85 - Characterization of Group B streptococcus Strains with Reduced Susceptibility to Beta-lactam Antibiotics, Active Bacterial Core Surveillance, 1998–2017

Background: In the United States, approximately 30,000 invasive group B Streptococcus (iGBS) infections occur annually; beta-lactam antibiotics (BL) are the first choice for prevention in young infants and treatment in all age groups. We obtained phenotypic and genotypic data for iGBS isolates from U.S. population-based surveillance sites to describe the emergence and characteristics of strains with reduced beta-lactam susceptibility (RS) over a 20-year period.

Methods: We analyzed RS iGBS isolates from eight Active Bacterial Core surveillance sites from 1998–2017. Through 2014, minimum inhibitory concentrations (MIC) for six BL were determined by broth microdilution, followed by whole genome sequencing (WGS) of RS isolates exceeding pre-defined breakpoints (Table 1). In 2015, WGS and MIC testing were performed for all isolates. After 2015, all isolates underwent WGS. MIC testing was continued on approximately 25% of isolates; otherwise, only those with modified penicillin binding protein (PBP) 2x transpeptidase amino acid sequence types or suboptimal WGS (< 1 % of isolates) underwent MIC testing.  Clinical information on RS cases was abstracted from medical charts.

Results: Of 26,058 out of 27,269 iGBS isolates (95.6%) tested to date, 107 (0.4%) exhibited RS, increasing from 0% in 1998 to a peak of 1.1% in 2016 (P< 0.05 for trend) (Figure 1). Seven (6.5%) RS strains were from infants aged < 90 days; the rest were from adults aged ≥30 years (Table 2). RS strains consisted of 52 PBP2x types with diverse susceptibility patterns (Table 1). Seven RS strains (6.5%) had wild-type (non-modified) PBP2x; all met the RS criteria based on a single cephalosporin with a confirmed (repeated) MIC value at the break point (Table 1). Compared to non-RS strains, RS strains were more common in patients who presented with cellulitis and osteomyelitis and with underlying conditions such as diabetes or chronic skin breakdown (Table 2). Of 82 (85.4%) patients with RS strains and additional clinical information, 8.3% had known prior GBS infection; 26.8% had known BL exposure in the preceding year. Phenotypic Characterization and Diversity of Represented PBP2x Types of Invasive Group B Streptococcus (iGBS) Strains with Reduced Beta-lactam Susceptibility (RS), ABCs 1998–2017 (N=107)
Characteristics of Invasive Group B Streptococcus (iGBS) Infections with Reduced Beta-Lactam Susceptibility (RS) Isolates, ABCs 1998–2017
Number of GBS Isolates and Proportion with Reduced Beta-Lactam Susceptibility (RS)*, ABCs 1998-2017


Conclusion: Preliminary results show that RS increased in recent years; strains RS to penicillin and ampicillin remain low. Variable pbp2x mutations have emerged and predominant strains have not yet been identified.

Presenting Author(s)

• 

  Miwako Kobayashi, MD, MPH

  Medical Epidemiologist
  Centers for Disease Control and Prevention
  Atlanta, GA

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.

  Slides Slides and Audio

Co-Author(s)

• LM

  Lesley McGee, Ph.D

  Microbiologist
  Centers for Disease Control and Prevention
  Atlanta, Georgia

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• SC

  Sopio Chochua, M.D., Ph.D.

  Microbiologist
  Centers for Disease Control and Prevention
  Atlanta, Georgia

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• MA

  Mirasol Apostol, MPH

  Project Coordinator
  California Emerging Infections Program
  Oakland, California

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• NA

  Nisha B. Alden, MPH

  Respiratory and Invasive Bacterial Disease Program Manager
  Colorado Department of Public Health and Environment
  Denver, Colorado

  Disclosure: CDC: Grant/Research Support
• MF

  Monica M. Farley, MD

  Professor
  Emory University
  Atlanta, Georgia

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• LH

  Lee Harrison, MD

  Head, Infectious Diseases Epidemiology Research Unit
  University of Pittsburgh
  Pittsburgh, Pennsylvania

  Disclosure: Dynavax (Consultant)GSK (Consultant)Merck (Consultant)OMVax (Consultant)Pfizer (Consultant)Sanofi Pasteur (Consultant)
• CH

  Corinne Holtzman, MPH

  Epidemiologist Senior
  Minnesota Department of Health
  St. Paul, Minnesota

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• ST

  Salina Torres, PhD, MPH

  Active Bacterial Core Surveillance Project Coordinator
  New Mexico Department of Health
  Santa Fe, New Mexico

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• AT

  Ann Thomas, MD, MPH

  Public Health Physician
  Oregon Public Health Division
  Portland, Oregon

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• BB

  Bernard Beall, PhD

  Director, Streptococcus Laboratory
  Centers for Disease Control and Prevention
  Atlanta, Georgia

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• SS

  Stephanie Schrag, DPhil

  Epidemiologist
  CDC
  Atlanta, Georgia

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.