Life span of PSA

Question

Hello,

my question relates to the life span of CF problem germs (particularly PSA) outside the human body. E.g., how many hours should pass between treatments of CF patients who have been tested positive and those who are negative in a physiotherapy practice or at the dentist’s who treats several CF individuals? I know that the germ disappears quickly on dry surfaces and remains in the air for a few hours, but what about sinks, shower, and toilette? Is regular rinsing sufficient if (at the dentist’s) sputum has been spit into the sink?

Answer

Dear questioner,

P. aeruginosa and some other bacteria that can cause infections in CF patients are so-called water bugs. This means that they typically live in humid environments or, respectively, that humid areas can easily be colonized/contaminated by these germs and then become a possible source of infections.

Conversely, these germs are relatively sensitive against dehydration, i.e. they gradually die if the moisture content declines. On surfaces, water bugs can remain viable for several hours. It is impossible to generally and reliably predict after what time a humid area or an object does not need to be considered contaminated anymore, since the rate at which germs die depends on several factors such as the extent of the bacterial load, temperature, nutrient availability, etc. The most secure procedure would be to wait for a complete drying out, like many authors have recommended for the use of toothbrushes. Sinks (siphons) or toilets always bear the risk of a continued contamination with water bugs such as P. aeruginosa, since these germs can remain there in the form of biofilms. Here, it is therefore especially important from a hygiene perspective to avoid the use of aerosols. Additionally, sputum should be coughed into a handkerchief, not into the sink or the toilet, and then be disposed of.

Concerning the risk of transmission of P. aeruginosa and, respectively, hygiene recommendations, one has to distinguish between the home and medical institutions (clinics, physiotherapy or dental practices, etc.). The latter always focus on disinfection provisions (esp. hand and surface disinfection). Indeed, the air in the rooms may be contaminated with P. aeruginosa and the bacteria may remain for several hours after the patient has left the room (according to studies, they can last for 45 minutes up to three hours). The risk of a nosocomial infection (i.e., an infection acquired in the hospital or during medical treatment at a clinic) can be minimized by airing the rooms and using surface disinfection, but also particularly by the spatial and/or temporal separation of Pseudomonas-free and Pseudomonas-colonized patients, which should particularly be promoted today.

The aspects addressed in this question are quite complex and cannot be answered comprehensively here. Further details should be discussed with your doctor/CF team. Many questions are also treated in recommendations that are available (sources 1-3 below). Furthermore, recommendations on hygiene measures with CF patients will soon be published (in German) by a working group of the Commission for Hospital Hygiene at Robert Koch Institute, Berlin. [Translator’s note: question was originally asked in the German expert advice.]

Kind regards,
Michael Hogardt

1. Doring, G. & Hoiby, N. (2004) Early intervention and prevention of lung disease in cystic fibrosis: a European consensus. J Cyst Fibros 3: 67-91.
2. Saiman, L., Macdonald, N., Burns, J. L., Hoiby, N., Speert, D. P. & Weber, D. (2000) Infection control in cystic fibrosis: practical recommendations for the hospital, clinic, and social settings. Am J Infect Control 28: 381-385.
3. Saiman, L. (2011) Infection prevention and control in cystic fibrosis. Curr Opin Infect Dis 24: 390-395.
4. muko.info/forschung/therapiefoerderung/leitlinien.html

28.02.2012