Nasopharyngeal versus Oropharyngeal Sampling for Detection of Pneumococcal Carriage in Adults

Abstract

Several studies have shown that nasopharyngeal sampling is more sensitive than oropharyngeal sampling for the detection of pneumococcal carriage in children. The data for adults are limited and conflicting. This study was part of a larger study of pneumococcal carriage on the Navajo and White Mountain Apache Reservation following a clinical trial of a seven-valent pneumococcal conjugate vaccine. Persons aged 18 years and older living in households with children enrolled in the vaccine trial were eligible. We collected both nasopharyngeal and oropharyngeal specimens by passing a flexible calcium alginate wire swab either nasally to the posterior nasopharynx or orally to the posterior oropharynx. Swabs were placed in skim milk-tryptoneglucose-glycerin medium and frozen at ؊70°C. Pneumococcal isolation was performed by standard techniques. Analyses were based on specimens collected from 1,994 adults living in 1,054 households. Nasopharyngeal specimens (11.1%; 95% confidence interval [CI], 9.8 and 12.6%) were significantly more likely to grow pneumococci than were oropharyngeal specimens (5.8%; 95% CI, 4.8 to 6.9%) (P < 0.0001). Few persons had pneumococcal growth from both specimens (1.7%). Therefore, both tests together were more likely to identify pneumococcal carriage (15.2%; 95% CI, 13.7 to 16.9%) than either test alone. Although we found that nasopharyngeal sampling was more sensitive than oropharyngeal sampling, nasopharyngeal sampling alone would have underestimated the prevalence of pneumococcal carriage in this adult population. Sampling both sites may give more accurate results than sampling either site alone in studies of pneumococcal carriage in adults.Infection with Streptococcus pneumoniae (pneumococcus) can result in a range of illnesses, including bacteremia, meningitis, pneumonia, otitis media, and sinusitis, which together cause substantial morbidity and mortality worldwide. The ascertainment of pneumococcal colonization is important for many types of studies. Several investigators have demonstrated that nasopharyngeal (NP) sampling is more sensitive than oropharyngeal (OP) sampling for detecting pneumococcal carriage in children (4,8,10,14), although contrary results exist (3). The optimal sampling method for identifying pneumococcal colonization in adults is not clear for several reasons. First, few studies have compared the yields from different sampling sites. Second, in some studies the sampling methods are not clearly specified. Third, the optimal sampling method may vary depending on the type of medium and the microbiologic methods used. Four studies that have compared NP and OP sampling in adults have come to different conclusions (2, 6, 9, 10). To our knowledge, no studies have been published that compared sampling sites when skim milk-tryptone-glucose-glycerin (STGG) medium was used to collect and store specimens. The inoculation of STGG medium is at least as sensitive as direct plating (12) and is a commonly used methodology that can be used under a wide variety of conditions. The objec...

Nasopharyngeal versus Oropharyngeal Sampling for Isolation of Potential Respiratory Pathogens in Adults

“…The second issue is the use of the rigid swab applicator to sample the nasopharynx, as was done in some earlier studies (1, 6), and not the flexible swab applicator, as was done in others (4,9,12). At the preliminary stage of this study the investigators tested both types of applicators for nasopharyngeal sampling.…”

“…The sensitivities of these two methods for identification of colonization by PRP in adults were compared in several earlier studies, particularly regarding S. pneumoniae, but the results were not consistent (1,2,4,6,9,12). The nasopharyngeal wash technique, which is commonly used to isolate viruses in children, has not gained popularity as a method to test for PRP colonization in adults.…”

How Valid Is Single-Colony Isolation for Surveillance of Streptococcus pneumoniae Carriage?

“…Although multiple strains can colonize simultaneously (4,5,(7)(8)(9)(10), most surveillance studies characterize only single colonies-but how valid is this information (12)? Nasopharyngeal swabs capture more pneumococci than throat swabs (1,6,14), but throat swabs can uncover different phenotypes (13,16). Our carriage studies (submitted for publication) characterizing multiple colonies from nose and throat samples revealed that Tanzanian children were colonized by a mean of three different serogroups or -types (SGT) and two different antibiograms for penicillin and cotrimoxazole.…”

Identification of a Peptide-Based Neutralizer That Potently Inhibits Both Shiga Toxins 1 and 2 by Targeting Specific Receptor-Binding Regions

“…21 A predicted carriage rate of 20% in 800 participating older children and adults would enable the determination of true carriage to within ±2.8% (95% confidence). 9 Participant recruitment Participants were selected from 20 GP practices within the Wessex Primary Care Research Network (PCRN) South West (East hub) area, in Southern England. GP practices were chosen to reflect a mix of urban/rural locations, practice sizes and area deprivation levels.…”

“…Methods for assessing carriage have included swabbing, nose blowing and nasopharyngeal aspiration. [5][6][7][8][9][10][11][12] However, no single study has evaluated the use of different swabbing methods using a large population-based sample. Streptococcus pneumoniae remains the…”