Bacterial Culture, Cystic Fibrosis, Respiratory
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Life expectancy of patients with cystic fibrosis (CF) has increased steadily over the past 50 years, in large part due to improvements in the management of lung disease in this patient population. Still, chronic lung infection is responsible for 75% to 85% of deaths in patients with CF. Appropriate treatment for the causative organism can reduce morbidity and mortality.
The number of microbial species associated with CF lung disease is relatively limited. These include Pseudomonas aeruginosa (mucoid and nonmucoid), Staphylococcus aureus, Burkholderia cepacia complex, Stenotrophomonas maltophilia, other nonfermenting gram-negative rods, Haemophilus influenzae, and Streptococcus pneumoniae. Nontuberculous mycobacteria and Aspergillus species may also play a role in CF lung disease, in addition to common respiratory viruses. This culture, which is specifically designed for CF patients, utilizes conventional and additional selective media (compared to non-CF respiratory cultures) to isolate bacteria commonly associated with pulmonary disease in CF patients.
In selected centers, lung transplantation is performed on CF patients. This test is appropriate for lung transplant patients with underlying CF because they can continue to harbor the same types of organisms as they did pretransplantation. CF patients may be colonized or chronically infected by these organisms over a long period of time.
Detection of aerobic bacterial pathogens from cystic fibrosis patient specimens
A negative test result is no growth of bacteria or growth of only usual flora. A negative result does not rule out all causes of infectious lung disease (see Cautions).
Organisms associated with lower respiratory tract infections are reported.
For positive test results, pathogenic bacteria are identified. Cystic fibrosis patients may be colonized or chronically infected by some organisms over a long period of time, therefore, positive results must be interpreted in conjunction with previous findings and the clinical picture to appropriately evaluate results.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
When culture of sputum is delayed, successful isolation of bacterial pathogens is less likely, due to the overgrowth of usual oropharyngeal flora.
Some bacterial agents that cause lower respiratory infections (eg, mycobacteria, Legionella species, Mycoplasma pneumoniae) are not detected by this assay and require special procedures. If the bacterial culture is negative, clinicians should consider additional testing to detect other bacterial, viral, or fungal agents.
Results must be interpreted in conjunction with clinical findings and previous culture results.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
No growth or usual flora
Identification of probable pathogens
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. York MK, Gilligan P, Alby K: Lower Respiratory Tract Cultures. In Clinical Microbiology Procedures Handbook, Vol 1, Fourth edition. Edited by AL Leber. Washington DC, ASM Press, 2016, Section 3.11.2.
2. LiPuma JJ, Currie BJ, Peacock SJ, VanDamme PAR: Burkholderia, Stenotrophomonas, Ralstonia, Cupriavidus, Pandoraea, Brevumndimonas, Comamonas, Delftia, and Acidovorax. In Manual of Clinical Microbiology, Tenth edition. Edited by J Versalovic. Washington DC, American Society for Microbiology Press, 2011, pp 692-713