McKay agar enables routine quantification of the 'Streptococcus milleri' group in cystic fibrosis patients.
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.
Sibley
Christopher D
CD
Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada.
Grinwis
Margot E
ME
Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada.
Field
Tyler R
TR
Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada.
Parkins
Michael D
MD
Adult Cystic Fibrosis Clinic, University of Calgary, Calgary, AB T2N 4N1, Canada.|Department of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.
Norgaard
Jens C
JC
Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada.
Gregson
Daniel B
DB
Department of Pathology and Laboratory Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.|Division of Microbiology, Calgary Laboratory Services No. 9, 3535 Research Road NW, Calgary, AB T2L 2K8, Canada.|Department of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.
Rabin
Harvey R
HR
Adult Cystic Fibrosis Clinic, University of Calgary, Calgary, AB T2N 4N1, Canada.|Department of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.|Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada.
Surette
Michael G
MG
Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB T2N 4N1, Canada.|Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, AB T2N 4N1, Canada.
D000328:Adult; D000362:Agar; D015169:Colony Count, Microbial / Q000379:methods; D003470:Culture Media / Q000737:chemistry*; D003550:Cystic Fibrosis / Q000150:complications*; D005260:Female; D006801:Humans; D008297:Male; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D013290:Streptococcal Infections / Q000382:microbiology*; D034366:Streptococcus anginosus / Q000302:isolation & purification*; D034365:Streptococcus constellatus / Q000302:isolation & purification*; D034367:Streptococcus intermedius / Q000302:isolation & purification*
D003470:Culture Media; D000362:Agar