Selective media for the quantitation of bacteria in cystic fibrosis sputum

Abstract

SUMMARY. We used selective media together with aerobic and anaerobic incubation for the quantitation of common pathogens in liquefied sputum from children with cystic fibrosis. The accuracy of the technique was verified by reconstruction studies in which laboratory strains with antibiotic-resistance markers were added to sputum from cystic fibrosis patients. Comparison of the numbers of bacteria found on quantitative culture of clinical specimens with the "predominant" organism found on routine culture yielded a poor correlation. When Pseudomonas aeruginosa was the most prevalent on routine culture, it was present in the highest numbers on quantitative culture (mean count = 1 O8 cfu/g). However, large numbers of Haemophilus influenzae (mean count = l O7 cfu/g), Staphylococcus aureus (mean count = 2 x 1 O6 cfu/g), and streptococci (mean count = 2 x 1 O6 cfu/g) were also present in these cultures. When S. aureus was the predominant organism, H . influenzae and P. aeruginosa were also present in similar numbers (c. lo7 cfu/g). When H. influenzae was the predominant species on routine culture, the mean count was 7 x lo6 cfu/g and P. aeruginosa was often completely absent, We conclude that the selective technique permits reliable enumeration of sputum bacteria, and offers a more accurate assessment of the microbial flora of sputum in cystic fibrosis than does simple plating of unhomogenised sputum.

Preimmunization Anti-Pneumococcal Antibody Levels Are Protective in a Majority of Patients With Cystic Fibrosis

“…7,8 Once S pneumoniae grows from either respiratory secretions or blood, the subsequent determination of a particular serotype may be problematic. In addition, colonization of the respiratory tract in CF may be transient.…”

“…In patients with cystic fibrosis (CF), S pneumoniae has been reported as the fourth most common bacterial organism isolated from sputa-after Pseudomonas aeruginosa, Staphylococcus aureus, and Haemophilus influenzae-and this prevalence may be underestimated, as S pneumoniae is difficult to isolate from sputa often heavily colonized with these other organisms. 7,8 This pneumococcal colonization has been documented to be transient in CF patients even in the absence of antibiotic therapy. 9,10 CF patients may have an attenuated antibody response to pneumococcus for the following reasons.…”

Nitrate- and nitrite-reducing bacteria in the achlorhydric stomach

“…were isolated on Skirrow's Selective Medium (Oxoid) incubated in micro-aerophilic conditions at 37°C for 5 days. Aerobic plates included blood agar, MacConkey's agar and selective media for staphylococci (Medium 110, Oxoid), haemophili (Wong et al, 1984) and lactobacilli (Rogosa et al, 1951). All plates were incubated aerobically at 37°C for 2 days.…”

Use of selective medium for Burkholderia cepacia isolation in respiratory samples from cystic fibrosis patients

“…Sputum samples were collected directly by expectoration in a sterilized plastic receptacle, and throat swabs were collected by direct friction of a sterile cotton swab in the posterior pharynx, if possible after coughing and with concomitant use of a tongue depressor. Sputum samples were initially processed as described by WONG et al 30 . Briefly, an equal volume of a sterile solution of dithithreitol (DTT) 50 µg/mL in phosphate buffered saline with 0.1% of gelatin was added to the sputum samples and after 30 minutes homogenized by vortexing.…”