Respiratory Pathogen In Cystic Fibrosis Patients Research Articles

Pseudomonas aeruginosa Alters Staphylococcus aureus Sensitivity to Vancomycin in a Biofilm Model of Cystic Fibrosis Infection.

ABSTRACTThe airways of cystic fibrosis (CF) patients have thick mucus, which fosters chronic, polymicrobial infections. Pseudomonas aeruginosa and Staphylococcus aureus are two of the most prevalent respiratory pathogens in CF patients. In this study, we tested whether P. aeruginosa influences the susceptibility of S. aureus to frontline antibiotics used to treat CF lung infections. Using our in vitro coculture model, we observed that addition of P. aeruginosa supernatants to S. aureus biofilms grown either on epithelial cells or on plastic significantly decreased the susceptibility of S. aureus to vancomycin. Mutant analyses showed that 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO), a component of the P. aeruginosa Pseudomonas quinolone signal (PQS) system, protects S. aureus from the antimicrobial activity of vancomycin. Similarly, the siderophores pyoverdine and pyochelin also contribute to the ability of P. aeruginosa to protect S. aureus from vancomycin, as did growth under anoxia. Under our experimental conditions, HQNO, P. aeruginosa supernatant, and growth under anoxia decreased S. aureus growth, likely explaining why this cell wall-targeting antibiotic is less effective. P. aeruginosa supernatant did not confer additional protection to slow-growing S. aureus small colony variants. Importantly, P. aeruginosa supernatant protects S. aureus from other inhibitors of cell wall synthesis as well as protein synthesis-targeting antibiotics in an HQNO- and siderophore-dependent manner. We propose a model whereby P. aeruginosa causes S. aureus to shift to fermentative growth when these organisms are grown in coculture, leading to reduction in S. aureus growth and decreased susceptibility to antibiotics targeting cell wall and protein synthesis.

Ability of device to collect bacteria from cough aerosols generated by adults with cystic fibrosis

Background: Identifying lung pathogens and acute spikes in lung counts remain a challenge in the treatment of patients with cystic fibrosis (CF). Bacteria from the deep lung may be sampled from aerosols produced during coughing. Methods: A new device was used to collect and measure bacteria levels from cough aerosols of patients with CF. Sputum and oral specimens were also collected and measured for comparison. Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae, and Streptococcus mitis were detected in specimens using Real-Time Polymerase Chain Reaction (RT-PCR) molecular assays. Results: Twenty adult patients with CF and 10 healthy controls participated. CF related bacteria (CFRB) were detected in 13/20 (65%) cough specimens versus 15/15 (100%) sputum specimens. Commensal S. mitis was present in 0/17 (0%, p=0.0002) cough specimens and 13/14 (93%) sputum samples. In normal controls, no bacteria were collected in cough specimens but 4/10 (40%) oral specimens were positive for CFRB. Conclusions: Non-invasive cough aerosol collection may detect lower respiratory pathogens in CF patients, with similar specificity and sensitivity to rates detected by BAL, without contamination by oral CFRB or commensal bacteria.

Ability of device to collect bacteria from cough aerosols generated by adults with cystic fibrosis.

Background: Identifying lung pathogens and acute spikes in lung counts remain a challenge in the treatment of patients with cystic fibrosis (CF). Bacteria from the deep lung may be sampled from aerosols produced during coughing. Methods: A new device was used to collect and measure bacteria levels from cough aerosols of patients with CF. Sputum and oral specimens were also collected and measured for comparison. Pseudomonas aeruginosa, Staphylococcus aureus, Klebsiella pneumoniae, and Streptococcus mitis were detected in specimens using Real-Time Polymerase Chain Reaction (RT-PCR) molecular assays. Results: Twenty adult patients with CF and 10 healthy controls participated. CF related bacteria (CFRB) were detected in 13/20 (65%) cough specimens versus 15/15 (100%) sputum specimens. Commensal S. mitis was present in 0/17 (0%, p=0.0002) cough specimens and 13/14 (93%) sputum samples. In normal controls, no bacteria were collected in cough specimens but 4/10 (40%) oral specimens were positive for CFRB. Conclusions: Non-invasive cough aerosol collection may detect lower respiratory pathogens in CF patients, with similar specificity and sensitivity to rates detected by BAL, without contamination by oral CFRB or commensal bacteria.

