A 5-week-old girl is brought to the emergency department due to several hours of fever, irritability, and vomiting. This morning she was warm to the touch and refused to drink. Her temperature is 40.1 C (104.2 F). Lumbar puncture reveals cerebrospinal fluid pleocytosis; additional fluid is sent for Gram stain and culture. Empiric cefotaxime and vancomycin therapy is initiated. However, no clinical improvement is seen. Cerebrospinal fluid culture yields an organism that is resistant to cefotaxime. Which of the following organisms is most likely causing this patient's infection?

Question

A 5-week-old girl is brought to the emergency department due to several hours of fever, irritability, and vomiting.  This morning she was warm to the touch and refused to drink.  Her temperature is 40.1 C (104.2 F).  Lumbar puncture reveals cerebrospinal fluid pleocytosis; additional fluid is sent for Gram stain and culture.  Empiric cefotaxime and vancomycin therapy is initiated.  However, no clinical improvement is seen.  Cerebrospinal fluid culture yields an organism that is resistant to cefotaxime.  Which of the following organisms is most likely causing this patient's infection?

Quizplus · Accepted Answer

11ec160b_3845_26d1_9249_832d40143613_MD0001_00 This infant with high fever, irritability, vomiting, and cerebrospinal fluid pleocytosis has meningitis. Empiric treatment with cefotaxime and vancomycin would cover the majority of likely pathogens in this age group including Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, group B streptococcus, and Escherichia coli. However, it would not cover Listeria monocytogenes, which has intrinsic resistance to third-generation cephalosporins (eg, cefotaxime, ceftriaxone) due to the presence of penicillin-binding proteins that have a low-affinity for this drug class. Coverage of Listeria requires the addition of ampicillin, a beta-lactam antibiotic with a specialized side-group that allows it to bind to and inactivate the penicillin binding proteins of Listeria. (Choice A) Although many Haemophilus influenzae organisms produce beta lactamases, they are effectively treated with a beta lactam/beta lactamase inhibitor (eg, amoxicillin/clavulanate) or with third-generation cephalosporins. (Choice C) Neisseria meningitidis is effectively treated with third-generation cephalosporins. (Choice D) Streptococcus agalactiae (group B Streptococcus) is universally susceptible to ampicillin or penicillin as well as third-generation cephalosporins. (Choice E) Streptococcus pneumoniae is the most common cause of meningitis in older infants and children. Although this organism has increasing penicillin and cephalosporin resistance, vancomycin provides effective coverage (and would result in symptomatic improvement). Educational objective: Ampicillin is the treatment of choice for Listeria, which is not sensitive to cephalosporins. Listeria most commonly causes disease in those with deficient cell-mediated immunity, such as young infants or immunocompromised patients. __________ References: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC172923/pdf/100345.pdf (http://www.ncbi.nlm.nih.gov/pubmed/1)

A 5-Week-Old Girl Is Brought to the Emergency Department Due