Pseudomonas aeruginosa
Chronic Pseudomonas aeruginosa infection of CF airways is associated with increased rate of decline of lung function. The importance of detecting and treating new isolations of Pseudomonas is one of the major reasons for carrying out frequent cough swab/sputum cultures. Ps aeruginosa infection is initally non-mucoid and has the potential to be cleared. Once Ps becomes mucoid, it can form colonies protected by a coating of jelly (alginate) making eradication impossible with current treatments. For these reasons whenever a new isolation of P aeruginosa is identified, attempts should be made to treat it as soon as possible, even if the patient has no symptoms.
Eradication of Pseudomonas in patients not on long term nebulised antibiotics
The most effective eradication method is not known. The choice is between nebulised antibiotics, with or without oral ciprofloxacin, or iv antibiotics, often followed by nebulised antibtiocis. The TORPEDO-CF trial showed that iv treatment was not more efficacious than oral therapy when combined with 3 months of nebulsed colomycin . Our standard approach for children who grow Pseudomonas on airway culture and who are not already on long term nebulised antibiotics is as follows:
- In children who have significant cough, start iv antibiotics as first line treatment, followed by 3 months nebulised colomycin.
- In children who are well, use 3 weeks of oral ciprofloxacin and 3 months nebulised colomycin. (change from 3 months of ciprofloxacin made in June 2019)
If P. aeruginosa is still present after 3 months, there are 2 options:
- 1 month of nebulised tobramycin (if the child is well)
- a 2 week course of iv antibiotics.
If despite this treatment, P. aeruginosa infection persists, then colomycin should be continued and the patient is likely to remain chronically or intermittently infected.
Evidence from a local audit suggests that more than 90% of first isolates will be eradicated by the combination of cipro and colomycin. Time to recurrence is also important. 65% of children in our 2012 audit had a recurrence within 12 months of stopping the 3 month course of colomycin. This is similar to the findings of the TORPEDO-CF study.
When to start long term nebulised antibiotics
Long term nebulised antibiotics are used to treat chronic Pseudomonas infection. There is no agreed definition of what chronic means in this context and so there are differences in the criteria used in different CF centres for starting long term therapy. We recommend long term treatment for:
- any child who has grown Pseudomonas on 3 occasions in any 12 month period
- any child who has grown mucoid Pseudomonas
We consider long term treatment for:
- any child who has grown Pseudomonas on 3 occasions ever - depending on interval between the positive cultures and severity of any cough or loss of lung function.
Long term usually means life-long. Occasionally children who had recurrent Pseudomonas in early life will go for a number of years with no further detected Pseudomonas infection. If these children have excellent lung function and minimal symptoms, a trial of cessation of treament can be considered.
Treatment of Pseudomonas infection in patients on long term nebulised antibiotics
Children with a new positive airway culture for Pseudomonas, who are on long term colomycin, but have not grown Pseudomonas for 12 months, should be treated with a 3 week course of ciprofloxacin if they are well, or with a 2 week course of iv antibiotics if are unwell.
Children (usually older teenagers) with chronic mucoid Pseusdomnas infection on long term suppressive nebulsed treatment (see below) will only need additional treatment for Pseudomonas infection if they are unwell - either with oral or intravenous antibiotics.
Choice of nebulised antibiotics
The first line long-term nebulised antibiotic is colomycin (colistimethate) - in young children this will via a jet nebuliser (Pari Sprint) and in older children as Promixin via the ineb. Children on long term colomycin who grow Pseudomonas 2 or more times in 12 months should be switched to alternate month inhaled tobramycin. If they are have poor lung function or frequent exacerbations, or persistent cough, they colomycin should be used on the alternate month. If children on alternate month tobramycin have any further positive cultures for Pseudomonas, they should also start using colomycin in the alternate month.
Aztreonam lysine for inhalation (Cayston) is licensed for children >6 years old. It is given tds rather than bd. Aztreonam lysine may be considered if there chronic Pseudmonas infection is despite therapy with an alternating regimen of tobramycin and colistin and progressive loss of lung function (defined as greater than 2% per year decline in FEV1 as % of predicted) or there is continued need for IV therapy for exacerbations i.e., more than 2 per year despite therapy. Aztreonam lysine may be prescribed either alternating with colistin or tobramycin depending on the clinical response to those medications previously.
Dry powder inhaled antibiotics
Dry powder tobramycin (Tobi podhaler) can be used in children over the age of 6 who require long term inhaled tobramycin for the management of Pseudomonas airway infection. It must be provided by a home care company
Dry powder colistimethate (Colobreathe) can be used in children over the age of 6 for the management of Pseudomonas airway infection "if the child will clinically benefit from continued colistin but does not tolerate it in its nebulised form and thus tobramycin therapy would otherwise be considered". This means that children who have got to the stage of needing inhaled tobramycin and colomycin alternate months can use dry powder colistin
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