WHEN THE CHOICE IS MADE TO PROTECT IMMUNOCOMPROMISED PATIENTS WITH POINT OF USE FILTERS, DO NOT FORGET SOME CRITICAL POINTS.

WHEN THE CHOICE IS MADE TO PROTECT IMMUNOCOMPROMISED PATIENTS WITH POINT OF USE FILTERS, DO NOT FORGET SOME CRITICAL POINTS.

In a very interesting paper published by the University Hospital of Montpellier (Tracking the spread routes of opportunistic premise plumbing pathogens in a haematology unit with water points-of-use protected by antimicrobial filters. Baranovsky S. et al. Journal of Hospital Infection,2018,98,53-59) the confirmation of the necessity to not forget some critical points in the water safety plan is scientifically proven.

The objective of this study was to assess the effectiveness of water filtration in daily practice and to track secondary non-filtered water routes in the ward, leading to the potential circulation of opportunistic premise plumbing pathogens (0PPPs). The Adult Haematology Unit (AHU) of the University Hospital of Montpellier welcomes patients with acute haematological malignancies and comprises 19 single patient’s bedrooms including a bathroom with shower, washbasin and toilet. For protecting patients from a waterborne Health-care Associated Infection (HAI) a water safety plan identified 73 water Points-Of-Use (POU), including 52 « high-risk POU » wich were equipped with Point-of-Use Filters (POUFs). These 52 POU were taps and showers in patient’s rooms and washbasins used for healthcare or for handwashing, plus only one equipped tap dedicated to high-risk practices   in housekeeping rooms, patient’s satellite kitchen and in nurse tearoom. All POUFs were changed monthly.

From January 2011 to December 2014, even the 52 « high-risk water POU » were already equipped with antimicrobial filters, 31 strains of Pseudomonas aeruginosa and 12 strains of Stenotrophomonas maltophilia were isolated in blood cultures from respectively 19 and 6 patients. From February 2014 to April 2014, one patient presented with bacteraemia due to a genotype ST308 of Pseudomonas aeruginosa, dominant both in patients and in the environment of the AHU. This strongly suggested a waterborne infection despite the presence of efficient POUFs, supporting the hypothesis of secondary water routes in this unit. Sampling and analysis were performed uptream and downstream of the filters leading to interesting results : no bacteria were found downstream of the POUFs but, of course, many strains of Pseudomonas aeruginosa, other Pseudomonas species and Stenotrophomonas maltophilia were isolated upstream the filters and in the environment, especially in siphons and moist environments.

For tracking bacteria in secondary water routes observations and interviews were performed by the infection control team and also surface sampling. Pseudomonas aeruginosa was identified through two routes, « Nurse tearoom » and « cleaning ». In the tearoom, Pseudomonas aeruginosa did spread 4 m away from its source and persisted on a dry surface (table) but did not spread outside the room. For the cleaning route, a specific clone was isolated in many places of the housekeeping rooms and spreaded in two rooms separated by 30 m, probably via objects common to both rooms such as the cleaning trolley or buckets. This may explain the contamination of immunocompromised patients in their room via cares given by nurses or cleaning equipment and surfaces.

As a conclusion of their study, the authors underlines the efficiency of antimicrobial filtration in daily use conditions and the transfer of hydric bacteria originating from non-filtered POUs, spreading in the ward through secondary routes out of the plumbing system. They concludes that the strategy consisting of filtration at only at-risk POU in a ward is sufficient to limit the spread of OPPPs but a residual spread of OPPPs may take place, linked to the use of non-filtered POU, far away from the source POU. Thus, the use of non-filtered POU in at’risk ward should be carefully framed by clear signboards and recommendations regarding the hygienic bundles.

APPLICATION NOTE : Publi Baranovsky, tracking the spread routes of opportunistc pathogens in a haematology unit.

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