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.
BACKGROUND AND AIMS: S. anginosus, constellatus and intermedius, also known as the Streptococcus milleri group (SMG) are three streptococcal species more frequently detected in cases of invasive disease, abscesses and empyema in particular. Recent research suggests they play a role in exacerbations of cystic fibrosis (CF). Owing to poor recovery on standard culture media and difficult differentiation from non-pathogenic streptococci, SMG may be underdiagnosed in routine settings. We aimed to establish the incidence of SMG in chronic obstructive pulmonary disease (COPD) patients compared to CF patients and to examine possible links of SMG to exacerbations that plays a key role in progression of COPD. METHODS: Altogether, 90 respiratory tract samples of patients suffering from CF or COPD were examined during the period from July 2012 to December 2013. Semi-selective McKay agar was used for primary cultivation of SMG and MALDI TOF MS was used for species identification that was confirmed by biochemical profiling and specific PCR. RESULTS: We confirmed the presence of SMG in CF (17.6% incidence in adult patients) and newly established its presence in COPD (10.3% incidence). In COPD, SMG was detected in 4 cases of acute exacerbations, where no other bacterial pathogen was detected. In 3/4 cases, increased CRP level indicated bacterial infection as a cause of the exacerbation and in all 3 cases, patients recovered during antibiotic treatment. CONCLUSIONS: Our data indicate SMG may act as opportunist pathogens able to cause exacerbations in COPD.
- MeSH
- akutní nemoc MeSH
- chronická obstrukční plicní nemoc MeSH
- cystická fibróza mikrobiologie MeSH
- dospělí MeSH
- infekce dýchací soustavy mikrobiologie MeSH
- lidé středního věku MeSH
- lidé MeSH
- oportunní infekce mikrobiologie MeSH
- senioři MeSH
- skupina Streptococcus milleri izolace a purifikace MeSH
- sputum mikrobiologie MeSH
- streptokokové infekce mikrobiologie MeSH
- Check Tag
- dospělí MeSH
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři MeSH
- Publikační typ
- časopisecké články MeSH
- kazuistiky MeSH
