Post J C, Aul J J, White G J, Wadowsky R M, Zavoral T, Tabari R, Kerber B, Doyle W J, Ehrlich G D
Department of Pathology, School of Medicine, University of Pittsburgh Medical Center, Pennsylvania 15261, USA.
Am J Otolaryngol. 1996 Mar-Apr;17(2):106-11. doi: 10.1016/s0196-0709(96)90005-8.
Bacterial deoxyribonucleic acid (DNA) has been previously detected by polymerase chain reactions (PCR) in a significant percentage of culturally-sterile pediatric middle-ear effusions. The current study was designed to determine whether this represents the existence of viable bacteria or the persistence of residual DNA in the middle-ear cleft.
The middle-ear cavities of two sets of chinchillas were inoculated with either: 1) 100 colony-forming units (CFU) of live Haemophilus influenzae, 2.2 x 10(6) CFU of pasteurized Moraxella catarrhalis, and 1000 ng of DNA (>10(8) genomic equivalents) from Streptococcus pneumoniae; or 2) 100 CFU of live S pneumoniae, 2.2 x 10(6) CFU of pasteurized M catarrhalis and 1000 ng of purified DNA from H influenzae. Animals were treated with ampicillin for 5 days beginning on day 3. A single-point longitudinal study design was used for sampling to eliminate the possibility of contamination.
No DNA was detectable from the heat-killed bacteria or the purified DNA after day 3. However, DNA from the live bacteria persisted through day 21, even though all specimens were culture-negative following the initiation of antimicrobial therapy.
These findings indicate that purified DNA and DNA from intact but nonviable bacteria do not persist in the middle-ear cleft in the presence of an effusion, even following high copy inoculation. In contrast, antibiotic-treated bacteria persist in some viable state for weeks as evidenced by the differential ability of the PCR-based assay systems to detect the live bacteria, but not detect the heat-killed organisms.
先前通过聚合酶链反应（PCR）在相当比例的培养无菌的小儿中耳积液中检测到细菌脱氧核糖核酸（DNA）。本研究旨在确定这是代表中耳裂中存在活菌还是残留DNA的持续存在。
两组龙猫的中耳腔接种以下物质：1）100个流感嗜血杆菌活菌落形成单位（CFU）、2.2×10⁶个经巴氏消毒的卡他莫拉菌CFU以及1000 ng来自肺炎链球菌的DNA（>10⁸个基因组当量）；或2）100个肺炎链球菌活CFU、2.2×10⁶个经巴氏消毒的卡他莫拉菌CFU以及1000 ng来自流感嗜血杆菌的纯化DNA。从第3天开始，动物用氨苄西林治疗5天。采用单点纵向研究设计进行采样以消除污染的可能性。
第3天后，从热灭活细菌或纯化DNA中均未检测到DNA。然而，即使在开始抗菌治疗后所有标本培养均为阴性，但活菌的DNA一直持续到第21天。
这些发现表明，即使在高拷贝接种后，纯化DNA和来自完整但无活力细菌的DNA在存在积液的中耳裂中也不会持续存在。相比之下，经抗生素治疗的细菌以某种存活状态持续数周，基于PCR的检测系统能够检测活菌但不能检测热灭活生物体的差异能力证明了这一点。
