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The molecular epidemiology of penicillin-resistant Streptococcus pneumoniae in the United States, 1994-2000
S S Richter1, K P Heilmann, S L Coffman
1Medical Microbiology Division, Department of Pathology, University of Iowa College of Medicine, Iowa City, IA 52242, USA. sandra-richter@uiowa.edu
Abstract:
The genetic relatedness of 672 penicillin-resistant isolates of Streptococcus pneumoniae (PRSP) recovered during national surveillance studies conducted in the United States during the periods of 1994-1995, 1997-1998, and 1999-2000 was determined by use of pulsed-field gel electrophoresis (PFGE). Overall, 104 different PFGE types were elucidated. For all study periods combined, the 12 most prevalent PFGE types included >75% of all isolates, and 5 types were closely related to widespread clones (Spain(23F)-1, France(9V)-3, Spain(6B)-2, Tennessee(23F)-4, and Taiwan(19F)-14). From 1994-1995 to 1999-2000, 3 major PFGE types (not closely related to 16 recognized clones) increased in prevalence. Multidrug resistance was identified among 96%-100% of the isolates in 9 of 12 predominant PFGE types. The prevalence of erythromycin resistance increased within 4 major PFGE types. These observations support the hypothesis that the dominant factor in the emergence of PRSP in the United States during the 1990s has been human-to-human spread of relatively few clonal groups that harbor resistance determinants to multiple classes of antibiotics.
Insights
Penicillin-resistant Streptococcus pneumoniae (PRSP) in the US primarily spread through a few dominant clones. These clones carry multiple antibiotic resistance genes, contributing to the rise of PRSP.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- Penicillin-resistant Streptococcus pneumoniae (PRSP) poses a significant public health challenge.
- Understanding the genetic diversity and spread of PRSP is crucial for effective control strategies.
Purpose of the Study:
- To determine the genetic relatedness of PRSP isolates in the United States.
- To identify the dominant clones and their contribution to the emergence of PRSP.
Main Methods:
- Utilized pulsed-field gel electrophoresis (PFGE) to analyze the genetic profiles of 672 PRSP isolates.
- Covered national surveillance data from 1994-1995, 1997-1998, and 1999-2000.
Main Results:
- Identified 104 distinct PFGE types, with 12 predominant types accounting for over 75% of isolates.
- Five prevalent PFGE types were closely related to known widespread international clones.
- Observed an increase in prevalence for 3 major PFGE types not related to recognized clones.
- Found high rates of multidrug resistance (96%-100%) in 9 of the 12 predominant PFGE types.
- Noted an increased prevalence of erythromycin resistance within 4 major PFGE types.
Conclusions:
- The emergence of PRSP in the US during the 1990s is largely attributed to the human-to-human transmission of a limited number of clonal groups.
- These dominant clones possess resistance determinants to multiple antibiotic classes, facilitating their widespread dissemination.