Tamara Ryan

Clinical posts from members and guests of the Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine (ASHM) from various international medical and scientific conferences on HIV, AIDS, viral hepatitis, and sexual health.

Resistance in STIs

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Evolution and global spread of resistance in STIs- a very useful and insightful topic and very relevant working clinically in the field of STIs. 

The session started with Dr Magnus Unemo who presented ´Evolution and global spread of resistance in Neisseria Gonorrhoeae´. Antimicrobial resistance (AMR) has mostly emerged in post- modern times due to both SNPs and recombinations. Specific linegaes are more prone to develop resistance and remain susceptible.  Extended spectrum cephalosporin (ESC) resistance has emerged from Japan as highlighted in the paper by Shimuta et. al 2015 (BMC Infectious Diseases). Genotype 1407 has accounted for most decreased susceptibility to ESCs worldwide. Most microbial resistance is due to use or misuse of antimicrobials. AMR is a global concern requiring enhanced surveillance, need for new antimicrobials and development of a vaccine is crucial.

Dr Catriona Bradshaw discussed ´Evolution and Global Spread of Resistance in Mycoplasma Genitalium´.

Mycoplasma Genitalium (MG) is a fastidious and slow growing organism making NAAT the only diagnostic solution (difficult to culture). Treatment options are limited as mycoplasma lack a cell wall and are unaffected by many antimicrobials.

Doxycyline is used as first line treatment in many areas of the world but it exhibits low overall efficacy with cure rates of 20-40%. Azithromycin however is widely recommended as first line treatment but there has been a notable decline in efficacy over the past decade. Selected macrolide resistance has been demonstrated, at least 10% of the time following 1g of azithromycin. 

Widespread use of azithromycin for syndromic management of STIs has likely contributed to resistance. Prevalence of resistance is worse in the Asia Pacific region.  Prevalence of resistance to azithromycin appears to be less in countries that preference doxycycline for 1st line treatment of MG.

Moxifloxacin is most commonly used as 2nd line treatment in NG. The recommended dose is 400mg daily for 7-10 days. However in 2007 there were the first reports of moxifloxacin treatment failures for MG.

The experience in Melbourne has been a 12-15% moxifloxacin treatment failure rate. These treatment failures have been associated with ParC mutations. ParC mutations have been observed at low rates in Europse when compared to the Asia Pacific region.

What is concerning is that dual class resistance is emerging which will have huge clinical implications. The priorities now are review of using azithromycin for STIs and syndromal management, development of new antimicrobials and evaluating the use of exiting registered antimicrobials. This particular talk was followed up later in the day with a session from Dr Jorgen Jensen and a late breaker session which I will blog about later on. 

These particular sessions I feel were extremely worthwhile and will have a huge impact on clinical practice. It reiterated the need to be mindful of antibiotic prescribing and be aware of emerging resistance.

 

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Guest Thursday, 27 July 2017