Chemiluminescence (CL) was used to investigate the competence of turkey monocytes to mount a respiratory burst response upon interaction with Chlamydia psittaci. The oxidative activity of purified turkey monocytes, following inoculation with the avian C. psittaci serovar D strain 92/1293, was studied using luminol- and lucigenin-enhanced CL. Purified turkey monocytes were inoculated with C. psittaci at multiplicity of infection (MOI) of approximately 100, 10 and 1. In the presence of luminol, no detectable CL or only a weak CL response was obtained, and if present it increased with increasing MOI. Either sham inoculated monocytes, or monocyte-free control assays supplemented with C. psittaci, gave no detectable luminol-enhanced CL responses. In the lucigenin-enhanced assays, monocytes inoculated with C. psittaci demonstrated an immediate CL peak, the height of which was proportional to the MOI used. Following inoculations at a MOI 1, a faint second peak was observed, when applying high concentrations of lucigenin. Sham inoculated monocytes gave no detectable lucigenin-enhanced CL responses. However, in the presence of lucigenin, the addition of C psittaci to monocyte-free controls also resulted in an immediate CL peak, though no second peak was detected. This immediate lucigenin-dependent CL peak induced by C. psittaci was similar to the one observed in the presence of monocytes, and was not inhibited by superoxide dismutase. We demonstrated that this avian C. psittaci strain induces only a very weak respiratory burst response in turkey monocytes. In contrast, C. psittaci itself elicited an intense non-superoxide mediated lucigenin-dependent CL, indicating that in chlamydial research the detection of superoxide, using lucigenin, should be confirmed with a specific superoxide inhibitor
