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Published on: January 17, 2014
Penicillin minimum inhibitory concentration drift in identical sequential Streptococcus pneumoniae isolates from
B A Sisson1, G Buck, S M Franco
1Children and Youth Project, University of Louisville, Louisville, KY 40202, USA.
Insights
In healthy infants, Streptococcus pneumoniae colonization is common, with some developing penicillin resistance. Sequential isolates showed a shift from penicillin-susceptible to resistant strains over time.
Area of Science:
- Pediatrics
- Microbiology
- Infectious Diseases
Background:
- Nasopharyngeal colonization by Streptococcus pneumoniae is a critical factor in disease transmission and development of antibiotic resistance.
- Understanding the dynamics of pneumococcal colonization in infants is essential for public health strategies.
- Penicillin resistance in S. pneumoniae poses a significant challenge in pediatric infectious disease management.
Purpose of the Study:
- To monitor the acquisition and evolution of nasopharyngeal Streptococcus pneumoniae colonization in healthy infants.
- To investigate the development of penicillin resistance in sequential pneumococcal isolates from infants.
- To determine the genetic relatedness of pneumococcal strains exhibiting changes in penicillin susceptibility.
Main Methods:
- Longitudinal monitoring of 125 healthy infants for Streptococcus pneumoniae colonization during their first two years of life.
- Isolation and antimicrobial susceptibility testing (MIC) of S. pneumoniae from nasopharyngeal swabs.
- Pulsed-field gel electrophoresis (PFGE) to assess the genetic identity of sequential pneumococcal isolates.
Main Results:
- Streptococcus pneumoniae was isolated from 47% of infants between 2 and 18 months of age.
- Penicillin-resistant S. pneumoniae colonized 19% of infants during the study period.
- Sequential isolates from 5 infants showed an increase in penicillin MIC values over time, with 4 isolates being genetically identical by PFGE.
Conclusions:
- Nasopharyngeal isolates of Streptococcus pneumoniae in healthy infants can exhibit a temporal drift in penicillin minimum inhibitory concentration (MIC) values.
- This drift can progress from penicillin-susceptible to penicillin-resistant phenotypes within the same infant.
- The findings highlight the dynamic nature of pneumococcal colonization and the emergence of antibiotic resistance in young children.
Abstract:
We monitored the timing of acquisition of nasopharyngeal colonization of Streptococcus pneumoniae in 125 healthy infants during their first 2 years of life. S. pneumoniae was isolated at least once from 59 (47%) of 125 infants aged between 2 and 18 months. Twenty-four infants (19%) were colonized with penicillin-resistant S. pneumoniae at some time during the study. During the course of this investigation, we identified sequential pneumococcal isolates of the same serotype from 5 infants, in which the penicillin minimum inhibitory concentration (MIC) increased over time. For 4 of the 5 infants, sequential isolates were identical, as determined by pulsed-field gel electrophoresis. Sequential S. pneumoniae nasopharyngeal isolates from some healthy infants demonstrated drift in penicillin MIC values over time, from penicillin-susceptible to penicillin-resistant.
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