Mutations that permit residual CFTR function delay acquisition of multiple respiratory pathogens in CF patients

BackgroundLung infection by various organisms is a characteristic feature of cystic fibrosis (CF). CFTR genotype effects acquisition of Pseudomonas aeruginosa (Pa), however the effect on acquisition of other infectious organisms that frequently precede Pa is relatively unknown. Understanding the role of CFTR in the acquisition of organisms first detected in patients may help guide symptomatic and molecular-based treatment for CF.MethodsLung infection, defined as a single positive respiratory tract culture, was assessed for 13 organisms in 1,381 individuals with CF. Subjects were divided by predicted CFTR function: 'Residual': carrying at least one partial function CFTR mutation (class IV or V) and 'Minimal' those who do not carry a partial function mutation. Kaplan-Meier estimates were created to assess CFTR effect on age of acquisition for each organism. Cox proportional hazard models were performed to control for possible cofactors. A separate Cox regression was used to determine whether defining infection with Pa, mucoid Pa or Aspergillus (Asp) using alternative criteria affected the results. The influence of severity of lung disease at the time of acquisition was evaluated using stratified Cox regression methods by lung disease categories.ResultsSubjects with 'Minimal' CFTR function had a higher hazard than patients with 'Residual' function for acquisition of 9 of 13 organisms studied (HR ranging from 1.7 to 3.78 based on the organism studied). Subjects with minimal CFTR function acquired infection at a younger age than those with residual function for 12 of 13 organisms (p-values ranging: < 0.001 to 0.017). Minimal CFTR function also associated with younger age of infection when 3 alternative definitions of infection with Pa, mucoid Pa or Asp were employed. Risk of infection is correlated with CFTR function for 8 of 9 organisms in patients with good lung function (>90%ile) but only 1 of 9 organisms in those with poorer lung function (<50%ile).ConclusionsResidual CFTR function correlates with later onset of respiratory tract infection by a wide spectrum of organisms frequently cultured from CF patients. The protective effect conferred by residual CFTR function is diminished in CF patients with more advanced lung disease.

Comparison of Prevalence Calculations Using Infection Control Surveillance Methods and Cystic Fibrosis Foundation Patient Registry Guidelines

BACKGROUND: In May 2003, the consensus document was published entitled, Infection Control Recommendations for Patients with Cystic Fibrosis (CF): Microbiology, Important Pathogens, and Infection Control Practices to Prevent Patient-to-Patient Transmission. The recommendations are based on the basic principle that CF pathogens are transmitted by the droplet and contact routes. The CF Foundation Patient Registry (CFFPR) compiles and publishes the age-specific prevalence of respiratory pathogens in CF patients each year. Our CF Center participates in this registry and uses the data to compare our pathogen-specific prevalence with national data. Discrepancies were found when comparing our data with those from the CFFPR due to difference in the methods of calculating prevalence. OBJECTIVE: To understand how different methods of analysis might influence the interpretation of center-specific, as compared to national registry, infection control data. METHODS: The Department of Infection Prevention and Control at Children's Hospital of Philadelphia (CHOP), in collaboration with the CHOP Cystic Fibrosis Center, conducts active surveillance of cystic fibrosis patients for Burkholderia cepacia (BC) and methicillin-resistant Staphylococcus aureus (MRSA). Traditionally, prevalence data at our institution were reported based on the number of patients ever colonized with BC or MRSA (termed IPC prevalence). Upon review of CFFPR reporting guidelines, we calculated the period prevalence of colonization based on isolation of BC or MRSA within the past calendar year (termed CFFPR prevalence) and stratified our data by age group. RESULTS: Comparison of IPC and CFFPR prevalence revealed discrepant results. For active patients in the CHOP CF Center, IPC prevalence of MRSA was 10.0%. However, the prevalence of MRSA as determined by CFFPR reporting guidelines was markedly lower; CFFR prevalence was 5.5%. In contrast, IPC prevalence of BC was 7.4%, while CFFPR prevalence was 6.7%. Consistent with national data, we observed higher prevalence of these two critical pathogens was observed in the 11–17 and 18–24 age groups compared to younger age groups. CONCLUSIONS: Caution is needed when comparing data from national registries with data collected by infection control departments within individual centers. Differences in collecting and reporting data to the CF Foundation from traditional infection control surveillance methods must be fully appreciated by those using these data for benchmarking purposes.