Drainage systems, an occluded source of sanitation related outbreaks

Blom, Kristina

Sewage sludge can end up on landfills but this is problematic since the leakages from the landfill may reach the groundwater [39] . WWTP then offer better management of the sewage since it has to go through different stabilization treatments in order to produce safe sewage sludge [40] . However, WWTPs are focusing mainly on stabilizing organic residues and heavy metals while microbes are neglected. Sewage sludge commonly contains high load of microbes that are able to infect both humans and animals but currently ways of accurate detection and treatment are lacking [32, 41] . Detection with conventional plate count technique is most likely not working since bacteria can exist in viable but non-culturable stage and hence the load will be underestimated [42] . These reservoirs of microbes could then go undetected and be spread to the environment and infect crops, animals, and humans [43] . Yet another spread from the environment to the microbiome can be genetic information coding for resistance and virulence [44] [45] [46] . This mode of genetic transfer is most likely to have occurred in the case of the rise of the German isolate of Escherichia coli (E. coli) that was found to have two different mechanisms of virulence [47] . This isolate belonged to enteroaggregative E. coli (EAEC) carrying virulence factors on a plasmid (a mobile genetic material) and it obtained the shiga toxin gene carried on a phage (a mobile genetic element) from a shiga toxin producing E. coli (STEC). It caused unpredictable novel clinical manifestations in a severe outbreak in Germany 2011 with nearly 7,000 reported cases and 18 deaths due to gastroenteritis and 35 deaths due to hemolytic uremic syndrome [47] . The ease by that bacteria can share genetic information on mobile elements and the knowledge that genes coding for resistance is coded by mobile genetic elements probably will present further unwanted surprises [48] . The fear of creation of multi-resistant bacteria is enforced by the fact that antibiotics are discharged from manufacturers and hospitals and will stress the bacteria in the sewage or environment to develop and disseminate resistance [46, 49, 50] . Evidence was presented at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy that hospital sewage is breeding ground for genetic exchange of resistance between bacteria in the environment and clinical isolates [51] . Furthermore, it was recently proven that resistance cassettes against five classes of antibiotics (β-lactams, aminoglycosides, amphenicols, sulfonamides, and tetracyclines) had a perfect genetic match in a clinical relevant bacteria and an environmental bacteria [52] . This study explained the mechanism of lateral spread but also how antibiotic resistance disseminate and can have clinical implications. In the era of increased antibiotic resistance and less available effective therapies, it is increasingly difficult to treat infections. Still with effective antibiotics, infections remain a primary cause of morbidity and mortality in the developed world [53] . Predictions say that unless immediate and consorted actions are taken we will face mortality rate like the pre-antibiotic era. In relation to this dark prediction, the WHO has stated that: "Antibiotic resistance is one of the greatest threats to global health security extending far beyond the human health sector". The future looks dark also in respect to the possibility of finding the substance that will kill