Detection of Streptococcus pneumoniae from Different Types of Nasopharyngeal Swabs in Children

Abstract

BackgroundA better understanding of the epidemiology of nasopharyngeal carriage of Streptococcus pneumoniae is important to assess the impact of vaccination and the pathogenesis of pneumococcal disease. We compared the recovery of S. pneumoniae from nylon flocked, Dacron and rayon swabs.MethodsThe recovery of S. pneumoniae from mocked specimens using flocked, Dacron and rayon swabs were compared by culture. The yield from paired nasopharyngeal (NP) samples obtained from healthy children sampled with flocked and Dacron swabs was also determined using culture and lytA-targeted real-time polymerase chain reaction (qPCR).ResultsUsing mock specimen, the percentage recovery of S. pneumoniae ATCC 49619 (serotype 19F) strain from the flocked swabs was 100%, while it was 41% from Dacron swabs and 7% from rayon swabs. Similar results were observed for S. pneumoniae serotypes 1 and 5. S. pneumoniae was cultured from 18 of 42 (43%) paired NP samples from the healthy children (median age 8 [interquartile range (IQR) 5–16] months). The median number of colony-forming units (CFU) recovered from flocked swabs was two-fold higher (8.8×104 CFU/mL [IQR, 2.0×102 – 4.0×105 CFU/mL]) than Dacron swabs (3.7×104 CFU/mL [IQR, 4.0×102–3.2×105 CFU/mL], p = 0.17). Using lytA-targeted qPCR from paired NP samples, the median copy number of S. pneumoniae detected from flocked swabs was significantly higher than from Dacron swabs (3.0×105 genome copies/mL [IQR, 1.3×102−1.8×106] vs. 9.3×104 genome copies/mL [IQR, 7.0×101−1.1×106]; p = 0.005).ConclusionFlocked swabs released more S. pneumoniae compared to both Dacron and rayon swabs from mock specimens. Similarly, higher bacterial loads were detected by qPCR from flocked swabs compared with Dacron swabs from healthy children.

Pharyngeal Colonization by Streptococcus pneumoniae in Older Children and Adolescents in a Geographical Area Characterized by Relatively Limited Pneumococcal Vaccination Coverage

“…17 Finally, a flocked nylon fiber tip was used for the sampling because previous studies have shown that this ensures the highest rate of detection of S. pneumoniae, particularly in comparison with the more widely used Dacron and rayon swabs. 20 We did not observe differences in cycle threshold values comparing pneumococcal colonization in vaccinated and unvaccinated children, although it may be technically challenging to compare density of carriage using bacteria recovered on a small nylon tip as the size of the tip may be a limiting factor in assessing the magnitude of colonization.…”

Streptococcus pneumoniae oropharyngeal colonization in children and adolescents with cystic fibrosis

“…Oropharyngeal sampling was used to collect the pharyngeal secretions; it has recently been shown that it is a significantly better means of detecting the colonization by S. pneumoniae in adolescents, and young adults than the nasopharyngeal sampling used in the previous studies of younger children [13,15,16]. Finally, a flocked nylon fiber tip was used for sampling because previous studies have shown that this ensures the highest rate of detection of S. pneumoniae, particularly when compared with the more widely used Dacron and rayon swabs [17].…”

Advances in the diagnosis of pneumonia in children

“…Flocked nasopharyngeal swabs provide a similar yield to aspirates, are simpler to obtain than aspirates, 77 78 and may provide a better yield than other swab types. [79][80][81] Studies are inconsistent regarding the relative yield of nasopharyngeal versus oropharyngeal specimens for the detection of viruses; there may be incremental yield from testing of both specimen types for specific viruses such as influenza A or adenovirus. [82][83][84][85] Nasopharyngeal specimens may also be useful for the diagnosis of tuberculosis using the polymerase chain reaction (PCR) in children from whom it is not possible to obtain more representative lower respiratory tract samples.…”