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Chlamydia psittaci: growth characteristics and enumeration of serotypes 1 and 2 in cultured cells
Abstract:
The growth characteristics of Chlamydia psittaci serotypes 1 and 2 (ovine and bovine origin) were studed in mouse L cells. Formation of inclusions and yield of infectious progeny for serotype 1 were maximal when host cells were treated with cycloheximide and the pH in the cell culture medium was 7.2-7.4. The number of cells that contained inclusions and the infectivity yield for serotype 2 were maximal when the pH was 6.6-7.0. Treatments with diethylaminoethyl dextran and cycloheximide increased inclusion formation in serotype 2 but decreased the yield per infected cell. For both serotypes, centrifugation of the chlamydiae onto monolayers infected 50-1,200 times the number of cells infected with use of stationary adsorption. An enumeration method for L-cell infectious units was developed that gave higher titers than the chicken embryo 50% lethal dose after yolk sac inoculation.
Insights
Chlamydia psittaci growth varies by serotype and culture conditions. Optimizing pH and using cycloheximide or diethylaminoethyl dextran impacts inclusion formation and infectious progeny yield in mouse L cells.
Area of Science:
- Veterinary Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Chlamydia psittaci is an important veterinary pathogen causing significant economic losses.
- Understanding the optimal growth conditions for different serotypes is crucial for developing effective control strategies.
- Mouse L cells are a common model system for studying Chlamydia growth.
Purpose of the Study:
- To investigate the growth characteristics of Chlamydia psittaci serotypes 1 (ovine) and 2 (bovine) in mouse L cells.
- To determine the optimal conditions for inclusion formation and infectious progeny yield.
- To compare different methods for enhancing Chlamydia infection in cell culture.
Main Methods:
- Chlamydia psittaci serotypes 1 and 2 were cultured in mouse L cells.
- Host cells were treated with cycloheximide and diethylaminoethyl dextran.
- Cell culture pH was varied between 6.6 and 7.4.
- Centrifugation was used to enhance chlamydial adsorption.
- An enumeration method for L-cell infectious units was developed.
Main Results:
- Serotype 1 growth was optimal at pH 7.2-7.4 with cycloheximide treatment.
- Serotype 2 growth was optimal at pH 6.6-7.0.
- Diethylaminoethyl dextran and cycloheximide increased inclusion formation for serotype 2 but reduced yield per cell.
- Centrifugation significantly increased infected cell numbers for both serotypes compared to stationary adsorption.
- The developed L-cell enumeration method yielded higher titers than the chicken embryo lethal dose assay.
Conclusions:
- Optimal growth conditions for Chlamydia psittaci are serotype-specific.
- pH and specific cell treatments significantly influence Chlamydia replication in L cells.
- Centrifugation is an effective method for increasing Chlamydia infection efficiency in cell culture.
- The L-cell enumeration method provides a sensitive and efficient way to quantify infectious Chlamydia units.