ABSTRACT
Human listeriosis is an infectious disease caused by Listeria monocytogenes. The invasive form of this disease leads to a high rate of hospitalizations and fatality. The main mode of transmission is through contaminated ready-to-eat foods such as dairy, vegetables and meat products. The knowledge of the diversity and population dynamics of isolates collected from human and food sources is essential for the detection of clusters and the identification of common sites of infection. The aim of this study was the molecular characterization of L. monocytogenes isolates in Argentina. We sequenced a total of 63 isolates, 35 from human and 28 from food sources, collected between 2018 and 2023. Our genomic study divided the isolates into two lineages, four serogroups, 17 sequence types and 15 clonal complexes (CCs). The hypervirulent clone CC1 (lineage I; serogroup IVb) predominated in human and food samples. The phylogenomic analysis showed a high and possible epidemiological relationship between isolates from human and/or food sources, suggesting the presence of transmission chains in our country. These findings highlight the need to strengthen genomic surveillance of L. monocytogenes in Argentina. The identification of geographic distribution and characteristics of predominant and emerging clones from human and food sources might help to focus action plans and public health policies better directed at the control and prevention of listeriosis.
ABSTRACT
Azithromycin combined with ceftriaxone is the recommended dual therapy for uncomplicated gonorrhea in many countries. Nevertheless, the increasing prevalence of azithromycin resistance compromises the effectiveness of this treatment strategy. From 2018 to 2022, we collected 13 gonococcal isolates with high-level azithromycin resistance (MIC ≥ 256 µg/mL) across Argentina. Whole-genome sequencing revealed that these isolates were mainly represented by the internationally spreading Neisseria gonorrhoeae multi-antigen sequence typing (NG-MAST) genogroup G12302, containing the 23S rRNA A2059G mutation (in all four alleles) together with mosaic mtrD and mtrR promoter 2 loci. This information is important to develop targeted public health policies to control the spread of azithromycin-resistant N. gonorrhoeae in Argentina and internationally. IMPORTANCE Azithromycin resistance in Neisseria gonorrhoeae has been increasing in numerous populations worldwide, which is of concern, as azithromycin is part of the recommended dual treatment in many countries. Here, we report 13 N. gonorrhoeae isolates with high-level azithromycin resistance (MIC ≥ 256 µg/mL). This study observed that high-level azithromycin-resistant gonococcal strains have shown sustained transmission in Argentina and are related to the successful international clone NG-MAST G12302. Genomic surveillance together with real-time tracing and data-sharing networks will be crucial in controlling the spread of azithromycin resistance in gonococcus.
Subject(s)
Azithromycin , Gonorrhea , Humans , Azithromycin/pharmacology , Neisseria gonorrhoeae/genetics , Anti-Bacterial Agents/pharmacology , Argentina/epidemiology , Drug Resistance, Bacterial/genetics , Microbial Sensitivity Tests , Gonorrhea/drug therapy , Gonorrhea/epidemiology , Ceftriaxone , Antigens, BacterialABSTRACT
Azithromycin-nonsusceptible Neisseria gonorrhoeae strains are an emerging global public health threat. During 2015-2018, the prevalence of azithromycin-nonsusceptible gonococcal infection increased significantly in Argentina. To investigate the genomic epidemiology and resistance mechanisms of these strains, we sequenced 96 nonsusceptible isolates collected in Argentina during 2005-2019. Phylogenomic analysis revealed 2 main clades, which were characterized by a limited geographic distribution, circulating during January 2015-November 2019. These clades included the internationally spreading multilocus sequence types (STs) 1580 and 9363. The ST1580 isolates, which had MICs of 2-4 µg/mL, had mutations in the 23S rRNA. The ST9363 isolates, which had MICs of 2-4 or >256 µg/mL, had mutations in the 23S rRNA, a mosaic mtr locus, or both. Identifying the geographic dissemination and characteristics of these predominant clones will guide public health policies to control the spread of azithromycin-nonsusceptible N. gonorrhoeae in Argentina.
