[Show abstract][Hide abstract] ABSTRACT: The 'Streptococcus milleri' group (SMG) has recently been recognized as a contributor to bronchopulmonary disease in cystic fibrosis (CF). Routine detection and quantification is limited by current CF microbiology protocols. McKay agar was developed previously for the semi-selective isolation of this group. Here, McKay agar was validated against a panel of clinical SMG isolates, which revealed improved SMG recovery compared with Columbia blood agar. The effectiveness of this medium was evaluated by appending it to the standard CF sputum microbiology protocols in a clinical laboratory for a 6-month period. All unique colony types were isolated and identified by 16S rRNA gene sequencing. Whilst a wide variety of organisms were isolated, members of the SMG were the most prevalent bacteria cultured, and McKay agar allowed routine quantification of the SMG from 10(3) to >10(8) c.f.u. ml(-1) directly from sputum. All members of the SMG were detected [Streptococcus anginosus (40.7 %), Streptococcus intermedius (34.3 %) and Streptococcus constellatus (25 %)] with an overall prevalence rate of 40.6 % in our adult CF population. Without exception, samples where SMG isolates were cultured at 10(7) c.f.u. ml(-1) or greater were associated with pulmonary exacerbations. This study demonstrates that McKay agar can be used routinely to quantify the SMG from complex clinical samples.
Preview · Article · May 2010 · Journal of Medical Microbiology
[Show abstract][Hide abstract] ABSTRACT: Lung disease is the leading cause of morbidity and mortality in cystic fibrosis (CF) patients. A modest number of bacterial pathogens have been correlated with pulmonary function decline; however, microbiological and molecular evidence suggests that CF airway infection is polymicrobial. To obtain a more complete assessment of the microbial community composition and dynamics, we undertook a longitudinal study by using culture-independent and microbiological approaches. In the process, we demonstrated that within complex and dynamic communities, the Streptococcus milleri group (SMG) can establish chronic pulmonary infections and at the onset of 39% of acute pulmonary exacerbations, SMG is the numerically dominant pathogen. We report the comprehensive polymicrobial community dynamics of a CF lung infection in a clinically relevant context. If a given organism, such as Pseudomonas aeruginosa, becomes resistant to antibiotic therapy, an alternative treatment avenue may mediate the desired clinical response by effectively managing the composition of the microbial community.
Full-text · Article · Oct 2008 · Proceedings of the National Academy of Sciences