adequate coverage against the most common and life-threatening pathogens in febrile sickle cell patients, such as encapsulated bacteria. *Prednisone* - **Prednisone** is a corticosteroid used for its **anti-inflammatory** and immunosuppressive effects. It is not indicated for the initial management of fever and suspected bacterial infection. - Administering corticosteroids in a patient with suspected infection without appropriate antibiotic coverage could worsen the infection. *Vancomycin* - **Vancomycin** is a powerful antibiotic primarily used to cover **multi-drug resistant gram-positive bacteria**, especially **MRSA** and drug-resistant *S. pneumoniae*. - While it covers gram-positive organisms well, it does **not cover gram-negative bacteria** such as *H. influenzae* or *Salmonella* species, which are important pathogens in sickle cell patients. **Ceftriaxone** provides broader coverage including both gram-positive and gram-negative encapsulated organisms, making it the preferred empiric choice. *Levofloxacin* - **Levofloxacin** is a fluoroquinolone that provides broad-spectrum coverage, including against atypical organisms and some gram-negatives and gram-positives. - However, **fluoroquinolones** are generally avoided in children due to potential adverse effects on cartilage development, and it is not the first-line empiric choice for severe bacterial infections in this age group, especially when **cephalosporins** are highly effective and safer.

Neonatal infections US Medical PG Question 10: A 4-year-old girl is brought to the physician because of diarrhea and vomiting for 5 days. Vaccinations are up-to-date. She appears pale and irritable. Her vital signs are within normal limits. Examination shows petechiae on her trunk and extremities. Abdominal examination shows diffuse abdominal tenderness with hyperactive bowel sounds. The remainder of the exam shows no abnormalities. Laboratory studies show: Hemoglobin 8 g/dL Leukocyte count 17,000/mm3 Platelet count 49,000/mm3 Serum Creatinine 1.6 mg/dL Lactate dehydrogenase 300 U/L Coagulation studies are normal. A peripheral blood smear is shown. Which of the following is the most likely underlying cause of these findings?

• A. Parvovirus B19 infection
• B. Disseminated intravascular coagulation
• C. Acute lymphocytic leukemia
• D. Immune thrombocytopenic purpura
• E. Escherichia coli infection (Correct Answer)

Neonatal infections Explanation: ***Escherichia coli infection*** - The constellation of **diarrhea, vomiting, hemolytic anemia, thrombocytopenia, and acute kidney injury** (elevated creatinine) is characteristic of **hemolytic uremic syndrome (HUS)**, which is most often caused by **Shiga toxin-producing *E. coli*** (STEC), particularly O157:H7. - The peripheral blood smear showing **schistocytes** (fragmented red blood cells) further supports the diagnosis of microangiopathic hemolytic anemia seen in HUS. *Parvovirus B19 infection* - Parvovirus B19 primarily causes **transient aplastic crisis** in individuals with underlying hemolytic disorders or fifth disease (erythema infectiosum) with a "slapped cheek" rash, not typically **hemolytic uremic syndrome**. - While it can cause anemia, it does not typically lead to the **combination of thrombocytopenia and acute kidney injury** seen in this patient. *Disseminated intravascular coagulation* - DIC would present with **abnormal coagulation studies** (prolonged PT/aPTT, decreased fibrinogen, elevated D-dimer), which are explicitly stated as normal in this case. - Although it involves microangiopathic hemolysis and thrombocytopenia, the normal coagulation profile makes DIC unlikely. *Acute lymphocytic leukemia* - ALL typically presents with **pancytopenia** or various cytopenias, but the primary features are often **blast cells** on the peripheral smear and bone marrow biopsy, along with frequent **lymphadenopathy, hepatosplenomegaly**, and constitutional symptoms, which are not described. - It does not primarily cause **acute kidney injury** or the specific combination of hemolytic anemia and thrombocytopenia seen in HUS. *Immune thrombocytopenic purpura* - ITP is characterized by **isolated thrombocytopenia** with otherwise normal blood counts and morphology. Hemolytic anemia and renal failure are not features of ITP. - The presence of **schistocytes and hemolytic anemia** rules out ITP as the primary diagnosis.

Neonatal infections Flashcard 1 of 10

Question: What is the first type of immunoglobulin produced in a neonate? _____

Answer: IgM

Neonatal infections Flashcard 2 of 10

Question: HSV-_____ commonly causes neonatal herpes

Answer: 2

Neonatal infections Flashcard 3 of 10

Question: What GI pathology is associated with neonatal respiratory distress syndrome due to hypoxemia? _____

Answer: Necrotizing enterocolitis

Neonatal infections Flashcard 4 of 10

Question: What is the most common cause of meningitis in neonates?_____

Answer: Group B Strep (Streptococcus agalactiae)

Neonatal infections Flashcard 5 of 10

Question: What is the treatment of neonatal HSV infection?_____

Answer: IV acyclovir

Neonatal infections Flashcard 6 of 10

Question: Congenital toxoplasmosis presents with _____, characterized by ring-enhancing lesions

Answer: intracranial calcifications

Extra Information:   Watch Toxoplasma gondii [https://dashboard.sketchy.com/study/medical/courses/medical-microbiology/units/medical-microbiology-parasites/videos/medical-microbiology-parasites-protozoa-of-the-cns-toxoplasma-gondii?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical] https://onlinemeded.org/spa/microbiology/protozoa/acquire?ref=anki 

Neonatal infections Flashcard 7 of 10

Question: Congenital toxoplasmosis presents with _____, characterized by seizures

Answer: hydrocephalus

Extra Information:   * due to scarring of meninges Watch Toxoplasma gondii [https://dashboard.sketchy.com/study/medical/courses/medical-microbiology/units/medical-microbiology-parasites/videos/medical-microbiology-parasites-protozoa-of-the-cns-toxoplasma-gondii?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical] Watch Hydrocephalus [https://dashboard.sketchy.com/study/medical/courses/medical-microbiology/units/medical-microbiology-parasites/videos/medical-microbiology-parasites-protozoa-of-the-cns-toxoplasma-gondii?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical] https://onlinemeded.org/spa/microbiology/protozoa/acquire?ref=anki 

Neonatal infections Flashcard 8 of 10

Question: Erythromycin eye ointment is indicated as prophylaxis for _____ conjunctivitis in the newborn

Answer: gonococcal

Extra Information:    https://onlinemeded.org/spa/infectious-disease?ref=anki 

Neonatal infections Flashcard 9 of 10

Question: _____ is the deposition of bilirubin in the brain, especially basal ganglia, causing neurologic deficits and possibly death

Answer: Kernicterus

Extra Information: Watch associated Bootcamp video [https://app.bootcamp.com/med-school/gastroenterology/videos/pancreatic-and-biliary-pathology?index=16] https://onlinemeded.org/spa/gastroenterology/jaundice/acquire?ref=anki Atlas: 

Neonatal infections Flashcard 10 of 10

Question: Streptococcus agalactiae (GBS) causes neonatal meningitis, _____, and pneumonia

Answer: sepsis

Extra Information:   https://onlinemeded.org/spa/infectious-disease/pneumonia/acquire?ref=anki