Abstract
Summary The majority of contaminating organisms found in the routine cultivation of pathological specimens for tubercle bacilli using the standard Petroff's method of pretreatment and Kirchner's medium were found to be members of the coliform group. A method of pretreatment using 4% NaOH and 5% oxalic acid is described. A comparison of the contamination rate and the positive culture rate using the standardmethod of pretreatment and the new oxalic acid method was carried out on 982 specimens consisting of samples of sputum, gastric washings, faeces and infected tissues and known to contain coliform organisms. A sample of each specimen was pretreated by each method sparately and inoculated into Kirchner's medium. The contamination rate using the standard method was 11·6%, using the new oxalic acid method of 0·4%. The positive culture rate following the standard Petroff method was 3·4%, using the newoxalic acid method 5·8%. It is concluded that the most satisfactory method for the cultivation of tubercle bacillifrom material from all sources suspected of containing contaminants of the coliform group is by pretreatment with 4% NaOH and 5% oxalic acid as in the method described.
Published Version
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