| 1. |
- Holley, Concerta L., et al.
(författare)
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A Single Amino Acid Substitution in Elongation Factor G Can Confer Low-Level Gentamicin Resistance in Neisseria gonorrhoeae
- 2022
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Ingår i: Antimicrobial Agents and Chemotherapy. - : American Society for Microbiology. - 0066-4804 .- 1098-6596. ; 66:5
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Tidskriftsartikel (refereegranskat)abstract
- The continued emergence of Neisseria gonorrhoeae isolates which are resistant to first-line antibiotics has reinvigorated interest in alternative therapies such as expanded use of gentamicin (Gen). We hypothesized that expanded use of Gen promotes emergence of gonococci with clinical resistance to this aminoglycoside. To understand how decreased susceptibility of gonococci to Gen might develop, we selected spontaneous low-level Gen-resistant (GenR) mutants (Gen MIC = 32 μg/mL) of the Gen-susceptible strain FA19. Consequently, we identified a novel missense mutation in fusA, which encodes elongation factor G (EF-G), causing an alanine (A) to valine (V) substitution at amino acid position 563 in domain IV of EF-G; the mutant allele was termed fusA2. Transformation analysis showed that fusA2 could increase the Gen MIC by 4-fold. While possession of fusA2 did not impair either in vitro gonococcal growth or protein synthesis, it did result in a fitness defect during experimental infection of the lower genital tract in female mice. Through bioinformatic analysis of whole-genome sequences of 10,634 international gonococcal clinical isolates, other fusA alleles were frequently detected, but genetic studies revealed that they could not decrease Gen susceptibility in a similar manner to fusA2. In contrast to these diverse international fusA alleles, the fusA2-encoded A563V substitution was detected in only a single gonococcal clinical isolate. We hypothesize that the rare occurrence of fusA2 in N. gonorrhoeae clinical isolates is likely due to a fitness cost during infection, but compensatory mutations which alleviate this fitness cost could emerge and promote GenR in global strains.
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| 2. |
- Kakooza, Francis, et al.
(författare)
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Genomic surveillance and antimicrobial resistance determinants in Neisseria gonorrhoeae isolates from Uganda, Malawi and South Africa, 2015-20
- 2023
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Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press. - 0305-7453 .- 1460-2091. ; 78:8, s. 1982-1991
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Global antimicrobial resistance (AMR) surveillance in Neisseria gonorrhoeae is essential. In 2017-18, only five (10.6%) countries in the WHO African Region reported to the WHO Global Gonococcal Antimicrobial Surveillance Programme (WHO GASP). Genomics enhances our understanding of gonococcal populations nationally and internationally, including AMR strain transmission; however, genomic studies from Africa are extremely scarce. We describe the gonococcal genomic lineages/sublineages, including AMR determinants, and baseline genomic diversity among strains in Uganda, Malawi and South Africa, 2015-20, and compare with sequences from Kenya and Burkina Faso.METHODS: Gonococcal isolates cultured in Uganda (n = 433), Malawi (n = 154) and South Africa (n = 99) in 2015-20 were genome-sequenced. MICs were determined using ETEST. Sequences of isolates from Kenya (n = 159), Burkina Faso (n = 52) and the 2016 WHO reference strains (n = 14) were included in the analysis.RESULTS: Resistance to ciprofloxacin was high in all countries (57.1%-100%). All isolates were susceptible to ceftriaxone, cefixime and spectinomycin, and 99.9% were susceptible to azithromycin. AMR determinants for ciprofloxacin, benzylpenicillin and tetracycline were common, but rare for cephalosporins and azithromycin. Most isolates belonged to the more antimicrobial-susceptible lineage B (n = 780) compared with the AMR lineage A (n = 141), and limited geographical phylogenomic signal was observed.CONCLUSIONS: We report the first multi-country gonococcal genomic comparison from Africa, which will support the WHO GASP and WHO enhanced GASP (EGASP). The high prevalence of resistance to ciprofloxacin (and empirical use continues), tetracycline and benzylpenicillin, and the emerging resistance determinants for azithromycin show it is imperative to strengthen the gonococcal AMR surveillance, ideally including genomics, in African countries.
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| 3. |
- Matoga, Mitch, et al.
(författare)
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Gentamicin susceptibility in Neisseria gonorrhoeae and treatment outcomes for urogenital gonorrhea after twenty-five years of sustained gentamicin use in Malawi
- 2022
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Ingår i: Sexually Transmitted Diseases. - : Lippincott Williams & Wilkins. - 0148-5717 .- 1537-4521. ; 49:4, s. 251-256
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Gentamicin has been used for the treatment of gonorrhea in Malawi since 1993. However, declining clinical cure rates have been suspected. We evaluated current Neisseria gonorrhoeae susceptibility to gentamicin in vitro and clinically.METHODS: Men with acute urethritis were recruited at the Bwaila District Hospital STI Clinic in Lilongwe, Malawi, between January 2017 and August 2019. All men provided urethral swabs for etiological testing at enrollment and test of cure (TOC), one week later, using Gram-stained microscopy and culture. We used Etest to determine minimum inhibitory concentrations (MICs) of gentamicin, azithromycin, cefixime, ceftriaxone, ciprofloxacin, and spectinomycin, disc diffusion for tetracycline susceptibility and whole genome sequencing (WGS) to verify/refute treatment failure.RESULTS: Among 183 N. gonorrhoeae culture-positive men enrolled, 151 (82.5%) had a swab taken for TOC. Of these 151 men, 16 (10.6%) had a positive culture at TOC. 141 baseline isolates were tested for gentamicin susceptibility using Etest; 2 (1.4%) MIC = 2 μg/mL; 111 (78.7%) MIC = 4 μg/mL; and 28 (19.9%) MIC = 8 μg/mL. All isolates were susceptible to azithromycin, cefixime, ceftriaxone, and spectinomycin while 63.1% had intermediate susceptibility or resistance to ciprofloxacin. Almost all (96.1%) isolates were resistant to tetracycline. All examined isolates cultured at TOC (n = 13) had gentamicin MICs ≤8 μg/mL. Ten men had pre- and post-treatment isolates examined by WGS, 2 (20%) were verified new infections (4119 and 1272 single-nucleotide polymorphisms (SNPs)), while 8 (80%) were confirmed treatment failures (0-1 SNP).CONCLUSIONS: Gentamicin MICs poorly predict gonorrhea treatment outcome with gentamicin, and treatment failures are verified with gonococcal strains with in vitro susceptibility to gentamicin. The first-line treatment for gonorrhea in Malawi should be reassessed.
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