Intractable, and here’s why

Although the imprudent use of antibiotics is considered to be a major reason behind the emergence and spread of antibiotic resistance,1 bacteria isolated from pristine environments show substantial tolerance to antibiotics. For example, bacterial strains from several genera isolated from different samples from the Antarctic (soil, fast ice, cyanobacterial material) and tested at the Centre for Molecular Biology in Hyderabad, India, were resistant to several therapeutically useful antibiotics.2 The problem is further complicated by the fact that genes that confer resistance to antibiotics and heavy metals occur on the same plasmid. Thus antibiotic resistant bacteria are selected to flourish in a natural environment polluted by heavy metals even in the absence of antibiotics.

At IGB-Neuglobsow (Germany) we recently analysed 66 bacterial isolates from samples taken from waterways in some of the least populated areas of north Germany.3 We found co-occurrence of resistance to antibiotics (ampicillin, streptomycin, erythromycin, chloramphenicol, oxytetracycline, kanamycin, rifampicin, norfloxacin, ciprofloxacin, trimethoprim, vancomycin) and heavy metal salts (zinc chloride, cadmium chloride, potassium chromate) in various combinations.3 Ten of the isolates were resistant to five antibiotics and three heavy metals. Surprisingly 13 of the isolates were resistant to chloramphenicol, which is no longer used in clinical practice in Western countries.

Plasmids, which carry genes for both antibiotic and heavy metal resistance, are remarkably stable even in the absence of any selection pressure.4 The emergence of antibiotic resistance can only be deferred: it cannot be bypassed simply by minimising the use of antibiotics.