Related Experiment Videos
Comparison of two selective media developed to isolate Pseudomonas cepacia from patients with cystic fibrosis
Abstract:
Two media selective for Pseudomonas cepacia have been described recently: OF-polymyxinbacitracin-lactose agar (OFPBL) and P. cepacia agar (PCA). We compared these by culturing sputum from 27 patients with cystic fibrosis. Sputum from each patient was studied using streak-plate (SP) and quantitative (Q) culture methods. Five strains of P. cepacia were isolated from four patients (15%). P. cepacia was not found on routine media by SP or Q methods in three of the four patients. All five isolates grew on both OFPBL and PCA and all were recovered by SP and Q culture methods. Colony counts of P. cepacia obtained by Q cultures were similar on both selective media. Each of the selective media allowed the growth of other organisms; nineteen of 27 specimens cultured on OFPBL yielded non-P. cepacia spp. and six of 27 specimens cultured on PCA yielded non-P. cepacia spp. species (p less than 0.005). Pseudomonas aeruginosa was isolated from 26 of 27 patients on routine media (96%). This organism was recovered from four specimens cultured on OFPBL but from none on PCA (p less than 0.05). OFPBL and PCA are both selective for P. cepacia and enhance the ability to recover this organism from patients with cystic fibrosis using either SP or Q cultures of sputum; however, PCA is significantly more inhibitory for non-P. cepacia spp. than OFPBL.
Insights
Two new selective media, OFPBL and PCA, effectively detect Pseudomonas cepacia in cystic fibrosis patients. PCA demonstrates superior inhibition of non-P. cepacia species compared to OFPBL.
Area of Science:
- Medical Microbiology
- Clinical Diagnostics
Background:
- Pseudomonas cepacia is an opportunistic pathogen, particularly significant in cystic fibrosis (CF) patients.
- Accurate and efficient laboratory detection of P. cepacia is crucial for patient management.
Purpose of the Study:
- To compare the efficacy of two recently developed selective media, OF-polymyxinbacitracin-lactose agar (OFPBL) and P. cepacia agar (PCA), for isolating P. cepacia from sputum of CF patients.
- To evaluate the recovery rates and selectivity of OFPBL and PCA using both streak-plate (SP) and quantitative (Q) culture methods.
Main Methods:
- Sputum samples from 27 cystic fibrosis patients were cultured using both OFPBL and PCA media.
- Both streak-plate (SP) and quantitative (Q) culture techniques were employed for each specimen.
- Isolation rates and colony counts of P. cepacia and other organisms were recorded and compared.
Main Results:
- P. cepacia was isolated from 15% of patients (4/27).
- Both OFPBL and PCA successfully recovered all P. cepacia isolates, with similar colony counts via Q cultures.
- PCA showed significantly greater inhibition of non-P. cepacia species (6/27) compared to OFPBL (19/27).
- Pseudomonas aeruginosa was recovered from OFPBL (4/27) but not from PCA (0/27).
Conclusions:
- Both OFPBL and PCA are valuable selective media for enhancing P. cepacia recovery from CF patient sputum using SP or Q methods.
- PCA offers superior selectivity by inhibiting a broader range of non-P. cepacia contaminants.
- Consideration of P. aeruginosa recovery may be necessary when choosing between OFPBL and PCA.