EuroPneumo Special Issue / pneumonia 2015 Oct 21;7:I–72

was assessed through overlay competition assays and their blp locus was characterised regarding BlpC type (signalling

peptide), integrity of the secretion system, and bacteriocin/immunity content. Approximately one-third of co-colonising

strains displayed inhibitory activity (29%) and more than half were cheaters (54%) (expression of immunity without

cost of bacteriocin secretion). Cheater strains co-existed with other cheaters (28%) and with inhibitory strains (25%)

at a comparable frequency. The 5 known BlpC types were not equally distributed in the population—BlpCT4 was the

most prevalent (37%) and BlpCP155 was rare (2%). The proportion of co-colonisation events involving matched (41%) or

unmatched (59%) BlpC types was not significantly different (p = 0.32). Also, the observed proportions of co-colonisation

events predicted to result in inhibition of one strain (41%) or no-inhibition (59%) were not different from the estimated

proportions based on the observed frequency in the population (p = 0.81). The results show that bacteriocin producers

often co-colonise with susceptible strains, suggesting that phenotypes of bacteriocin secretion alone do not explain the

co-existence of pneumococci in the nasopharynx.


Molecular surveillance on Streptococcus pneumoniae carriage in the

Netherlands: does the pneumococcus change its niche preference with

increasing host age?

Anne L. Wyllie 1 , Nynke Y. Rots 2 , Jody van Engelsdorp Gastelaars 1 , Lidewij W. Rümke 1 , Jacob P.

Bruin 3 , Elisabeth A.M. Sanders 1, 2 , Krzysztof Trzciński 1


Paediatric Immunology and Infectious Diseases, Wilhelmina’s Children Hospital, University Medical Center Utrecht, Utrecht, The Netherlands;


Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands;


Regional Laboratory of Public Health, Haarlem, The Netherlands

Pneumococcal colonisation of the upper airways is a disease prerequisite, which disproportionally affects infants and

elderly. Unlike in children, carriage of Streptococcus pneumoniae is rarely detected in elderly by the gold standard

method of conventional diagnostic culture. We suspected contemporary carriage rates to be underestimated and that

molecular-based analysis of samples from additional niches would enhance pneumococcal carriage detection. Here,

we compared the sensitivity of conventional and molecular methods in upper-airway samples from infants, adults and

elderly. Nasopharyngeal and saliva samples were collected from asymptomatic 24-month-old children (n = 289), parents

(n = 298) and 135 elderly aged 60–89 (2 time points, n = 270). Oropharyngeal samples were also obtained from all

adults. Following conventional diagnostic culture on pneumococci-selective media, DNA extracted from all plate growth

was tested by qPCR targeting 2 species-specific genes. For all age groups, molecular methods significantly increased

the number of carriers detected. There was no significant difference in the number of culture-positive nasopharyngeal

samples and qPCR-positive saliva samples from infants, while in both parents and elderly, qPCR-detection of pneumococci

in saliva samples was the most sensitive method. Accurate detection of S. pneumoniae is essential for monitoring

direct and indirect effects of infant pneumococcal vaccination. We demonstrate that no single method of detection is

optimal for all age groups, which is an important consideration for future surveillances. Our findings suggest a change

in niche preference with age and indicate that carriage rates in adults and elderly are underestimated when based on

nasopharyngeal samples alone. We propose that for sensitive pneumococcal carriage detection, nasopharyngeal and

saliva samples should be collected from children aged 0–6 years and that oropharyngeal and saliva samples should be

collected from all individuals aged 6–80 years.

pneumonia 2015 Volume 7


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