A term neonate develops fever, poor feeding and seizures on day 9 of life. CSF shows neutrophilic pleocytosis and gram-negative bacilli. Culture grows E. coli. The capsular antigen most frequently associated with E. coli strains causing neonatal meningitis is:
- A Vi polysaccharide antigen
- B O157 lipopolysaccharide antigen
- C K1 antigen, a polymer of sialic acid ✓
- D K88 fimbrial antigen
Correct answer: C. K1 antigen, a polymer of sialic acid
Explanation
Approximately 75 to 80 percent of E. coli strains causing neonatal meningitis possess the K1 capsular antigen, a homopolymer of sialic acid. Its structural mimicry of neural cell adhesion molecules and poor immunogenicity help the organism evade complement and cross the blood brain barrier. Vi antigen is a Salmonella Typhi capsule, O157 denotes the EHEC serogroup, and K88 is an enterotoxigenic E. coli pilus antigen of veterinary importance.
Reference: Nelson Textbook of Pediatrics, 22nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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