Abstract
Streptococcus milleri group (SMG) is a group of three streptococcal species (S. anginosus, intermedius and constellatus) that act as opportunist pathogens, among others in cystic fibrosis. Due to their fastidious character, they are both difficult to cultivate and to differentiate from less pathogenic streptococcal species, therefore being most probably underdiagnosed. Semi-selective McKay agar and NAS agar were developed to facilitate SMG recovery from clinical samples; however, direct comparison of recovery rates has not been published yet. We tested the performance of both media on 123 patient samples and demonstrated general superiority of NAS agar for SMG recovery during primary cultivation convincingly. This observation was also confirmed by quantitative drop tests during subculture. Despite the undisputed overall superiority of NAS agar over McKay agar, a smaller fraction of strains grew better on McKay agar. Inter-strain differences were the most probable explanation. Therefore, when economic conditions are not limiting and maximum recovery rate is desirable, both plates are advised to be used in parallel for primary cultivation of clinical samples.
This is a preview of subscription content, log in via an institution to check access.
References
Miravitlles M, Espinosa C, Fernandez-Laso E, Martos JA, Maldonado JA, Gallego M (1999) Relationship between bacterial flora in sputum and functional impairment in patients with acute exacerbations of COPD. Study Group of Bacterial Infection in COPD Chest 116:40–46
Navratilova L, Bardon J, Novotny R, Zatloukal J, Jakubec P, Kolek V, Zapalka M, Kopriva F, Prochazkova P, Raclavsky V (2016) The Streptococcus milleri group in chronic obstructive pulmonary disease. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. Apr 21, 2016
Parkins MD, Sibley CD, Surette MG, Rabin HR (2008) The Streptococcus milleri group—an unrecognized cause of disease in cystic fibrosis: a case series and literature review. Pediatr Pulmonol 43(5):490–497
Sibley CD, Parkins MD, Rabin HR, Duan K, Norgaard JC, Surette MG (2008) A polymicrobial perspective of pulmonary infections exposes an enigmatic pathogen in cystic fibrosis patients. Proc Natl Acad Sci U S A 105(39):15070–15075
Sibley CD, Grinwis ME, Field TR, Parkins MD, Norgaard JC, Gregson DB, Rabin HR, Surette MG (2010) McKay agar enables routine quantification of the ‘Streptococcus milleri’ group in cystic fibrosis patients. J Med Microbiol 59(Pt 5):534–540
Waite RD, Wareham DW, Gardiner S, Whiley RA (2012) A simple, semiselective medium for anaerobic isolation of anginosus group streptococci from patients with chronic lung disease. J Clin Microbiol 50(4):1430–1432
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
All procedures performed in this study were in accordance with the ethical standards of the Ethical Board of University Hospital Olomouc, which approved the study, and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.
Funding
This work was supported by the Ministry of Health of the Czech Republic (NT/13560), by RVO (61989592), by IGA LF UP (LF_2015_035), and by the Ministry of Education, Youth and Sports of the Czech Republic (LO1304).
Conflict of interest
The authors declare that they have no conflict of interest.
Rights and permissions
About this article
Cite this article
Raclavsky, V., Novotny, R., Stary, L. et al. NAS agar is more suitable than McKay agar for primary culture of Streptococcus milleri group (SMG) fastidious bacteria, S. intermedius in particular. Folia Microbiol 62, 11–15 (2017). https://doi.org/10.1007/s12223-016-0470-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12223-016-0470-y