Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry, India.
Department of Preventive and Social Medicine, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry, India.
Indian J Tuberc. 2020 Oct;67(4):466-471. doi: 10.1016/j.ijtb.2020.07.016. Epub 2020 Jul 19.
Tuberculosis (TB) is a major public health problem worldwide. Contamination rate and poor recovery of Mycobacterium tuberculosis complex (MTBC) in MGIT960 culture may affect the early diagnosis of TB. Evidence is needed to determine the factors associated with contamination rates and MTBC recovery in MGIT960. Hence, we undertook this study to compare the factors influencing MTBC culture positivity and contamination rates in MGIT960 in patients with Pulmonary tuberculosis (PTB).
A total of 849 sputum samples from newly diagnosed smear-positive TB cases enrolled into the Regional Prospective Observational Research for Tuberculosis India cohort between May 2014 to March 2017 were analyzed. Samples were inoculated into MGIT960 and positive cultures were examined for the presence of MTBC by immunochromatographic test for detection of MPT64 antigen.
Of the 849 cases, 811 (95.5%) were culture positive for MTBC, 23 (2.7%) were culture negative and 15 (1.8%) were contaminated. Salivary sputum showed significantly less culture yield compared to mucopurulent/blood stained samples (p = 0.021). Sputum from individuals <20 or ≥60 years showed lower culture yield of 93.9%, compared to those aged 20-59years (98.2%) (p = 0.002). Based on smear grading, culture isolation of MTBC by MGIT960 was 86.1%, 93.6% and 99.5% for negative, scanty and positive (1+/2+/3+) samples, respectively (p ≤ 0.0001). Sputum from HIV negative patients showed higher culture yield, compared to HIV positive patients (p ≤ 0.0001). Chest X-Ray revealed that patient with cavity showed higher culture isolation of MTBC compared to patients without cavity (p = 0.035). Contamination rates were higher in smear negatives (6.0%), compared to scanty (2.1%) and smear positives (1.1%) (p = 0.007). However, delay in transport of the specimen to the laboratory was the only independent factor significantly associated with increase in culture contamination.
Our results highlight that extremes of age, smear negativity, HIV infection, sputum quality and cavitation significantly influence the culture yield of MTBC, whereas transport duration and smear grading affected the contamination rates in MGIT960. Hence, addressing these factors may improve the diagnostic performance of MGIT960.
结核病（TB）是全球主要的公共卫生问题。分枝杆菌复合群（MTBC）在 MGIT960 培养物中的污染率和较差的恢复可能会影响结核病的早期诊断。需要证据来确定与 MGIT960 中 MTBC 培养阳性和污染率相关的因素。因此，我们进行了这项研究，以比较新诊断为涂阳肺结核（PTB）患者中 MTBC 在 MGIT960 中的培养阳性和污染率的影响因素。
对 2014 年 5 月至 2017 年 3 月期间纳入印度地区前瞻性观察性结核病研究队列的 849 例新诊断为涂阳结核病病例的痰液样本进行分析。将样本接种到 MGIT960 中，用 MPT64 抗原免疫色谱检测法对阳性培养物进行 MTBC 存在的检测。
在 849 例病例中，811 例（95.5%）MTBC 培养阳性，23 例（2.7%）培养阴性，15 例（1.8%）污染。与黏液脓性/血污样本相比，唾液痰的培养产量明显较低（p=0.021）。20 岁以下或≥60 岁的个体的培养产量为 93.9%，明显低于 20-59 岁的个体（98.2%）（p=0.002）。根据涂片分级，MGIT960 对 MTBC 的培养分离率分别为阴性、稀少和阳性（1+/2+/3+）样本的 86.1%、93.6%和 99.5%（p≤0.0001）。与 HIV 阳性患者相比，HIV 阴性患者的培养产量更高（p≤0.0001）。胸部 X 光显示有空腔的患者与没有空腔的患者相比，MTBC 的培养分离率更高（p=0.035）。涂片阴性患者的污染率（6.0%）明显高于涂片稀少（2.1%）和涂片阳性（1.1%）患者（p=0.007）。然而，标本向实验室的运输延迟是唯一与培养污染率显著相关的独立因素。
我们的结果强调，年龄极端、涂片阴性、HIV 感染、痰质量和空洞显著影响 MTBC 的培养产量，而运输时间和涂片分级影响 MGIT960 中的污染率。因此，解决这些因素可能会提高 MGIT960 的诊断性能。
