Flaming of biopsy specimens for bacteriological culture: surface sterilization and effect on bacteria in the...

The effect of flaming (i.e. dipping biopsy specimens in alcohol and igniting them by drawing them rapidly through an open flame) on the reduction of bacterial surface contamination and on true bacterial concentrations in underlying tissue was investigated in different sizes of liver biopsy specimens in an experimental model suitable for quantitative and statistical calculations. Different degrees of surface contamination and of bacterial concentrations in underlying tissue were examined after a varying number of flaming procedures, the study comprising a total of 400 biopsy specimens. The flaming procedure repeated three times was able to eradicate a surface contamination of up to 10(4) E. coli per biopsy specimen, whereas a contamination of 10(6) E. coli per biopsy specimen was reduced to only 10(3) E. coli. Undesirable reduction in the true bacterial concentrations in tissue did not invalidate the method from a quantitative bacteriological point of view, since the median reduction in bacteria per gram tissue in biopsy specimens of 1 cm3 size did not exceed a factor of 3 after three repeated flamings. It is concluded that in regard to surface sterilization the method is unreliable as a routine in postmortem bacteriological studies.