Two Independent Acquisitions of Multidrug Resistance Gene lsaC in Streptococcus pneumoniae Serotype 20 Multilocus Sequence Type 1257.

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.