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Updated: Mar 22, 2026
Isolation, Transfection, and Culture of Primary Human Monocytes
Published on: December 16, 2019
Low-pathogenicity Mycoplasma spp. alter human monocyte and macrophage function and are highly prevalent among
T J Nolan1, N J Gadsby2, T P Hellyer3
1MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, UK.
Background:
Ventilator-acquired pneumonia (VAP) remains a significant problem within intensive care units (ICUs). There is a growing recognition of the impact of critical-illness-induced immunoparesis on the pathogenesis of VAP, but the mechanisms remain incompletely understood. We hypothesised that, because of limitations in their routine detection, Mycoplasmataceae are more prevalent among patients with VAP than previously recognised, and that these organisms potentially impair immune cell function.
Methods And Setting:
159 patients were recruited from 12 UK ICUs. All patients had suspected VAP and underwent bronchoscopy and bronchoalveolar lavage (BAL). VAP was defined as growth of organisms at >10(4) colony forming units per ml of BAL fluid on conventional culture. Samples were tested for Mycoplasmataceae (Mycoplasma and Ureaplasma spp.) by PCR, and positive samples underwent sequencing for speciation. 36 healthy donors underwent BAL for comparison. Additionally, healthy donor monocytes and macrophages were exposed to Mycoplasma salivarium and their ability to respond to lipopolysaccharide and undertake phagocytosis was assessed.
Results:
Mycoplasmataceae were found in 49% (95% CI 33% to 65%) of patients with VAP, compared with 14% (95% CI 9% to 25%) of patients without VAP. Patients with sterile BAL fluid had a similar prevalence to healthy donor BAL fluid (10% (95% CI 4% to 20%) vs 8% (95% CI 2% to 22%)). The most common organism identified was M. salivarium. Blood monocytes from healthy volunteers incubated with M. salivarium displayed an impaired TNF-α response to lipopolysaccharide (p=0.0003), as did monocyte-derived macrophages (MDMs) (p=0.024). MDM exposed to M. salivarium demonstrated impaired phagocytosis (p=0.005).
Discussion And Conclusions:
This study demonstrates a high prevalence of Mycoplasmataceae among patients with VAP, with a markedly lower prevalence among patients with suspected VAP in whom subsequent cultures refuted the diagnosis. The most common organism found, M. salivarium, is able to alter the functions of key immune cells. Mycoplasmataceae may contribute to VAP pathogenesis.
Insights
Mycoplasmataceae, including M. salivarium, are frequently found in patients with ventilator-acquired pneumonia (VAP) and can impair immune cell function, contributing to VAP pathogenesis.
Area of Science:
- Critical care medicine
- Infectious diseases
- Immunology
Background:
- Ventilator-acquired pneumonia (VAP) is a significant ICU challenge.
- Mechanisms of VAP, particularly immunoparesis, are not fully understood.
- Mycoplasmataceae may be underdiagnosed in VAP and impact immune function.
Purpose of the Study:
- To investigate the prevalence of Mycoplasmataceae in VAP patients.
- To explore the impact of Mycoplasmataceae on immune cell function.
Main Methods:
- 159 ICU patients with suspected VAP underwent bronchoscopy and bronchoalveolar lavage (BAL).
- PCR and sequencing were used to detect and speciate Mycoplasmataceae.
- In vitro experiments assessed the effect of Mycoplasma salivarium on human monocyte and macrophage function.
Main Results:
- Mycoplasmataceae were detected in 49% of VAP patients versus 14% of controls.
- M. salivarium was the most common species identified.
- M. salivarium impaired monocyte and macrophage TNF-α response and phagocytosis.
Conclusions:
- Mycoplasmataceae are prevalent in VAP and may contribute to its pathogenesis.
- M. salivarium can directly impair key immune cell functions.
- Further research into Mycoplasmataceae as VAP pathogens is warranted.
