The coronavirus disease COVID-19 was first described in December 2019. The peripheral blood of COVID-19 patients have increased numbers of neutrophils which are important in controlling the bacterial infections observed in COVID-19. We sought to evaluate the cytotoxic capacity of neutrophils in COVID-19 patients. 34 confirmed COVID-19 patients (29 severe, five mild disease), and nine healthy controls were recruited from the Masih Daneshvari Hospital (Tehran, Iran) from March to May 2020. Polymorphonuclear (PMN) cells were isolated from whole blood and incubated with green fluorescent protein (GFP)-labelled methicillin-resistant Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA). Bacterial growth was determined by measuring the florescence of co-cultures of bacteria and neutrophils and reported as the lag time before exponential growth. The number of viable bacteria was determined after 70 hours as colony-forming units (CFU). The immunophenotype of tested cells was evaluated by flow cytometry. Isolated neutrophils have higher surface expression of CD16 and CD62L with negative markers for PMN-MDSC. Bacterial growth in the presence of SA (22 ± 0.9 versus 9.2 ± 0.5 h, P < .01) and PA (12.4 ± 0.6 versus 4.5 ± 0.22, P < .01) was significantly reduced in COVID-19 patients. After 70 h incubation of PMN with bacteria (SA and PA), CFUs were significant increased in COVID-19 patients SA (2.6 ± 0.09 × 10⁸ CFU/mL-severe patients and 1.4 ± 0.06 × 10⁸ CFU/mL-mild patients, P < .001) and PA (2.2 ± 0.09 × 10⁹ CFU/mL-severe patients and 1.6 ± 0.03 × 10⁹ CFU/mL-mild patients, P < .001). Gentamycin proliferation assays confirmed the presence of intracellular bacteria. Reduced bacterial killing by neutrophils from COVID-19 patients may be responsible for the high bacterial yield seen in these patients.

中文翻译：

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COVID-19 患者中性粒细胞介导的细菌杀灭作用减少


冠状病毒病 COVID-19 于 2019 年 12 月首次被描述。COVID-19 患者的外周血中中性粒细胞数量增加，这对于控制 COVID-19 中观察到的细菌感染非常重要。我们试图评估 COVID-19 患者中性粒细胞的细胞毒性能力。 2020 年 3 月至 5 月，从 Masih Daneshvari 医院（伊朗德黑兰）招募了 34 名确诊的 COVID-19 患者（29 名重症患者，5 名轻度患者）和 9 名健康对照者。从全血中分离出多形核 (PMN) 细胞，并与绿色荧光蛋白（GFP）标记的耐甲氧西林金黄色葡萄球菌（SA）和铜绿假单胞菌（PA） 。通过测量细菌和中性粒细胞共培养物的花期来确定细菌生长，并报告为指数生长之前的滞后时间。 70小时后确定活细菌的数量作为菌落形成单位(CFU)。通过流式细胞术评估测试细胞的免疫表型。分离的中性粒细胞具有较高的 CD16 和 CD62L 表面表达，且具有 PMN-MDSC 阴性标记。在 SA（22 ± 0.9 与 9.2 ± 0.5 小时， P < .01）和 PA（12.4 ± 0.6 与 4.5 ± 0.22， P < .01）存在的情况下，COVID-19 患者的细菌生长显着减少。 PMN 与细菌（SA 和 PA）孵育 70 小时后，COVID-19 患者 SA 中的 CFU 显着增加（重度患者为 2.6 ± 0.09 × 10 ⁸ CFU/mL，轻度患者为 1.4 ± 0.06 × 10 ⁸ CFU/mL） ， P < .001) 和 PA (2.2 ± 0.09 × 10 ⁹ CFU/mL-重度患者和 1.6 ± 0.03 × 10 ⁹ CFU/mL-轻度患者， P < .001)。 庆大霉素增殖测定证实了细胞内细菌的存在。 COVID-19 患者中性粒细胞杀灭细菌的减少可能是这些患者细菌产量高的原因。