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Associations between capsular serotype, multilocus sequence type, and macrolide resistance in Streptococcus

M Morozumi1, T Wajima1, Y Kuwata1

  • 1Laboratory of Molecular Epidemiology for Infectious Agents, Kitasato Institute for Life Sciences, Kitasato University, Tokyo, Japan.

Epidemiology and Infection
|July 23, 2013
PubMed

Insights

Group B Streptococcus (GBS) invasive infections in infants are often caused by serotype III strains. While penicillin resistance is absent, macrolide resistance is emerging, necessitating improved prevention strategies and vaccine development.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Pediatrics

Background:

  • Streptococcus agalactiae, or group B Streptococcus (GBS), is a significant cause of invasive infections in infants.
  • Understanding the genetic and antimicrobial resistance profiles of GBS is crucial for effective treatment and prevention.

Purpose of the Study:

  • To analyze capsular serotype, multilocus sequence type (MLST), and antibiotic susceptibility of GBS isolates from infants with invasive infections.
  • To identify predominant serotypes and sequence types associated with early- and late-onset GBS disease.
  • To assess the prevalence of antibiotic resistance genes, particularly macrolide resistance, in GBS isolates.

Main Methods:

  • Analysis of 150 GBS isolates from infants with invasive infections (2006-2011).
  • Determination of capsular serotype, MLST, and antibiotic susceptibility profiles.
  • Detection of macrolide resistance genes (mef(A/E), erm(A), erm(B)).

Main Results:

  • Serotype III was the most common (58.7%), followed by Ia (21.3%) and Ib (12.7%).
  • Predominant sequence types for serotype III were ST17 (50.0%) and ST19 (26.1%).
  • No penicillin resistance was observed, but 22.0% of strains carried macrolide resistance genes. A new ST335 with mef(A/E) showed increasing frequency.

Conclusions:

  • Serotype III and specific sequence types (e.g., ST17) are dominant in invasive infant GBS infections.
  • Emerging macrolide resistance, particularly in a new ST335, is a concern.
  • Timely identification and vaccine development are essential for preventing invasive GBS infections in infants.

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