Drainage systems, an occluded source of sanitation related outbreaks

Blom, Kristina

The clinical impact of drains as reservoirs of microorganisms has not yet been fully explored although it is widely established that human excretions such as faeces, urine, oral-nasal aerosols, and skin flakes will carry microbial burden consisting of bacteria and/or virus. For instance, there are 120 different viruses in human faeces [43] . It is also reported that patient flora can be detected in sinks and building drains [10, 12, 60] . In a new longstay hospital, it was discovered that identical strains were found in the sinks as well as in the admitted patients [60] . The major correlating strains were pathogens such as the Escherichia coli, Klebsiella, Pseudomonas and Acinetobacter species, all being gram-negative bacteria, with higher correlation to strains isolated from the throats and intestines of patients. Actually, the major reservoir of multi-drug resistant Gram-negative bacilli is the gut of man and animals. At hospitals, discharge of antibiotics are also high [49] . Clearly, drains are reservoirs for microbes and antibiotic residues. It is also clear that microbes in drains and pipes adheres to the surfaces of drains and draining pipes as microbial biofilms, creating a complex ecosystem of different microbes that are fed by organic and inorganic matters [61] . Hota et al. elegantly showed the presence of Pseudomonas aeruginosa (P. aeruginosa) biofilm in drainage systems and their role in the propagation of an outbreak [61] . It is also known that bacteria such as S. aureus promote the transfer of antibiotic resistance to other bacteria when present in biofilm [62] . Certainly, drains seem to act as cradles to the emergence of bacteria armed with abilities to resist multiple antibiotics. The development of resistance is probably enhanced at hospitals due to that more bacteria and more antibiotics are flushed down the drains due to the very nature of hospitals constantly caring for numerous different patients that are ill and treated with antibiotics. Thus, biofilm in building drains, not properly maintained, have the potential of spreading even more resistant bacteria. This was indicated in the extended non-frequent outbreak of Carbapenem resistant Klebsiella pneumonia (KPC) at an ICU [16] . The source of transmission was found to be drains that was detected by molecular profiling to be the only source to harbor KPC, persistently. Outbreak with P. aeruginosa, revealed that patients were not colonized on admittance, but acquired a multi-resistant P. aeruginosa during hospitalization [17] . By running antibiogram and molecular profiling, drains were found to be the only source. Therefore these reservoirs are crucial to control. Maintenance of proper sanitation must then be guarded where seepage and backflow never should occur. However, it seems that the management of maintenance is more difficult in practice than in theory. The difficulty of eradicating antibiotic resistant bacteria from sink drains at an intensive care unit (ICU) was recently reported [9] . Several different cleaning methods were tried including hypochlorite, mechanical, and pressurized steam at a temperature of 170°C. However, none of these methods worked. This highlights the need for physical barriers such as water seals for drains that prevent the exposure to microbes in the drains and a way to control the integrity of the barrier.