When Al Gore became a best-selling author with “An Inconvenient Truth” he warned about climate change. When it comes to antibiotic resistance and the current situation of “Bad Bugs, No Drugs”, there are many voices warning us about a return to the pre-antibiotic era.
Why does it take so long to create awareness when receding glacier and arctic ice give us documented facts and figures? Why don’t regulators stop the use of antibiotics in veterinary medicine when antimicrobial resistance trends are overwhelmingly showing the consequence of current practices? What does it take to change a mindset, or health policies?
Take campylobacter as an example. A common enteric pathogen in humans, its source is livestock. This organism was only recognized in 1972 as a cause of human GI infection but we soon learned that it is a leading cause in most bacterial intestinal infections.
Enter ciprofloxacin, enrofloxacin and other fluoroquinolones (FQs). Microbiologic data in the early 1980ies showed universal activity against campylobacter and other enterics. A great new drug class for humans, and great for animals too, had entered the scene. Unsurprisingly, broiler units in many countries found it to great advantage to use FQs. In fact, most chickens were given FQs for 30+ days during their 35 days of broiler life before slaughter.
As would be expected, with widespread use, resistance to ciprofloxacin rose at an alarming rate:
Is there really a difference in resistance rates between the US and other parts of the world? While the table seems to suggest a lower incidence in the US, this impression may not be accurate.
Comparing resistance rates across regions runs into a major confounder: different breakpoint definitions. A campylobacter with an MIC of 1 mg/L designated as R (resistant) by EUCAST criteria would still be considered fully susceptible in the US using CLSI criteria.
Clearly, MIC data clarity would provide more clarity than breakpoint categories which change ever so often. If cross-country comparisons are impossible because source MIC data are not available, one would hope that longitudinal surveillance data would provide reasonable trend information.
A PubMed search (2010 till now) with the search terms: campylobacter / ciprofloxacin / resistance / poultry came up with recent publications from: France, Poland, Portugal, China, Italy, Turkey, the Philippines, Canada, UK, Chile, Brazil, Germany, Japan, Australia, even Vietnam, Jordan and Ethiopia. Blatantly missing were publications from the USA describing the US situation.
When concerns about quinolone resistance finally resulted in legislative action preventing their indiscriminate use in veterinary use, it came much later in the US (2004) than in EU countries which had implemented safeguards and initiated surveillance measures earlier. Unfortunately, there is hardly any data to show whether the situation in US broiler units has changed since 2004.
So, what do with know about campylobacter resistance in the US? Surprisingly little. The CDC report quoted above is based on data before 2010.
What is available is spotty and uninterpretable for most part. Zhao reports that US meat sampled for campylobacter were ciprofloxacin-resistant in 58%[1]. Lower rates were found in pigs (17%) [2] and in cattle (38%) [3]. As would be expected, resistance rates vary widely and are influenced by campylobacter species, geographic location, livestock tested, broiler unit, antibiotic use…
Once upon a time, erythromycin and FQs were the treatment of choice for human campylobacter infections. No longer: now treatment with azithromycin (for moderately severe infection) or penems, chloramphenicol and gentamicin (for severe infections) is recommended[4].
It seems that carbapenems are being used so much nowadays that the end of their effective life-span is forseeable. If the fear of CRE pathogens and the advent of KPC strains not enough to convince everyone that our current practice is irresponsible and shortsighted, if not to say foolish, what does it take to stop current practice?
Al Gore to the rescue? He is already solidly booked out …sorry, no such luck!!
References:
[1] Zhao J Antimicrob Chemother. 2015 May;70(5):1314
[2] Macarena Appl Environ Microbiol. 2012 Apr; 78(8): 2698
[3] Sanat PLoS One. 2011; 6(10): e25778
[4] Mandell Principles and Practice of Infectious Diseases. Chapter 218: Campylobacter jejuni and related species
