Differential susceptibility of type 1 and type 4 gonococci to chlorhexidine (Hibitane).

Waitkins, Sheena A.; Geary, I.

doi:10.1136/sti.51.4.267

Cited by 2 publications

(2 citation statements)

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“…Previous studies reported similar chlorhexidine MICs in N. gonorrhoeae as in the current study (range 2-8mg/L) (Waitkins and Geary, 1975;Rabe and Hillier, 2000;Victoria et al, 2018). Here, we were able to effect a 10-fold increase in chlorhexidine MIC and concomitant minor increases in azithromycin, ciprofloxacin and cefixime MICs.…”

Section: Discussionsupporting

confidence: 88%

“…We cannot conclude from our results that even extensive clinical use of chlorhexidine would have an influence on antimicrobial susceptibility. On the other hand, in vivo , chlorhexidine concentrations and substantivity in the oral cavity can be affected by food, drinks, pH, saliva and serum ( Waitkins and Geary, 1975 ; Rabe and Hillier, 2000 ; Tomás et al, 2010 ; Abouassi et al, 2014 ; Cieplik et al, 2019 ). Furthermore, chlorhexidine is unlikely to penetrate and kill N. gonorrhoeae localized within pharyngeal epithelial cells intracellularly or in crypts ( Veien et al, 1976 ; Lewis, 2015 ; Chow et al, 2020 ).…”

Section: Discussionmentioning

confidence: 99%

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Sub-Inhibitory Concentrations of Chlorhexidine Induce Resistance to Chlorhexidine and Decrease Antibiotic Susceptibility in Neisseria gonorrhoeae

et al. 2021

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Objectives: Chlorhexidine digluconate (chlorhexidine) and Listerine® mouthwashes are being promoted as alternative treatment options to prevent the emergence of antimicrobial resistance in Neisseria gonorrhoeae. We performed in vitro challenge experiments to assess induction and evolution of resistance to these two mouthwashes and potential cross-resistance to other antimicrobials.Methods: A customized morbidostat was used to subject N. gonorrhoeae reference strain WHO-F to dynamically sustained Listerine® or chlorhexidine pressure for 18 days and 40 days, respectively. Cultures were sampled twice a week and minimal inhibitory concentrations (MICs) of Listerine®, chlorhexidine, ceftriaxone, ciprofloxacin, cefixime and azithromycin were determined using the agar dilution method. Isolates with an increased MIC for Listerine® or chlorhexidine were subjected to whole genome sequencing to track the evolution of resistance.Results: We were unable to increase MICs for Listerine®. Three out of five cultures developed a 10-fold increase in chlorhexidine MIC within 40 days compared to baseline (from 2 to 20 mg/L). Increases in chlorhexidine MIC were positively associated with increases in the MICs of azithromycin and ciprofloxacin. Low-to-higher-level chlorhexidine resistance (2–20 mg/L) was associated with mutations in NorM. Higher-level resistance (20 mg/L) was temporally associated with mutations upstream of the MtrCDE efflux pump repressor (mtrR) and the mlaA gene, part of the maintenance of lipid asymmetry (Mla) system.Conclusion: Exposure to sub-lethal chlorhexidine concentrations may not only enhance resistance to chlorhexidine itself but also cross-resistance to other antibiotics in N. gonorrhoeae. This raises concern regarding the widespread use of chlorhexidine as an oral antiseptic, for example in the field of dentistry.

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Section: Discussionsupporting

confidence: 88%