Summary auto-generated
This study analyzed the porphyrin composition of fluorescent pus samples using absorption spectrophotometry and high-performance liquid chromatography (HPLC). Nineteen pus samples exhibiting red fluorescence under UV light were examined, along with three non-fluorescent controls. All fluorescent samples displayed absorption spectra characteristic of metal-free porphyrins. HPLC analysis revealed that contrary to previous assumptions, protoporphyrin IX was not the predominant fluorescent pigment and was never present alone. Instead, the most common porphyrins were dicarboxylic porphyrins: deuteroporphyrin (found in 16 samples) and mesoporphyrin (found in 9 samples). An unknown porphyrin, possibly pemptoporphyrin, appeared in eight samples. Protoporphyrin IX was detected in only six samples. Black-pigmented Bacteroides and Porphyromonas species were isolated from 63% of fluorescent samples. The researchers propose that protoporphyrin IX, derived from haem demetallation by anaerobic bacteria, is subsequently degraded by bacterial metabolism of its labile vinyl side-chains to produce the dicarboxylic porphyrins observed in clinical pus.
Key findings
- Deuteroporphyrin and mesoporphyrin, not protoporphyrin IX, are the predominant porphyrins in fluorescent pus samples
- Protoporphyrin IX was present in only 6 of 19 fluorescent samples and never as the sole fluorescent pigment
- Black-pigmented Bacteroides and Porphyromonas species were isolated from 63% of fluorescent pus samples
- The porphyrin profile in fluorescent pus matches that previously reported in normal stools, suggesting bacterial degradation of protoporphyrin IX via vinyl side-chain metabolism
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Abstract
Extracts of 19 samples of pus which showed red fluorescence with ultraviolet light were screened for the presence of porphyrins by absorption spectrophotometry. All those which showed spectra typical of metal-free porphyrins were analysed by high performance liquid chromatography to identify the porphyrins present. These were predominantly the di-carboxylic porphyrins, deuteroporphyrin and mesoporphyrin, and another which was thought to be pemptoporphyrin. This combination matched those reported previously in normal stools. Protoporphyrin IX was shown not to be the most common fluorescent pigment in pus and was never present alone. However, the di-carboxylic porphyrins may be produced by bacterial metabolism of its labile vinyl side-chains. Black-pigmented bacteroides (the melaninogenicus group of Bacteroides spp. and Porphyromonas spp.) were isolated from 12 (63%) of the 19 pus samples; these may produce protoporphyrin IX by the demetallation of haem.