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Colonization with penicillin-resistant Streptococcus pneumoniae in a child-care center
D J Boken1, S A Chartrand, R V Goering
1Department of Pediatrics, Creighton University, Omaha, NE 68178, USA.
Insights
Penicillin-resistant Streptococcus pneumoniae strains were common in child-care centers. Horizontal transmission of resistant strains occurred, suggesting child-care settings are linked to resistant pneumococcal colonization.
Area of Science:
- Pediatrics
- Microbiology
- Epidemiology
Background:
- Streptococcus pneumoniae colonization is common in young children.
- Penicillin resistance in S. pneumoniae is a growing public health concern.
- Child-care centers (CCCs) are environments where respiratory pathogens can spread easily.
Purpose of the Study:
- To investigate the prevalence and genetic diversity of penicillin-resistant S. pneumoniae in a child-care center.
- To assess the transmission dynamics of S. pneumoniae within a CCC.
- To explore the impact of antibiotic selective pressure on resistant pneumococcal colonization.
Main Methods:
- Nasopharyngeal cultures were collected from children aged 2-24 months in an Omaha CCC.
- Pulsed field gel electrophoresis (PFGE) was used for DNA subtyping of S. pneumoniae isolates.
- Isolates were tested for penicillin resistance using minimal inhibitory concentration (MIC) breakpoints.
Main Results:
- 59% of children were colonized with S. pneumoniae.
- 53% of pneumococcal isolates were highly resistant to penicillin (HR-SP), and 22% were intermediately resistant (IR-SP).
- PFGE revealed distinct subtypes within serotypes, with a predominant strain suggesting horizontal transmission.
- Colonization rates remained similar after 4 months, but the proportion of resistant isolates decreased significantly (7% HR-SP, 39% IR-SP).
- Antibiotic use decreased between sampling periods, correlating with reduced resistant S. pneumoniae.
Conclusions:
- Multiple genetic clones of penicillin-resistant S. pneumoniae can coexist in CCCs.
- Individual clones of penicillin-resistant S. pneumoniae can spread among children in CCCs.
- Colonization with penicillin-resistant S. pneumoniae should be considered a CCC-associated phenomenon, particularly during periods of high antibiotic selective pressure.
Abstract:
We obtained nasopharyngeal cultures for Streptococcus pneumoniae from 54 children ages 2 to 24 months attending an Omaha child-care center (CCC) in April 1994. Thirty-two (59%) of the 54 children were colonized with S. pneumoniae belonging to serotypes 23, 19, 6 and 11. Seventeen (53%) of the pneumococcal isolates were highly resistant to penicillin (minimal inhibitory concentration > or = 2.0 micrograms/ml; HR-SP) and 7 (22%) were intermediately resistant to penicillin (0.12 < or = minimal inhibitory concentration < or = 1.0 microgram/ml; IR-SP). Within each pneumococcal capsular serotype, there were 1 to 3 DNA subtypes based on pulsed field gel electrophoresis analysis. A single pulsed field gel electrophoresis strain predominated in most CCC rooms, suggesting horizontal transmission among cohorted children. Nasopharyngeal cultures obtained 4 months later revealed similar S. pneumoniae colonization rates (28 of 52, 54%); however, only 2 (7%) of 28 isolates were HR-SP and 11 (39%) were IR-SP. Colonization with resistant pneumococci persisted after 4 months in 4 (12%) of 34 children cultured on both occasions. Antibiotic use by attendees had decreased notably between the two sampling periods, suggesting that selective pressure within the CCC might contribute to seasonal variation in colonization rates with HR-SP and IR-SP. We conclude that multiple genetic clones of penicillin-resistant pneumococci can occur simultaneously in a single CCC, especially during periods of heavy antibiotic selection pressure. However, individual clones of penicillin-resistant S. pneumoniae may be spread from child to child, suggesting that colonization with penicillin-resistant S. pneumoniae should now be considered a CCC-associated phenomenon.