Multiresistant Pseudomonas aeruginosa in a pediatric cystic fibrosis center: natural history and implications for segregation

Pseudomonas aeruginosa antibiotic resistance in Australian cystic fibrosis centres

BACKGROUND AND OBJECTIVE

In cystic fibrosis (CF), chronic Pseudomonas aeruginosa infection is associated with increased morbidity, antibiotic treatments and mortality. By linking Australian CF registry data with a national microbiological data set, we examined the association between where treatment was delivered, its intensity and P. aeruginosa antibiotic resistance.

METHODS

Sputa were collected from paediatric and adult CF patients attending 18 Australian CF centres. P. aeruginosa antibiotic susceptibilities determined by local laboratories were correlated with clinical characteristics, treatment intensity and infection with strains commonly shared among Australian CF patients. Between-centre differences in treatment and antibiotic resistance were also compared.

RESULTS

Large variations in antibiotic usage, maintenance treatment practices and multi-antibiotic resistant P. aeruginosa (MARPA) prevalence exist between Australian CF centres, although the overall proportions of MARPA isolates were similar in paediatric and adult centres (31% vs 35%, P = 0.29). Among paediatric centres, MARPA correlated with intravenous antibiotic usage and the Australian state where treatment was delivered, while azithromycin, reduced lung function and treating state predicted intravenous antibiotic usage. In adult centres, body mass index (BMI) and treating state were associated with MARPA, while intravenous antibiotic use was predicted by gender, BMI, dornase-alpha, azithromycin, lung function and treating state. In adults, P. aeruginosa strains AUST-01 and AUST-02 independently predicted intravenous antibiotic usage.

CONCLUSION

Increased treatment intensity in paediatric centres and the Australian state where treatment was received are both associated with greater risk of MARPA, but not worse clinical outcomes.

Halting the spread of epidemic pseudomonas aeruginosa in an adult cystic fibrosis centre: a prospective cohort study

Objectives

To assess if cohort segregation policies are effective in preventing cross-infection in cystic fibrosis (CF) clinics.

Design

A prospective cohort study.

Setting

A large adult CF centre in Northwest England.

Participants

All CF patients cared for at the Liverpool adult CF centre 2003–2009.

Methods

Regular sputum sampling with genotyping of pseudomonas aeruginosa (Psa) isolates led to a policy of inpatient and outpatient segregation by microbiological group.

Main outcome measures

Prevalence and cross-infection/super-infection rates of a transmissible Psa strain, i.e. the Liverpool epidemic strain (LES) in adult CF patients at the Liverpool adult CF centre from 2003 to 2009.

Results

There was a decline in the proportion of patients with LES (71–53%) and an increase in those with unique strains (23–31%) and without Psa infection (6–17%) from 2003 to 2009. There were two cases of LES super-infection and one case of new chronic Psa infection (with a unique strain). There were no cases of transmissible strain infection in patients previously uninfected by Psa.

Conclusions

Our segregation policy has halted the spread of the commonest highly transmissible strain in the UK (LES) in our clinic, without endangering patients who were not previously infected with Psa. It confirms that if genotypic surveillance is used, it is unnecessary to segregate patients infected with unique strains from those without Psa infection.

Multiple antibiotic-resistant Pseudomonas aeruginosa and lung function decline in patients with cystic fibrosis

BACKGROUND

The goal of this study was to determine the association of multiple antibiotic-resistant Pseudomonas aeruginosa (MARPA) acquisition with lung function decline in patients with cystic fibrosis (CF).

METHODS

Using data from Epidemiologic Study of Cystic Fibrosis (ESCF), we identified patients with spirometry data and MARPA, defined as PA (1) resistant to gentamicin and either tobramycin or amikacin, and (2) resistant to ≥1 antipseudomonal beta lactam. MARPA had to be detected in a respiratory culture after ≥2 years of PA-positive but MARPA-negative respiratory cultures. Multivariable piecewise linear regression was performed to model the annual rate of decline in forced expiratory volume in 1 second (FEV(1)) % predicted 2 calendar years before and after the index year of MARPA detection, adjusting for patient characteristics and CF therapies.

RESULTS

In total, 4349 patients with chronic PA and adequate PFT data were identified; 1111 subsequently developed MARPA, while 3238 patients were PA positive but MARPA negative. Compared with patients who did not acquire MARPA, MARPA-positive patients had lower FEV(1) and received more oral (p<0.013) and inhaled (p<0.001) antibiotic therapy. Mean FEV(1) decline did not change significantly after MARPA detection (-2.22% predicted/year before detection and -2.43 after, p=0.45). There was no relationship between persistent infection or FEV(1) quartile and FEV(1) decline.

CONCLUSIONS

Newly detected MARPA was not associated with a significant change in the rate of FEV(1) decline. These results suggest that MARPA is more likely to be a marker of more severe disease and more intensive therapy, and less likely to be contributing independently to more rapid lung function decline.