A reservoir of Moraxella catarrhalis in human pharyngeal lymphoid tissue.
BACKGROUND
Early exposure of infants and long-term immunity suggest that colonization with Moraxella catarrhalis is more frequent than is determined by routine culture. We characterized a reservoir of M. catarrhalis in pharyngeal lymphoid tissue.


METHODS
Tissue from 40 patients (median age, 7.1 years) undergoing elective tonsillectomy and/or adenoidectomy was analyzed for the presence of M. catarrhalis by culture, real-time DNA and RNA polymerase chain reaction (PCR), immunohistochemical analysis (IHC), and fluorescent in situ hybridization (FISH). Histologic sections were double stained for M. catarrhalis and immune cell markers, to characterize the tissue distribution of the organism. Intracellular bacteria were identified using confocal laser scanning microscopy (CLSM).


RESULTS
Twenty-nine (91%) of 32 adenoids and 17 (85%) of 20 tonsils were colonized with M. catarrhalis. Detection rates for culture, DNA PCR, RNA PCR, IHC, and FISH were 7 (13%) of 52, 10 (19%) of 52, 21 (41%) of 51, 30 (61%) of 49, and 42 (88%) of 48, respectively (P<.001). Histologic analysis identified M. catarrhalis in crypts, intraepithelially, subepithelially, and (using CLSM) intracellularly. M. catarrhalis colocalized with macrophages and B cells in lymphoid follicles.


CONCLUSIONS
Colonization by M. catarrhalis is more frequent than is determined by surface culture, because the organism resides both within and beneath the epithelium and invades host cells.
Heiniger
Nadja
N
Institute for Infectious Diseases, University of Bern, Bern, CH-3010, Switzerland.
Spaniol
Violeta
V
Troller
Rolf
R
Vischer
Mattheus
M
Aebi
Christoph
C
D000233:Adenoidectomy; D000234:Adenoids / Q000382:microbiology*; D002648:Child; D004269:DNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D004197:Disease Reservoirs; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D018613:Microscopy, Confocal; D001936:Moraxella catarrhalis / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D014066:Palatine Tonsil / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods; D012329:RNA, Bacterial / Q000032:analysis / Q000302:isolation & purification; D014068:Tonsillectomy
D004269:DNA, Bacterial; D012329:RNA, Bacterial