2025 – PAGE 322 – INFECTIOUS DISEASES

ADOLESCENT + PNEUMONIA + LOW GRADE FEVER

If an adolescent presents with a pneumonia and a low-grade fever, choose Chlamydia (diagnose with PCR or immunofluorescent antibodies) or Mycoplasma pneumonia (diagnose with PCR or IgM antibodies). Treat with either a macrolide or with doxycycline.

SPONTANEOUS BACTERIAL PERITONITIS (SBP)

Spontaneous bacterial peritonitis (SBP) is usually found in nephrotic children, so look for low IgG. Can also occur with ascites due to cirrhosis. The most likely etiology is E. coli. Give cefotaxime until there is a positive ID of the organism.

SECONDARY PERITONITIS

Secondary peritonitis is due to trauma and perforation of the intestines, most likely due to gram-negative orga­nisms and anaerobes. Ceftriaxone and metronidazole (or piperacillin-tazobactam) would be good choi­ces. If the peritonitis is in a patient getting peritoneal dialysis, the cause is likely Staph epidermidis; treat with VANCOMYCIN.

TOXIC SHOCK SYNDROME (TSS)

For the pediatric boards, a question on toxic shock syndrome (TSS) would likely provide the triad of FEVER + HYPOTENSION + SKIN INFECTION. Can be caused by Staphylococcus OR Streptococcus infection. If asked to choose which Streptococcus, choose GAS (Group A Strep). If due to a GAS infection, it may be a Strep pyogenes NECROTIZING FASCIITIS. If associated with Staph aureus, the patient may also have emesis, watery diarrhea, or a foreign body (tampon). Mortality is higher with STREP. Empiric treatment for suspected TSS is vancomycin AND clindamycin AND either penicillin/beta-lactamase inhibitor or carbapenem.

PEARLS: You may not be given a classic scenario of an adolescent girl using a tampon for days. BUT if the patient is an adolescent female with FEVER + HYPOTENSION, they might just be holding back a key piece of information.

DENTAL ABSCESS

A dental abscess can present as swelling below the jaw or periorbital swelling.

(DOUBLE TAKE) FEBRILE INFANT AND SEPTIC WORKUP

For babies with rectal temperatures of ≥ 38C°, workup and treatment depend on their age. The most common causes of neonatal sepsis are E. coli and group B strep, with E. coli being more common because of GBS screening and treatment. Risk factors for invasive bacterial illness (IBI) include temperature > 38.6 C° (101.5 F°), prematurity, congenital defects, indwelling catheters, recent antibiotic use (in the last 1 week), and maternal factors (fever, PROM, and +GBS status). The risk of IBI decreases with age. Consider HSV in babies if the mother has risk factors, if the CSF shows pleocytosis, or if the baby has seizures or suggestive skin lesions. For most babies admitted to the hospital due to a fever, they can be discharged after 36 hours if they are fever free and all cultures are negative. Babies 0-7 days old should be discharged after 48 hours. Please note that the decision tree can be complicated, and the AAP allows for variations based on the individual circumstances.

• 0-7 DAYS OLD: These babies are at high risk for early-onset bacterial infection. Obtain CBC, blood cultures, tracheal aspirates (if intubated), and lumbar puncture. A urinalysis is not needed since a positive urine culture in this age range is usually due to severe bacteremia. Obtain imaging only if symptoms warrant it. Inflammatory markers (procalcitonin and/or C-reactive protein PLUS ANC) are not required but may be obtained. Start empiric IV antibiotics immediately (do not delay for an LP). Treat with ampicillin PLUS gentamicin or use ampicillin PLUS an expanded-spectrum cephalosporin (ceftazidime, cefepime, or cefotaxime). Add acyclovir if HSV prophylaxis is indicated. Add vancomycin if MRSA infection rates are high (>10% of S. aureus infections) or when treating for meningitis (helps to cover resistant S. pneumoniae).
• 8-21 DAYS OLD: Same workup and treatment as previous age range, but also obtain a urinalysis and culture. May obtain inflammatory markers. Obtain additional diagnostics (e.g., cultures and imaging) if the history, exam, or symptoms warrant it. Treat with same antibiotics mentioned for previous age range. If cultures are negative at 24-36 hours, then antibiotics can be discontinued if.
• 22-28 DAYS OLD: Workup is similar to previous age range, but inflammatory markers should be obtained, and LP should only be done if inflammatory markers are elevated or if symptoms warrant it. If CSF is normal, then baby can be observed either at home or in the hospital. If observed at home, give a dose of IV antibiotics and reasses in 24 hours. If observed in the hospital, consider giving IV antibiotics. If CSF was unable to be obtained, showed pleocytosis, or is not able to be interpreted, parenteral antibiotics should be given and baby should be observed in the hospital. Treat with same antibiotics mentioned for previous age range. If cultures are negative at 24-36 hours, then antibiotics can be discontinued.
• 29-60 DAYS OLD: Workup is similar to previous age range, but LP is only needed if the inflammatory markers are elevated, or symptoms warrant it. If the urinalysis is positive, obtain a urine culture. If an LP was indicated but not done, or CSF results are unable to be interpreted, give IV antibiotics and consider observing either at home or in the hospital. If CSF results are positive, give IV antibiotics and observe in the hospital. If CSF results are negative (regardless of the urinalysis results), consider giving either IV or oral antibiotics and consider the setting of observation (i.e., home or in the hospital). If inflammatory markers are not elevated, then an LP is not needed. If urinalysis is positive, send urine culture, treat with an oral antibiotic, observe at home, and follow up in 12-24 hours. If urinalysis is negative, observe the baby at home without any antibiotics and follow up in 24-36 hours. For a baby in this age group, if the workup is negative at 24-36 hours, the baby can does not need further antibiotics or hospitalization.
• 60-90 DAYS OLD: The workup is more focused in this age group. Obtain a urinalysis and urine culture. Consider getting a CBC and a CXR if indicated. Consider seasonal viruses in your differential and send viral tests if appropriate. Treatment depends on whether the child is ill-appearing or well-appearing. Can monitor on an outpatient basis without antibiotics if the child is well-appearing and the workup is negative. Monitor on an outpatient basis with oral antibiotics if the workup suggests a UTI. If the child is septic and needs to be admitted, treat with ceftriaxone or cefotaxime PLUS ampicillin. Add acyclovir and vancomycin if indicated.