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Quantitative PCR of ear discharge from Indigenous Australian children with acute otitis media with perforation supports a role for Alloiococcus otitidis as a secondary pathogen

Marsh, Robyn L., Binks, Michael J., Beissbarth, Jemima, Christensen, Peter R., Morris, Peter S., Leach, Amanda J. and Smith-Vaughan, Heidi C. (2012). Quantitative PCR of ear discharge from Indigenous Australian children with acute otitis media with perforation supports a role for Alloiococcus otitidis as a secondary pathogen. BMC Ear Nose and Throat Disorders,12(11):1-10.

Document type: Journal Article
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IRMA ID cmartelxPUB46
Title Quantitative PCR of ear discharge from Indigenous Australian children with acute otitis media with perforation supports a role for Alloiococcus otitidis as a secondary pathogen
Author Marsh, Robyn L.
Binks, Michael J.
Beissbarth, Jemima
Christensen, Peter R.
Morris, Peter S.
Leach, Amanda J.
Smith-Vaughan, Heidi C.
Journal Name BMC Ear Nose and Throat Disorders
Publication Date 2012
Volume Number 12
Issue Number 11
ISSN 1472-6815   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-84870903108
Start Page 1
End Page 10
Total Pages 10
Place of Publication United Kingdom
Publisher BioMed Central Ltd.
HERDC Category C1 - Journal Article (DIISR)
Abstract Background
Otitis media is endemic in remote Indigenous communities of Australia’s Northern Territory. Alloiococcus otitidis is an outer ear commensal and putative middle ear pathogen that has not previously been described in acute otitis media (AOM) in this population. The aims of this study were to determine the presence, antibiotic susceptibility and bacterial load of A. otitidis in nasopharyngeal and ear discharge swabs collected from Indigenous Australian children with AOM with perforation.

Methods
Paired nasopharyngeal and ear discharge swabs from 27 children with AOM with perforation were tested by A. otitidis quantitative PCR (qPCR). Positive swabs were cultured for 21 days. Total and respiratory pathogen bacterial loads in A. otitidis-positive swabs were determined by qPCR.

Results
A. otitidis was detected by qPCR in 11 ear discharge swabs from 10 of 27 (37%) children, but was not detected in paired nasopharyngeal swabs. A. otitidis was cultured from 5 of 11 qPCR-positive swabs from four children. All A. otitidis isolates had minimum inhibitory concentrations consistent with macrolide resistance. All A. otitidis qPCR-positive swabs were culture-positive for other bacteria. A. otitidis bacterial load ranged from 2.2 × 104-1.1 × 108 cells/swab (median 1.8 × 105 cells/swab). The relative abundance of A. otitidis ranged from 0.01% to 34% of the total bacterial load (median 0.7%). In 6 of 11 qPCR-positive swabs the A. otitidis relative abundance was <1% and in 5 of 11 it was between 2% and 34%. The A. otitidis bacterial load and relative abundance measures were comparable to that of Haemophilus influenzae.

Conclusions
A. otitidis can be a dominant species in the bacterial communities present in the ear discharge of Indigenous children with AOM with perforation. The absence of A. otitidis in nasopharyngeal swabs suggests the ear canal as the likely primary reservoir. The significance of A. otitidis at low relative abundance is unclear; however, at higher relative abundance it may be contributing to the associated inflammation. Further studies to better understand A. otitidis as a secondary otopathogen are warranted, particularly in populations at high-risk of progression to chronic suppurative otitis media and where macrolide therapies are being used.

Keywords Alloiococcus otitidis
Otitis media
Acute otitis media with perforation
Indigenous Australian children
Bacterial load
DOI http://dx.doi.org/10.1186/1472-6815-12-11   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)


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