Related Experiment Videos
Survival of nontypeable Haemophilus influenzae in macrophages
J E Craig1, A Cliffe, K Garnett
1University of Manchester, School of Biological Sciences, 1.800, Stopford Building, Manchester M13 9PT, UK.
Abstract:
In this study we have investigated the ability of nonencapsulated, nontypeable Haemophilus influenzae, NT477 to survive in the J774 mouse macrophage-like cell line. Viable, intracellular nontypeable H. influenzae could still be recovered from macrophages 72 h after phagocytosis. In contrast, H. influenzae strain Rd, an avirulent, nonencapsulated variant of a serotype d strain, was killed within 24 h. These differences suggest that NT477, in comparison to Rd, possesses unique attributes that enable it to survive in macrophages for prolonged periods. To determine whether this trait is ubiquitous amongst nontypeable H. influenzae, 33 primary clinical isolates obtained from children with otitis media were screened for their ability to survive in macrophages. Of these isolates, 82% were able to persist in an intracellular environment for periods of at least 24 h. The number of viable organisms recovered at this time ranged from 2x10(4) to 50 colony-forming units per strain indicating that the extent to which nontypeable H. influenzae can resist macrophage-mediated killing varies between strains.
Insights
Nontypeable Haemophilus influenzae, NT477, survives longer within mouse macrophages than strain Rd. Most clinical isolates also resist macrophage killing, indicating varied survival capabilities in nontypeable strains.
Area of Science:
- Microbiology
- Immunology
- Bacterial Pathogenesis
Background:
- Nontypeable Haemophilus influenzae (NTHi) is a significant human pathogen, often causing respiratory tract infections.
- The ability of NTHi to evade host immune responses, particularly macrophage clearance, is crucial for its pathogenesis.
- Understanding NTHi survival mechanisms within macrophages can inform therapeutic strategies.
Purpose of the Study:
- To investigate the intracellular survival of a specific NTHi strain (NT477) in a mouse macrophage cell line.
- To compare the survival of NT477 with an avirulent control strain (Rd).
- To determine the prevalence of macrophage survival traits among clinical NTHi isolates from otitis media patients.
Main Methods:
- Phagocytosis assays using J774 mouse macrophage-like cells and bacterial strains NT477 and Rd.
- Enumeration of viable intracellular bacteria at various time points post-infection (24h and 72h).
- Screening of 33 primary clinical NTHi isolates for intracellular survival in macrophages.
Main Results:
- Nontypeable Haemophilus influenzae NT477 survived intracellularly in macrophages for up to 72 hours.
- In contrast, the avirulent strain Rd was killed within 24 hours.
- 82% of 33 clinical NTHi isolates demonstrated persistence within macrophages for at least 24 hours, with varying recovery levels.
Conclusions:
- NTHi strain NT477 possesses unique attributes for prolonged intracellular survival in macrophages compared to strain Rd.
- The capacity for macrophage survival is a common trait among clinical NTHi isolates from otitis media.
- There is significant inter-strain variability in the ability of NTHi to resist macrophage-mediated killing.