Two Independent Acquisitions of Multidrug Resistance Gene lsaC in Streptococcus pneumoniae Serotype 20 Multilocus
Abstract:
Among >25,000 invasive pneumococcal disease isolates recovered in US locations during 2015-early 2024 through population-based surveillance, we detected 17 case isolates carrying the lsaC gene, which has been shown to confer resistance to clindamycin in group B Streptococcus. Sixteen isolates carried the mef, msrD, tetM, and lsaC genes on a 29-kb mobile element acquired through an interspecies recombination event and were intermediately clindamycin resistant. One isolate acquired a 62-kb mobile element containing the ermB, tetM, and lsaC genes through a transposition event. All 17 cases were in adults, including 4 adults experiencing homelessness and 9 with substance abuse problems. All 17 lsaC-positive isolates shared a 5.2-kb lsaC-containing element precisely integrated within the conserved oriT site of their respective mobile element. Those 17 lsaC-positive strains were all serotype 20, multilocus sequence type 1257, and were recovered recently (2021-2024); isolates 1-16 represented emergent disease clusters in New York and Connecticut.
Insights
Seventeen invasive pneumococcal disease isolates resistant to clindamycin were identified in US adults. These strains, primarily serotype 20, carried the lsaC gene on mobile elements, indicating potential public health concerns.
Area of Science:
- Microbiology
- Genetics
- Epidemiology
Background:
- Invasive pneumococcal disease (IPD) remains a significant public health concern.
- Emergence of antimicrobial resistance in Streptococcus pneumoniae is a growing threat.
- The lsaC gene, known to confer clindamycin resistance in other bacteria, was investigated in IPD isolates.
Purpose of the Study:
- To detect and characterize isolates of Streptococcus pneumoniae carrying the lsaC gene.
- To investigate the genetic elements and mobile DNA associated with lsaC acquisition.
- To understand the epidemiological context of lsaC-positive IPD cases.
Main Methods:
- Population-based surveillance of invasive pneumococcal disease isolates in the US (2015-early 2024).
- Molecular detection of antimicrobial resistance genes, including lsaC, mef, msrD, and tetM.
- Analysis of mobile genetic elements and their integration sites.
- Serotyping and multilocus sequence typing (MLST) of identified isolates.
Main Results:
- Seventeen IPD isolates carrying the lsaC gene were identified among >25,000 isolates.
- Sixteen isolates harbored lsaC on a 29-kb mobile element with other resistance genes (mef, msrD, tetM), showing intermediate clindamycin resistance.
- One isolate contained a 62-kb mobile element with ermB, tetM, and lsaC.
- All 17 lsaC-positive isolates were serotype 20, MLST 1257, and recovered recently (2021-2024).
- Cases were exclusively in adults, with significant proportions experiencing homelessness or substance abuse.
- Emergent disease clusters linked to isolates 1-16 were observed in New York and Connecticut.
Conclusions:
- The lsaC gene has emerged in invasive pneumococcal disease isolates in the US, conferring clindamycin resistance.
- Acquisition via mobile genetic elements, including interspecies recombination and transposition, facilitates spread.
- Serotype 20, MLST 1257 strains carrying lsaC represent a concerning emergent threat, particularly in vulnerable adult populations.
- Continued surveillance is crucial to monitor the dissemination of clindamycin resistance in Streptococcus pneumoniae.
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