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Dispatch
Saliva and Meningococcal Transmission
Hilary J. Orr,* Steve J. Gray,† Mary Macdonald,‡ and James M. Stuart*1
*Health Protection Agency (South West), Gloucester, England,
United Kingdom; †Meningococcal Reference Unit, Manchester, England, United
Kingdom; and ‡County Hospital, Hereford, England, United Kingdom
Suggested citation
for this article:
Orr HJ, Gray SJ, Macdonald M, Stuart JM. Saliva and meningococcal transmission.
Emerg Infect Dis [serial online] 2003 Oct [date cited]. Available
from: URL: http://www.cdc.gov/ncidod/EID/vol9no10/03-0444.htm
Neisseria meningitidis
carriage was compared in swab specimens of nasopharynx, tonsils, and
saliva taken from 258 students. We found a higher yield in nasopharyngeal
than in tonsillar swabs (32% vs. 19%, p<0.001). Low prevalence of
carriage in saliva swabs (one swab [0.4%]) suggests that low levels
of salivary contact are unlikely to transmit meningococci.
Invasive meningococcal disease has a high case-fatality rate and an immediate
risk of further cases among household contacts. Public health measures
therefore include prompt identification of contacts for chemoprophylaxis
(1). One question that commonly arises is whether salivary
contact through sharing cups or glasses is an indication for prophylaxis,
but the evidence base to inform an answer is weak, and national guidelines
are inconsistent (1,2). Although saliva is thought to
inhibit meningococcal growth (3), carriage rates in saliva
are not known, and swabs to detect carriage are usually taken from tonsils
or nasopharynx (4–6). We compared meningococcal isolation
rates in swabs of saliva (front of mouth), tonsils, and nasopharynx.
We recruited volunteers among students from two colleges in Hereford,
England. After giving written consent, students completed a short questionnaire
on age, sex, smoking, recent antimicrobial drug use, and meningococcal
vaccine status. Three sterile, dry, cotton-tipped swabs were used to take
samples from each volunteer: one from the nasopharynx (through the mouth
and swept up behind the uvula), one from both tonsils, and one swab of
saliva between the lower gum and lips. Swabs were plated directly onto
a selective culture medium primarily designed for the isolation of pathogenic
Neisseria species (modified New York City base containing vancomycin,
colistin, and trimethoprim), prepared by Taunton Media Services, UK (7).
The plates were transported to Hereford Public Health Laboratory, where
they were spread once from the primary inoculum and incubated in 7% CO2
at 37°C for 48 h. Putative Neisseria species isolated were sent
to the Meningococcal Reference Unit, Manchester Public Health Laboratory,
for Neisseria meningitidis confirmation and serologic phenotypic
characterization. Data were entered into the computer using Excel (Microsoft
Corp., Redmond, WA). Carriage rates by site were compared with McNemar’s
test and by risk factor using chi-square tests. Ethical approval was obtained
from the Public Health Laboratory Service Ethics Committee and Herefordshire
District Ethics Committee.
Of the 258 participants, 90 (35%) were identified as carrying Neisseria
meningitidis from one or more sites. The site with the highest yield
was the nasopharynx (32.2%), whereas tonsillar carriage was 19.4% (Table).
One (0.4%) of the 258 saliva swab specimens was positive. No one had positive
specimens from all three sites, and the person with the positive saliva
swab had negative swabs from the other two sites. Differences in carriage
rates between the nasopharynx and tonsils and between the nasopharynx
and saliva were statistically significant (p<0.001 in both cases).
The predominant serogroup among carried strains was B. No serogroup C
strains were identified. Of the 44 carriers with positive swabs from both
nasopharynx and tonsils, each pair of isolates was considered to be phenotypically
indistinguishable by serogroup, serotype, and sero-subtype. In three of
these pairs, one isolate expressed serogroup B, and the paired isolate
could not be serogrouped but had identical serotype and sero-subtype.
Of the 258 participants, 116 (45%) were men, and 142 were women. Most
(86%) were 18 to 21 years of age. Carriage rates were higher among men
than women (54/116 vs. 36/142, p<0.001), and among smokers than nonsmokers
(49/90 vs. 51/168, p<0.001). Carriage rates were similar when persons
were stratified by age, meningococcal vaccination status, and recent antimicrobial
drug use. Although duplicate swabs from the nasopharynx sometimes yield
different meningococcal strains (3), none of the paired
isolates in this study were distinguishable by phenotype.
The yield of meningococci from nasopharyngeal swabs was nearly twice
as high as that from tonsillar swabs. Previous researchers have found
a lower sensitivity of nasopharyngeal swabs taken through the nose using
small cotton-tipped wire swabs compared to tonsillar swabs taken using
larger cotton-tipped swabs (5,6). Our use of the same
type of swab to sample both sites provided a more valid comparison. The
carriage rate was higher than expected for this age group (4),
suggesting that we had efficient swabbing and microbiologic techniques.
We suggest that throat swabs to detect meningococcal carriage should always
be taken from the nasopharynx (through the mouth whenever practical) and
not from the tonsils.
The very low isolation rate from saliva swabs suggests that low levels
of salivary contact are unlikely to transmit meningococci (1).
This observation is supported by results of a case-control study among
university students that found no association between meningococcal acquisition
and sharing of glasses or cigarettes (8). On the basis
of this evidence, we propose that guidelines for public health management
of meningococcal disease should not include low-level salivary contact
(e.g., sharing drinks) with a case-patient as an indication for chemoprophylaxis.
Acknowledgments
We thank all staff
and students at Hereford College of Technology and Hereford College
of Art and Design who were involved in this study and Erika Duffell
and Nicky Maxwell for their help with sampling.
This study was supported
by Gloucester Public Health Laboratory Trust Fund.
Ms. Orr is an epidemiology
research nurse in southwest England, working for the Health Protection
Agency. She has a research interest in the epidemiology of infectious
diseases.
References
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for public health management of meningococcal disease in the UK.
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- Communicable Diseases Network Australia. Guidelines on the early clinical
and public health management of meningococcal disease in Australia.
[Accessed 3 June 2003]. Available from: URL: http://www.health.gov.au/pubhlth/cdi/pubs/mening.htm
- Gordon MH. The inhibitory action of saliva on growth of the meningococcus.
Great Britain Medical Research Committee, Special Report Series 3; 1917.
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- Hoeffler DF. Recovery
of Neisseria meningitidis from the nasopharynx. Comparison of
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- Neal KR, Nguyen-Van-Tam J, Jeffrey N, Slack RC, Madeley RJ, Ait-Tahar
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during the first week of term: cross sectional study. BMJ 2000;320:846–9.
| Table.
Carriage of Neisseria meningitidis by sitea |
|
|
Site of swab
|
One site positive
|
Two sites positive
|
Three sites positive
|
Total positive
|
Overall carriage %
|
|
|
Nasopharynx
|
39
|
44
|
0
|
83
|
32.2
|
|
Tonsils
|
6
|
44
|
0
|
50
|
19.4
|
|
Saliva
|
1
|
0
|
0
|
1
|
0.4
|
|
| a(n=258). |
1H.O. was responsible for recruiting students,
obtaining specimens, swabs, and drafting the paper with J.S.; S.G. and
M.M. were responsible for microbiologic processing and analysis; and J.S.
designed the study and drafted the paper with H.O. All authors contributed
to the final draft.
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