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Drug resistance

Warding off the scourge of untreatable gonorrhoea?

4 Feb, 16 | by Leslie Goode, Blogmaster

 

A recent analysis (Kircaldy & Papp (K&P) of 2006-2014 US CDC (Centre for Disease Control and Prevention) data on Neisseria gonorrhea (NG) susceptibility to cefixime and ceftriaxone in isolates suggests a halt in the drift to resistance over the period 2011-13 followed by a return in 2014 to the upward trend. Among isolates from MSM the proportion with resistance rose from 0.2% in 2008 to 4% in 2010, then fell incrementally to 0.8% in 2013, before rising once again to 1.3%. It is tempting to see a correlation between these resistance trends and recent treatment guideline changes. After all, 2010 – the year before the beginning of this fall in NG resistance – saw the establishment in the US of a therapeutic regime involving combination therapy with cefixime or ceftriaxone plus a second antimicrobial; whereas 2012 – the year before the trend reached its lowest point – saw the further attempt to safeguard cefixime susceptibility through a regime of ceftriaxone-based combination therapy as the single recommended therapy. However, K&P caution against assuming a causal relation between resistance trends and these measures, since various factors might have contributed to the improvement. But, even if we do assume a causal relation, the 2014 data suggest that, as K&P put it, ‘the improvement in susceptibility may be short-lived’.

Nevertheless, experts seem broadly in favour of antimicrobial stewardship – and, more specifically, the currently recommended regime – as a last-ditch attempt to postpone the progress of multi-resistant NG. Yet, the chances of combination therapy achieving more than a temporary reprieve are slender – at least according to a recent comprehensive examination of the question (Rice (STIs). So what is to be done? Much is made in the literature of the role of ‘core’ populations – chiefly MSM and female sex workers – in sustaining epidemics, and of the importance of developing interventions directed specifically to these groups (Lewis/2013 (STIs); Guiguere & Alary (STIs). (For example, the alarmingly increased proportion of resistant isolates registered by K&P has hitherto affected, almost exclusively, MSM in the West of the US.) The problem with this, however, is that, while NG control is achievable only when core groups are treated, the treatment of those groups maximizes dissemination of antimicrobial-resistant strains (Chan & Fisman (STIs). One possible way out of this epidemiological ‘catch-22’ is indicated in another recent paper (Lewis/2015 (STIs). Lewis draws attention to the importance of the oropharyngeal niche in enabling the dissemination of NG resistant-strains, and proposes widespread screening of core populations, using state-of-the-art resistance-detecting NAATs and treatment with those antimicrobials known to be of greater efficacity for the oropharyngeal site – such as ciprofloxacin. Even where such interventions were affordable, however, there remains, given the largely asymptomatic character of oropharyngeal NG, the not inconsiderable problem of defining and accessing the core group (Guiguere & Alary (STIs)) – and time may be short.

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