Azithromycin susceptibility of Neisseria gonorrhoeae in the USA in 2017: a genomic analysis of surveillance data
Kim M. Gernert, Sandra Seby, Matthew Schmerer, Jesse C. Thomas, Cau D. Pham, Sancta St. Cyr, Karen Schlanger, Hillard Weinstock, William M. Shafer, Brian H. Raphael, Ellen N. Kersh, Sopheay Hun, Chi Hua, Ryan Ruiz, Olusegun O. Soge, Catherine Dominguez, Ami Patel, Jillian Loomis, John Leavitt, Jenny Zhang, Tamara Baldwin, Chun Wang, Christina Moore, Christian Whelen, Pamela O'Brien, Alesia Harvey
Abstract
BACKGROUND: is increasing (555 608 reported US cases in 2017, and 87 million cases worldwide in 2016). Many countries report declining in vitro susceptibility of azithromycin, which is a concern because azithromycin and ceftriaxone are the recommended dual treatment in many countries. We aimed to identify strain types associated with decreased susceptibility to azithromycin. METHODS: isolates obtained by the US Gonococcal Isolate Surveillance Project. Isolates were whole-genome sequenced based on decreased susceptibility to azithromycin (minimal inhibitory concentration [MIC] ≥2 μg/mL, using agar dilution antibiotic susceptibility testing) and geographical representation. Bioinformatic analyses established genomic diversity, strain population dynamics, and antimicrobial resistance profiles. FINDINGS: two of 313 [1%]; p<0·0001). Of the remaining 313 isolates, 57 (18%) had decreased susceptibility to azithromycin (MIC ≥4 μg/mL), which was attributed to 23S rRNA variants (56 of 57 [98%]) and formed phylogenetically diverse clades, showing various levels of clonal expansion. INTERPRETATION: locus, on the fitness and expansion of strains with decreased susceptibility has important implications for the public health response to minimise gonorrhoea transmission. FUNDING: US Centers for Disease Control and Prevention (CDC), CDC Combating Antibiotic Resistant Bacteria initiative, Oak Ridge Institute for Science Education, US Department of Energy/CDC/Emory University, National Institutes of Health, and Biomedical Laboratory Research and Development Service of the US Department of Veterans Affairs.