Capsular type and antibiotic resistance in Streptococcus agalactiae isolates from patients, ranging from newborns to the elderly, with invasive infections.

Streptococcus agalactiae isolates (n = 189) from patients with invasive infections were analyzed for capsular type by PCR, for antimicrobial susceptibility, and for the presence of resistance genes. In contrast to the predominance of capsular type III in children, types Ib and V were most common among adults. All 45 levofloxacin-resistant strains had two amino acid substitutions, Ser(81)Leu in the gyrA gene and Ser(79)Phe in the parC gene, and showed similar pulsed-field gel electrophoresis patterns.