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Volume 31, Number 11—November 2025

Research

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

Bernard BeallComments to Author , Wuling Lin, Zhongya Li, Theresa Tran, Benjamin J. Metcalf, Bridget J. Anderson, Keipp H. Talbot, Lesley McGee, and Sopio Chochua
Author affiliation: ASRT, Inc., Smyrna, Georgia, USA (B. Beall, Z. Li); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (W. Lin, T. Tran, B.J. Metcalf, L. McGee, S. Chochua); New York State Department of Health, Albany, New York, USA (B.J. Anderson); Vanderbilt University School of Medicine, Nashville, Tennessee, USA (K.H. Talbot)

Main Article

Figure 1

Core-genomic phylogeny representative serotype 20/ST1257 invasive pneumococcal disease isolates recovered during 2015–2024 in study of independent acquisitions of multidrug resistance gene lsaC in serotype 20/ST1257 Streptococcus pneumoniae isolates, United States. Of 367 serotype 20/ST1257 invasive pneumococcal disease isolates recovered during 2015–2024, we included 358 with <200 short-read genome contigs in the phylogram. Only 3 year–2024 isolates, including 1 of the depicted lsaC-positive isolates 1–16, were included. There were 6,727 variable positions. Isolates 1–16 are indicated on a single branch with the red box divided into 2 subclusters specific to New York (10 isolates) and Connecticut (6 isolates) Active Bacterial Core surveillance sites. The 10-isolate New York subcluster has an inner subbranch of 6 isolates and outer subbranch of 4 isolates. The main branch containing isolates 1–16 and the outward New York subbranch are labeled with Rec, indicative of the disproportionate contribution of recombination to the long branch lengths. Asterisks indicate 50 isolates from adults experiencing homelessness. The remaining isolates were susceptible to antibiotics, except for 2 mef/msrD-positive isolates (green arrows), 2 tetM-positive isolates (black arrows) and 1 ermB-positive isolate (blue arrow). Isolate 17 (positive for ermB, tetM, lsaC) is indicated with a solid red rectangle. ST, sequence type.

Figure 1. Core-genomic phylogeny representative serotype 20/ST1257 invasive pneumococcal disease isolates recovered during 2015–2024 in study of independent acquisitions of multidrug resistance gene lsaC in serotype 20/ST1257 Streptococcus pneumoniae isolates, United States. Of 367 serotype 20/ST1257 invasive pneumococcal disease isolates recovered during 2015–2024, we included 358 with <200 short-read genome contigs in the phylogram. Only 3 year–2024 isolates, including 1 of the depicted lsaC-positive isolates 1–16, were included. There were 6,727 variable positions. Isolates 1–16 are indicated on a single branch with the red box divided into 2 subclusters specific to New York (10 isolates) and Connecticut (6 isolates) Active Bacterial Core surveillance sites. The 10-isolate New York subcluster has an inner subbranch of 6 isolates and outer subbranch of 4 isolates. The main branch containing isolates 1–16 and the outward New York subbranch are labeled with Rec, indicative of the disproportionate contribution of recombination to the long branch lengths. Asterisks indicate 50 isolates from adults experiencing homelessness. The remaining isolates were susceptible to antibiotics, except for 2 mef/msrD-positive isolates (green arrows), 2 tetM-positive isolates (black arrows) and 1 ermB-positive isolate (blue arrow). Isolate 17 (positive for ermB, tetM, lsaC) is indicated with a solid red rectangle. ST, sequence type.

Main Article

Page created: September 19, 2025
Page updated: November 25, 2025
Page reviewed: November 25, 2025
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